Yields, growth and water use under chemical topping in relations to row configuration and plant density in drip-irrigated cotton

Background Water deficit is an important problem in agricultural production in arid regions. With the advent of wholly mechanized technology for cotton planting in Xinjiang, it is important to determine which planting mode could achieve high yield, fiber quality and water use efficiency (WUE). This study aimed to explore if chemical topping affected cotton yield, quality and water use in relation to row configuration and plant densities. Results Experiments were carried out in Xinjiang China, in 2020 and 2021 with two topping method, manual topping and chemical topping, two plant densities, low and high, and two row configurations, i.e., 76 cm equal rows and 10+66 cm narrow-wide rows, which were commonly applied in matching harvest machine. Chemical topping increased seed cotton yield, but did not affect cotton fiber quality comparing to traditional manual topping. Under equal row spacing, the WUE in higher density was 62.4% higher than in the lower one. However, under narrow-wide row spacing, the WUE in lower density was 53.3% higher than in higher one (farmers' practice). For machine-harvest cotton in Xinjiang, the optimal row configuration and plant density for chemical topping was narrow-wide rows with 15 plants m.sup.-2 or equal rows with 18 plants m.sup.-2. Conclusion The plant density recommended in narrow-wide rows was less than farmers' practice and the density in equal rows was moderate with local practice. Our results provide new knowledge on optimizing agronomic managements of machine-harvested cotton for both high yield and water efficient. Keywords: Yield components, Fiber quality, Transpiration, Water use efficiency, Heat ratio method (HRM)