Browsing by Subject "Fertilizer"

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Biogas production vs. dung combustion as household energy in rural Ethiopia
(2011) Müller, Joachim; Barfuss, Isabel; Gwavuya, Stanley; Abele, Steffen
The objective of the study was to investigate the potential of dung as primary and secondary energy source, i.e. direct combustion of dung and combustion of its secondary products biogas or dried digestate, under consideration of its quality as fertilizer. The results of the analysis show the similarity of dung and digestate regarding combustion characteristics. Fertilizer values proved better for digestate. However, calorific value of dung proved much lower than those of biogas. Thus, biogas represents a good alternative energy source with double benefit. Besides its better combustion characteristics compared to dried dung, it also delivers a superior fertilizer.
Emission von Ammoniak (NH₃) und Lachgas (N₂O) von landwirtschaftlich genutzten Böden in Abhängigkeit von produktionstechnischen Maßnahmen
(2003) Leick, Barbara Cornelia Elisabeth; Engels, Christof
The goal of this research was to quantify event-based NH₃ and N₂O emissions in various farming systems and to propose emission-avoidance strategies. Emission measurements were made on pasture land (Allgaeu, Hohenheim) and on cultivated fields (Hohenheim, Biberach). These measurements were made after applying organic and mineral fertilizers, after incorporating crop residues, and after freeze / thaw cycles; furthermore, experiments were conducted using container plants of different species (leguminous, and non-leguminous) and different fertilizers. NH3 emissions data was gathered under field conditions using the wind tunnel method and the IHF method (Integrated Horizontal Flux). In the container experiments, data was gathered by taking photo-acoustic measurements. N₂O emissions data was compiled using closed chambers (Hohenheim measuring chambers) and using an open-chamber system in which an exchange occurred between the air in the chambers and the ambient air. N₂O levels were determined using a gas chromatograph or by photo-acoustic measurements. The NH₃ emissions after applying liquid manure to pasture land varied between 11 and 40% of the total nitrogen applied. Emission levels of less than 20% occurred when it rained shortly after spreading liquid manure causing it to be washed into the soil. The application technique (splash plate, surface banding and liquid manure injection) had no apparent influence on NH₃ emissions under these conditions. The N₂O emissions after liquid manure fertilization on pasture land in Hohenheim were 0.16% of the total NH4+-N. In comparison, the emissions in the Allgäu were between 1.7 and 2.3% of the total NH4+-N applied. Liquid manure injection led to higher emissions as did application using a splash plate. In the Allgäu, the N₂O emissions after mineral-nitrogen fertilization were markedly lower (0.3 to 0.8% of applied N) than after liquid manure application. In Hohenheim, the nitrogen form had no distinct influence on the emissions (<0.16% of applied N). Definitive differences between the two locations were observed during the experiments. These differences were based on N₂O losses due to the respective soil and weather conditions (precipitation, temperature). The higher emissions after applying liquid manure compared to those after applying mineral nitrogen fertilizer are explainable in that aside from the nitrogen compounds found in liquid manure, carbon compounds which promote the microbial formation of N₂O were also entering the soil. The NH3 emissions after liquid manure fertilization on cultivated fields using a splash plate varied between 25 and 35% of the applied NH4+-N. By using a slurry cultivator which combines application with immediate incorporation, the NH3 emissions can be clearly reduced to 6% of the applied NH4+-N. Application with a drag hose, in comparison to using a splash plate, did not always result in an emission reduction; however, in taller plants, a readable emission reduction was measured. The N₂O emissions after liquid manure application on cultivated fields varied between 0.1 and 2.2% of the applied NH4+-N whereby the emissions after guided application with the drag hose were always higher than after using a splash plate. Mineral fertilizer had lower N2O emissions (<0.13% of applied N), especially when ammonium fertilizer was brought out in combination with a nitrification inhibitor. The incorporation of green manure crops notedly increased N₂O emissions. N₂O emission after the incorporation of legumes was especially high. In the container experiments, a diurnal rhythm of the N₂O and NH₃ flows in growing rape and vetch was observed. This indicated a stomatal flow of these gaseous nitrogen forms. N₂O emissions also occurred outside of the vegetation period at temperatures between 0 and 5°C, with the N₂O emissions from the nitrogen fertilized parcels being greater than the emissions from the unfertilized parcels. In container experiments, the N₂O emissions after freeze / thaw cycles were greater from white clover than from perennial rye grass. In fallow soil columns, the N₂O emissions after freeze / thaw cycles were especially high if the content of nitrate and water-soluble organic carbon in the soil was large. The results of this research show that the emission of nitrogen-containing compounds after organic and inorganic fertilization can be reduced through application methods (immediate incorporation), appropriate fertilization technology (addition of nitrification inhibitors), but also through fertilizer application under favourable weather conditions to include seasonal and volume adjustment of the fertilizer based on the growth requirements of the plants. Because high N₂O emissions can also occur at low temperatures, cultivation practices that influence the availability of mineral nitrogen and easily degradable organic substances in the soil during cold weather have a large impact on the N₂O emissions from agricultural land.
