Maize silage yield, quality, and crop water productivity functions in the semi‐arid Northwest United States

Abstract Water shortages have resulted in the need for data to guide deficit water management in irrigated maize ( Zea mays L.) silage production in the semi‐arid areas of the Northwest United States. The objective of this study was to develop relationships of maize silage yield and quality with maize water use (ETc, measured crop evapotranspiration) under low and optimum nitrogen (N) input systems. The treatments consisted of two N inputs (0 and 246 kg N ha −1 year −1 ) and four water input treatments ranging from 25% to 100% of full irrigation. The full irrigation treatment ETc was 16% less than model‐calculated crop ET (ETm), indicating that crop coefficients (Kc) may need to be adjusted for maize in the semi‐arid Northwest United States. There were no silage yield response differences between N input treatments in 2017, but during 2018 and 2019, yield water production functions (WPFs) were different for the N treatments. In general, the silage quality was impacted by water input treatments but not N input treatments. The WPFs were developed using quadratic relationships between ETc, and production and quality measurements. The range of maize silage yield across all years and treatments was 4.0–19.7 Mg ha −1 . The range of crop water production (CWP) across all years and treatments was 2.1–5.2 kg m −3 . The ETc at maximum CWPs across all years and treatments was 56% of ETm. These WPFs are valuable to understanding maize response over a range of water availability and in developing tools to assess future production under water shortages.