Study On Control Indicator Of Automatic Irrigation About Cotton Under Film Drip Irrigation

With the rapid development of computer technology and data communication technology,the impact of modern agriculture and irrigation technology on crop growth and effective utilization of water resources is increasing.The application of automatic control technology in farmland irrigation has become an inexorable trend to realize the information and automation of irrigation development in irrigation area.So the exploration and attempt of automatic drip irrigation to the cotton field instead of the traditional drip irrigation can provide theoretical basis and technical support for the informationization,irrigation automation and management modernization of agricultural irrigation district in Xinjiang.Selectting the "Xinluzao 48" cotton as the research object,the law of water and salt migration,photosynthetic index,physiological index,dry matter and yield in the growth period of cotton were monitored through the field automatic drip irrigation test,and water consumption,economic coefficient and marginal yield of cotton were calculated in three irrigation threshold（high,medium and low,soil moisture percentage of field capacity,upper and lower limits of water content plus or minus 3%）and three depth of sensor（20cm,40 cm and 60cm）,the optimization design of seven automatic irrigation district（LLD1-LLD7）compared with the conventional irrigation（CK）was on the basis of orthogonal test design.The automatic irrigation design compared with traditional drip irrigation design was carried out by selecting the optimal test scheme parameters.A,The variation tendency of soil moisture during the whole growth period under the automatic drip irrigation was basically contrary to that of soil salinity,which can fully reflect the characteristics of water and salt movement——salt comes with water,salt goes with the water,and the water goes rather than the salt.The influence of automatic drip irrigation under the condtion of appropriate threshold and sensor depths on plant height,leaf area,growth,net photosynthetic rate,transpiration rate,stomatal conductance and other photosynthetic physiology was important.Finally the yield and water use efficiency of cotton were impacted.Automatic irrigation ensured the sufficient and stable water supply to root areas of cotton through the proper irrigation threshold and sensor depth,adjustting the appropriate amount of irrigation and increasing a certain irrigation frequency.So as to promote the increase of plant height,leaf area,net photosynthetic rate,transpiration rate,stomatal conductance and yield of cotton,as well as promoting cotton as soon as possible into the next growth period.B,The marginal yield was calculated by differentiating(dyY/dET=-0.31805×2ET+305.57737,dWUE/dET==-2.57079×10^-5ET+0.02385),and the equation(yY=-0.31805ET²+305.57737ET-67621.63459（R2=0.94723）;WUE=-2.57079×10^-5ET²+0.02385ET-5.03968（R²=0.93223）)was fitted by the water consumption,yield and water use efficiency,finding that the most reasonable water allocation stage was in the range of 461.54mm⁴80.50 mm,where the optimum water consumption was.The cotton yield with LLD5 treatment（sensor depth is 20 cm,high threshold）was the highest,increased by 31.67% compared with which of CK treatment.The water use efficiency with LLD6 treatment（sensor depth is 40 cm,moderate threshold）was the highest,increased by 16.67% compared with which of CK.And the maximum economic coefficient（seed）with LLD6 is 0.3337.C,Eight rotational irrigation group with automatic irrigation,reduced by 22 than that of the traditional drip irrigation through the comparison between the automatic irrigation and the traditional drip irrigation.The number of the rotational irrigation group was greatly reduced,which meant that the operation cost was debased.The utilization rate of the capillary tube in the actual operation was high.The area of the rotational irrigation group was large,while there was a few of the total rotational irrigation group in the system.The flow of the rotational irrigation group was relatively dispersed,relatively debasing the investment in the system.The irrigation frequency of the automatic irrigation was short,and the mode of "eat less and eat more" could ensure a higher frequency of irrigation,which was beneficial to keep optimal water content of soil in root layer and to make for the growth of crop.The comparative test found that the rated flow and the pump head of the automatic irrigation were respectively reduced by 87.77m³/h and 6.07 m compared with the traditional drip irrigation.However,the investment in unit area of automatic irrigation was higher,increased by two thousand and seven hundred yuan per hectare than that of traditional drip irrigation.D,The effect of water saving and production increase of cotton of the automatic irrigation compared with that of the traditional and artificial membrane management were better.Although the investment cost per unit area of the automatic irrigation compared with that of traditional drip irrigation was relatively high,the technology will have great application potential of automatic and large-scale planting in arid area of Northwest China and even in the whole country,comprehensively considering the characteristics——large control area,labor saving,high degree of automation and other features.