新疆北部膜下滴灌棉田的蒸散特征

Evapotranspiration of a Film-mulched Cotton Field under Drip Irrigation in North Xinjiang

利用乌兰乌苏农业气象试验站2009年6月至2010年6月的涡度相关资料,分析新疆北部膜下滴灌棉田不同生育期的蒸散变化特征及蒸散量。结果表明:各生育期蒸散量与净辐射的日变化表现出很高的一致性,午间蒸散强度最大;播种-出苗期、苗期和吐絮期蒸散量主要受净辐射控制,蕾期与花铃期蒸散量主要受叶面积指数控制;在现行膜下滴灌灌溉制度下(年灌溉定额340～390 mm),除吐絮期外,其他生育期土壤含水量均可以满足棉田蒸散耗水;播种-出苗期、苗期、蕾期、花铃期和吐絮期平均日蒸散量分别为1.8 mm/d,1.7 mm/d,3.7 mm/d,3.8mm/d和1.2 mm/d,全生育期蒸散量为514.3 mm。

Evapotranspiration including evaporation and transpiration is a main expenditure of water budget at farmland,and it plays an important role in agricultural water management,especially in arid region.In Xinjiang,as a cotton growing area in arid region,water-saving irrigation of cotton is significant for agricultural production.Previous studies on evapotranspiration of cotton reported the total monthly or growth-stage values,however,the daily observations were unavailable.As a method with high time resolution,the eddy covariance has been widely used in measuring evapotranspiration.In this paper,the values of evapotranspiration in the whole cotton growing season were calculated and analyzed based on the observations by eddy covariance at a cotton field under drip irrigation with plastic film in North Xinjiang during the period from June 2009 to June 2010.Under the clear and cloudless terms,daily variation of evapotranspiration was highly consistent with net radiation at each cotton growth stage.The evapotranspiration was affected by net radiation during the period from sowing to emergence and at seedling and boll opening stages,and also by leaf area index at squaring,flowering and boll formation stages.Under the present irrigation regime,soil moisture content could meet the water demand for evapotranspiration in the whole cotton growing season except at boll opening stage.Daily mean evapotranspiration was 1.8,1.7,3.7,3.8 and 1.2 mm/d during the period from sowing to emergence and at seedling,squaring,flowering,boll formation and boll opening stages,respectively.The total evapotranspiration in the whole cotton growing season amounted to 514.3 mm.