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Browsing by Person "Claupein, Wilhelm"

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Die Auswirkungen einer einmalig variierten Bodenbearbeitung auf Ertragsbildung, Verunkrautung und Bodennitratgehalt unter ökologischen Produktionsbedingungen
(2007) Häberle, Annette; Claupein, Wilhelm
Although organic farming is a very non-polluting kind of agriculture, nitrate leachate losses can also be found under this management. Restrictions in organic fertilization have the purpose to keep the nitrate leachate with soil tillage and crop rotation on a low level. Due to this aim field experiments were conducted to investigate the short-term effect of timing and method of cultivation after the harvest of legumes and crops with high-N crop residues on N mineralization, nitrate leaching, crop growth, diseases and weeds in wheat crops. The study was designed to compare the effects of the ?Schutz- und Ausgleichsverordnung? (SchALVO) in Baden-Württemberg and tillage strategies which are normally used in practice, like reduced and conventional tillage in autumn and to compare different times of conventional tillage in winter and spring in three different areas of Baden-Württemberg with typically soil types. The areas were located in the Main-Tauber-Kreis with soils from Keuper and shell lime, in the Gäu-Region with soils from löss and the Schwäbische Alb with soils of limestone. Especially organic farms use, for the admancement of yield und for the regulation of weed population, a timely and increased requirement of soil tillage. In the results of October 2002 till summer 2005 there was no significant influence of timing and method of cultivation, for example reduced tillage in autumn or tillage in winter or spring, on the productivity of organic farms. In the most cases the conditions on the experimental fields were very good resulting of a low weed density and a good farming management. On fields with a high density of perennial weeds the risk of multiplication of weed population persists even after a short-term variation of tillage. There were only a few, not significant differences in the development of wheat growth because of different soil tillage. The most differences were seen between the growth of winter wheat and summer wheat. The yield of summer wheat was not significantly lower than the yield of winter wheat. Summer wheat reached nearly the same yield potential with higher amounts of crude protein. Especially in areas with strong winters and low N-input the yield of summer wheat was higher than the yield of winter wheat. Because of a second peak of mineralization in spring there was a better adaptation of NO3-release to the growth of summer wheat after soil tillage in November, December and February. Because of the better utilization of soil-N from summer wheat the lower yield potential in comparison to winter wheat was relativised in the most areas. With regard to N mineralization a time displacement of soil tillage in winter or spring didnt reduce the N-mineralization before winter in all cases. But in this time displaced treatments there was a second peak in N-mineralization additional to the first peak in autumn. Short-term practice of reduced soil tillage did not reduce N-release in the field experiments. Altogether a time displaced soil tillage in winter or spring could be, based on the experiments, a practical alternative for N-conservation through winter with regard to N-mineralization as well as with regard to corn yield. With the cultivation of a fast-growing catch crop farmers could reach an additional reduction of mineralised N amount over winter. In the farming practice a well timed sowing of catch crops is not always possible, like it is shown in the experiments, but it should be kept in mind for N conservation.
Biomass production for bioenergy as an interface between yield optimisation, ecology and human nutrition : a question of resource efficiency
(2012) Gauder, Martin; Claupein, Wilhelm
In this thesis, specific questions dealing with sustainability of bioenergy were analysed on regional scales. One focus was put on food security and the connections to bioenergy production. Therefore a study, based on the comprehensive range of information available, was conducted for ethanol production in Brazil. The second focus laid on Europe and the potentials and environmental risks which come along with bioenergy production. A study on interannual yield performance of long-term Miscanthus plantations was conducted to evaluate potentials and genotype diversities of Miscanthus cropping in Southwest Germany. To identify the possible contribution of by-products from agriculture, a third study dealt with amount and distribution of surplus straw in Southwest Germany. Environmental aspects were addressed in a field trial, which monitored trace gas fluxes from soils under different energy plants also in Southwest Germany. The last study examined the potential of establishing large-scale poplar plantations in Romania and how this could contribute to the regional energy security.
Comparative performance of annual and perennial energy cropping systems under different management regimes
(2007) Böhmel, Ute Constanze; Claupein, Wilhelm
The theme of this thesis was chosen against the background of the necessary substitution of fossil fuels and the need to reduce greenhouse gas emissions. One major solution for these topics may be the energy generation from domestically produced biomass. The overall aim of this thesis was the identification of one or more efficient energy cropping systems for Central Europe. The target was set to supply high quality biomass for existent and currently developing modern conversion technologies. Renewable energy production is thought to be environmentally benign and socially acceptable. The existence of diverse production environments necessitates further diversification and the identification of several energy crops and the development of energy cropping systems suited to those diverse environments. This thesis starts with an introductory essay (chapter 1), which provides the background for renewable energy production, its features, demands and potentials, and the scientific basis of this thesis. Chapters 2 to 6 consist of five manuscripts to be published in reviewed journals (Papers I, II, IV and V) or in a multi-author book (Paper III). Subsequently, the results from all papers are discussed in a general setting (chapter 7), from which a general conclusion is formulated (chapter 8). The basis of the research formed four field experiments, which were conducted at the experimental sites Ihinger Hof, Oberer Lindenhof and Goldener Acker of the University of Hohenheim, in south-western Germany. Paper I addresses the overall objective of this thesis. Selected cropping systems for this experiment were short rotation willow, miscanthus, switchgrass, energy maize and two different crop rotation systems including winter oilseed rape, winter wheat and winter triticale with either conventional tillage or no-till. The systems were cultivated with three different nitrogen fertilizer applications. An energy balance was calculated to evaluate the biomass and energy yields of the different cropping systems. Results indicate that perennial lignocellulosic crops combine high biomass and net energy yields with low input and potential ecological impacts. Switchgrass, which produced low yields at the study site, may better perform on marginal sites. Switchgrass is an example of the need to grow site-adapted energy crops. The annual energy crop maize required the highest input, but at the same time yielded the most. The two crop rotation systems did not differ in yield and energy input, but the system with no-till may be more environmentally benign as it has the potential to sequester carbon. The objective of Paper II was the optimization of crop cultivation through the differentiation of input parameters to enhance the quality of the energy crop triticale, without influencing the biomass yield. The intention was to minimize the content of combustion-disturbing elements (potassium and chlorine) and the ash residue of both aboveground plant parts (grain and straw). It was done through different straw and potassium fertilizer treatments. It could be shown that the removal of straw from the previously cultivated crop and no additional potassium fertilizer could reduce the amount of combustion-disturbing elements. A high influence must also be expected from site and weather conditions. Papers III to V address the supply of different high quality biomasses, with the focus on maize for anaerobic digestion. The objective of Paper III was the assessment of the requirements of biogas plants and biomass for anaerobic digestion. It introduces potential energy crops, along with their advantages and disadvantages. Alongside maize, many other biomass types, which are preserved as silage and are high in carbohydrates and low in lignocelluloses, can be anaerobically digested. The development of potential site-specific crop rotation systems for biomass production are discussed. The objective of Papers IV and V was the identification of suitable biomass and production systems for the anaerobic digestion. The focus lay on the determination of (i) suitable energy maize varieties for Central Europe, (ii) optimal growth periods of energy crops, (iii) the influence of crop management on quality parameters and (iv) environmentally benign crop rotation systems. Differently maturing maize varieties were grown in six different crop rotation systems (continuous maize with and without an undersown grass, maize as a main crop partially preceded by different winter catch crops and followed by winter wheat) and tested at two sites. Additional factors were sowing and/or harvest dates. Maize and cumulative biomass yields of the crop rotation systems were compared. Specific methane yield measurements were carried out to evaluate the energy performance of the tested crops. Quality was assessed either by measurements of the dry matter content or by using the near infrared reflectance spectroscopy for the determination of chemical composition. Results indicate that an environmentally benign crop rotation system requires nearly year-round soil cover to minimize nitrogen leaching. This can be achieved through the cultivation of undersown or catch crops and additional main crops alongside maize, such as winter wheat. Late maturing maize varieties can be cultivated at a site where the maize can build adequate dry matter contents due to a long growth period (late harvest date). The energy generation in terms of methane production was primarily dependent on high biomass yields. It could be further shown that the specific methane yield of maize increased with increasing starch content, digestibility and decreasing fiber content. To conclude, selected site-specific energy crops and crop rotation systems, with suitable crop management, (fertilizer and soil tillage) can produce high quality biomass and the highest net energy return. Lignocellulosic biomass can be optimized for combustion. Wet biomass is an optimal substrate for anaerobic digestion. Profitable energy production is characterized by a high land and energy use efficiency and especially high net energy yields.
Designing, modeling, and evaluation of improved cropping strategies and multi-level interactions in intercropping systems in the North China Plain
(2010) Knörzer, Heike; Claupein, Wilhelm
Adjusting cropping systems in order to increase their efficiency is a global issue. High yield and sustainability are the catchphrases of production in the 21st century, and agricultural production has to solve the balancing act between ecology and economy. Therefore, the requests for farmers, consultants and researchers are rising, and production modes are changing. Nevertheless, solutions have to be detected spatially explicit and locally adapted and accepted in order to be implemented successfully. Taking the North China Plain as an example, the productivity of arable land needs to be further increased by applying strategies to reduce or avoid negative environmental effects. Further yield increases are not possible by increasing input factors like N-fertilizer or irrigation water as N-fertilizer rates are extremely high and irrigation water is limited. However, yield increases might be possible by developing improved cropping strategies operated by cropping designs. Taking modeling and simulation tools into account back up the acceleration of research attainments and the understanding of cropping systems. The present thesis embraces the designing and modeling of such a potential cropping system, to wit strip intercropping. Thus, the main goals of the study were to analyze, design, evaluate, and in the end model intercropping. Intercropping systems are complex systems which strongly need to be designed and evaluated carefully in order to fulfill the premises of ecological and economical efficiency as well as sustainability. Multi-level interactions have to be weighted and taken into regard for evaluating datasets applicative for modeling and simulating intercropping. The main results of the study indicated, that traditional cropping systems like intercropping are widespread in China, where approximately one third of arable land is under intercropping. Reviewing cereal intercropping systems in China, the four agro-ecological regions ?Northeast and North?, the ?Northwest?, the ?Yellow-Huai River Valley? and the ?Southwest? could be classified, distinguished and described. Intercropping offers a great variation of species combination, benefits as well as challenges for cropping systems design and farmers. Carefully balanced between facilitation and competition, intercropping bears the potential of increased yield and yield stability, income security, resource use efficiency and biodiversity. Intercropping gives evidence about traditional cropping systems with the potential for future production systems under the paradigm of sustainability. Further, results from conducted field experiments indicated that border effects are the key component of intercropping performance. Nevertheless, analyzing strip intercropping statistically has peculiarities as they lack in randomization because the cropping system imposes alternating strips. Thus, spatial variability and its effect on yield were regarded differently within a geo-statistical analysis. In addition to the geo-statistical analysis, the crop growth modeling approach paid tribute to monocropping effects as well as to field border effects occurring in strip intercropping systems. Further on a model-based approach was tested to quantify multi-level interactions with special regard to changing microclimatic conditions and to optimize intercropping systems from an agronomical point of view. In comparison to other interspecific competition modeling approaches, a shading algorithm was evaluated and implemented into the process-oriented crop growth model DSSAT in order to simulate competition for solar radiation. More common in modeling mixed intercropping, a modified Beer?s law subroutine has been used instead, e.g. in APSIM. APSIM and DSSAT were compared by modeling the conducted field trials. As a result, the Beer?s law approach was not capable to model strip intercropping. In contrast, the modeling with a changed DSSAT model showed that applying a simple shading algorithm that estimated the proportion of shading in comparison to the monocropping situation and in dependency from neighboring plant height seems to be a promising approach. The results indicated that competition for solar radiation in those systems is a driving force for crop productivity but neither the most dominant nor the one and only. Resource distribution and allocation in space and time seems to be more important than the total amount of resources. Those effects have to be taken into account when simulating interspecific competition.
