Vertical Regulation of Crop Root Zone Soil Moisture and Estimation of Evapotranspiration
To avoid encountering 504 error when downloading big files,please take CAJ download or PDF download by chapter as your first priority.
【Author in Chinese】 周始威；
【Author's Information】 西北农林科技大学， 农业水土工程， 2017， 硕士
【Abstract in Chinese】 局部根区水分胁迫可调节作物产量及品质、提高水分利用效率,其节水效应的实现需要作物根区土壤水分在水平或垂向上形成空间分布差异。土壤水分作为影响作物蒸发蒸腾量的重要因素,其空间分布也会对作物蒸发蒸腾量估算造成影响。本研究以石羊河流域春小麦为研究对象,通过控制灌水上、下限及不同生育期计划湿润层深度来实现根区土壤水分的垂向调控,并对其调控效果进行了讨论;基于RZWQM模型对根区土壤水分调控方案中的灌水上限及不同生育期计划湿润层深度进行优化,实现节水效益最大化。以石羊河流域春玉米为研究对象,探究了因灌水量差异所引起的土壤水分空间分布变化对作物蒸发蒸腾量估算的影响。本论文主要取得以下研究成果:(1)通过控制不同生育期计划湿润层深度可以实现对根区土壤水分分布及作物根系分布的调控,垂向调控措施的作用区域主要在0~60cm土层,其中,40~60cm土层的土壤含水量及根长密度受调控影响最显著。不同灌水处理间产量差异较小,但所需灌水量有较大差异,存在节水空间。(2)RZWQM模型可以较准确的模拟石羊河流域春小麦农田土壤水分运动及作物生长过程,可用于灌水制度的优化。应用模型模拟了灌水上限及不同生育阶段计划湿润层深度对春小麦籽粒产量、灌水量、籽粒灌溉水利用效率及灌水次数的影响。结果表明:灌水上限对于灌水量的影响要远远大于对产量的影响,灌水上限的降低会增加灌水次数,从而提高小麦产量;通过调控灌水上限和各生育期计划湿润层深度可以达到节水增产的目的。建议该地区春小麦灌溉制度为:灌水上限选择80%田间持水量,苗期-拔节计划湿润层深度为30cm,拔节期-抽穗期计划湿润层深度为60cm,抽穗期-灌浆期计划湿润层深度为50cm,灌浆期-成熟期计划湿润层深度为70cm。(3)FAO-56对不同灌水处理下作物蒸发蒸腾量的估算精度存在较大差异,可较精确的估算低灌水处理下作物蒸发蒸腾量;随灌水量增加,其估算精度有所降低,对高灌水处理下作物蒸发蒸腾量的估算误差达-14.13%。根区上部土层含水量与土壤水分胁迫状况关系紧密,以缓变层及以上土层含水量平均值代替整个根区含水量平均值用于土壤水分胁迫系数计算,可有效改善高灌水处理下旱区作物蒸发蒸腾量计算精度,估算误差降至-9.97%,亦可较为精确的估算低灌水处理下作物蒸发蒸腾量。
【Abstract】 Partial root zone water stress was a new water-saving technology.The difference of soil moisture distribution on space was necessary for the implementation of water-saving effect.Soil moisture was a important factor that affected crop evapotranspiration.The spatial distribution of soil moisture also could affect the estimate crop evapotranspiration.This paper regarded spring wheat and spring maize wheat in Shiyang River Basin as the research object,and achieved the crop root zone soil water distribution in vertical direction by the way of controlling the upper bounds of water application,the lower bounds of water application and the scheming wetted soil layer depth in different growth periods.The objectives of this study were to(1)study the effects of vertical regulation of root zone soil moisture;(2)study the optimization of irrigation schedule for spring wheat with RZWQM model in order to achieve maximum benefits of water-saving;(3)study the effect of irrigation water on estimation accuracy of evapotranspiration of crop by comparing calculated value with measured value.Results showed that:(1)It can regulate soil moisture profile and effect the distribution of crop root system better by the control scheming wetted soil layer depth in different growth periods,which also can impact on absorption and utilization of soil water greatly.The acting position of vertical regulation of root zone soil moisture is 0~60cm layer.The soil moisture content and root length density of 40~60cm layer was affected significantly.The yield difference of different water treatment is small,but there is a big difference of irrigation among treatments.As a result,it can achieve water-saving and stable yield effects by regulating soil wetted depth in different growth stage of spring wheat.(2)RZWQM can be used to evaluate the effect of various irrigation upper limits and scheming wetted soil layer depth in different growth period on crop yield,irrigation amount and water use efficiency.The yield in different irrigation treatment is not obvious change compared with the needed irrigation rate.The effect of irrigation upper limit on irrigation rate was more remarkable than that of crop yield.The reducing of irrigation upper limit will increase the irrigation rate,thus improving the yield of spring wheat.The appropriate scheming wetted soil layer depth can effectively improve the utilization efficiency ofirrigation water,and achieve the purpose of water saving.Through regulating irrigation upper limit and scheming wetted soil layer depth in different growth period,it can save water saving and improve production of spring wheat.Considering the influence of the control factors on the yield,irrigation amounts and GIWUE,we choose 80% of field capacity as irrigation upper limit.And the optimal supply model of water is 30 cm,60 cm,50 cm and 70 cm of irrigation at seeding,jointing,heading and filling stages,respectively.(3)There were differences for the root zone soil water content and its spatial distribution under different irrigation water.Irrigation water can affect the estimation accuracy of evapotranspiration of crop in arid.FAO-56 can estimate evapotranspiration of crop accurately under low irrigation water treatment,however,the estimate accuracy decreased with the increase of irrigation water.The estimation error of evapotranspiration under high irrigation water was-14.13%.Relation between soil water content of the upper layer and soil water stress condition is close.The soil water stress coefficient was calculated with the average soil water content of part layer in the root zone,which can effectively improve estimation accuracy of evapotranspiration under high irrigation treatment in arid areas.The estimation error reduce to-9.97%.