Effect of experimental warming on nitrogen uptake by winter wheat under conventional tillage versus no-till systems

Despite the perceived importance of nitrogen (N) to growth and production of wheat, few studies have attempted to examine the effect of warming on wheat N uptake or its preference for NO3--N vs. NH4+-N, especially under different tillage systems. In the North China Plain, an experimental warming (2 degrees C increase in soil during the jointing stage) study was conducted using in situ N-15 labeling under till and no-till systems. We aimed to investigate the uptake of NO3--N, NH4+-N, and glycine-N by winter wheat. Warming strongly enhanced wheat biomass (14.7% and 13.2% for till and no-till, respectively) and N content in biomass (11.1 and 7.4 g N m(-2) for till and no-till, respectively). Total N uptake rates increased by 47% and 40% under till and no-till treatments, respectively. Warming changed the uptake pattern for the three N forms by significantly increasing the contributions of NO3-N by 16% and glycine-derived N by 5%, while decreasing the contribution of NH4+-N by 20% under the two tillage systems, on average. Collectively, high soil temperatures accelerated N uptake in winter wheat and improved the preferential contribution of NO3--N and glycine-N due to the increase in soil glycine and NO3- content. Our findings suggest that enhanced N uptake improved growth of wheat and could reduce N losses through increased uptake of NO3- under till and no-till systems in the North China Plain under the warmer conditions that are likely in future.