Fertilizer Management and Environmental Factors Drive N 2 O and NO 3 Losses in Corn: A Meta‐Analysis

Abstract

© 2017 Soil Science Society of America. Effective management of nitrogen (N) in agricultural landscapes must account for how nitrate (NO3) leaching and nitrous oxide (N 2 O) emissions respond to local field-scale management and to broader environmental drivers such as climate and soil. We assembled a comprehensive database of fertilizer management studies with data on N 2 O (417 observations, 27 studies) and NO 3 (388 observations, 25 studies) losses associated with 4R fertilizer N management in North American corn-cropping systems. Only one study measured both losses, and studies of N 2 O and NO3 differed by location, time period, and management practices. Meta-analysis of side-by-side comparisons found significant yield-scaled N 2 O emission reductions when SUPERU replaced urea or UAN, and when urea replaced anhydrous ammonia. Hierarchical regression models found near-equivalent magnitude effects on N 2 O emissions of 1°C rise in average July temperature (+), increase in soil C by 10 g kg -1 (+), nitrification inhibitors (-), side-dressed fertilizer timing (-), broadcast fertilizer (-), and 100 kg N ha -1 decrease in fertilizer rate (-). Average NO3 leaching response to 100 kg N ha -1 reduction in fertilizer rate (-) were comparable to effects of 100 mm less annual precipitation (-), 10 g kg -1 more soil C (-), or replacing continuous corn with corn-soybean rotations (-). The large effects of climate and soil, and the potential for opposite reactions to some management changes, indicate that more simultaneous measurements of N 2 O and NO3 losses are needed to understand their joint responses to management and environmental factors, and how these shape tradeoffs or synergies in pathways of N loss.