Effects Of Deficit Irrigation In Growth Period On Cotton Growth,water And Nitrogen Use In Southern Xinjiang Of China

The shortage of water resources,low water use efficiency of crops and land salinization in southern Xinjiang,this paper uses cotton "Xinluzhong 66" as a test material for field plot trials.Three irrigation levels(50% ETc: W1,65% ETc: W2,80% ETc: W3,ETc is the crop evapotranspiration)were set in the cotton budding stage,flowering stage and bolling stage(Recorded as B,F and L respectively),controlled by 100% ETc irrigation during full growth period.Throughout the growing period,the cotton growth characteristics,soil water and salt transport were monitored and the dry matter accumulation on the ground was counted,as well as the yield,fiber quality and nitrogen accumulation amount were measured.The effects of deficit irrigation at different growth stages on cotton growth,yield,nitrogen uptake,soil water and salt transport,water use efficiency under mulched drip irrigation were studied,in order to explore the deficit irrigation model to suitable for local water saving and salt controlling.The main conclusions of the study are as follows:(1)The effects of different irrigation periods and levels on cotton growth were explored.Compared with fully irrigated(CK),the water deficit at the budding stage and the bolling stage has no significant effect on the plant height,stem thickness and number of fruit branches of the cotton under the mild water deficit(W3)level.Deficit irrigation at the budding stage has no effect on the LAI,while the Leaf Area Index of the water deficit treatment during the bolling stage was significantly reduced.All the morphological indicators of the remaining deficit treatments were significantly reduced,in particular,the lack of water at the flowering stage has a significant inhibitory effect on cotton plant height,stem thickness,LAI and number of fruit branches.(2)The effects of different irrigation periods and levels on cotton dry matter accumulation and nitrogen absorption were analyzed.Compared with full irrigation CK,different levels of deficit irrigation at different growth stages have a significant inhibitory effect on dry matter and nitrogen absorption and accumulation of cotton aboveground.Under the same deficit degree,the inhibitory effect of deficit irrigation at different growth stages has shown as flowering > bolling > budding.In the three growth periods,deficit irrigation at any growth period is conducive to the transfer of dry matter and nitrogen accumulation above the ground to the reproductive organs,increasing the cumulative distribution ratio of dry matter and nitrogen accumulation in the reproductive organs,and showing as flowering > bolling >budding.(3)The effects of deficits and irrigation levels on cotton yield,quality and water use efficiency at different growth stages were discussed.Compared with fully irrigated(CK),the mild(W3)deficit irrigation at budding stage has no significant effect on cotton 100-boll weight,and seed cotton yield is reduced by 3.48%,but the WUE has been significantly improved,up to 1.57 kg?m-3;and the fiber quality was greatly improved.Deficit irrigation at flowering stage,both seed cotton yield and water use efficiency were significantly reduced,and fiber quality is reduced to a certain extent,which was not conducive to cotton production.(4)The effects of growth period deficit and irrigation level on the dynamic law of water and salt migration in cotton fields were analyzed.Compared with the full irrigation CK,in the0-40 cm soil layer,the soil water content of the irrigation treatment in each growth period is reduced to varying degrees,and it was shown as narrow row> wide row> bare land;while the soil salt content has increased to varying degrees,and showing the opposite law.The treatment with low total salt accumulation: CK <BW3 <FW1 <BW2.Mild deficit irrigation at budding stage has no significant difference between 0 ~ 40 cm soil salt accumulations and CK,which was significantly lower than other deficit treatments.It showed that the effect of salt control on mild deficit irrigation in the budding stage was better than other deficit treatments.(5)A deficit irrigation system and model suitable for the efficient production of cotton in southern Xinjiang was proposed.Comprehensive consideration to ensure the goals of cotton yield,quality,water saving and salt controlling;It is recommended to implement 80%ETc irrigation at budding stage,and implement the deficit irrigation mode of full irrigation in other growth stages.It can guarantee the vegetative growth and reproductive growth of cotton go hand in hand,and achieve high yield and high water use efficiency.