Nitrogen use efficiency and optimization of nitrogen fertilization in conservation agriculture
The world population increases and diets change to include more meat. Since livestock mostly have a cerealbased diet, this means global cereal yields have to double by 2050 to meet the demands of the increasing population and dietary changes. Over the past 50 years, N fertilizer application has increased 20-fold, and its application is projected to increase to 180 million tons by 2030. Also, the N fertilizer prices have climbed more than 2.5-fold over the past decade. The use and efficiency of N fertilizers is very different for different types of environment: For high-input environments, an efficient and nonpolluting approach to mineral fertilizer use is essential to prevent excessive N fertilization. Excesses may cause NO3-N leaching which results in eutrophication (excessive plant growth or decay due to extra nutrients in the water) of water bodies and the destruction of water ecosystems. Over-application of N fertilizer also increases environmentally harmful NOx/N2O emissions. Worldwide, N use efficiency (NUE, see below) averages 33% in cereals, indicating substantial potential for improvement. In low yielding, rainfed environments where fertilizer use is marginal and cereal grain yields are low, the focus should be on yield and quality increase by moderate and efficient N fertilizer application rather than over-application. Small grain quality is mainly determined by grain N concentration. The higher the N concentration, the higher the farmers’ profits will be, on the condition that farmers are remunerated for higher quality, which is not always the case. Conservation agriculture (CA) has been proposed as a combination of management principles to improve water use efficiency, reduce soil erosion and conserve resources such as farmers’ time, labor and fossil fuels. It is based on three key components: (1) minimal soil movement, so less or no tillage operations (2) partial retention of residues of the crops as a soil cover (3) economically viable crop rotations. Conservation agriculture has been found to change physical, chemical and biological soil quality components compared to conventional practices involving tillage and thus affects N cycling in the soil (see also the material Conservation agriculture, improving soil quality for sustainable production systems?). Therefore, it is likely that N fertilization will have a different effect on the crops growing under CA-conditions and hence, the fertilization will have to be adjusted in CA-based cropping systems.
| Main Authors: | , , , , |
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| Format: | Handbook biblioteca |
| Language: | English |
| Published: |
CIMMYT
2014
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| Subjects: | AGRICULTURAL SCIENCES AND BIOTECHNOLOGY, CONSERVATION AGRICULTURE, NITROGEN FERTILIZERS, |
| Online Access: | http://hdl.handle.net/10883/4022 |
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| Summary: | The world population increases and diets change to include more meat. Since livestock mostly have a cerealbased diet, this means global cereal yields have to double by 2050 to meet the demands of the increasing population and dietary changes. Over the past 50 years, N fertilizer application has increased 20-fold, and its application is projected to increase to 180 million tons by 2030. Also, the N fertilizer prices have climbed more than 2.5-fold over the past decade. The use and efficiency of N fertilizers is very different for different types of environment: For high-input environments, an efficient and nonpolluting approach to mineral fertilizer use is essential to prevent excessive N fertilization. Excesses may cause NO3-N leaching which results in eutrophication (excessive plant growth or decay due to extra nutrients in the water) of water bodies and the destruction of water ecosystems. Over-application of N fertilizer also increases environmentally harmful NOx/N2O emissions. Worldwide, N use efficiency (NUE, see below) averages 33% in cereals, indicating substantial potential for improvement. In low yielding, rainfed environments where fertilizer use is marginal and cereal grain yields are low, the focus should be on yield and quality increase by moderate and efficient N fertilizer application rather than over-application. Small grain quality is mainly determined by grain N concentration. The higher the N concentration, the higher the farmers’ profits will be, on the condition that farmers are remunerated for higher quality, which is not always the case. Conservation agriculture (CA) has been proposed as a combination of management principles to improve water use efficiency, reduce soil erosion and conserve resources such as farmers’ time, labor and fossil fuels. It is based on three key components: (1) minimal soil movement, so less or no tillage operations (2) partial retention of residues of the crops as a soil cover (3) economically viable crop rotations. Conservation agriculture has been found to change physical, chemical and biological soil quality components compared to conventional practices involving tillage and thus affects N cycling in the soil (see also the material Conservation agriculture, improving soil quality for sustainable production systems?). Therefore, it is likely that N fertilization will have a different effect on the crops growing under CA-conditions and hence, the fertilization will have to be adjusted in CA-based cropping systems. |
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