咸水补灌对滴灌棉花光合特性及产量的影响OA

[Objective]The severe shortage of freshwater has severely restricted cotton production in the arid and semi-arid areas of Xinjiang,and water deficit during the key growth stages exerts an even more adverse effect on yield.Saline water supplemental irrigation can alleviate freshwater shortages,but its optimal salinity threshold remains unclear.This study investigated the effects of supplemental irrigation with saline water of different salinity levels on the photosynthetic characteristics and yield formation of cotton,aiming to determine the suitable salinity threshold for cotton supplemental irrigation in arid areas.[Methods]A two-year field experiment was conducted during the cotton growing seasons in 2023 and 2024.The conventional fresh water without supplemental irrigation was used as the control(CK,irrigation quota of 3 600 m3·hm-2),and five saline water supplemental irrigation treatments were established:3.5 g·L-1(S3.5),5.0 g·L-1(S5),6.5 g·L-1(S6.5),8.0 g·L-1(S8),9.5 g·L-1(S9.5).The saline supplemental irrigation regime consisted of one application at the bud stage(375 m3·hm-2)and two applications at the boll-setting stage(375 m3·hm-2+450 m3·hm-2).The total irrigation amount was 4 800 m3·hm-2(including 1 200 m3·hm-2 of saline water and 3 600 m3·hm-2 of freshwater).Gas exchange parameters,chlorophyll fluorescence parameters in functional leaves after saline water irrigations,and yield components of cotton were measured.[Results]During the early boll-setting stage,the two-year average net photosynthetic rate(Pn)of treatments with salinity levels of S3.5,S5,and S6.5 increased by 6.89％-18.00％compared with CK,and the S3.5 treatment was significantly higher than CK.The transpiration rates(Tr)of the S3.5 and S5 treatments were significantly increased by 18.96％and 9.10％,respectively,compared with CK,and the stomatal conductances(Gs)were increased by 12.95％and 3.90％,respectively.After three saline water supplementary irrigations,the initial fluorescence(F0)of the S9.5 treatment was significantly increased by 5.99％(in 2023)and 6.54％(in 2024)relative to CK,while the maximum photochemical efficiency(Fv/Fm)of the S3.5 treatment was significantly higher than that of the S9.5 treatment.The boll-leaf ratio of cotton was the lowest in the S3.5 treatment,with two-year values of 24.58 and 24.87,followed by the S5 treatment with values of 25.02 and 25.05.The two-year average seed cotton yield of treatments with salinity levels of 3.5-6.5 g·L-1 significantly increased by 2.73％-12.67％compared with CK(5 721.00 kg·hm-2).[Conclusion]Supplemental irrigation with saline water with a salinity level of 3.5-6.5 g·L-1 can optimize the photosynthetic performance of cotton and achieve stable or increased yields.However,excessively high salinity level(＞6.5 g·L-1)is prone to cause photo inhibition,leading to a significant reduction in cotton yield.This study provides an important theoretical basis for determining the salinity threshold for saline water irrigation in arid areas.