灌溉策略对冬小麦水分利用和生长的影响

为探究不同灌溉策略下冬小麦水分利用和生长的情况,在总灌溉量相同的前提下设置拔节水+开花水单次参比蒸散30%灌溉(W1)、拔节水+开花水单次参比蒸散60%灌溉(W2)和拔节水+开花水大水漫灌(W3)3种灌溉策略,利用称重式蒸渗仪和diviner 2000研究了不同灌溉策略下冬小麦的耗水动态、蒸散特征和水分利用效率。结果表明,大水漫灌处理(W3)下冬小麦主要利用上层(0～50 cm)土壤水分,而低速率灌溉(W2和W1)处理增强了植株根系对深层(70～100 cm)土壤水分的吸收;同时,低速率灌溉可以降低蒸散速率,W3、W2和W1的日蒸散速率最大值在拔节水灌溉期间分别为13.20、10.82和10.58 mm·d^-1,在开花水灌溉期间分别为15.10、10.57和9.10 mm·d^-1,其中低速率灌溉主要降低了单日蒸散的午间高峰值,减少了无效耗水。大水漫灌处理不利于生长后期株高的增加,而低速率灌溉不仅有利于株高的形成,也有利于叶片维持较高水平且稳定的SPAD值,保证了籽粒灌浆,使得W2处理的穗粒数和千粒重较W3处理分别提高7.25%和3.93%。综合来看,低速率灌溉策略通过低量持续的供水改变了冬小麦植株根系对土壤水利用的层次,减少无效水蒸散,维持叶片稳定的光合能力,提高了产量和水分利用效率。

Influence of Irrigation Strategies on Water Using and Growth of Winter Wheat Based on Weighting Lysimeters

Reducing soil water evaporation is the important way to improve water use efficiency for winter wheat(Triticum aestivum L.). This study was conducted to determine whether the water use efficiency and growth of winter wheat could be influenced through the different irrigation speed under the same total irrigation amount. Treatments were 30% irrigation of reference evapotranspiration at every turn(W1) during the jointing and flowering,60% irrigation of reference evapotranspiration at every turn(W2) during the jointing and flowering,and flood irrigation(W3) during the jointing and flowering. Additionally,we monitored water use dynamics continuously by weighting lysimeters system,determined the change of soil moisture content in 0-100 cm by diviner 2000 in Nation Experiment Station for Precision Agriculture,Changping,Beijing. The results showed that either during the jointing or flowering irrigation period,plants mainly absorbed the surface(0-20 cm) soil moisture under flood irrigation. However,the root system of plants under low-rate irrigation enhanced the soil moisture absorption in deeper soil layer(70-100 cm). At the same time,the low speed irrigation reduced the evapotranspiration rate of winter wheat. During jointing irrigation,the maximal daily evapotranspiration rates of W3,W2,and W1 were 13.20 mm·d^-1,10.82 mm·d^-1,and 10.58 mm·d^-1 ,respectively. The maximal daily evapotranspiration rates of W3,W2,and W1 were 15.10 mm·d^-1,10.57 mm·d^-1,and 9.10 mm·d^-1,respectively during flowering irrigation. The low-rate irrigation mainly reduced the peak value of single-day evapotranspiration and reduced the ineffective water consumption.In addition,low-speed irrigation was beneficial to the formation of winter wheat height.In contrast,it was not enough to increase plant height at the later stage of W3 treatment under high irrigation(increasing degree: early jointing stage-late jointing stage: W1-19.80 cm,W2-19.07 cm,and W3-17.98 cm; late jointing stage-filling stage: W1-18.22 cm,W2-13.96 cm,and W3-9.39 cm). Simultaneously low-speed irrigation can maintain a stable and high level of leaf SPAD value,ensuring the leaf photosynthetic capacity during the grain filling stage. Spike grain number of W2(36.82) was increased by 7.25% than that of W3(34.33). And thousand-grain weight of W2(43.61 g) was increased by 3.93%,compared to that of W3(41.96 g). In summary,low-rate irrigation strategy changed the layer of plant roots to soil water utilization,reduced the evapotranspiration of ineffective water through continuous slight water supply,maintained the photosynthetic capacity of leaves and increased the yield and water use efficiency.