| To study the influence of drip water quantities on root growth of soybean. Using tube plant method by W1( 7.5 kg, tube-1, 5 times), W2( 11.0 kg, tube-1, 5 times), W3( 17.6 kg, tube-1, 6 times), W4( 21.8 kg,tube-1, 6 times) four drip irrigation quantities treatments on water content of soil layer in 0-100 cm, root dry weight distribution and root length and root activity of Xindadou 27 in 0-100 cm soil layer, plant characters, photosynthesis, flower and pod formation, yield and water use efficiency were studied. The main results are as follows:(1) With the increasing of irrigation amount obviously enhanced lower limit of water content in 0-40 cm soil layer, decreased storage water consumption in 40-100 cm soil layer; Increase the total amount of root from pod to mature stages and total root length, the main reason is that the root dry weight and root length were increased in 0-40 cm soil layer, decreased dry weight of roots and root length in 80-100 cm soil layer, obviously increase the root flux activity and root activity in 0-40 cm soil layer; The maximum root dry weight and root length of W4 than W1 increased by 60.29%, 65.51% respectively; Increase the root volume and the absorption of root. Increasing irrigation amount, crease the depth of soil humid, enhance the water content in 0-40 cm soil layer, at the flowering and poding period can promoted root growth in0-40 cm soil layer and delayed the roots aging in seed filling is the most important reason of improve yield and water use efficiency.(2) With the increasing of irrigation amount obviously enhanced the leaf areas and the content of chlorophyll, mainly increased upper leaf areas, show that W4>W3>W2>W1; During the pod setting the net photosynthesis rate, stomatal conductivity and transpiration rate presented a double-peak curve, having an obvious “midday depressionâ€, all show that W4>W3>W2>W1, the intercellular CO2 concentration was decreased. Increasing of irrigation amount enhanced the photosynthesis of leaf, improve the ability of synthetic organic compounds and yield.(3) With the increasing of irrigation amount obviously enhanced the plant height and stem diameter,all show that W4>W3>W2>W1, the plant height of W4 than W1, W2 and W3 increased by 56.48%, 37.92%,19.22% respectively. The stem diameter of W4 than W1, W2, W3 increased by 12.77%, 11.28%, 5.70%respectively. During the flower pod increasing of irrigation amount can enhanced the soluble sugar, sucrose and starch content of leaves, petiole and stem. Dry matter accumulation increased large-sized, W4 than W1,W2 and W3, increased by 94.63%, 66.46%, 32.48% respectively, eventually lead to the yield increased.(4) With the increasing of irrigation amount obviously enhanced the flowers, pods and cavities. Delay and prolong the date of poding, increase the pods per plant. The yield of W4 than W1 increased by 87.72%,water use efficiency of W4 than W1 increased by 4.88%, the irrigation water use efficiency was decreased.Increase the irrigation amount can promote root growth, upper leafs growth and flowers, pods and grain number was the main reason of improve yield. |
