Nutrient and tillage strategies to increase grain yield and water use efficiency in semi-arid areas

Water and fertilizer are major factors that influence crop productivity in dryland farming. The ridge and furrow rainfall harvesting (RFRH) system is known to be an effective planting method for improving rainwater utilization, but suitable fertilizer application rates for foxtail millet under RFRH planting have not yet been determined. In 2014 and 2015, we examined the effects of four fertilizer application rates (F0, F1, F2, and F3) under RFRH planting (RFRHP) and traditional flat planting (TFP) on the soil water content (SWC), evapotranspiration (ET), plant growth, grain yield, and resource use efficiency for foxtail millet. We found that RFRHP improved the SWC, where the SWC exhibited a decreasing trend as the fertilizer rate increased, but generally there was no significant difference among F1, F2 and F3 under both planting patterns. Compared with TFP, RFRHP produced a slightly higher maximum leaf area and dry matter accumulation, although the differences were not significant, while total ET was reduced and there were general improvements in the harvest index, grain yield, water use efficiency (WUE), agronomic efficiency, and net economic benefit. Foxtail millet responded positively to fertilizer, and F2 was the economical fertilizer input rate, where the leaf area, dry matter accumulation, and grain yield were increased slightly with no significant difference when the fertilizer rate was increased beyond F2, while agronomic efficiency was significantly decreased. The highest economic net benefit was achieved by RFRHP combined with F2, which also obtained significantly higher grain yield, WUE and agronomic efficiency compared with TFP. Thus, we recommend the RFRH system with F2 (186:96 kg N:P ha−1) for high productivity and efficient foxtail millet production in semi-arid areas.