7 - Efficient Nitrogen Management Under Predominant Cropping Systems of India

Abstract

Nitrogen (N) is the most limiting plant nutrient globally and its efficiency in field crops rarely exceeds ∼40%. Low recovery of N is associated to its loss by volatilization, leaching, surface runoff, and denitrification. Irresponsible use of N not only enhances the cost of crop production but also results in serious implications on soil ecology and environment. The increased nitrate level in the groundwater and nitrous oxide emissions in the croplands are often linked with the excessive use of N fertilizers. Research evidences, however, suggest that the N use efficiency (NUE) can be enhanced substantially using modified urea materials, nitrification inhibitors, integrated plant nutrient supply systems, and management practices involving right source, time, rate, and method of N application. Multilocation studies conducted under All India Coordinated Research Project (AICRP) on Long Term Fertilizer Experiments (LTFE), AICRP on Integrated Farming Systems (IFS), or elsewhere established that instead of enhanced use of fertilizer N alone, conjoint use of organics and fertilizer N is a better way to sustain high yields of cropping systems obviously due to an improvement in soil productivity and NUE. Inclusion of legumes under cereal-based cropping systems as green manure, grain crop, or fodder crop is another important management option for improving NUE and minimizing N losses. Precision N management through tools such as leaf color chart, chlorophyll meter, GreenSeeker, and Nutrient Expert enhances NUE and thus helps preventing wasteful use of N. In the present chapter, important pathways of N inflow and outflow, and the best management options for improving NUE in pre-dominant cropping systems and for mitigating N losses are discussed.