Response Of Cotton Yield And Water Efficiency To Irrigation Amount And Its Regional Adaptability In Southern Xinjiang

The problem of residual film pollution in cotton fields not only leads to a decrease in raw cotton yield and quality,but also seriously affects soil physical and chemical properties,thereby threatening ecological environment and sustainable agricultural development.Film-free cultivation is one of the fundamental means to solve residual film pollution.Therefore,to explore the law of water migration in cotton field and its influence on cotton growth and development,yield and quality formation under drip irrigation without film is a key scientific problem that needs to be solved urgently in the popularization and application of cotton without film cultivation technology in Xinjiang.In this study,the early maturing cotton variety CRI619（Gossypium hirsutum L）was used to conduct a field trial at the Irrigation Experiment Station of Agricultural Division of Xinjiang Production and Construction Corps in 2019 and 2020.Under the conditions of different irrigation volumes without film（W1,0.8W3;W2,0.9W3;W3,conventional irrigation volumes with film mulch;W4,1.1W3;W5,1.2W3;W6,1.3W3）,the laws of cotton growth and development,yield and quality formation,canopy temperature and humidity,canopy light interception,soil water temporal and spatial distribution,water use efficiency of cotton under different growth stages were discussed to reveal the relationship between cotton growth and development without film drip irrigation and water transport in cotton fields,Thereby,suitable irrigation strategies are proposed to evaluate the suitability of non-film cultivation in Xinjiang.The main results are as follows:（i）The effects of different irrigation amount on cotton growth and development,yield and quality in cotton fields with drip irrigation without film were revealed.The plant height and main stem growth of cotton from bud stage to flower boll stage were significantly correlated with irrigation amount,and the leaf area index at flower boll stage increased with the increase of irrigation amount;The irrigation amount at seedling stage mainly affected the vegetative growth of cotton,and the irrigation amount at flower boll stage mainly affected the reproductive growth of cotton;With higher irrigation amount（W5）,the biomass rapid accumulation period lasted long（43-45 d）,and the maximum accumulation rate(239-276 kg ha^-1 d^-1)was higher,so the seed cotton yield was the highest(4420 kg ha^-1),and the fiber quality（length and strength）was better;Leaf area index and aboveground biomass had the highest correlation with yield at flower boll stage.（ii）The spatial distribution of soil moisture and water consumption of cotton at different irrigation levels in cotton fields under drip irrigation without film were clarified.The variation of soil water in cotton field was larger in the upper layer（0～40 cm）and smaller in the lower layer（60～80 cm）.The soil volume moisture content at seedling stage of cotton was 20%-35%in the range of 0-40 cm and 15%-20%in the range of 60 cm,and the variation range of moisture content gradually increased with the progress of growth,the variation range of flower boll stage was the largest,but the variation of 80 cm soil layer in the whole growth period was small.The two-dimensional distribution of soil moisture content was related to irrigation amount and the distance from the drop head,soil water content was the lowest in the vertical direction from 0 to 10 cm,and the lowest in the horizontal direction from 50 cm to the drop head.The water consumption of cotton at different growth stages was in the order of flowering boll stage,flocculation stage,bud stage and seedling stage,W5(4860 m³ ha^-1)treatment was beneficial to improve water use efficiency under the premise of ensuring high cotton yield.（iii）The main crop parameters of the WOFOST model were corrected,and the simulation process of effective photosynthesis leaf area index was improved to simulate the growth and water transport of cotton under drip irrigation without membrane culture.The calibrated WOFOST model showed well simulation accuracy of phenological development,and the errors of simulated seedling emergence,flowering and maturity were+1 day,+2 days and+4 days,respectively.The leaf area index（LAI）simulation performance of the improved model was effectively improved,the coefficient of determination（R²）value was 0.48,and the root mean square error（RMSE）was decreased to 0.15 m² m^-2（7.5%）.In terms of cotton growth simulation performance,the simulated WLV,WST,WSO and TAGP were in good agreement with the measured values,with R²of 0.96,0.97,0.99 and 0.99,respectively,and showed high simulation accuracy with RMSE values of 175,210,199 and 251 kg ha^-1,respectively.The simulated soil moisture（SM）was in good agreement with the measured values（R²=0.87）with high accuracy(RMSE=0.022 cm³ cm^-3).In addition,the simulated TAGP,Yield,ETa and WUE also showed similarly high accuracy under all treatments with RMSE values of 465 kg ha^-1,200kg ha^-1,48.8 mm,and 0.1 kg m^-3,respectively.（Ⅳ）Adaptability evaluation of cotton cultivation without film in Xinjiang.The adaptability of cotton film-free cultivation in Xinjiang was evaluated using the modified and improved WOFOST model.The results showed that the simulated length of phenological development and yield distribution better reflected the influence of meteorological factors on the growth development process and final yield of CRI619,the simulated evapotranspiration explained the water requirements of CRI619 in different cotton regions.According to the yield potential,cotton film-free cultivation areas in Xinjiang were divided into four categories:seven regions with higher than 5000 kg ha^-1,seven regions with 4500～5000 kg ha^-1,five regions with 4000～4500 kg ha^-1,and seven regions with lower than 4000 kg ha^-1.Among them,Yingjisha county and Luntai County could not reach the temperature condition of cotton mature without film cultivation.Overall,the temperature and radiation conditions in southern Xinjiang were more suitable for cotton cultivation without film,and the yield was significantly higher than that in northern Xinjiang,but the water demand is larger.In conclusion,the irrigation amount increased by 20%compared with that of conventional mulching culture can obtain higher cotton yield under the conditions of drip irrigation without film;The soil moisture within 40 cm was most affected by irrigation amount,and the water demand at flowering and bud stages was greater;The modified model showed good performance in cotton growth and water transport simulation,and the simulated water demand law was consistent with the measured value;The simulated average yield of cotton without membrane in the main cotton planting areas in southern Xinjiang was close to that with membrane cultivation.Therefor,the south Xinjiang area has the potential to popularize cotton without membrane cultivation in a large area.