Effects of Different Water Treatments on Physiological Characteristics of Film Free Cotton in Southern Xinjiang

In order to explore the effects of different irrigation methods on the physiological characteristics of film free cotton in southern Xinjiang, the following experiments were carried out: (1) Different irrigation amounts test: 300, 375, 450, 525 and 600 mm (represented by W1, W2, W3, W4 and W5) and a control (450 mm for film free cotton, represented by WCK) were set; (2) Drip irrigation frequency test: drip irrigation 12 times, 10 times, 8 times and 6 times during the growth period (expressed as P12, P10, P8 and P6), chlorophyll fluorescence, leaf area index, SPAD, single leaf photosynthesis, stress enzyme activities and MDA content were observed. The results showed that: compared with film cotton, the average leaf green fluorescence parameters of film free cotton under suitable water treatment (W3 and W4) decreased by 9.03%~50.44%, the photosynthetic indexes (Pn: net photosynthetic rate, Gs: stomatal conductance, Tr: transpiration rate, Ci: intercellular CO2 con-centration) decreased by 4.64%-12.93%, the activities of protective enzymes (SOD: superoxide dis-mutase, POD: peroxidase) decreased by 3.36%-3.58%, the SPAD value decreased by 5.55%, and the MDA content increased by 3.17%, indicating that film free cotton reduced the physiological function of cotton leaves, and the yield decreased by 42.07%. With the increase of irrigation water and irriga-tion frequency, the initial fluorescence (F0) of leaves in each period of film free cotton showed a downward trend, and the maximum fluorescence (Fm), variable fluorescence (FV), maximum pho-tochemical efficiency (FV/Fm), potential photochemical activity of PS Ⅱ (FV/F0), electron transfer of PS Ⅱ (Fm/F0), and photosynthetic performance index (PIABS) showed an upward trend. In all water treatments, W3 and P12 had the highest SPAD value, photosynthetic index and protective enzyme activity, and the lowest MDA content, which was significantly different from other treatments ex-cept W4 and P10. The yield order of different treatments was W3>W4>W5>W2>W1, and the differ-ence between W3 and W4 was not significant, but significant with W2 and W1; The irrigation fre-quency test was P12>P10>P8>P6, and there was no significant difference between P12 and P10. Conclusion: no film mulching has a certain impact on the physiological function of cotton leaves. When the irrigation amount is 450-525 mm and irrigation times is 10-12 times, it is beneficial to play the physiological function of film-free cotton leaves, which can provide reference for water man-agement in production practice.