15 - Nitrogen and Soil Quality

Abstract

Excessive nitrogen (N) fertilization may impair soil health through negative effects on the soil biological community and soil reaction. Given the limited and conflicting reports of N fertilizers in relation to soil health, there is a need to look into positive and negative effects of using fertilizer N in cropping systems in India. It has been endeavored in this chapter to analyze research data from India to answer some specific questions: Does high and continuous N input threaten soil quality? Do Indian farmers overuse N? What is the soil health issue vis-à-vis crop productivity? What happens to soil quality when N is used only as mineral fertilizer, or manures/sewage, or a combination of the two? How to use N for a better soil health? The chapter concludes that: (1) mineral fertilizers (and even N) use can enhance soil health in many soils (mainly in the alkaline and neutral pH range) in India through increasing soil organic matter as a result of the greater root growth associated with improved crop yields and often accompanied by enhanced microbial activity; (2) in acid soils, long-term N use has deleterious impacts on soil quality and crop productivity; and (3) the combined use of mineral fertilizers and organic nutrient sources is the best way forward.