Soil fertility is the ability of soil to support plant growth and optimise crop yields. It can be improved by applying organic and inorganic fertilisers to the soil. Nuclear techniques provide data to improve soil fertility and crop production while minimising environmental impacts.
Increasing food security and environmental sustainability in agricultural systems requires an integrated approach to soil fertility management that maximises crop production while minimising depletion of nutrient reserves and degradation of soil physical and chemical properties, which can lead to land degradation, including soil erosion. Such soil fertility management practices include the use of fertilisers, organic inputs, crop rotation with legumes, and the use of improved germplasm, combined with the knowledge needed to adapt these practices to local conditions.
The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture assists member countries in the development and adoption of nuclear-based technologies to optimize soil fertility practices, thereby supporting crop production intensification and natural resource conservation.
Different approaches to effective soil fertility management
Integrated soil fertility management aims to optimise the efficiency of nutrient use for agronomic purposes and to increase crop productivity. This can be achieved through grain legumes, which improve soil fertility through biological nitrogen fixation, and the application of chemical fertilisers.
Whether planted for seed or green manure, or as pasture or woody crops in agroforestry systems, legumes are particularly important because of their ability to fix atmospheric nitrogen, which helps to reduce the use of commercial nitrogen fertilisers and improve soil fertility. They form the basis of sustainable agricultural systems involving integrated nutrient management. The use of N provides an understanding of the dynamics of the different components of farming systems and their interactions, including N fixation by legumes and the use of soil N and fertilisers by crops, both in single-crop and intercropping systems.
Soil fertility can be further improved not only by the introduction of cover crops, which add organic matter to the soil, thus improving its structure, condition and fertility, but also by the addition of green manures or leguminous crops, which fix atmospheric nitrogen through the process of biological nitrogen fixation, the application of micro-doses of fertiliser to compensate for losses due to plant consumption and other processes, and by drastically reducing leaching losses below the plant rooting zone through improved water and nutrient use.
Contribution of nuclear and isotopic techniques
The isotope technique involving nitrogen 15 and phosphorus 32 is used to monitor the movement of nitrogen and phosphorus labelled fertilisers in soils, crops and water, providing quantitative data on the efficiency of the use of these fertilisers, as well as their movement, residual effects and transformation. This information is valuable for the development of improved fertiliser application strategies. The N-15 isotope technique is also used to determine the amount of nitrogen fixed from the atmosphere by biological nitrogen fixation by legumes.
The carbon-13 isotope signature can be used to determine the amount of crop residues incorporated into the soil to stabilise it and improve its fertility. This technique can also be used to assess the effects of conservation measures, such as the incorporation of crop residues, on soil moisture and soil quality. This information can be used to determine the origin and contribution of different types of crops to soil organic matter.
Source : iaea.org