Research On Effects Of Night Warming Irrigation On Physiological Growth And Yield Of Cotton Under Mulch Drip Irrigation

Object: In order to alleviate the adverse effects of low water temperature for irrigation and low soil temperature at night on cotton growth,this study analyzed and studied biomass allocation of physiological growth,phenology and reproductive growth plants of cotton in soil environment under mulch drip irrigation under different irrigation water and different irrigation periods through two-year experiments.In order to provide theoretical support and technical reference for the application of temperature increasing irrigation in Xinjiang region,the thesis discussed the suitable irrigation water moderate irrigation period for cotton growth.Methods: Four irrigation water temperature levels(15,20,25,and 30 ℃)and two irrigation timing levels(daytime and nighttime)were set and constituted eight treatments.The heating irrigation treatment mainly used the abundant light and heat resources in Xinjiang to increase the temperature of irrigation water,and electric energy was used to assist the heating when necessary.Results:(1)The change of soil temperature caused by warming irrigation gradually reduce with the increase of soil depth.Improving irrigation water temperature could increase the water absorption by cotton root and significantly improve the soil respiration rate and the nutrients absorption by cotton root system.Under the same irrigation water temperature,nighttime irrigation could further promote the absorption of nutrients and moisture.(2)With the same irrigation timing,the plant height,stem diameter,leaf area index and net photosynthetic rate Pn of cotton increased firstly and then decreased with the increase of irrigation water temperature.When the irrigation water temperature was 25 ℃,the plant height,stem diameter,leaf area index and net photosynthetic rate of cotton reached the maximum value.Under the same irrigation water temperature,nighttime irrigation could promote the photosynthesis of cotton,and further increase the plant height,stem diameter and leaf area index of cotton.(3)Both warming irrigation and nighttime irrigation could advance the boll-opening stage by decreasing the duration of cotton seedling stage and budding stage.However,they had no significant effect on the duration of cotton flowering and boll-forming stage.In addition,warming irrigation could promote cotton reproductive growth.Nighttime irrigation could promote the reproductive growth of cotton with the water temperature of 20,25,and 30 ℃.(4)Both warming irrigation and nighttime irrigation could increase the biomass,N concentration,and N content of cotton to varying degrees.The warming irrigation could increase the allocation of biomass and N to cotton stem and bud but reduce the biomass allocation to cotton leaf and boll.It also could reduce the biomass allocation to cotton root before boll-opening stage and the N allocation to boll.At budding stage and flowering and boll-forming stage,warming irrigation decreased N allocation to cotton leaf.Nighttime irrigation could increase the N allocation to cotton stem at flowering and boll-forming stage and increase biomass allocation to cotton stem.Nighttime irrigation had no significant effect on other organs.(5)With the same irrigation timing,the increase of irrigation water temperature could increase the number of bolls per plant and reduce the single boll weight.The seed cotton yield showed the trend that increased first and decreased then with the increase of water temperature.Warming irrigation could increase seed cotton yield by 5.88% to 11.46%.With the same irrigation water temperature,nighttime irrigation could further improve the number of bolls per plant and the single boll weight.In addition,nighttime irrigation could improve seed cotton yield by 2.95% to 4.31%.The treatment of nighttime irrigation at 25 ℃ had reached the maximum of seed cotton yield and improved the seed cotton yield by14.13% to 14.90%,compare with CK treatment.(6)Under the same irrigation timing,increasing irrigation could improve fiber strength,elongation,micronaire but reduce the uniformity index and fiber length.With the same irrigation water temperature,nighttime irrigation could improve fiber length,strength,and elongation but reduce uniformity index.Night irrigation could reduce the micronaire with the irrigation water temperature of 15 ℃.When irrigation water temperature was 20,25,or 30 ℃,night irrigation could increase micronaire.Conclusions: In general,warming irrigation and nighttime irrigation with a certain irrigation water temperature range could promote the absorption of water and nutrients by cotton roots to varying degrees,promote cotton physiological growth and advance crop phenology,and ultimately improve the seed cotton yield of cotton.In general,nighttime irrigation at 25 ℃ water temperature is the most suitable irrigation combination for mulch drip irrigation cotton in Xinjiang.