Development of a generic, model-based approach to optimize light distribution and productivity in strip-intercropping systems
(2014) Munz, Sebastian; Claupein, Wilhelm
Due to a growing world population, an extension of bioenergy production and the larger proportion of meat and dairy products in the human diet, with the latter particularly in India and China, the demand for agricultural products will further increase. Under decreasing resources and negative environmental impacts related to past intensification, more sustainable agricultural production systems need to be developed in order to meet the future demand for agricultural products. China, as the most populous nation with an enormous economic growth since the end of the 1970’s, plays a major role in global agricultural production. On a national level, agricultural production has to be increased by 35% during the next 20 years. However, land and water resources in China are very limited. With this in mind, the Sino-German International Research Training Group (IRTG) entitled ‘Modeling Material Flows and Production Systems for Sustainable Resource Use in Intensified Crop Production in the North China Plain’ was initiated by the Deutsche Forschungs-Gemeinschaft (DFG) and the Chinese Ministry of Education (MOE). The present doctoral thesis was embedded in the IRTG and focused, in particular, on exploring combinations of different crops produced on the same land at the same time, known as intercropping. In general, the higher productivity in intercropping, compared with monocropping, arises from the complementary use of resources (radiation, water, and nutrients) over space and time by crops that differ in physiology, morphology and phenology. The decisive question is how to optimize intercropping systems over space and time. To address this question, the present doctoral thesis combined field experiments with modeling approaches with the following aims: (i) to investigate the light availability on high temporal and spatial resolutions; (ii) to develop and validate a model that simulates the light availability for the smaller crop and accounts for the major aspects of cropping design; (iii) to determine the effect of the modified light availability on growth of maize and the smaller, shaded crop; (iv) to evaluate the plant growth model CROPGRO for its ability to simulate growth of the smaller, shaded crop; (v) to investigate the interactions between maize cultivar, cropping design and local growth conditions; and, (vi) to identify promising cropping designs and detect future research needs to increase the productivity of strip-intercropping systems. For this purpose, field experiments comprising of strip-intercropping with maize (Zea mays L.) and smaller vegetables, including bush bean (Phaseolus vulgaris L. var. nana), were carried out over three growing seasons from 2010-2012 in southwestern Germany and in the North China Plain. Growing the crops in strips facilitates mechanized management, addressing the ongoing decrease of intercropping in China due to labor scarcity in rural areas. The crop combination of maize, a tall C4-crop with erectophile leaves, and bush bean, a small, N-fixating C3-crop with a more horizontal leaf orientation, was chosen due to the large potential for a complementary resource use. Special emphasis was given on the competition for light as it plays a major role in this cropping system due to the large height differences between the crops. In this context, measurements of the photosynthetically active radiation (PAR) were conducted on high spatial (individual rows across the strip) and temporal resolutions (five-minute intervals) at the top of the bush bean canopy over a two-month co-growing period with maize. The collected data formed the basis of the simulation study towards investigating competition for light and its influence on plant growth with modeling approaches. Experimental results showed that maize yields increased in the border rows of the strip due to a higher lateral incoming radiation in years with a sufficient water supply. On average, maize yields calculated for strips consisting of 18 to four rows increased by 3 to 12% and 5 to 24% at the German and Chinese sites, respectively. Analysis of yield components revealed that yield increases in the border rows of the maize strip were mainly determined by a larger number of kernels per plant. On the other hand, shading by the taller adjacent maize induced considerable shade adaptations of bush bean, such as larger canopy dimensions and a substantially increased leaf area index due to thinner, larger leaves. These shade adaptations increased light interception, and indicated that bush bean could tolerate shading up to 30%, resulting in a total and pod dry matter similar to that of monocropped bush bean. These results suggested that there is a good potential for utilizing bush bean in strip-intercropping systems in combination with taller crops. However, higher shade levels (>40%) resulted in considerable decreases of total and pod dry matter. The high temporal and spatial resolution of the PAR measurements clearly revealed a highly heterogeneous diurnal distribution of PAR across the bush bean strip. The developed light model simulated this heterogeneity with a high accuracy under both clear and cloudy conditions. Comparison of simulated and observed hourly values of PAR across several rows within the strip of bush bean showed a root mean square error (RMSE) ranging between 47 and 87 μmol m-2 s-1 and a percent bias (PBIAS) ranging between -3.4 and 10.0%. Furthermore, the model reasonably captured the influence of different widths of the bush bean strip, strip orientations and maize canopy architecture (height, leaf area index, and leaf angle distributions). Simulations run for different latitudes and sky conditions, including different strips widths, maize canopy heights and leaf area indices (LAI), indicate that: (i) increasing the strip width might only reduce shading in the border rows of the smaller crop at lower latitudes under a high fraction of direct radiation; (ii) at higher latitudes, the selection of a maize cultivar with reduced height and LAI are suitable options to increase the light availability for the smaller crop. The present doctoral thesis presents the first approach to use the monocrop plant growth model CROPGRO to simulate growth of a legume crop grown in an intercropping system. The CROPGRO model was chosen because it provides an hourly simulation of leaf-level photosynthesis, and algorithms that account for the effects of radiation intensity on canopy dimensions and specific leaf area. CROPGRO, calibrated on data of monocropped bush bean, captured, quite well, the effects of the strongly reduced radiation on leaf area, and total and pod dry matter in the most shaded bush bean row. This indicated the models’ applicability on other intercropping systems exhibiting high levels of shading. Under a lower level of shading, cultivar and ecotype parameters had to be calibrated individually for a respective row within the bush bean strip to achieve a high accuracy of the simulations. Model simulations aided in explaining the effects arising from different shares of direct and diffuse radiation on canopy photosynthesis. This is a very important point to be further explored as diffuse radiation remains a part of light distribution and photosynthesis hardly studied in general; and, in particular, becomes more important with the increasing impact of shading. The simulation of the light availability, plant growth and yield formation within the strip of maize can be handled in a similar way as described for the smaller crop, bush bean. Modifications of the light model and a suitable plant growth model are presented and discussed. In conclusion, the main outcomes of this thesis indicate that the selection of cultivars adapted to the modified light environment have the largest potential to increase the productivity of strip-intercropped maize and bush bean. The most important characteristics of suitable maize cultivars include: (i) a high potential of kernel set; (ii) a higher water stress tolerance; and, (iii) reduced canopy height and LAI. The importance given to each of the components would subsequently be determined by the local weather and management conditions and the shade tolerance of the neighboring crop. On the other hand, to optimize yields of the smaller shaded crop, we present two options: (i) to modify the co-growing period of the intercrops temporarily to alleviate light competition during shade-sensitive growth stages; and, (ii) to modify the cropping design spatially and/or select different maize cultivars to reduce shading to the tolerated degree during the respective growth stage of the smaller crop. When the shade tolerance during the respective growth stages is determined, the light model developed can be used to optimize the cropping system temporarily and spatially. In this thesis, a promising approach, which combines a specific light partitioning model with process-oriented monocropping plant growth models, was developed. All models included in the approach can be applied at any location, and their generic nature also facilitates the integration of other crops. These attributes present a highly valuable contribution to intercropping research as their future optimization will depend strongly on the efficiency of the research efforts given: (i) the complexity of the underlying processes that determine the productivity; and, (ii) the minor share of time and money invested in intercropping research. Intercropping research has to prevent reinventing the wheel by identifying aspects in common with and already studied in monocropping systems and focus on aspects particularly inherent to intercropping systems.
Development of management strategies to control soil erosion in field grown vegetables with a focus on white cabbage (Brassica oleracea convar. capitata var. alba L.)
