膜下滴灌绿洲棉田蒸散机理与棉花需水模型研究

As the key basis to evaluate the field soil water, determine crop water requirement and irrigation system, filed evapotranspiration is always the focus in the study of irrigation. In field under mulched drip irrigation, the crop growing conditions are different from those in ordinary field and it’s evapotranspiration will change as well. The technology of mulched drip irrigation has been widely used in oasis of Manas River Basin for almost 20 years. However, the evapotranspiration characters and mechanisms of cotton field under mulched drip irrigation are still unclear. The cotton water requirement model used in practical projects is that under routine conditions. As a case of oasis at the Manas River Basin, based on experiment station for on-site study, data such as evapotranspiration, stemflow and weather were observed. The objectives of this projects are to analyze the characters of evapotranspiration, release mechanisms of cotton field under mulched drip irrigation, determine cotton water requirement model. The projects will provide scientific bases for planning, designing and managing of irrigation-drainage engineering, which also provide scientific bases for determining irrigation system, sustainable development and efficient utilization of the basin water resources.

田间蒸散作为正确评价农田水分状况、科学确定作物需水量和农田灌溉制度的关键依据，一直是农田灌溉研究的重点。膜下滴灌农田在地膜覆盖和滴灌技术的综合效应下，作物生长与常规条件下不同，田间蒸散特征也必然发生变化，呈现新的特征。玛纳斯河流域绿洲大面积推广应用膜下滴灌棉花已有近20年的历史，然而，该区膜下滴灌棉田的蒸散特征和机理，目前还尚不清楚，工程实际中所采用的棉花需水模型仍然是常规条件下的模型。本研究以新疆玛纳斯河流域绿洲为例，开展定点实验研究，通过实时监测棉田蒸散量、茎流量以及气象等数据，分析棉田全生育期蒸散特征，揭示膜下滴灌措施对绿洲棉田蒸散过程的影响机理，确定膜下滴灌条件下棉花需水模型，为绿洲农田灌排工程的科学规划、设计和管理，科学制定棉花灌溉制度，以及流域水资源的可持续开发和高效利用，提供科学依据。

本项目以新疆玛纳斯河流域绿洲膜下滴灌棉田为研究对象，分析滴灌棉田全生育期蒸散特征，揭示膜下滴灌措施对绿洲棉田蒸散过程的影响机理，确定膜下滴灌棉花需水规律，制定膜下滴灌棉花高效节水灌溉制度，主要结论如下：.(1)确定了玛纳斯河流域绿洲膜下滴灌棉田的蒸散规律：苗期蒸散强度1.64 mm/d，蕾期蒸散强度3.81 mm/d，花铃期蒸散强度为5.72 mm/d，吐絮期蒸散强度为2.80 mm/d；全生育期覆膜滴灌总蒸散量为539.94 mm，不覆膜滴灌总蒸散量为607.89 mm，覆膜滴灌比不覆膜滴灌使棉田蒸散量降低了67.95 mm（11.18%），蒸散强度降低了0.37 mm/d（10.16%）。.(2)覆膜滴灌能显著提高土壤含水率和土壤温度，全生育期覆膜较不覆膜表层土壤温度和土壤含水率增加了5.1%和22.7%，土壤温度和土壤含水率的增加有利于棉花的出苗和前期的生长。.(3)全生育期覆膜滴灌条件下的棉花植株散发量始终大于不覆膜滴灌条件下的棉花植株散发量，而棵间蒸发量始终小于不覆膜条件。.(4)综合不同灌水量处理对棉花生长、产量的影响以及不同时期Kc值，初步拟定玛纳斯河流域绿洲膜下滴灌棉花高效节水灌溉制度：在中等肥力土壤条件下，整个生育期总灌水量4200 m3/hm2，产量为7200 kg/hm2左右，灌水9次左右，4月份一次出苗水，6月份2次，7月份3次，8月份3次。.(5)全生育期覆膜滴灌条件下凝结水量为72.12 mm（占生育期降水量的52.92%），不覆膜滴灌条件下凝结水量为89.2 mm（占生育期降水量的66.37%），不覆膜比覆膜凝结水量提高了25.42%。不覆膜更有利于凝结水的产生，覆膜不利于凝结水进入土壤。.(6)基于对Penman-Monteith公式的改进，得到了绿洲棉田凝结水量估算模型。