Agriculture and the Nitrogen Problem in India: Environmental Implications

Abstract

Much of the excess nitrogen (N) inputs in the Indian region are from agriculture. We quantified soil surface N loads for agro-ecological zones (AEZs) in India using a mass balance approach. We estimate nearly 35.0 Tg of N inputs from different sources, with output N from harvested crops of about 21.0 Tg. The soil surface N balance, estimated as inputs minus outputs, is found to be about 14.4 Tg surpluses from the agricultural land of India. Livestock manure constituted a major percentage of total inputs (44 %), followed by inorganic fertilizer (32.4 %), atmospheric deposition (11.86 %) and N fixation (11.58 %). Nitrogen balance varied from deficit to surplus for different Indian states and AEZs. The lowest N loads were found for AEZs in the Eastern Himalaya, with 19 kg ha−1 surplus, and highest surplus in AEZs with >111 kg ha−1 in areas such as the Deccan plateau and southern India. Environmental implications of these excess N loads in India are discussed, in addition to some best management practices to reduce the loads from agricultural sources.