Study On Simulation Of Evapotranspiration Under The Condition Of Mulch-trickle Irrigation Cotton Field

On the basis of unique climate condition and cultivation pattern of northern Xinjiang, this research discussed the effect of film mulching degree, and irrigation mode to the total evapotranspiration of whole cotton growth period, stage average daily evapotranspiration and stage total evapotranspiration. analysis the effect of water stress to drip irrigation cotton field's evapotranspiration, the relation of leaf area index to growing degree days and the influence of weather factors on evapotranspiration in local cotton field. During the course of simulating for crop coefficient, film mulching degree coefficient was introduced, simulating the crop coefficient indirectly by the temperature and film mulching degree, reducing the difficulty of obtaining input parameters for evapotranspiration model. Finally, through the crop coefficient and water stress index simulated in this paper, cooperated with the model of Penman—Montieth, reached the goal of simulating evapotranspiration for mulch-trickle cotton field accurately.The result indicate that the mulch-trickle cotton field's total evapotranspiration of whole growth period is ranged from 540 to 620 millimeter, film mulching degree and cotton variety can make a notability influence on the evapotranspiration. Stage total evapotranspiration and average daily evapotranspiration from big to small in turns are flowering to opening, three leaves to flowering, after opening, sowing to three leaves. As for the change of daily evapotranspiration, the appearance time of the biggest and smallest evapotranspiration intensity is separately ranged from 13:00 to 15:00 and from 21:00 to the morrow's 7:00. There is no evidence difference between furrow irrigation evapotranspiration and drip irrigation evapotranspiration, but as for the stage evapotranspiration their different. There is very remarkable relativity between leaf area index and growing degree days, we can simulated the leaf area index by growing degree days, moreover, leaf area index and film mulching degree index can make a good simulation of crop coefficient. By the data of water stress experiment, this paper simulated the water stress index by relatively effective moisture of soil, the precision test result of simulation showed, estimate the reference evapotranspiration by the model of Penman—Montieth, on the same time, cooperating with the simulated crop coefficient and water stress index can estimate the evapotranspiration of mulch-trickle cotton field well.