(2014) Übelhör, Annegret; Claupein, Wilhelm
Soil erosion by wind and water is a widely recognized problem throughout the world. Field grown vegetables, such as white cabbage (Brassica oleracea convar. capitata var. alba L.), are particularly endangered by soil erosion because of high disturbance tillage, including deep inversion tillage by the mouldboard plough. Furthermore, wide row spacing and late soil covering by leaves intensify the problem. In light of this, field experiments were conducted from 2011 to 2013 in southwest Germany to investigate, develop and adapt soil erosion control strategies, in particular for field grown vegetables, with white cabbage as a model crop. Focus was placed first, on the use of row covers (fleece and nets), which are usually used as frost protection or for pest control in organic farming, and second, on the development and adoption of strip-tillage for field grown vegetables, which combine the benefits from conventional tillage (high yields) and no-tillage (erosion control). Artificial rainfall simulations demonstrated a high erosion control by row covers. Soil loss under fleece cover was reduced on average by 76% and under net cover by 48% compared to the uncovered control treatment. In 2012, fresh matter head yield was significantly higher under fleece (80 t ha-1) than control treatment (66 t ha1). The opposite was found in 2013, with highest yield under the non-covered control (64 t ha-1) and lowest under fleece cover (53 t ha-1). A higher prevalence of diseases under row covers compared to the control was only found in 2012 with Sclerotinia sclerotiorum on 4% of cabbage heads under fleece cover. Soil loss under strip-tillage during artificial rainfall simulations in 2011 was reduced by an average of 80% compared to conventional tillage (512 g m-2). In 2012, soil losses were reduced by an average of 90% under non-intensive strip-tillage and by 48% under intensive strip-tillage compared to conventional tillage (210 g m-2). The fresh matter head yield in 2011 and 2013 under strip-tillage (58 t ha-1 and 57 t ha-1, respectively) was similar to conventional tillage (59 t ha-1 and 58 t ha-1, respectively). In 2012, cabbage yield was significantly higher under strip-tillage (74 t ha-1) than under conventional tillage (65 t ha-1). The intensive strip-tillage treatments with broadcast and band-placed nitrogen fertilization did not show a yield increase. Yield potential under band-placed fertilized strip-tillage was, at 67 t ha 1 (2012) and 50 t ha-1 (2013), the lowest within the strip-tillage treatments. The CROPGRO cabbage model was evaluated for cabbage production under temperate European climate conditions. After calibration of main parameters of phenology and plant growth, the model showed a high accuracy with indices of agreement mostly above d=0.94. Observed dry matter cabbage head yields of the different years and different locations ranged between 6574 kg ha-1 and 11926 kg ha 1 which were predicted by the model with an accuracy of R2=0.98. Also the sensitivity analysis, conducted under different nitrogen fertilizer amounts and different fertilizer application strategies, generated realistic values from an agronomic point of view. Overall, row covers and strip-tillage seem to be suitable for minimizing the erosion risk in vegetable production. The hypotheses of high erosion control under row covers and strip tillage can be accepted. Due to the modified microclimate under row covers, the infestation with pests and diseases can increase and the influence on cabbage growth can result in either a yield increase or decrease. Based on the study results, there is no evidence that the intensive, double-tilled strip-tillage treatment or the band-placed nitrogen fertilization lead to a yield increase. The non-intensive strip-tillage with only soil preparation in autumn showed the highest yield potential within the strip-tillage treatments, with similar or even higher yields than under conventional tillage. Furthermore, the CROPGRO cabbage model is suitable to simulate growth parameters and yield potential of white cabbage under temperate European climate conditions. For the future, due to the prediction of increased frequency of heavy rainfall events, soil conservation will focus increasingly on intensive crop production and farmers, particularly vegetables growers, will be increasingly dependent on erosion control strategies. For this reason, the approaches presented in this thesis can contribute significantly to produce field grown vegetables in a sustainable way that promotes soil protection.
Einfluss der Bearbeitungsintensität beim Umbruch von Luzerne-Kleegras auf die Stickstoffmineralisation zur Folgefrucht Winterweizen im organischen Landbau
(2003) Wald, Fabian; Claupein, Wilhelm
In the crop rotation of organic farming grass-legume mixtures play an important role due to the legumes´ ability to assimilate N. Ploughing-in of established grass-legume mixtures results in releasing the assimilated N by mineralisation of organic matter. In practice the mineralisation can only be controlled by means of soil cultivation. The aim of the present study is to analyse the relations between different intensities of soil cultivation and N-mineralisation. The data were used to test the simulation model CANDY. The field experiment of each 0.1 ha was set up at three sites in two different locations, which were cultivated from 1999 to 2001: Hohenheim (with trials 610 and 611) and Kleinhohenheim (with trial 660). In the beginning all sites had a three-year old grass-clover-alfalfa mixture, which was ploughed-in for trial 610 and 660 in the late summer of 1999 and in the year 2000 for trial 611. The factor soil tillage was varied in three stages as follows: RT+RT+plough: double rototill cultivation (RT, 10 cm deep) in intervals of approx. 2 weeks, followed by ploughing (plough, 25 cm deep); RT+plough: single rototill cultivation, followed by ploughing (depths as mentioned above); Plough: ploughing without any preceding cultivation (depth 25 cm). After uniform seedbed preparation with a rotary harrow, wheat was sown on all trial sites in autumn, and in trials 610 and 660 it was followed by oat in 2001. Nitrogen content in the soil was determined by repeated sampling at a depths of 0-10, 10-20, 20-30, 30-60 and 60-90 cm. Monitoring boxes were installed in 1 m depth in an undisturbed soil body from September 2000 until April 2001 to record nitrate leaching. Ploughing-in of the grass-clover-alfalfa by means of rototiller cultivation (treatments RT+RT+plough and RT+plough) was followed by a significant increase of mineralisation, which in case of the plough treatment was less pronounced. In this case the date of cultivation, 6 weeks after the rototilling, may have had an influence. Nmin-contents in autumn 1999 were higher after RT+RT+plough than after RT+plough. It has to be taken into consideration that there was a time gap between both treatments of 9 days. But also in the following year (611), when both treatments were cultivated the same date, there was a significant, slight difference of the Nmin values depending on the treatment. Nitrate leaching was only measured in trial 611. Quantities of 86, 84 and 64 kg N/ha were observed in treatments RT+RT+plough, RT+plough and plough, respectively during winter. Due to high Nmin-contents in autumn, for the rototill treatments higher nitrate losses can be assumed compared to the plough treatment for both years of experiment. Depending on the location, nitrogen uptake and yields of wheat turned out to be different. In Kleinhohenheim they were lower in treatments RT+RT+plough and RT+plough than in the plough treatment. It was the other way round in Hohenheim on a higher production level. Due to strong hail impact, this relation between the treatments was not to be proved in trial 611. Oat was the second crop. In this case no effects of intensity of soil cultivation on nitrogen uptake and yield could be observed between treatments and locations. The CANDY model was used for simulating the results of trials 610 and 611. First, the model seemed to be inadequate because it could not model the N-dynamic after soil cultivation. Adding fictitious organic material to the system helped to overcome this problem and then, on average, the N-dynamic model fit was satisfying. An estimate to overcome the general insufficient fit of the model could be mineralisation of parts of the physically protected organic matter (SOS), which is already implemented in the model, right at the moment of cultivation. Data of soil moisture of trial 611 served to calibrate the model successfully. With amended soil parameters the model was then easily applied to the corresponding data of trial 610. In contrast, CANDY did not predict well the nitrate leaching - possibly because the model did not consider preferential flow.
Feasibility of microbial biodiesel and carotenoid production considering the potential of food processing wastewaters as low cost carbon sources using the example of red yeast Rhodotorula glutinis
(2013) Braunwald, Teresa; Claupein, Wilhelm
Due to the increasing demand for sustainable biofuels, microbial oils as feedstock for the transesterification into biodiesel have gained scientific and commercial interest. Also microbial carotenoids have a considerable market potential as natural colorants. Against this background this thesis assessed the feasibility of biodiesel produced by heterotrophic microorganisms, particularly yeasts, using the example of oleaginous red yeast Rhodotorula glutinis. To improve the economic efficiency of this process, several studies have been conducted in order to test (i) whether wastewaters from the agricultural processing industry can be utilized as low-cost carbon and nutrient source for growth and lipid production by R. glutinis and (ii) if they also facilitate the simultaneous production of beta-carotene and other carotenoids as high-value by-products. It has been shown at a small scale, that agricultural processing wastewaters can be used as feedstock for the microbial production of lipids and carotenoids. The general discussion continues to assess the approach of microbial biodiesel production in a broader context in terms of its economic, environmental and energetic performance. The calculated break-even price of microbial oil, excluding the cost of the carbon source for fermentation, is around double the price of conventional plant oils as competing products. To reduce the costs, cultivation in open raceway ponds was proposed, which led to a cost reduction of around 20 %. In order to assess the potential environmental benefits different life cycle assessments from algae biodiesel production, which share common features with the proposed process, have been analyzed. It was concluded, that microbial biodiesel cannot outperform common 1st generation biodiesel in terms of GHG emissions, whereas factors of eutrophication potential and land competition could be significantly improved. The high climate relevant emissions were mainly driven by the high energy requirements connected to the extraction of microbial oil, which also puts a heavy burden on the energetic efficiency of the process. Considering the potential of continued research and technical development along with the political commitment to promote 2nd and 3rd generation biofuels, it was concluded, that in the long term microbial biodiesel could become a commercial reality above laboratory and pilot scale. Due to the different restrictions this will probably not happen within the next 20-30 years. Contrary to biodiesel, carotenoids are high-value products, with beta-carotene yielding around US$ 600 per kg. Sustained by this high price and allowing for certain improvements regarding beta-carotene yields and extraction techniques, it can be possible to economically and sustainable produce beta-carotene from R. glutinis in the near future.
Genotypische Variation der Überdauerungsneigung von transgenem und konventionell gezüchtetem Raps und Möglichkeiten der Beeinflussung durch Bodenbearbeitung als Beitrag zur Sicherheitsforschung bei transgenen Kulturpflanzen
(2004) Gruber, Sabine; Claupein, Wilhelm
High losses during harvesting of oilseed rape in combination with secondary dormancy of the seeds can result in a large soil seed bank which may persist for several years. Volunteers emerging from this seed bank cannot be controlled completely, particularly when they develop in another rapeseed population. In addition to well known agricultural problems, the risk of temporal and spatial gene dispersal by persistent seeds and volunteers gets more significant. With regard to genetically modified (GM) cultivars, seed dormancy and persistence of oilseed rape volunteers have to be reconsidered. The aim of the current study was to investigate the chances for a reduction of seed persistence and gene dispersal by growing specific genotypes and by the implementation of appropriate tillage operations. Four publications describe and discuss experiments in the laboratory and the field on the aspects ?genotype? and ?soil tillage?. One central point was the characterisation of the genotypic variation of secondary dormancy and seed persistence in GM (herbicide tolerant) and conventionally bred oilseed rape. A gradual approach towards field conditions was performed by three experiments. The first experiment examined potential seed persistence by artificial induction of secondary dormancy in the laboratory. The second experiment was a burial of seeds in the soil for six months on a field. The third experiment examined persistence of seeds actually lost during harvest and exposed afterwards to different tillage operations in a field experiment. All three experiments showed a high genotypic variability in seed dormancy and persistence. In the laboratory the level of secondary dormancy of conventional cultivars was a total of 3?76% and of the GM cultivars 1?31%. The number of persistent seeds in the burial experiment was 7?90% in the conventional and 12?79% in the GM assortment. Seeds from the seed rain of the four conventionally bred cultivars in the field experiment persisted in the soil from 0?11% over six months. A significant, positive correlation was found between the laboratory results for cultivars from two crop years as well as between the results from laboratory and burial experiments. This is an indication for a genetic background of seed dormancy and persistence of oilseed rape. It has been demonstrated that a laboratory method for induction of secondary dormancy can describe differences of seed persistence in the field. This result gives a chance for screening new cultivars in the laboratory to identify desired, low persistent genotypes. The other focus of the study was the effect of various tillage treatments on seed persistence and seedling recruitment in the field. Four differently intensive tillage operations incorporated the seeds of two near-isogenic cultivars at different times and soil depths, or left the soil untilled. Winter wheat was sown as following crop in all treatments whereby no weed control was performed. The highest number of seeds generally entered the soil seed bank when seeds were incorporated into the soil by stubble tillage immediately. After six months 1?14% of the initial seed input was found again in the soil in these treatments, and in one isolated case about 28%. Delaying the stubble breaking, the soil seed bank was 0?3%. Leaving the seeds undisturbed on the soil surface until direct drilling resulted in a soil seed bank of 0?17%. Therefore, the first tillage operation after harvest of oilseed rape should be performed with some time delay to avoid large soil seed banks. Soil inversion by a mouldboard plough shifted the majority of seeds into deep soil horizons from where a successful germination was restricted. In contrast, primary tillage by a rigid tine cultivator or zero tillage mainly distributed the seeds within the upper soil layer. Thus the number of flowering volunteers in the first spring was highest in these treatments, with a maximum of one volunteer m-2. Gene dispersal from oilseed rape volunteers to other rape crops and feral relatives was possible because their flowering periods overlapped. The volunteers were able to produce viable seeds, despite high levels of damage by pests and diseases. Overall, a high genotypic variability was found for seed persistence of oilseed rape. Tillage operations, particularly the time of stubble tillage, can also influence seed persistence and the occurrence of volunteers. Combined with a thorough knowledge of the processes involved, the selection of low persistent genotypes and adequate tillage operations offer chances to limit or even to avoid undesired gene dispersal from oilseed rape volunteers, and to make gene dispersal a predictable factor.