Heavy metals from phosphate fertilizers in maize-based food-feed energy systems
(2023) Niño Savala, Andrea Giovanna; Fangmeier, Andreas
The problem of polluted agricultural lands with heavy metals due to anthropogenic activities, including applying phosphorous (P) fertilizers polluted with cadmium (Cd) and other metal such as uranium, has been extensively studied. Several reviews, including the one in the present dissertation, have elaborated this issue with often the same results: the application of P fertilizers with high Cd levels is strongly correlated to Cd accumulation in arable soil, which could imply environmental risks as well as health risks for humans and animals through the food chain. Therefore, these reviews have often the same conclusion: the application of low Cd-P fertilizers, either mineral, organic or recycled, is diminishing the risks of Cd pollution at the soil, crop and consumption level. However, globalization, trade politics, economy, dependency on Morocco mineral P fertilizers, and the finite stock in the raw material have challenged this possibility, especially in the European Union. Meanwhile, in China, polluted arable soils are related to other anthropogenic activities and type of fertilizers rather than Cd-polluted phosphate rock and mineral P fertilizers. At the farm level, other options to diminish Cd pollution in soil and crops, besides low Cd-P fertilizers, could consist of different fertilizer and crop management. These options were studied in this dissertation. A different P management, including different rate applications and placements, did not influence the total Cd concentration in silage maize grown in Germany, regardless of the developmental stage of the crop and the Cd levels in P fertilizer. Silage maize might take up Cd derived from P fertilizers under unpolluted soils, without high risks due to its high biomass production. However, significant changes in the labile Cd fraction were already visible after applying Cd-polluted P fertilizers at 150% of the required amount to the soil after only two growing seasons. Further research should be done to understand the correlations between the bioavailable metal fraction and the actual Cd uptake by silage maize, especially in unpolluted soils. This recommendation also follows the meta- analysis results presented in the second publication, which indicated a possible bias as most of the studies are performed under polluted conditions. Considering the results of the third and fourth publication, the Cd uptake by silage maize was strongly correlated to labile Zn in the soil and the Zn uptake at the early development stage after two field seasons. Placed P fertilizer had a significant and negative effect on the Zn uptake by young silage maize. Further research is needed to understand the behavior of Cd and Zn in the uptake process by maize under P fertilization in unpolluted soils. According to three of the four publications presented in this dissertation, the soil pH was the main soil characteristic influencing the bioavailability and the plant uptake of Cd under unpolluted conditions, regardless of the P treatment, the development stage, and the maizes intended use. However, the total Cd concentration in the soil was the dominant variable for the Cd concentration in maize grain when the soil was polluted with high Cd levels, which was the case in several experiments analyzed in the second publication. P fertilizers with average Cd contamination might enhance labile Cd accumulation in arable land and crops when applied to low biomass crops, such as wheat and legume crops. In this regard, crop management such as crop rotation in the central field experiment indicated that the wheat rotation induced a lower Cd accumulation in maize-soil systems, owing to wheat likely accumulating Cd at higher levels than other crops. The results presented in the second publication also indicated high Cd accumulation by the wheat crop: the wheat grain accumulated more Cd than the maize grain. Thus, potential hazards related to Cd accumulation in wheat grain should also be considered in wheat-maize systems. In conclusion, suitable crop rotations considering the crop-specific potential of Cd accumulation, efficient P management including soil P levels and nutrient use efficiency, and low Cd-P fertilizers remain the most viable options and the main challenge to avoid Cd accumulation in arable soils.
