Sap velocity, transpiration and water use efficiency of drip-irrigated cotton in response to chemical topping and row spacing

Yongfan Chen, Zeshan Zhang, Xuejiao Wang, Shuai Sun, Yutong Zhang, Sen Wang, Mingfeng Yang, Fen Ji, Chunrong Ji, Dao Xiang, Tianshan Zha and Lizhen Zhang

Agricultural Water Management, 2022, vol. 267, issue C

Abstract: Directly measuring plant transpiration of field crops and determining water use efficiency are difficult but essential to understand plant-water relations. In this study, we aimed to quantify plant transpiration and water use efficiency at diurnal and daily bases using sap flow measurements in cotton growing under plastic film cover and drip irrigation in relation to row configurations and chemical topping. Field experiment was carried out in 2020–2021 in Xinjiang, China. The experiment included two topping treatments: chemical topping using heavy amount of mepiquat chloride and traditional manual topping; and two typical row spacing for machine-harvesting: equal row spacing (76 cm) and narrow-wide row spacing (10 cm + 66 cm). Sap flow was measured using a heat ratio method after cotton first flowering stage and then calculated to transpiration per plant and per unit ground area. Chemical topping increased cotton plant height by 12%, leaf area index by 13%, and stem diameter by 9% but did not affect cotton lint yield compared with manual topping across two years and row configurations. The sap velocity of drip-irrigated cotton ranged overall from 20 to 45 cm hr−1 at the daytime and close to zero at nighttime. Across two years, the daily transpiration in chemical topping after flowering was 5.57 mm d−1 and 14.8% higher than in manual topping. That in narrow-wide row spacing was higher than in equal rows. However, the water use efficiency did not differ between topping and row spacing treatments, being 5.64 kg m−3 on average for aboveground dry matter. This knowledge would be useful to optimize cotton irrigation managements and to improve crop models by knowing exact plant transpiration at both plant and system levels.

Keywords: Growth rate, heat ratio method (HRM); Mepiquat chloride; Plant-water relations; Yield (search for similar items in EconPapers)
Date: 2022
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Persistent link: https://EconPapers.repec.org/RePEc:eee:agiwat:v:267:y:2022:i:c:s0378377422001585

DOI: 10.1016/j.agwat.2022.107611

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