Grasping the complexity of intercropping - developing and testing an integrated decision support system for vegetable production in the North China Plain
(2010) Feike, Til; Claupein, Wilhelm
This cumulative dissertation consists of six papers published, accepted or submitted to international high standard journals or books. To detect and describe the status quo of vegetable intercropping in the North China Plain (NCP), a survey was conducted from autumn 2007 to spring 2008. The results of the interviews with researchers, extensionists and farmers embedded in the first article revealed a huge variety of intercropping systems being practiced by farmers in the region. The first article furthermore elaborated farmers? underlying motives and concepts and described the knowledge transfer systems involved. When evaluating the prevailing systems against the background of the rapidly changing socio-economic frame conditions for farming in rural China, it became obvious that a great proportion of the systems practiced nowadays are prone to extinction in a long run. Therefore the second article discussed possible adjustments of the intercropping systems to fit the demands of modern agriculture, while maintaining their potential agronomic and environmental benefits. To enable mechanization, it was suggested to either adjust the machinery to the traditional row intercropping systems, or adjust the cropping system to the prevailing and available machinery. The latter approach was then followed throughout the thesis, using an agronomic modeling approach. The combination of Chinese cabbage and maize was selected, as it is a traditional intercropping system, with strong interspecific effects. In the course of this study, the two crops were strip intercropped in four field experiments at three sites in Germany and in China in 2008 and 2009. To understand, explain and predict plant behavior under the impact of complex cropping structures, crop growth models present a viable and powerful tool. However, two constrains had to be overcome within the framework of this thesis i) Chinese cabbage is not integrated in the common process-oriented crop growth models, ii) a method had to be developed to quantify resource competition and simulate intercropping. Therefore the integration of Chinese cabbage, the number one field vegetable of China, into the CROPGRO model constituted the first step for the simulation of intercropping systems in China. Two greenhouse experiments, testing crop growth and development under different temperature regimes, served as the data base for the accurate parameterization of Chinese cabbage and built the baseline for the third article. Cardinal temperatures of Chinese cabbage were identified by correlating mean relative growth rates and mean leaf appearance rates to temperature. Minimum growth temperature was identified at 0 °C, optimum temperature ranges between 14 °C and 24 °C, and maximum temperature is 34 °C. The further adjustment and testing of the model, which was executed on up to six independent data sets, is presented in the fourth article. The key to successfully simulate intercropping systems is the knowledge on changes in resource availability compared to monocropping. Therefore, a method was developed to quantify the availability of the most crucial growth factor solar radiation at any location within a Chinese cabbage strip, presented in the fifth article. The method was extended in the sixth and final article to enable the estimation of available radiation in Chinese cabbage strips of different widths. The ?environmental modifications? option of CROPGRO was employed to simulate the effects of the estimated reduction in incoming radiation in Chinese cabbage strips of different width. Simulations were conducted over up to thirty years of weather data of 12 locations throughout the NCP, and were additionally tested on different soil texture types. The results were extended over the entire NCP by linking them to a GIS-system. The developed approach constitutes a reliable decision support for the optimization of the spatial arrangements in Chinese cabbage strip intercropping systems, according to local soil and climate conditions. The described approach can be extended to develop a comprehensive decision support system that allows testing of various intercrop combinations under a wide range of climate and especially radiation environments. The presented thesis is a valuable contribution to the development of sustainable vegetable production systems in the NCP. A new method to quantify availability of solar radiation in strip intercropping was developed, which can be applied in various other intercropping systems. The integration of Chinese cabbage into CROPGRO, offers great opportunities not only for studying intercropping systems, but also for improving input levels and resource use efficiency in Chinese cabbage production in China and throughout the world. Understanding farmers? concepts and estimating the production potential of intercropped Chinese cabbage created additional value, which substantially contributes to realizing the potential of intercropping in the NCP.
Implementation and improvement of an unmanned aircraft system for precision farming purposes
(2016) Geipel, Jakob; Claupein, Wilhelm
Precision farming (PF) is an agricultural concept that accounts for within-field variability by gathering spatial and temporal information with modern sensing technology and performs variable and targeted treatments on a smaller scale than field scale. PF research quickly recognized the possible benefits unmanned aerial vehicles (UAVs) can add to the site-specific management of farms. As UAVs are flexible carrier platforms, they can be equipped with a range of different sensing devices and used in a variety of close-range remote sensing scenarios. Most frequently, UAVs are utilized to gather actual in-season canopy information with imaging sensors that are sensitive to reflected electro-magnetic radiation in the visual (VIS) and near-infrared (NIR) spectrum. They are generally used to infer the crops’ biophysical and biochemical parameters to support farm management decisions. A current disadvantage of UAVs is that they are not designed to interact with their attached sensor payload. This leads to the need of intensive data post-processing and prohibits the possibility of real-time scenarios, in which UAVs can directly transfer information to field machinery or robots. In consequence, this thesis focused on the development of a smart unmanned aircraft system (UAS), which in the thesis’ context was regarded as a combination of a UAV carrier platform, an on-board central processing unit for sensor control and data processing, and a remotely connected ground control station. The ground control station was supposed to feature the possibility of flight mission control and the standardized distribution of sensor data with a sensor data infrastructure, serving as a data basis for a farm management information system (FMIS). The UAS was intended to be operated as a flexible monitoring tool for in-season above-ground biomass and nitrogen content estimation as well as crop yield prediction. Therefore, the selection, development, and validation of appropriate imaging sensors and processing routines were key parts to prove the UAS’ usability in PF scenarios. The individual objectives were (i) to implement an advanced UAV for PF research, providing the possibilities of remotely-controlled and automatic flight mission execution, (ii) to improve the developed UAV to a UAS by implementing sensor control, data processing and communication functionalities, (iii) to select and develop appropriate sensor systems for yield prediction and nitrogen fertilization strategies, (iv) to integrate the sensor systems into the UAS and to test the performance in example use cases, and (v) to embed the UAS into a standardized sensor data infrastructure for data storage and usage in PF applications. This work demonstrated the successful development of a custom rotary-wing UAV carrier platform with an embedded central processing unit. A modular software framework was developed with the ability to control any kind of sensor payload in real-time. The sensors can be triggered and their measurements are retrieved, fused together with the carrier’s navigation information, logged and broadcasted to a ground control station. The setup was used as basis for further research, focusing on information generation by sophisticated data processing. For a first application of predicting the grain yield of corn (Zea mays L.), a simple RGB camera was selected to acquire a set of aerial imagery of early- and mid-season corn crops. Orthoimages were processed with different ground resolutions and were computed to simple vegetation indices (VI) for a crop/non-crop classification. In addition to that, crop surface models (CSMs) were generated to estimate the crop heights. Linear regressions were performed with the corn grain yield as dependent variable and crop height and crop coverage as independent variable. The analysis showed the best prediction results of a relative root mean square error (RMSE) of 8.8 % at mid-season growth stages and ground resolutions of 4 cm px −1 . Moreover, the results indicate that with on-going canopy closure and homogeneity accounting for high ground resolutions and crop/non-crop classification becomes less and less important. For the estimation of above-ground biomass and nitrogen content in winter wheat (Triticum aestivum L.) a programmable multispectral camera was developed. It is based on an industrial multi-sensor camera, which was equipped with bandpass filters to measure four narrow wavelength bands in the so-called red-edge region. This region is the transition zone in between the VIS and NIR spectrum and known to be sensitive to leaf chlorophyll content and the structural state of the plant. It is often used to estimate biomass and nitrogen content with the help of the normalized difference vegetation index (NDVI) and the red-edge inflection point (REIP). The camera system was designed to measure ambient light conditions during the flight mission to set appropriate image acquisition times, which guarantee images with high contrast. It is fully programmable and can be further developed to a real-time image processing system. The analysis relies on semi-automatic orthoimage processing. The NDVI orthoimages were analyzed for the correlation with biomass by means of simple linear regression. These models proved to estimate biomass for all measurements with RMSEs of 12.3 % to 17.6 %. The REIP was used to infer nitrogen content and showed good results with RMSEs of 7.6 % to 11.7 %. Both NDVI and REIP were also tested for the in-season grain yield prediction ability (RMSE = 9.0–12.1 %), whereas grain protein content could be modeled with the REIP, except for low-fertilized wheat plots. The last part of the thesis comprised the development of a standardized sensor data infrastructure as a first step to a holistic farm management. The UAS was integrated into a real-time sensor data acquisition network with standardized data base storage capabilities. The infrastructure was based on open source software and the geo-data standards of the Open Geospatial Consortium (OGC). A prototype implementation was tested for four exemplary sensor systems and proved to be able to acquire, log, visualize and store the sensor data in a standardized data base via a sensor observation service on-the-fly. The setup is scalable to scenarios, where a multitude of sensors, data bases, and web services interact with each other to exchange and process data. This thesis demonstrates the successful prototype implementation of a smart UAS and a sensor data infrastructure, which offers real-time data processing functionality. The UAS is equipped with appropriate sensor systems for agricultural crop monitoring and has the potential to be used in real-world scenarios.
Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses
(2005) Link, Eva Johanna; Claupein, Wilhelm
The aim of this study was the "Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses". The background for the investigation could be seen in the increasing number of environmental pollution by agricultural land use. The dissertation was embedded in the context of the Graduiertenkolleg "Strategies to Reduce the Emission of Greenhouse Gases and Environmental Toxic Agents from Agriculture and Land Use" at the University of Hohenheim. The objective of this Graduiertenkolleg was to develop methods for quantifying and modeling the origin and the emission of greenhouse gases and environmentally toxic agents from agriculture and land use and for assessing them economically in the sense of practicable avoidance strategies. In order to determine the optimization potential of adapted nitrogen fertilization strategies in corn the study was organized in the following parts: 1. Investigation of the spatial variability and temporal stability of corn grain yield on three fields in the Upper Rhine Valley. 2. Determination of underlying yield-limiting factors in each field by the use of simple and complex models. 3. Development of adapted nitrogen fertilization strategies in consideration of the yield variability and the underlying yield-limiting factors. The area of investigation was located in the Upper Rhine Valley, which is characterized as a region with intense corn cultivation. At the same time this region belongs to the most important water protection areas in Europe. Thus, a conflict between agricultural land use associated with high fertilizer inputs on one hand and the protection of water bodies on the other hand rose, because measured nitrate concentrations in the groundwater increased constantly within the last decades. The study was conducted on three farm fields in the boundary of Weisweil, which is located northwest of Freiburg, Germany. Since 1998 the three fields were planted continuously with corn. In a 7-year field experiment spatial variability and stability of yield could be indicated. The determined yield pattern in each field raised assumptions about varying growth conditions within and among the fields. Thus, on the one hand the corn yield seemed to be influenced by temporal variations in cultivar, climate and management and by spatial and temporal variation of possible yield-limiting factors like nutrient availability or water supply on the other hand. In order to optimize management strategies the underlying yield-limiting factors causing the spatial and temporal yield variability needed to be determined in these three fields. Whereas plant yield parameters did not explain the existing yield variability very well, soil characteristics were identified as the major factors affecting the observed yield variability in all three fields. Significant relationships were found between combinations of soil nutrient levels, soil characteristics and yield. Based on these results, it appeared that soil characteristics were the primary factor affecting spatial yield variability in the three farmer fields in the Upper Rhine Valley. However, some of the spatial yield variability remained unexplained by simple regression analysis. In a more complex approach crop growth models were implemented to simulate the spatial yield variability within the field and to get information about the underlying yield-limiting factors. Therefore the process-oriented crop growth model APOLLO was implemented to evaluate the causes of spatial yield variability of corn in the three fields. APOLLO (Application of Precision Agriculture for Field Management Optimization) is a precision farming decision support system, which is based on the CERES and CROPGRO family of crop growth models and includes different soil parameter to calibrate the model. In general the APOLLO model performed well in simulating spatial yield variability in the fields. The results indicated that the spatial yield variability was mainly affected by a varying restrictive layers and reduction of root growth within the three fields. The correlation between simulated and measured yields provided information about the strength of the soil parameter affecting the yield within these fields. The calibration results were influenced by the grid size. Whereas smaller grids provided more random monitor yield data, larger grids provided a more representative set of yield monitor data, due to the coverage of a larger area. Consequently, the APOLLO model performed better when yields belonging to larger grids were used for model calibration. The applicability of the APOLLO model can be extended by developing prescriptions for different management strategies and thus enhancing the possibilities of successfully implementing site-specific management strategies. Thus, APOLLO was used to simulate the current uniform nitrogen management strategy of the producers in Weisweil over a 28-year period. Additionally an optimum uniform management and an optimum variable-rate management were developed and simulated. For these strategies also the different weather pattern were taken into account. All three strategies were evaluated based on the simulated yield, the simulated leaching potential and the simulated economics. It was obvious, that variable-rate nitrogen fertilization strategies were most advantageous compared to the other strategies, especially, when the nitrogen application rates were differentiated for dry, normal and wet weather scenarios. Adapted nitrogen fertilization strategies, as optimum uniform management and variable-rate management indicated a potential to reduce the amount of nitrogen, which is left in the soil after harvest, and associated that the potential nitrate leaching was reduced. In a case study the cumulative denitrification under these weather and fertilization scenarios over the growing season was simulated. The results indicated a reduction of cumulative denitrification under adapted fertilization strategies when compared to current uniform management. Summarizing, the results of this study suggest, that the implementation of adapted fertilization strategies (especially the variable-rate management of nitrogen) could lead to a reduction of nitrogen losses, as nitrogen leaching and nitrogen emissions could be minimized. Generally, the optimization potential for adapted nitrogen fertilizer strategies (optimum uniform management and variable-rate management) could be improved for cropping systems that were associated with higher risk for nitrogen losses.
Lentil production in Germany : testing different mixed cropping systems, sowing dates and weed controls
(2012) Wang, Lina; Claupein, Wilhelm
As a kind of legume crop, lentils (Lens culinaris Medik.) with their high nutritional value are grown mainly for human consumption in many regions of the world. The crop has benefits in crop rotation due to its symbiotic N-fixation, which is important especially in organic farming, and it can also increase crop biodiversity in arable land. In Europe, lentils are considered one of the popular leguminous food crops. However, the cultivation and scientific research on lentils were neglected in Germany and Central Europe over the past 50 years. Recently, farmers have begun to realize the value of lentils and have re-introduced the crop into organic and conventional farming in Central Europe. The lentil plant has a weak stalk and is easily lodging. Lodging plants cannot be completely cut and picked up by combine harvesters, and result in yield loss, especially under the wet conditions that often occur in Central Europe. To avoid lodging of crop, lentils were commonly grown in mixed cropping with cereals, such as oat (Avena sativa L.), barley (Hordeum vulgare L.) and rye (Secale cereale L.). However, there is little current information on lentil cultivation under temperate climates in this region. One of the most relevant challenges for growing lentil is how to explore its yield potential adapt to the local conditions. Moreover, lentil plant has a low competition capacity against weeds which are always one of the big agronomic problems especially on organic farm. Therefore, three field experiments presented in this dissertation were carried out to design and improve lentil cropping systems under organic farming in Germany in terms of productivity and competitiveness performance, suitable species and proportion of companion crops, lentil cultivars, sowing dates, weed control, and seed quality. The results should be used to adapt lentil cropping systems to different local climatic conditions in Germany. The specific objectives were (i) to optimize lentil-based mixed cropping systems through different combinations of companion crops (barley, wheat (Triticum aestivum L.), oat, linseed (Linum usitatissimum L.) and buckwheat (Fagopyrum esculentum Moench)) and mixing ratios, which were expected to show different performance on crop productivity, weed infestation, and lentil lodging, (ii) to determine whether different sowing time (early, medium, late) have effects on a standard lentil-barley mixed cropping system in regard to crop yield and weed control, (iii) to test whether woodchip mulch can help suppressing weeds and increasing crop yield in lentil monocropping and mixed cropping, (iv) to determine whether different mixing ratios affect seed protein content in lentil-cereals (barley, wheat) mixed cropping system. To achieve the first objective, a two-year field experiment of mixed cropping of lentils with five spring-sown companion crops: naked-barley, wheat, oats, linseed and buckwheat was conducted at the organic research station Kleinhohenheim in 2009 and 2010. Besides sole lentil and sole companion crops, three mixing ratios (3:1, 1:1, 1:3) were used. Lentil grain yield was 1.47 t ha-1 in monocropping and 0.58-1.07 t ha-1 in mixed cropping, depending on the mixing ratio and companion crop (Chapter 2). The land equivalent ratio (LER) was higher in mixed cropping than in monocropping generally. Lentil-wheat and lentil-barley mixed cropping with a ratio of 3:1 resulted in the highest LER (ca. 1.50) whereas lentil-linseed had the lowest LER in all ratios. Lowest lodging was observed in lentil-wheat and lentil-oat mixed cropping. Additionally, mixed cropping with ratios of 3:1, 1:1 and 1:3 (lentil: companion crop) reduced weed biomass by 29 %, 41 % and 24 %, respectively, compared with lentil monocropping. The results indicated that lentil mixed cropping in the study seemed more promising than monocropping under the given conditions of the location. Except for the linseed, all tested species can be well used as companion crops especially the two cereals (barley and wheat) which can be recommended. The mixing ratio should consider the total yield advantage (LER), the risk of crop lodging, and marketing considerations of both crops. To achieve the second objective of the study, another two-year (2009-2010) field trial was carried out at two sites: the organic research station Kleinhohenheim (KH) and the conventional research station Oberer Lindenhof (OLI) (Chapter 3). The crop was sown at three dates (early, medium and late) in the period from March to May. Four genotypes of lentil: Anicia, Schwarze Linse, Hellerlinse and Berglinse were mixed-cropped with naked-barley at a ratio of 3:1 (lentil:barley) at each sowing date. Results showed that grain yield of crops was significantly higher at the earliest sowing both for lentils (3.0 t ha-1 at KH, 2.4 t ha-1 at OLI) and barley (1.2 t ha-1 at KH, 2.6 t ha-1 at OLI). Lentil seed per plant, barley seed per ear, and thousand kernel weight of crops decreased significantly with delayed sowing. At KH experimental site, weed biomass increased significantly with delayed sowing and was independent of the lentil genotype, whereas sowing date had no significant effect on overall weed biomass production at OLI. The results indicated that early sowing can increase the yield of lentils, and can also be used as an indirect method of weed control in organic farming. To further control weeds to achieve the third objective, a field experiment of applying woodchips mulch on lentils was carried out at the organic research station Kleinhohenheim, in the years 2009 and 2010 (Chapter 4). Two years on average, an amount of 160 m3 ha-1 (fresh matter) woodchips mulch reduced weed biomass and weed density in both cropping systems compared to no mulch treatment, with a reduction by 43 % and 29 % (sole), and by 51 % and 30 % (mixed) respectively. Mixed cropping of lentils with barley (3:1) also decreased weed biomass compared with lentil sole cropping; however, no effect on weed density was observed. Lentil grain yield from sole and mixed cropping was 3.0-3.4 t ha-1 and 2.1-2.2 t ha-1 (2009), and 1.0-1.1 t ha-1 and 0.8-0.9 t ha-1 (2010). Barley grain yield was 1.4 t ha-1 in 2009 and 0.7 t ha-1 in 2010. Despite decreasing weeds, the mulch did not improve crops grain yields in mixed or sole cropping. The combination of woodchip mulch and mixed cropping is useful to reduce weed infestation in cropping systems where chemical or mechanical weed control is not possible and for crops with a low capacity for competition against weeds. Another focus of the study was on seed quality (protein content), especially for the cereals (Chapter 5). The two mixed cropping systems: lentil-wheat and lentil-barley with five seeding ratios (4:0, 3:1, 1:1, 1:3, 0:4) were tested at the organic research station Kleinhohenheim in 2009 and 2010 (originated from the experiment 1). Results showed that cereal grain protein increased significantly when their proportion was reduced in the mixture with lentils. Wheat crude protein increased from 10.3 % (2009) and 11.0 % (2010) in monocropping to 11.5 % (2009) and 15.1 % (2010) in mixed cropping with 75 % lentils. Barley crude protein increased in the same way from 13.7 % in monocropping to 15.8 % in mixed cropping with 75 % lentils. However, lentil protein content did not differ significantly across all mixing ratios. Total crude protein in a mixture was significantly higher than that in cereals or lentils monocropping. Mixed cropping with lentils can thus be an option to obtain a high protein content of wheat which is important for a suitable breadmaking quality, particularly in organic farming. Summarizing, the overall results of the study will open new options for growing lentils in Central Europe from where the crop has vanished over the last decades and may guide the future of lentil production in multi-cropping.
