Maize grain yield and crop water productivity functions in the arid Northwest U.S.

Abstract

Increased water demands and drought have resulted in the need to provide data to guide deficit water management decisions in irrigated maize (Zea mays L.) for grain production. The objective of this study was to develop relationships between maize grain yield and maize water use (ETc, crop evapotranspiration) under low and high nitrogen (N) input systems on a soil type (silt loam) common to maize production in the arid Northwest U.S. The treatments consisted of two N inputs (0 and 246 kg N ha-1 year-1, -N and +N, respectively) and four water input treatments ranging from 100% to 25% of full irrigation. The full irrigation treatment was 20% less than evapotranspiration model calculated crop use (ETm), indicating that crop coefficient (Kc) values may need to be adjusted for maize in the arid Northwest U.S. There were no grain yield response differences between N input treatments in 2017 but during 2018 and 2019 (treatments on same plots), ETc versus grain yield relationships were different for the -N and +N treatments. Crop water production functions were developed using quadratic relationships between ETc and maize grain yield. The range of grain yield across all years and treatments were 15.03–7.23 Mg ha-1. The range of crop water productivity (CWP) across all years and treatments were 1.6–2.6 kg m-3. The ETc at maximum CWPs across all years and treatments had a range of 60–71% of ETm. These relationships are valuable to understanding maize response over a range of water availability and in developing tools to assess future production under water shortages.