Study Of Evapotranspiration Under Cotton In Plastic Film Using Drip Irrigation In The Arid Areas

Water-shortage is a key factor that restricting the agricultural production innorthwest arid areas. Evapotranspiration of drip irrigation under mulch film consistsof plant transpiration and soil evaporation.Cotton evapotranspiration is an importantpart of the water cycle in arid and semi-arid areas, and a main content in the study offarmland water balance. The researches on the evapotranspiration of drip irrigationunder mulch film in total fertility period and the daily evaporation at different stagescan provide the scientific basis for exploitation and utilization of water resources andestablish scientific and reasonable irrigation system in the northwest arid areas.This article used the Penman-Monteith model to estimate the referenceevapotranspiration and the large steam lysimeter to measure the actual evaporation.Through researching, main conclusion was as follows:(1) There was little difference between using the Penman-Monteith model toestimate reference evapotranspiration and using lysimeter to measure the actualevapotranspiration. In northwest arid areas, the Penman-Monteith model can be usedto estimate the cotton-fields evapotranspiration.(2) The climate cases were the common factor influencing theevapotranspiration. Daily evapotranspiration reached the maximum of5.75mm inJune. The total evapotranspiration of drip irrigation under mulch film in thereproductive period was438mm, the daily evapotranspiration reached maximum of4.7mm in flowering time. The biggest water consumption period was from June20thto September10th, the total water consumption was265.2mm, and needed aboutseven times with per irrigation40mm. Time interval was about8or9days.(3) When the vegetative growth completely stopped in cleft bell times withleaf senescence，leaf area index reached the maximum of4.5, accessing reproductivegrowth stage. The reproductive growth rate rapidly accelerating67.6g/(m2*day) inboll opening peak stage.(4) After precipitation or irrigation, the main factor affects the evaporation ofcotton fields was climate. As the soil moisture content reduced, cotton transpirationbecame a major factor and the evaporation decreased.(5) In flowering previously, E601evapotranspiration was always higher thanthe lysimeter. The leaf area index was greater than2in blossom, the lysimeterevapotranspiration was between12-17points, higher than the E601.(6) The daily soil evaporation rule in the soil of10cm deep, was membranewith gauze back cover> membrane with film back cover> outside membrane with gauze back cover> outside membrane with film back cover. In the situation of thesame opening area, the larger miniature evaporator area was, the less evaporationwas.