Mapping the rain use efficiency of maize under three management practices on the Chinese Loess Plateau

Rain use efficiency (RUE, crop grain yield divided by annual precipitation) is key for agricultural production where water resources are limited. RUE of maize (Zea mays) was calculated based on grain yield data collected across the precipitation gradient on the Chinese Loess Plateau under three treatments: (1) CK, flat plot without mulch; (2) HM, half-mulch flat plot, i.e. alternating plastic film mulched row and bare row without ridge-furrow; and (3) DRM, two ridges and the furrow fully mulched with plastic film. RUE was highest in DRM treatment and lowest in CK. Plastic film mulch and ridge-furrow techniques significantly improve RUE, the improvement is largest in low precipitation regime. RUE under the three treatments trends to converge under higher precipitation regime. Regressions of RUE against annual precipitation were conducted and a unimodal RUE pattern was found across the precipitation gradient for CK and HM treatments; RUE linearly decreased (statistically significant) across the precipitation gradient under DRM treatment. RUE of maize showed positive associations with soil silt content in all three treatments, high silt content could be favorable for high RUE. Effects of soil silt content are larger in DRM and HM treatments than in CK, suggesting that reducing soil drainage is important for plastic film mulch and ridge-furrow techniques in dry areas. RUE in the DRM treatment was correlated to both precipitation (prcp) and soil silt content (silt, in %); stepwise regression for the DRM treatment produced the model RUE = - 0.02 × prcp + 0.16 × silt + 23.70 (r² = 0.39, p <; 0.05). Based on regression models, recent (averaging for 1950-2000) and future (averaging for 2010-2039) precipitation and soil texture data, the spatial distribution of RUE potential was mapped for the Loess Plateau. In the near future (the 2020s), mean annual precipitation is expected to increase on the Loess Plateau, which generally would have a posit- ve effect on RUE of maize especially in low precipitation regimes. Spatially, plastic film mulch and ridge-furrow technique would improve RUE on the whole plateau under both recent and future climates, with the highest improvements in low precipitation regimes of northwest the plateau.