Effect of different straw returning measures on resource use efficiency and spring maize yield under a plastic film mulch system

Straw returning is an effective measure for alleviating soil low organic carbon under film-mulched farmland but has not been widely adopted. A field experiment was conducted on the Loess Plateau to study the effects of different treatments on soil conditions, maize growth, yield, and nitrogen (N) accumulation and absorption to identify an appropriate straw returning measure under plastic film mulch. We investigated three straw returning measures—no straw returning with ridge–furrow plastic film mulch (RP), plow-crushed straw returning with ridge–furrow plastic film mulch (RP+S), ditch-buried straw returning with ridge–furrow plastic film mulch (RP+SD)—with two N fertilizer application rates—125 kg N·ha–1 (N125) and 175 kg N·ha–1 (N175). Combining straw returning and N application significantly improved soil hydrothermal conditions before sowing, and increased water use efficiency (WUE), N uptake efficiency (NupE), and maize yield. The RP+SD treatment had the highest aboveground biomass, root: shoot ratio, N accumulation, and NupE, and significantly increased maize yield by 13–16% at the two N fertilizer application rates, relative to RP. The RP+SD treatment had higher soil nitrate-nitrogen, total N and soil organic carbon contents, and soil water storage than the RP+S and RP treatments across both N treatments. The RP+SD–N175 treatment had the highest NupE, maize yield, and economic benefits in different treatments. In summary, ditch-buried straw returning combined with 175 kg N·ha–1 improved resource use efficiency and spring maize yield under plastic film mulch and is an effective measure for the sustainable development of film mulching systems in semi-arid areas.