Excavated farmland treated with plastic mulching as a strategy for groundwater conservation and the control of soil salinization

Abstract Soil salinization and water deficits in gully consolidation farmland including excavated farmland (EF) and sediment deposited farmland (SF) have become an increasing concern in the Loess Hilly region, China. However, the responses of different farmland types and tillage‐mulching practices on soil salt content (SSC) and water use efficiency (WUE) have not been widely studied in this region. Thus, we conducted a two‐year field experiment to assess the soil water content (SWC) and SSC and their effect on the spring maize yield and WUE under different tillage‐mulching practices in EF and SF. Eight treatments incorporating flat cropping without mulching (FC), ridge planting without mulching (RP), ridge cropping with straw mulching (SM), and ridge cropping with plastic mulching (PM) were applied to EF and SF plots, respectively. Our results indicated that the yield of spring maize was limited by SWC ( p < 0.01). Although EF had a low yield of spring maize compared to SF, it had the highest WUE ( p < 0.01), which was mainly due to the lower groundwater consumption. Meanwhile, the average SSC was significantly lower in EF than in SF ( p < 0.01). PM had the highest SWC (14.9%) and significantly reduced the accumulation of SSC (−0.09 g kg −1 ), thereby improving spring maize yield (12,200 kg ha −1 ) and WUE (1.71 kg m −3 ) ( p < 0.05). These results suggested that EF with PM is optimal for groundwater conservation, decreasing the risk of soil salinization, and improving WUE and maize yield in dryland agricultural areas.