Effects of Soils and Irrigation Volume on Maize Yield, Irrigation Water Productivity, and Nitrogen Uptake

In the newly cultivated oases of northwestern China, the soil properties of farmlands with different cultivation periods show a high degree of spatial heterogeneity on the field scale. However, the irrigation water allocation at the irrigation district scale was based mainly on cultivated area but soil conditions were not considered, which resulted in the shortage or super abound of the irrigation water in the farmlands with different soils. A deeper understanding of the effects of soils on crop IWP and irrigation water requirement is an essential prerequisite to accurately assessing regional irrigation water needs and water-saving potential. Therefore, measurements were taken of the yield, irrigation water productivity (IWP), and nitrogen (N) uptake of maize grown in sandy soils (S1, S2), loamy sand soil (S3), and sandy loam soils (S4, S5) and subjected to three irrigation treatments (full, medium, and low irrigation) in an arid oasis farming system in northwestern China. The results show that the highest yield was obtained under full irrigation in sandy loam. Medium and low irrigation reduced the maize yield by 12.5-21.8% and 13.5-20.6%, respectively, relative to full irrigation, with the greatest decrease in sandy loam. Maize IWP ranged from 1.06-1.20 kg m^-3 for sand to 2.27-2.58 kg m^-3 for sandy loam and was influenced by soil properties but not irrigation treatments. Soil properties also influenced crop N uptake, with sandy loam having a significantly higher such uptake than loamy sand or sand. Under a conventional flooding irrigation pattern, reduced irrigation does not appear to increase IWP in well-drained sandy soils. Crop irrigation water requirement and IWP were mainly influenced by soil texture and fertility. Soil management to improving water productivity should be addressed. In agricultural water management, reasonable irrigation water allocation based on soil conditions should be considered.