| 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. |
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