Biochar reduced soil N losses and improved N balance in a rainfed winter-wheat cropping agroecosystem

Abstract

Adding biochar to agricultural soils is an innovative method to improve soil fertility and sequester recalcitrant carbon. However, effects of biochar application on soil nitrogen balance under dryland conditions have not been assessed. In this study, we applied biochar at four rates [no biochar (B0), 5 t ha−1 (B5), 10 t ha−1 (B10), and 20 t ha−1 (B20)] to a rainfed winter-wheat agroecosystem on the Loess Plateau in China in October 2011 and 2016. Biochar application at the low and medium rates (5 and 10 t ha−1) reduced nitrogen losses through NH3 volatilization and N2O emissions by 9.23–15.41 % and 2.77–10.44 %, respectively, in all the three experimental study seasons from 2016 to 2019. In addition, biochar application reduced soil NO3−-N leaching by 14.71–37.96 % within 100 cm soil depth in a dose-dependent manner. The reduced nitrogen losses increased the retention of soil total nitrogen in the 0–60 cm soil layer (particularly in the 0–20 cm layer). Biochar application increased the crop and grain nitrogen uptake by 5.07–17.77 % and 1.73–21.74 %, respectively, and this effect was more pronounced at higher biochar application rates (10 and 20 t ha−1). Estimation of N inputs and outputs indicated that biochar application significantly (P < 0.05) increased the mean soil nitrogen balance by 52.09–116.84 % through decreased nitrogen losses and increased soil nitrogen retention. The results indicate that biochar application at 10 t ha−1 could be recommended as the optimal dose for sustainable nitrogen management in rainfed wheat cropping ecosystems on the Loess Plateau.