Browsing by Subject "Mineralisation"

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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.
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    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.
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    Rahmenbedingungen für eine vereinfachte „gabenreduzierte“ N-Düngung zu Winterweizen (Triticum aestivum L.)
    (2018) Makary, Thomas; Müller, Torsten
    The split N-fertilization with CAN in three or four doses was considered a measure to improve the nitrogen supply of winter wheat in the past and still is considered a guarantor for good yield and quality. The split N-fertilization with CAN is also recommended to synchronize and harmonize N-demand of the plants as well as soil N-content. The aim of the current study was to analyze simplified (reduced number of N-servings) CAN strategies to winter wheat and the necessity of split nitrogen servings in order to achieve yield and quality aims. This interest was occasioned by impressive results of experiments on farmers’ fields using simplified N- strategies with CAN. Simplified CAN fertilization strategies are able to produce high grain yield and protein contents with winter wheat when the N-supply is ensured. Therefore, the common split N-servings with CAN are not necessary. Simplified strategies with UAN seem to be possible, but this requires further research on application techniques to reduce NH3 losses. Simplified CAN fertilization strategies were tested based on modern wheat varieties and the high plasticity in the development of the yield compounds. Modern wheat varieties show low harvest-indices which is important to reduce the risk of lodging. Furthermore, these varieties are able to overcome omitted N-servings through remobilization of N in the plants. Suboptimal conditions during the development within one important growing stage can be compensated during later growing stages when the growing conditions are better. These properties in combination with a late first application (BBCH 29/31) of N turned out to be the “gold standard” in our experiments. Reduction processes during the tillering (BBCH 25/27) period when N is applied confirm these findings. In addition, the application date for the heading stages (BBCH 49/51) when temperatures are high and conditions very dry have to be considered. Simplified N-fertilization systems can also be applied on Luvisols if the soils are not long-term fertilized by liquid manure. The positive soil characteristics of these soils and the high soil-borne fertility support the approach with simplified CAN strategies. In this situation, N-leaching into deeper soil layers is not likely as high precipitation rates in a short time would be necessary to cause this. In fact, a long term liquid manure application with high rates is not necessary when simplified CAN treatments are applied. Moreover, high N amounts in soils caused by long term liquid manure applications are a risk for N-losses and environmental pollution. Notwithstanding the above, organic fertilizers like liquid manure show positive effects on the soil chemistry and the physical properties of the soil. It is important to apply a system to better include the N fertilization effect of liquid manure during the vegetation period. Additionally, simplified CAN fertilization reduces the work effort on the farms. Currently, especially for livestock farms, which rely on N-fertilization, simplified CAN treatments are a good alternative to the common practice. Whereupon on shallow or sandy soils the approach with simplified CAN treatments should be restricted since these soils mostly show low water holding capacities and high percolate water rates. Under suboptimal growing conditions with high precipitation rates simplified CAN treatments can be a risk for the environment and the groundwater. Apart from that, the volatile weather conditions are the most important factor for yield and quality outcome. Mild conditions during the early winter lead to prolonged growing of the plants. In spring the number of tillers per m-2 is already determinated. Therefore, a combination of N doses at the beginning of the growing season in order to promote the number of tillers doesn´t yield the aimed results. The properties of modern wheat cultivars, tested soils, weather conditions and constraints of simplified CAN treatments show the complexity of N fertilization of winter wheat. Standard measures like the common split CAN fertilization are neither wrong nor ideal to create high yield and protein contents with a minimum of input. The most important items for a successful wheat production are high knowledge and attention levels for the plants and growing conditions. Combining the fertilizer requirement calculation and the knowledge on the field yield potential, the yield and quality of winter wheat can be optimized with a minimum of input.