Effect of Irrigation Water Amount and Planting Pattern on Water Use and Yield of Cotton in Northern Xinjiang, China

This study aimed to clarify the effect of irrigation water amount and planting pattern on water use and yield of cotton in Northern Xinjiang. A field experiment was conducted during 2020–2021 comprising four irrigation water amounts (360, 450, 540, and 630 mm) and two planting patterns (same row spacing, R1; and wide-narrow row planting, R2). The results showed that the evapotranspiration ($ET$), soil evaporation ($Es$), and plant transpiration ($T$) of cotton under both planting patterns increased with the increasing irrigation amount. During the entire growth period, the annual average daily $ET$ and $T$ under R2 were higher than those under R1, but the annual average daily $Es$ under R2 were lower than those under R1. The daily $Es$ was highest between one and four days after irrigation. The $Es/ET$ under R1 was approximately 27.45%–31.82%, and that under R2 was approximately 24.52%–28.56% under the four irrigation treatments. The relationship between the $Es/ET$ and leaf area index was fitted based on an exponential equation ($R^2>0.85$). The yield increased with an increase in the irrigation amount, although there was no significant difference between the yields obtained with 540 mm and 630 mm irrigation amounts. The water use efficiency (WUE) increased first and then decreased with an increase in irrigation water amount, with the highest WUE observed under the 540 mm condition and the lowest under the 630 mm condition.