Ridge-furrow mulching combined with appropriate nitrogen rate for enhancing photosynthetic efficiency, yield and water use efficiency of summer maize in a semi-arid region of China

Ridge-furrow film mulching (RFFM) and nitrogen (N) fertilization have been widely used in semi-arid regions, it is particularly important to clarify the mechanism of crop physiological indicators in response to RFFM. A two-year (2018 and 2019) field experiment was conducted on summer maize under RFFM (including biodegradable film mulching (B) and plastic film mulching (P)) at N fertilizer application rate of 0 (N0), 90 (N1), 180 (N2) and 270 (N3) kg N ha–1. The aims of this research were to 1) explore the effects of different film mulching and N application rates under RFFM on photosynthesis, water utilization, and yield; 2) identify key factors and their contribution to yield. The results showed that RFFM and nitrogen application significantly improved net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intrinsic water use efficiency (WUEi) (grain-filling stage), the maximum quantum yield of PSII photochemistry (Fv/Fm), energy transformation potential activities of PSII (Fv/Fo), the effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching of variable chlorophyll fluorescence (qP), non-photochemical chlorophyll fluorescence quenching (NPQ), chlorophyll ab (Chl ab), evapotranspiration (ET) and yield, but decreased chlorophyll a/b (Chl a/b) and soil water storage (SWS). The maximum Pn, Tr, Gs, WUEi, Fv/Fm. Fv/Fo, ΦPSII, qP, and Chl ab (anthesis stage) all appeared in N2. At the same N application rate, the positive effects on photosynthetic and chlorophyll fluorescence (ChlF) of the plastic film were better than biodegradable film, especially in water use efficiency (WUE). Nitrogen deficiency had significantly negative effects on various parameters (Photosynthetic parameters, ChlF, Chl ab, grain yield), while nitrogen application (N > N1) had strong positive effects. Photosynthetic parameters, Fv/Fm, Fv/Fo, NPQ, Chl ab, ET, and WUE had strong positive effects on yield. The grain yield of the plastic film were slightly better (5.03% on average) than biodegradable film, but from the perspective of sustainable development, we recommend that biodegradable film and N2 should be used in the semi-arid regions of China. •Four N rates were applied to summer maize under ridge-furrow with polyethylene film and biodegradable film mulching.•RFFM and N application significantly improved Photosynthetic parameters, ChlF, and yield, but decreased Chl a/b and SWS.•Photosynthetic parameters, Fv/Fm, Fv/Fo, NPQ, Chl ab, ET and