Tools and techniques for nitrogen management in cereals

Abstract

Nitrogen is indispensable for highly productive agriculture. A number of sources supply nitrogen to growing crops. These sources include synthetic fertilizers, atmospheric deposition and fixation by soil microorganisms, and manures. It is estimated that about half of the total nitrogen fertilizers are applied to three cereals, namely, wheat, rice, and maize. However, only 33% of the total nitrogen applied could be converted to harvestable yields. Most of the nitrogen applied is lost to the environment, which contributes to the emission of greenhouse gases. The nitrogen losses have huge impact on environmental pollution and farm economics. Despite grave concerns, the increase in nitrogen use would probably continue to meet the food demands of the growing population. We have analyzed different approaches used to study the global trends for nitrogen use and nitrogen productivities for three major cereals, i.e., wheat, rice, and maize. These approaches include total N input, use of fertilizer N, N use efficiencies and agronomic efficiency for N, apparent N recovery, N surplus, and partial factor productivity for N. Additionally, we have also discussed the importance of development of nitrogen dilution curves for cereals under different environmental conditions and at regional and global scales. Use of these N performance indicators could help in improving the N productivities in cereals at regional, national, and global levels. We have explored the possible routes of N loss and modern agronomic techniques to improve nitrogen use efficiencies in cereal production systems.