Management of volunteers derived from imidazolinone-tolerant oilseed rape
(2016) Huang, Shoubing; Claupein, Wilhelm
Oilseed rape (OSR) has become the second most important oilseed crop after soybean worldwide, producing 70.95 million tons of seed yield, and providing 13.4% of world supply of oilseeds in 2014. The demand for OSR is expected to increase due to protein meals/cakes used in animal feed and vegetable oils/fats for biodiesel and human consumption. With increasing cultivation area, concern over volunteer OSR is rising, particularly if the variety in question is tolerant to specific herbicides. Currently, the introduction of imidazolinone-tolerant OSR (commercially named Clearfield® OSR; CL OSR) into Europe poses new challenges for chemical control of CL OSR volunteers because of their tolerance to imidazolinone herbicides and other acetolactate synthase (ALS) inhibiting herbicides. Additionally, the potential of gene dispersal in time and space by persistent dormant seeds in the soil and by volunteers is increasing. Volunteers emerge from the soil seed bank, the volume of which is predominantly dependent on seed dormancy. Therefore, the objectives of this study were (i) to investigate seed dormancy and dormancy formation of CL OSR, and (ii) to find out suitable agricultural strategies to reduce volunteers by growing OSR genotypes with low potential for seed dormancy and seed survival, and by implementing appropriate tillage operations. Focusing on these aims, several experiments were carried out with different methods, namely field experiments, germination tests in the laboratory, and genomic analysis, providing data for three scientific articles. Experiment 1. A 3-year field trial in south-west Germany investigated dormancy dynamics during seed development (primary dormancy and potential secondary dormancy; tested with an existing standard method in the laboratory) of 10 non-CL OSR varieties (lines) in 2009 and 2010, and of five CL OSR varieties (hybrids) in 2014. Experiment 2. A total of 15 CL OSR genotypes grown at two locations in south-west Germany in 2012/2013, and eight genotypes (two CL genotypes included) grown at 12 locations across Germany in 2011/2012, were tested for potential secondary seed dormancy with the aim to investigate dormancy traits of CL OSR and maternal environmental effects on dormancy formation. Experiment 3. A 5-year experiment (2011–2015) was conducted in south-west Germany with non-CL OSR and CL OSR (two CL varieties: high dormant and medium dormant) in the same rotation (non-CL winter oilseed rape - winter wheat - CL winter oilseed rape - winter wheat - corn) to investigate OSR volunteer dynamics under different modes of tillage (inversion tillage, non-inversion tillage, no-till, with or without additional stubble tillage prior to primary tillage). Following hypotheses were tested: Experiment 1. (i) There is primary (innate) and secondary (induced) dormancy in oilseed rape; (ii) primary dormancy decreases during seed development, the potential secondary dormancy increases; (iii) at maturity, the level of the remaining primary dormancy and the varietal potential to secondary dormancy correlate. These hypotheses have been approved. Primary dormancy decreased from a high dormancy level (ca. 99%) at about 30 days after flowering (DAF) to a quite low level (< 15%) at late seed development. Embryo growth probably regulates the dynamics of primary dormancy, at least during early seed development. Depending on variety and year, potential secondary dormancy initially increased from nearly 0% to the highest level (up to 90%) at about 70 DAF, and then slightly decreased with further seed development. The correlation between primary dormancy and potential secondary dormancy was high at early seed development, but was quite low at late seed ripening. Experiment 2: (i) There is variation in potential seed dormancy of CL OSR; (ii) F1 (seeded) and F2 (harvested) generations of hybrid CL-OSR show similar dormancy levels although changes through environmental effects are known; (iii) the environment (location) during seed development and maturation has an effect on the potential dormancy. The hypotheses were approved. The CL OSR genotypes differed in potential secondary dormancy from 0.0 to 95.7% in the F1 generation and from 3.5 to 77.9% in their corresponding offspring (F2). Out of the 15 CL genotypes, nine were considered to be low dormant (<30% dormancy level). High correlation (r = 0.96) between F1 and F2 generations indicates a strong inheritance of seed dormancy. Precipitation during seed development is thought to be a contributor to dormancy formation, e.g. the higher the precipitation the higher the dormancy level. These results indicate that selection or breeding for low dormancy CL OSR is feasible. A direct comparison of varieties by dormancy is only possible if they have been grown and harvested at the same location, due to environmental effects. Experiment 3: (i) The soil seed bank size of OSR is determined by post-harvest tillage (particularly tillage time) and seed dormancy traits of the cultivated variety; (ii) the emergence of volunteers from the seed bank also depends on the mode of tillage; (iii) gene segregation in herbicide-tolerance might occur among CL volunteers. These hypotheses were partly approved. There was no significant effect of tillage on the soil seed bank, but the soil seed bank was visibly higher if stubble tillage was done prior to primary tillage (179 vs. 56 seeds m-2; treatments with stubble tillage vs. corresponding treatments without stubble tillage). There were significant effects of tillage in general on volunteers in the next crop. Non-inversion tillage resulted in 30 times more volunteers in the following winter wheat crop than inversion tillage due to shallow seed burial depth. A high dormancy OSR variety resulted in a significantly larger soil seed bank than a medium dormancy variety (147 vs. 58 seeds m−2) but in fewer volunteers (0.9 vs. 1.9 volunteers m−2) in the first following crop winter wheat, probably due to slow release of seeds from dormancy. Hypothetically speaking, seeds from low dormancy varieties seem to be released from dormancy more rapidly than seeds from high dormancy varieties. Gene segregation with 10 zygosities of the imidazolinone-tolerance genes PM1 and PM2 was detected in the CL volunteers in the first following crop winter wheat. Approximately 90% of sampled plants were homozygous for PM1 and PM2, still conferring a high tolerance to imidazolinones. Overall, a high variation in potential secondary dormancy was detected for CL OSR, which is similar to non-CL OSR. The contribution of seed dormancy to the soil seed bank was confirmed. During seed development, maternal environment can influence seed dormancy dynamics to some extent. Tillage operations, particularly tillage time, can also influence the soil seed bank and the emergence of volunteers. A very new aspect is that the disposition of seeds to release from dormancy (instead of induction of dormancy) should be considered in further studies. Sound strategies to control volunteers should include (1) the use of low dormancy varieties with a low potential to establish a seed bank and with a fast release from dormancy, and (2) a combination of different tillage operations in the years following OSR cultivation, e.g. delayed inversion tillage with a deep burial depth in the first year, followed by shallow non-inversion tillage in subsequent years. Combined with a thorough knowledge of seed dormancy, of the development of the soil seed bank and of the release from dormancy, the occurrence of CL volunteers in following crops can be reduced or even avoided by a scope of practical methods and approaches proposed in this study.
Die Ökobilanz zur Abschätzung von Umweltwirkungen in der Pflanzenproduktion - dargestellt anhand von Praxisversuchen zur konservierenden Bodenbearbeitung und von unterschiedlich intensiv wirtschaftenden konventionellen Betrieben
(2003) Arman, Beate; Claupein, Wilhelm
In the agricultural field difficulties in life-cycle assessment result from the fact that the methods of life-cycle assessment were developed in techno-industrial production. Agricultural production, however, differs from industrial production in that it depends more strongly on natural resources and, moreover, has a direct influence on them. Hence, apart from preparing data for the used production goods, the expansion of environmental impact categories to include specific effects from agriculture is focused on in the adaptation of ecobalances as an agricultural method. Among others deficiencies here include the balancing of effects in agriculturally utilized soil. The ecobalances at hand were carried out with two different goals in mind. For one, the impact of conventional and conservational cultivation methods were to be balanced. The goal of this ecobalance was to show whether life-cycle assessment have adequate selective power in order to be used as a decision criterion in the optimisation of cultural methods and their environmental impact. For another, the intensity of cultivation of three agricultural enterprises was compared. It was to be shown here whether life-cycle assessment can provide transparency as to the environmental effects of various production methods, which would enable the consumer to obtain information on the environmental relevance of these methods. A further goal of this work was the development of a method for the recording of effects on the soil in life-cycle assessment. The examined farms are situated in the Hohenlohe region and were integrated in the subproject "Conservation Tillage" of the "Cultural Landscape Hohenlohe" project group. In order to balance soil working methods, the three methods plow, cultivator and mulch sowing were examined. The data was obtained from two test fields with the same crop rotation on one of the farms. Balancing of the intensity of cultivation was carried out on three conventionally working farms using varying levels of fertilizer, crop protectants and tillage. The balanced crop rotation of the three farms did not vary (sugar-beets, winter wheat, winter barley). When developing methods for balancing environmental effects on agriculturally utilized soil three aspects were decisive in the selection of balanced effects: 1. What soil properties are there? 2. Which of these properties are influenced directly by cultivation measures? 3. For which properties are relevant negative effects caused by agriculture known? Based on the indicated methods the impact was assessed for the following soil properties: - Soil depth is influenced by soil loss. Soil loss was calculated with the universal soil loss equation. - Impact on the nutrient content was assessed with the help of a nutrient field balance, humus content with the help of a humus balance. - Variations in soil density caused by loading were assessed with the help of the weighted soil load. - Soil life is affected by pollutant input, modelling of the effect potential was carried out with the help of the Critical-Surface-Time model. All in all the results show that in order to differentiate between the tillage variants with respect to their environmental impact, it is necessary to also consider effects on the soil. Comparison of the farms showed that life-cycle assessment can reflect the environmental relevance of different cultivation intensities and can make them visible for the consumer.