Impacts of fertilizer subsidy on farm-level productivity and food security : a case study of rice-producing households in Northtern Ghana
(2015) Wiredu, Alexander Nimo; Zeller, Manfred
Subsidies are policy tools that support specific sectors of an economy with the intention of revamping performance or protecting a sector. They are often criticized as ineffective policy tools since they can lead to dependency or even crowd out the private sector. Depending on the implementation strategy and the situation, policies can be beneficial, destructive, or have no apparent impact. Despite the debate about their appropriateness as policy tools, input subsidies have been re-introduced in sub-Saharan Africa with the initial intention of mitigating the effect of global food price hikes, which peaked in 2008. The new generation of subsidy programs are expected to improve access and use of fertilizers, increase agricultural production and productivity, and ultimately improve the well-being of arable crop farmers. So far, evidence only available for countries in eastern Africa, suggests that the programs have largely succeeded in increasing productivity, production, incomes, and food security. Between 2008 and 2013, the Government of Ghana spent over United States Dollar (USD) 215 million on 724,005 metric tons (MT) of subsidized fertilizers. Justification of these expenditures is therefore necessary. This research is motivated by the quest to provide evidence on the impacts the new subsidy programs in Western Africa. The research identifies and assesses the impacts of the Fertilizer Subsidy Program of Ghana on farm-level performance and food security of rice-producing households in the northern part of the country. Rice-producing households are the focus since rice is a commodity of strategic economic importance in Ghana, as well as in Africa as a whole. This is because domestic demand for rice in Ghana is far higher than domestic supply, causing a gap which is filled by imports. The cost of importing rice is paid for with scarce foreign currency. This situation may threaten national food security. The fertilizer subsidy is an imperative component of the national rice development strategy as it seeks to improve access to fertilizers with the aim to enhance productivity and production. Northern Ghana contributes about 30% of the nation’s rice production and has the potential to increase this share. Meanwhile, agriculture in northern Ghana is rain-fed and farmers struggle with declining soil fertility, which negatively impacts productivity and food security. Increasing fertilizer use through the subsidy could greatly improve the livelihoods of rice-producing households in northern Ghana. This research begins with an exploratory study on determinants of fertilizer adoption among 330 smallholder farmers. This exploratory study is, however, less robust since the sampled households were likely to be beneficiaries of a soil health project from the Alliance for a Green Revolution in Africa (AGRA) and, selectivity bias associated with participation in the subsidy program was not accounted for. The study however shows that fertilizer adoption decisions are in two stages. It recommends the need for regular training of members of farmer based organizations as a way of improving farm-level performance through the adoption of fertilizer. This recommendation is more general as it does not analyze any specific agricultural production system. The study provides useful insights on the design of activities and on analytic procedures which address the core questions of this research. Chapter 3 contains a more in-depth study of fertilizer use in rice-growing households. It examines the role of the fertilizer subsidy program in fertilizer adoption decisions based on data from a cross-section of 820 systematically selected rice-producing households. The analyses show that these rice-producing households use different combinations of fertilizers. Overall, nearly 67% use at least one type of fertilizer and 44% use a combination of nitrogen-phosphorus-potassium (NPK) and ammonium (NH4) fertilizers. Using Cragg’s two-step regression models, the fertilizer subsidy program is shown to increase the probability and intensity of fertilizer adoption. The study shows that effective adoption of the recommended combination of NPK and NH4 fertilizers can be achieved by linking farmers to training programs on good agricultural practices. Moreover, enhancing access to information and complementary technologies can improve adoption of the recommended fertilizer combination. Chapter 4 assesses the impact of the program on farm-level productivity and computes partial factor productivity of land and labor using the same database as the previous chapter. The average land productivity of rice, 1,309 kg/ha, is still below the national and global average of 2,539 kg/ha and 4,548 kg/ha, respectively. Correcting for endogeneity of participation in the fertilizer subsidy program, the estimated local average treatment effect (LATE) impact parameters show that the fertilizer subsidy increases land productivity modestly and decreases labor productivity. Increased access to fertilizers requires the use of additional labor for fertilizer application. The negative impact of the subsidy program on productivity may be because yield increases are not enough to compensate for the extra labor employed. Including the provision of labor saving technologies and intensive training in productivity enhancing techniques as part of fertilizer subsidy programs may help unleash the full benefits of the program. Chapter 5 examines the impact of the program on food security. More specifically, a sample of 740 rice-producing households is used to compute the amount of calories, proteins, and fats consumed in the abundant, normal, and lean periods of the year. The results show that at any point in time, some households are food insecure. The incidence of food insecurity is highest during lean periods and lowest during periods of abundance, implying instability in household food security throughout the year. Most households have adequate access to calories and proteins, although the majority does not have access to an adequate amount of fats. Improving the crop mix to include crops that can provide adequate access to these nutrients is recommended to improve food security. This part of the research also used the LATE procedure to estimate the impact of the subsidy program on food security. The results show a positive impact of the subsidy program on the nutritional value consumed food and the effect is highest during the lean period. In conclusion, this thesis shows that the fertilizer subsidy program is effective at increasing the adoption of fertilizers. The program increases the land productivity of rice, but decreases labor productivity. The subsidy leads to significant improvements in the food security of rice-producing households. Linking fertilizer subsidy programs to productivity enhancing interventions and the availability of complementary technologies is necessary to maximize its impact. Technology adoption studies should endeavor to consider technologies as a package, instead of individual components. Going forward, it is recommended that the Government should compare the cost effectiveness of the subsidy program to alternative policy options, such as rice importation, to guide the allocation of scarce financial resources. The focus of this study on lowland rice-ecologies in northern Ghana limits the ability to extend the recommendations to other rice ecologies and to the country as a whole. Nevertheless, the recommendations may be useful for neighboring countries which have similar ecologies, such as Ivory Coast, Burkina Faso, Togo, Benin, and Nigeria.
