Effects of conservation tillage measures on soil water and NO3--N leaching in dryland maize cropland

Abstract

Based on a field experiment on conservation tillage over 15 years in Weibei Highland maize cropland, six conservation tillage patterns, i.e., conventional tillage (CT), no-tillage (NT), no-tillage plus biochar (NB), no-tillage and straw mulching (NS), no-tillage and plastic film mulching (NF), and no-tillage and straw-plastic film mulching (NSF), were investigated for their effects on soil water and nitrate nitrogen(NO3--N) leaching, to seek sustainable agricultural cultivation measures suitable for the region. Results showed that, compared with NT treatment in the first water recharge period, CT had no effect on water recharge in 0-100 cm soil layer, and NS, NB, NSF and NF significantly reduced soil water recharge. In 100-300 cm soil layer, NS, NB, NF and NSF significantly increased soil water recharge, but CT significantly reduced soil water recharge. During the second water recharge period, water recharge depth was mainly concentrated in 0-100 cm soil layer, and there was no significant difference between each treatment and NT. During the water depletion period, compared with NT treatment, other treatments had no significant effect on water depletion in 0-100 cm soil layer, but NF and NSF increased soil water depletion by 33.9% and 59.9% in 100-300 cm soil layer, respectively. In 0-200 cm soil layer, compared to NT, CT significantly increased the accumulation of NO3--N by 2.2 fold, NS, NB, NF and NSF reduced soil NO3--N accumulation by 44.6%, 61.5%, 69.2% and 69.8%, respectively. In 200-300 cm soil layer, NS significantly reduced the accumulation amount of NO3--N, but CT had no significant effect on the accumulation amount of NO3--N, and NS, NB, and NSF all had negative effects on NO3--N accumulation. Soil water movement had significant effect on the distribution of NO3--N in soil profile. Soil NO3--N was mainly distributed in 0-40 cm soil layer for NB, NF and NSF treatments, in 0-100 cm and 200-300 cm soil layers for NS treatment, and over the entire profile for NT and CT, and NS, NT and CT treatments had two NO3--N accumulation peaks in soil profile. Different agricultural cultivation measures could reduce soil NO3--N leaching by regulating soil water content, and subsequently improve nitrogen utilization efficiency. Among those measures, NSF could effectively control soil water movement to reduce the NO3--N leaching and accumulation, and thus is a feasible measure to improve soil water and fertility conditions and increase dryland maize yields.