Pflanzenbauliche Untersuchungen zum ökologischen Anbau von Körnerleguminosen an sommertrockenen Standorten Südwestdeutschlands
(2007) Poetsch, Jens; Claupein, Wilhelm
Grain legumes, as nitrogen fixing crop, protein rich animal feed and marketable product are of great importance for organic agriculture. Due to staged abolition of the possibility to add non-organic products in organic animal feeding, the EU?s demand for organically produced protein feed is further increasing. Field bean (Vicia faba) and field pea (Pisum sativum) are large-scale crops but feature a limited feeding value. Lupin species (Lupinus spp.) excel by protein contents of up to 40% in the seed and higher protein value. At warmth favoured locations in southwestern Germany the valuable soybean (Glycine max) can be grown successfully and obtain above-average proceeds in natural food industry. Constraints of yield stability of grain legumes result amongst other things from frequently high weed infestation in organic cropping systems and suboptimal water supply at summer-dry locations. For lupins, moreover, particular soil requirements and the seed-borne fungal disease anthracnosis are problematic. Nitrogen residues after harvest are relevant for subsequent crop as well as groundwater protection. The presented work aimed at defining preconditions and developing cropping strategies to optimise yield stability and level of organically grown grain legumes with a main focus on summer-dry locations, to increase diversity of cultivatable crops and provide information on disposition of nitrogen residues. For this purpose from 2003 to 2005 trials at several locations as well as in greenhouse and laboratory were accomplished. Field trials on organic weed control in soybean as well as white and narrow-leafed lupin (Lupinus albus und L. angustifolius) were conducted at organically managed commercial sites in the upper rhine valley. At the same time agronomic measures for optimisation of competitiveness and machinery implementation were varied. Early high soil coverage and crop height contributed considerably to grain legumes? competitiveness. Delayed sowing at elevated temperatures supported rapid juvenile development and allowed for pre-sowing weed control. At optimum sowing date these effects may be used without yield depression or maturity problems. Reduced row distance was beneficial for optimum space utilisation and early crop closure, but effectiveness of mechanical means was highest at high row distance and large areal proportion for interrow cultivation. As an optimum compromise for grain legumes row distances of 30 - 35 cm are recommended. Optimum impact of mechanical means against weeds was achieved by combining interrow cultivation with harrow or fingerweeder. Forgoing interrow cultivation may be considered in strongly competitive crops like field bean. Lupin species appeared rather poor in competitiveness compared to other crops. Field trials on effects of cultivar and cropping strategy on overwintering and yield performance of autumn-sown field bean, field pea and white lupin were conducted at three locations. Summer drought caused substantial yield advantages of autumn-sown compared to spring-sown cultivars due to superior water supply at earlier flowering. With sufficient water supply a head start was not yield effective. Differing coincidence with pests and diseases could account for advantages (head start on aphid infestation) or disadvantages (fungal infections during winter period) of autumn-sown cultivars. Overwintering was excellent for winter field bean and good for winter field pea. For winter white lupin further trials are required. Temperatures down to -12°C were well endured by all of the three crops. The most important cropping parameter was the sowing date. Winter field bean permitted a relatively wide sowing window. Winter white lupin required strong development before winter and preferably early sowing. Sowing date of winter field pea presented an optimisation problem, because sowing too early leads to overdevelopment and reduced cold-tolerance, while sowing too late may reduce yield potential. Optimum sowing dates for southwestern Germany according to experimental results are in the range of early September (winter white lupin), mid-October (winter field bean) and late October (winter field pea). Water use efficiency may gain significantly in importance in the future. A two-year trial on cultivation prospects and yield performance of the notably drought tolerant chickpea (Cicer arietinum) in the upper rhine valley resulted in successful crop development, but problems with empty pods and inadequate grain quality. Further trials are considered promising. A field trial with white and narrow-leafed lupin confirmed that anthracnosis of lupin spreads less rapidly and yield effectively at summer-dry locations, and narrow-leafed lupin frequently stays unaffected. Laboratory studies for optimising detection methodology of the causative organism Colletotrichum lupini showed advantages of using sectioned petri dishes (quad plates), which confined propagation of disturbing organisms. A trial on seed storage under different temperatures, seed moisture contents and CO2-atmosphere produced no distinct treatment effect, but could confirm the general decrease of seed infection by storage. According to literature hot air (approx. 4 days at 65°C) also reduces seed infection effectively. Thus, storage or hot air treatment of basic seed and propagation at summer-dry locations appear as a viable over-all strategy. Difficult soil requirements of white and narrow-leafed lupin were studied by a pot trial as well as a comprehensive literature analysis. It is concluded that the so-called lime chlorosis is caused by HCO3--induced inactivation of physiologically relevant Fe(II) in the plant. Accumulation of HCO3- is basically caused by insufficient soil aeration and promoted by the presence of lime in the clay fraction. Furthermore, especially in narrow-leafed lupin, disturbances of root development are caused by high Ca-content or high and at the same time strongly buffered pH of soil solution. These conditions are often but not necessarily caused by lime. Analyses of harvest residues and soil were consulted for estimation of nitrogen dynamics. Immobilisation due to degradation of residues with high C:N ratio as well as uptake by catch crops contributed substantially to nitrogen conservation. Risk of leaching is predominantly site dependent. The over-all nitrogen balance of grain legumes when exporting the seed may be low or even negative. In conclusion, results of the presented work indicate that site adapted cropping systems with agronomic measures in the areas of crop rotation, choice of cultivar, sowing date or space allocation can still contribute considerably to yield stability in organic cultivation of grain legumes.
Reducing irrigation water supply to accomplish the goal of designing sustainable cropping systems in the North China plain
(2007) Binder, Jochen; Claupein, Wilhelm
An International Research Training Group (IRTG) of the University of Hohenheim and the China Agricultural University, entitled ?Modeling Material Flows and Production Systems for Sustainable Resource Use in the North China Plain? was launched in 2004. The major hypothesis was ?that adjustments in cropping systems and management practices provided potential for sustainable resource protection on a high yield level?. The research program was conducted in one of the most important economic and agricultural regions in China, the North China Plain (NCP). The NCP is one of the major maize (Zea mays L.) and wheat (Triticum aestivum L.) growing areas. A literature review indicated that over the last two decades yields for wheat and maize increased by more than 20%, which had mainly been achieved by augmenting the amount of irrigation water and fertilizer. Besides the positive effects on yield an increasing amount of these input factors leads to many environmental problems. Field experiments were carried out to compare different cropping systems. Currently, the double cropping of winter wheat and summer maize is the common cultivation system in the NCP. It consists of growing two crops mostly winter wheat and summer maize in one year. The winter wheat production depends on a supplemental irrigation, because rainfall is concentrated in the summer months during the maize growing season. An alternative to the intensive double cropping system could be the single cultivation of spring maize. Relative less irrigation water is required for spring maize production, because the rainy season coincides with the main part of the maize growing season. Due to the longer growing season spring maize normally realises higher yields in comparison to summer maize. However, the total yield of a double copping system of wheat and maize is higher. The evaluated system three harvests in two years (winter wheat and summer maize in the first year followed by spring maize in the second year) forms a balance between the double cropping system and the single cropping of spring maize. Due to the fact that three crops are grown in two years total yield is higher in comparison to single cropping of spring maize (two harvests in two years) but lower in comparison to the traditional double cropping system (four harvests in two years). However the lower cropping index in contrast to the double cropping of wheat and maize results in a lower demand of the input factors irrigation water and N-fertilizer whereas in comparison to the single cropping of spring maize a higher amount of input factor is required. Besides the conduction of field experiments for the collection of empirical datasets, the CERES-Maize and CERES-Wheat models were used to quantify the effects of different irrigation management practices on crop growth, productivity and sustainability of agricultural production. Results indicated that there is a considerable potential for reducing the irrigation amount for winter wheat. However, the results also showed that a supplemental irrigation at critical growth stages seems to be essential to maintain high yields and to ensure an adequate gross margin. In a more complex approach the CERES-Maize model was used to simulate the yield of summer maize and spring maize across the NCP. The spatial and temporal climate variability was taken into account by using up to 30 years of weather data from 14 meteorological stations. The simulated results were linked to a Geographic Information System (GIS). Results indicated that the yield distinction between summer maize and spring maize was partially very low as a result of water shortage at flowering stage. A delay in sowing and the use of adapted cultivars with a later flowering date could help to increase spring maize yields. Summarizing, the results of this study indicate that water is one of the most limiting factors for crop production in the NCP. Further, the reduction of total water consumption will become more and more important with water becoming increasingly scarce and thus costly. Consequently agriculture has to undergo and is already undergoing dramatic changes. The results of this study indicated that there are several possibilities optimize cropping systems in the NCP, focussing on a more sustainable use of water while maintaining high yields. In this context, crop models are valuable tools for e.g. irrigation planning or evaluating different cropping designs in the NCP.
