Responses of crop nitrogen partitioning, translocation and soil nitrogen residue to biochar addition in a temperate dryland agricultural soil

Abstract

Low nitrogen (N) use efficiency endangers world crop production and ground water. Biochar has been well documented in sequestering C in agricultural soils and improving soil quality. The objective of this study was to assess the multiyear impacts of biochar addition on crop performance, with a specific emphasis on crop N uptake, partitioning, translocation and mineral N distribution in the soil profile. A 3-year field experiment was carried out on the semiarid Loess Plateau of northern China. Maize-straw biochar was added to a spring maize monoculture cropping system at rates of 0 (BC0), 10 (BC10), 20 (BC20) and 30 (BC30) t ha−1 and combined with NPK fertilization in April 2012. Biochar addition increased the crop N uptake, grain N concentration and grain yield with an obvious increase in the kernel numbers per ear. In 2012, the highest rate of 30 t biochar ha−1 reduced leaf biomass and leaf N concentration at the V6 stage. Biochar addition had no effect on the pre-silking N accumulation but increased the post-silking N accumulation. Over the next two years, biochar addition increased the stem biomass and decreased the stem N concentration at the R1 and R6 stages. Biochar enhanced both the pre- and post-silking N accumulation; meanwhile, the N translocation efficiency in the biochar-added treatments was higher than in the control. The BC20 and BC30 treatments significantly improved the average NUE by 10.2% and 14.2%, respectively. Moreover, biochar addition decreased the soil NH4 +-N concentration in the surface 20 cm soil layer in 2012, and the BC10 and BC20 treatments increased the soil NO3 −-N concentrations in the 10–20 and 0–20 cm soil layers, respectively, in 2013. Biochar addition reduced the total residual soil NO3 −-N and the extent of NO3 −-N leaching across the 0–200 cm soil profile. The application of biochar is an effective method to improve grain yield, N uptake and NUE while simultaneously avoiding substantial NO3 −-N leaching loss.