Towards sustainable chemical fertilizer management in China : from theory to farm household
(2023) Yu, Xiaomin; Doluschitz, Reiner
Over the past few decades, China’s grain production has expanded drastically. On the one hand, this has eliminated food shortages and allowed China to feed its huge and still growing population. On the other hand, the rapid growth in grain productivity has come at a heavy cost. Excessive fertilizer use has led to a variety of negative consequences that threaten national food security and environmental sustainability. Since the 2010s, the Chinese government and academia have made considerable efforts to reduce the consumption of chemical fertilizers and improve nutrient management. These include a wide range of regulations to control or guide chemical fertilizer use, policies to eliminate subsidies for the fertilizer industry, and nationwide promotion of scientific fertilizer application methods. In response to these efforts, Chinas overall fertilizer application rate has been declining since 2016. However, China still applies far more fertilizers than its crops need, and the current crop Nitrogen Use Efficiency (NUE) and Phosphorus Use Efficiency (PUE) in China are both below the global average. Therefore, reducing dependence on chemical fertilizers for crop production and sustainably feeding a large population remains a key challenge for China. This dissertation aims to contribute to sustainable nutrient management in China by providing a comprehensive and in-depth understanding of fertilizer use and management at the national, regional, farm and household levels. In the first study (Chapter 2), a systematic review of the historical development and current status of chemical fertilizer use and management in China at the national level is presented. In addition, fertilizer nutrient surpluses are estimated for 30 provinces in China and the regional and temporal variations are visualized. In the second study (Chapter 3), the relationship between fertilizer nutrient surpluses and the regional economy at the provincial level is examined within the framework of the Environmental Kuznets curve (EKC) hypothesis. A panel cointegration approach is employed, using time-series data from 1988 to 2019. In the third study (Chapter 4), the research focus is further narrowed to the farm household resolution. Using cross-sectional survey data from 774 maize-growing farms in northern China in 2019, the study investigates the role of farm characteristics, farmers knowledge, perceptions, and socioeconomic context in farmers fertilizer use strategies. The studies confirm that by 2021, China has reached zero growth in fertilizer use and fertilizer nutrient surpluses at the national and regional level. However, regions with a high proportion of cash crops, such as the southeast coast and northwest, still suffer from high nutrient surpluses. Furthermore, in circa 2012, China has reached its EKC turning point between fertilizer nutrient surpluses and GDP per capita. With further economic growth, the fertilizer surpluses in most Chinese provinces will decrease, indicating a moderating of the tension between economic development and the environment. Looking at the farm and household level, the study shows that in northern China, small farms are more likely to overuse fertilizers in maize cultivation without further yield improvement. Current extension programs have had a positive impact on farmers’ fertilizer use strategies and environmental awareness; nevertheless, the coverage and effectiveness of trainings should be improved. In summary, the dissertation identifies the following key factors that impede sustainable chemical fertilizer management in China: small farm size; regional economic dependence on cash crops; the large discrepancy between farmers practices and scientific production guidelines; and the shrinking and aging of Chinas rural labor force. To address these aspects, the dissertation proposes recommendations at the national strategic level, policy level and implementation level, respectively. The findings and recommendations of this dissertation can serve as a robust decision support and scientific basis for policy makers, stakeholders and researchers in the field of sustainable nutrient management in China.