Studies on water-soluble carbohydrates in wheat (Triticum aestivum L.): regulating traits, model analysis, early chilling effects, and future perspectives
(2009) Valluru, Ravi; Claupein, Wilhelm
Wheat is one of the major staple food crops of the world. Although a wealth of research has been made a significant progress in wheat productivity through genetic interventions in the last two decades, there remains an untapped potential for further yield gain. Water-soluble carbohydrates (WSCs) are excess carbohydrates stored in vegetative organs such as stem, sheaths, and tiller base during vegetative period. They are highly heritable agronomic trait that regulates plant growth and development as well as grain yields. In addition, WSCs also contribute to plant adaptation to abiotic stresses. Improving current understanding of the multi-faceted roles of WSCs is therefore essential for future crop improvement. The present thesis provides information on WSCs, its associated traits and future perspectives that derived from several experiments conducted under field and glasshouse conditions. Typically, the thesis has four objectives dealing with a specific set of questions. The first objective explains the traits regulating WSCs under three N levels (0, 100 and 200 kg ha-1). N concentration in the plant is negatively correlated with WSCs storage. The traits associated with total WSCs storage are also influenced by N levels. Three vegetative traits, viz., total biomass, flag-leaf width, root: shoot ratio and two physiological traits, viz., radiation use efficiency, and leaf N concentration were considered. Under high N level, lower biomass, flag-leaf width and root: shoot ratio is beneficial to increase total WSC storage. In contrast, increasing biomass and flag-leaf width is advantageous under lower N level. However, a specific set of traits, rather than a single trait, appeared to evolve under N-specific selection maximizing total WSC storage. The second objective describes the simulation model for WSC accumulation under three N levels. A simple phenological model for carbon accumulation, in the form of WSCs, during vegetative period in four wheat genotypes was developed. This model was integrated and evaluated under crop management factors such as low (0 kg ha-1), medium (100 kg ha-1), and high (200 kg ha-1) nitrogen supply. The proposed model predicted higher rate of WSC accumulation in the early stages of crop growth and lower rates in the later stages. Overall, the model predicted the rate of WSC accumulation with a RMSE of 6.58, suggesting that the proposed model simulated well. Nevertheless, the predicted rate of WSC accumulation was close to the observed data only in low and high N level. The model predicted total WSCs well with the observed data; however, it overestimated total WSCs at early stages and underestimated total WSCs at later stages, largely due to the respective rate of WSC accumulation. Overall, evaluation of the model with the predicted dataset indicated that the prediction errors for the rate of WSC accumulation were more with RMSE between 20-30% in all N levels. For total WSC accumulation, the prediction errors were less, and the RMSE, in most cases, was less than 20% in all N levels. The third objective reveals the plasticity of the phenotypic expression of two primitive wheat species (Triticum monococcum L. and T. dicoccum S.) in response to early chilling stress (4 oC). Early chilling stress resulted in lower total WSCs, in addition to lower flag leaf size, total biomass, specific leaf area and early flowering. While lower specific leaf area may reduce the early chilling stress effects at an individual leaf level, a higher leaf mass ratio and utilization of reserve carbohydrates indicated that the compensatory growth of chilled plants during the recovery period relied on the concerted action of altered resource allocations and reserve carbohydrate consumption. However, the lack of direct selection on sucrose indicates that sucrose has indirect effects on total WSCs. Thus, the total effects of reserve sucrose on relative fitness seem to be buffered via rapid growth rate in chilled plants. Nevertheless, a significant cost of plasticity was evident only for fructans. Further, a regression of daily cumulative plant biomass derived from a crop growth simulation model (CERES-Wheat) on crop growing period revealed a divergent developmental pathway for early chilled plants. These results showed that not only are the characteristic architectures in two Triticum species plastic, but the regulating mechanism of intrinsic developmental (ontogenetic) pathway is also sensitive to early chilling stress. Fourth objective provides future perspectives for WSCs, in particular fructans. Fructans can be involved in freezing tolerance by protecting cellular membranes. This opinion postulates that fructans can be transported from vacuole (site of synthesis) to apoplast (site of action) through vesicles derived from the vacuole. These results can improve the current understanding of WSCs in plant growth and development as well as grain yields. Traits can be used as WSCs markers to prescreen a large number of wheat germplasm for high total WSCs contents. However, a further understanding of different dimensions of WSCs in grain yield improvement and plant growth and development deserves more attention.
Sustainable bioenergy cropping concepts : optimizing biomass provision for different conversion routes
(2014) Mast, Benjamin; Claupein, Wilhelm
Today energy from biomass already contributes to a considerable share to the global energy consumption. In particular, certain modern bioenergy streams like biogas, biofuels for transportation etc., are of increasing relevance. However, several of the beneficial aspects, which were initially attributed to the utilization of today’s bioenergy, had to be relativized and the controversies regarding environmental and socio-economic drawbacks have, in the meanwhile, been on the rise. Alongside a shift to advanced conversion technologies, the improvement of bioenergy cropping systems towards a sustainable biomass provision is a key element of future bioenergy production. Against this background, the present thesis assessed various aspects in terms of biomass production, biomass provision and biomass conversion mainly addressing the two bioenergy streams – 2nd generation biofuels and biogas. For biogas, the thesis addresses aspects regarding the development of alternative cropping systems, the evaluation of novel crops for biogas purpose, and the assessment of regional biogas potentials using a crop growth model. The second focus of the thesis was set on biofuels while special attention was given to the production of microbial biodiesel, and the characterization and evaluation of potential feedstocks for this purpose.
Untersuchung alternativer Unkrautmanagementsysteme für Kulturraps unter Einbeziehung von Möglichkeiten zur Reduzierung des Auftretens von Raps als Durchwuchs
(2022) Schwabe, Sebastian; Claupein, Wilhelm
Oilseed rape is the worlds second most important oil crop after soybeans. In the course of the European Green Deal of the European Union and the associated stronger promotion of renewable energies in the future, it can be assumed that the importance of oilseed rape cultivation will continue to increase. Due to the price pressure on conventional farms in Germany, cultivation systems have been changed from an economic point of view, partly to the detriment of sustainability. As a re-sult, crop rotations often consist of a few monetarily profitable crops and the proportion of spring crops in the crop rotation is reduced. Oilseed rape cultivation is attractive from an economic point of view, and its share in the crop rotation has been increased. The intensity of tillage and mechanical weed control has been reduced. The weed control success is strongly dependent on the effectiveness of numerically limited herbicidal active agents. Due to monotonous crop rotations and the lower tillage intensity, certain weed species are pro-moted more strongly, while at the same time these are controlled with only a few herbicid-al active agents. Adapted, difficult-to-control, and in some cases herbicide-resistant weed populations develop. For this reason, the purpose of this thesis is to evaluate alternative weed management systems in oilseed rape, while also investigating options for prophylac-tic prevention of the emergence of volunteer oilseed rape as a weed in crop rotation. The objectives of this thesis were: (i) To evaluate the feasibility of hoeing as a mechanical weed control method and the application of the Clearfield® system in oilseed rape as a comparison to common, field herbicide strategies. (ii) To focus on the volunteer oilseed rape issue. Volunteers resulting from Clearfield® oilseed rape are more difficult to control chemically in subsequent crops due to inherited herbicide tolerance. The potential of differ-ent seed treatments in oilseed rape to reduce the development of secondary dormancy, and therefore seed persistence in the soil and the volunteer oilseed rape issue, was investigat-ed. Following these objectives, several field and laboratory experiments were conducted to generate data for three published scientific papers. Paper I: A two-year field trial was conducted to evaluate the performance of the Clearfield® system in oilseed rape under different management intensities compared to a more com-monly used pre-emergence herbicide system. The Clearfield® system is an alternative weed management system for oilseed rape. It is a combination of a broad-spectrum post-emergence herbicide and a Clearfield® oilseed rape variety that has tolerance to the herbi-cide. This tolerance was implemented in Clearfield® oilseed rape varieties through conven-tional, non-GM breeding techniques. Clearfield® herbicides have lethal effects on non-Clearfield® oilseed rape varieties. Paper II: An investigation was made through laboratory and field trials on the effect of ger-mination-promoting substances (nutrients and gibberellic acid) on the development of sec-ondary dormancy of oilseed rape seeds and on their persistence in the soil. Paper III: In a three-year field trial, hoeing as a weed control method was compared with a commonly used herbicide strategy. The hypotheses made in the introduction were both confirmed and refuted by the findings obtained in the trials. Hypotheses stated in paper I: (i) The Clearfield® herbicide and herbicides of a common practice pre-emergence strategy show similar efficiencies; (ii) Management intensity has an effect on weed density but does not affect yield; (iii) Herbicide strategy does not affect yield. At higher management intensities, both herbicide systems achieved comparable efficien-cies. At lower management intensities, especially in terms of seeding density and tillage, weeds were less efficiently controlled with the Clearfield®-system, and yields were par-tially lower. At higher management intensities, higher yields and lower weed emergence were observed compared to lower intensities, presumably due to better weed control by plowing and more favorable emergence conditions due to a higher tillage intensity. Hypotheses stated in paper II: (i) All tested substances reduce the induction of secondary dormancy; (ii) the tested sub-stances reduce the induction of secondary dormancy to different extents; (iii) the tested substances have an effect on the induction of secondary dormancy, regardless of whether the tested oilseed rape seeds originate from varieties with a high or low tendency, to devel-op secondary dormancy; (iv) if a variety tends to develop high secondary dormancy, its in-duction is reduced to a greater extent by the tested substances than in seeds from a variety with a low tendency to develop secondary dormancy. Most of the tested substances reduced both the induction of secondary dormancy and the survivability of oilseed rape seeds. The efficiency of the reduction depended on the type of substance and the oilseed rape variety. Substances containing gibberellic acid proved most effective, followed by micronutrient treatments and potassium nitrate. Hypotheses stated in paper III: (i) Hoeing achieves the same weed control efficiency as herbicides; (ii) regardless of whether herbicides or hoeing are used as weed control, the same oilseed rape yield can be realized. Weed biomass was higher compared to herbicide application when hoeing was used as a weed control measure. This is probably due to the weather-dependent efficiency of hoe-ing and its only partial surface applicability. Weeds emerging in or close to the seed row cannot be controlled. Nevertheless, no yield differences were found between hoeing as a weed control measure and pure chemical weed control. The competitive strength of the varieties used was most likely large enough to ensure this yield stability. Both hoeing and applying the Clearfield® system under higher management intensities re-sulted in similarly high oilseed rape yields compared to conventional herbicide strategies, although weed control efficiency was lower. As long as no hard-to-control weeds occur on a conventional farm and a common herbicide strategy effectively controls existing weeds, changing the weed management system is less beneficial. Because the Clearfield® system increases selection pressure on weeds, the occurrence of weed herbicide resistance be-comes more likely. In addition, Clearfield® volunteer canola is more difficult to control chemically in subsequent crops. Hoeing efficiency is weather dependent, weeds are only captured between rows, and area performance is lower. However, when difficult-to-control weeds increasingly minimize the efficiency of existing, conventional chemical control strategies, both hoeing and the use of the Clearfield® system in combination with a common herbicide strategy can expand weed control options and in-crease their efficiencies. When applying the Clearfield® system, strategies should be em-ployed to minimize the occurrence of Clearfield® volunteer oilseed rape in subsequent crops. It has been shown in this thesis that germination-promoting compounds, particularly gib-berellic acid, prevent the induction of secondary dormancy, as well as the ability of oilseed rape seeds to persist, and therefore, have the theoretical potential to contribute to a reduc-tion in the volunteer oilseed rape occurrence problem. Overall, both hoeing and the application of the Clearfield® system as alternative weed man-agement systems can usefully complement established methods of weed control in oilseed rape, where necessary. In addition, the use of germination-promoting compounds in oilseed rape seeds has demonstrated the theoretical potential to contribute to a reduction of volun-teer oilseed rape as a weed in crop rotations.

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