Nitrogen leaching and grey water footprint affected by nitrogen fertilization rate in maize production: a case study of Southwest China.

Abstract

Effective nitrogen (N) management measures are required to control environmental problems caused by N fertilizer use in intensive maize production systems. Soil N losses associated with high precipitation and over-fertilization in maize production can cause substantial environmental problems, whereas there is a lack of quantitative data and effective study countermeasures. A 2-year field study was conducted in the subtropical maize production system in Southwest China to quantify N leaching under varying N application rates of 0, 90, 180, 270 and 360 kg N ha-1 yr-1 . The results indicated that N leaching accounted for 16-38% of N fertilizer input. For farmer practice treatment (360 kg N ha-1 yr-1 ), N leaching loss was high at 110 kg N ha-1 yr-1 and accounted for 31% of the N applied. As an indicator of the ambient water quality pollution, the grey water footprint across all treatments ranged from 376 to 1092 m3 Mg-1 , with an average of 695 m3 Mg-1 . Reducing N rate to agronomically optimized treatment (180 kg N ha-1 yr-1 ) significantly decreased N leaching by 77%, and maintained high grain yield of 8.1Mg ha-1 . The grey water footprint was reduced by 52-63% with N rates from 270 or 360 kg N ha-1 yr-1 to 180 kg N ha-1 yr-1 . Nitrogen surplus (applied N rate minus N uptake by maize) resulted in higher soil residual nitrate concentration and consequently high N leaching. High precipitation and low soil pH were the main ecological factors leading to high N leaching. © 2021 Society of Chemical Industry.