Conservation tillage enhances crop productivity and decreases soil nitrogen losses in a rainfed agroecosystem of the Loess Plateau, China

Abstract

Conservation tillage has been recommended as one of the effective soil management practices for mitigating the negative environmental effects of synthetic ammonia application and hence achieving cleaner agricultural production. However, information about how long-term conservation tillage affects agroecosystem nitrogen balance in dryland winter wheat-summer maize cropping is limited. Based on a long-term (>9 yr) field tillage experiment and in-situ observation, we assessed the effects of different tillage practices (i.e., chisel plough tillage (CPT), zero tillage (ZT), and conventional ploughing tillage (PT)) on soil nitrogen balance and crop productivity in the 2016–2017 and 2017–2018 growing seasons. Each tillage practice was exposed to a local widely adopted N application rate (240 kg ha−1 yr−1) in both seasons. Our results indicated that, compared with PT, CPT and ZT significantly (P < 0.05) reduced N2O emissions by 39.7% (2.8 kg N ha−1 yr−1) and 55.3% (3.9 kg N ha−1 yr−1), and N leaching by 52.3% (11.8 kg N ha−1 yr −1) and 147.7% (33.3 kg N ha−1 yr−1) across the two growing seasons, respectively. CPT significantly enhanced crop aboveground N uptake by 4.0%, and increased the annual crop yield by 5.9–8.1% (0.8–1.2 t ha−1 yr−1). Although CPT and ZT enhanced NH3 volatilization by 46.7% (14.6 kg N ha−1 yr−1) and 84.3% (26.3 kg N ha−1 yr−1), the total N losses under CPT and ZT were decreased on an average by 7.4% and 22.4%, respectively. Overall, CPT and ZT significantly increased the accumulation of soil total nitrogen in the 0–100 cm layer by 34.8 and 54.1 kg N ha−1 yr−1, respectively. Taking N inputs and outputs together, CPT achieved a lower N surplus mainly due to increased crop N harvest and reduced N losses including gaseous emissions and hydrological leaching. Our findings suggest that long-term chisel plough tillage in dryland agroecosystems could serve as a promising soil management practice in increasing crop productivity and maintaining sustainability through enhancing N removal from crop biomass and decreasing N losses via N2O emission and nitrate-N leaching.