Assessment of nitrate leaching loss on a yield-scaled basis from maize and wheat cropping systems

It is so far a gap in knowledge to assess nitrate (NO3 (-)) leaching loss linking with crop yield for a given cereal cropping system. We conducted a meta-analysis on 32 published studies reporting both NO3 (-) leaching losses and crop yields in the maize (N = 20) and wheat (N = 12) systems. On average, 22 % and 15 % of applied fertilizer N to wheat and maize systems worldwide are leached in the form of NO3 (-), respectively. The average area-scaled NO3 (-) leaching loss for maize (57.4 kg N ha(-1)) was approx. two times higher than for wheat (29.0 kg N ha(-1)). While, if scaled to crop yields, the average yield-scaled NO3 (-) losses were comparable between maize (5.40 kg N Mg-1) and wheat (5.41 kg N Mg-1) systems. Across all sites, the lowest yield-scaled NO3 (-) leaching losses were observed at slightly suboptimal fertilization rates, corresponding to 90 % and 96 % of maximum maize or wheat yields, respectively. Our findings suggest that small adjustments of agricultural N management practices can effectively reduce yield-scaled NO3 (-) leaching losses. However, further targeted field experiments are still needed to identify at regional scale best agricultural management practices for reducing yield-scaled NO3 (-) leaching losses in maize and wheat systems.