The Impacts Of Soil Water Storage Before Sowing And The Growing-Season Water Supply Operations On Yields And Water Use Efficiency Of Winter Wheat On The Loess Tableland

The aim of this study is to reveal the mechanism of effective utilization of limited water resources,and to raise the level of Winter Wheat dry farming productivity in the Loess Tableland.We studied the effect of soil water storage before sowing and growing period of different water supply on wheat yield,water consumption and water use efficiency.Three groups experiment of Winter Wheat were tested under the different soil water storage before sowing in the field by using measures of coverage water conservation and biological water consumption in summer fallow period of Winter Wheat:(1)4 dry treatments formed by different soil water storage before sowing and precipitation to analyze the response of wheat yield and water use efficiency to the change of soil water storage before sowing.(2)Under the same soil water storage of 501.8 mm before sowing,3 treatments with once irrigation(40 mm)in jointing stage,booting stage or filling stage was applied to explore the different response of equal water supply at different growth stages of Winter Wheat.(3)Under the high water storage of 542.3 mm and 571.6 mm,2 and 4 water treatments were carried out respectively to form the sufficient water supply condition of Winter Wheat of the whole growth period,to study the possible increase of Winter Wheat yield and the features of water use efficiency under low or no water stress.The Results showed the follows:(1)The best water conservation was film mulching and straw mulching in Winter Wheat summer fallow period,during the experiment,the rainwater storage rate reached 70.6%;At the high planting density of corn,rainwater storage rate is only 28.5%.During summer fallow period planting crops reversed the normal water storage process and consumption of deep soil moisture.(2)The soil water storage before sowing effect on plant height,plant density and LAI level,with the increasing soil moisture increased;Supplemental irrigation had no significant effect on plant height of Winter Wheat;High soil water storage before sowing and high irrigation of Winter Wheat with maximum aboveground biomass,and in the same moisture under,irrigation the same amount of water in different periods has no significant effect on the aboveground biomass of wheat.(3)The soil water storage before sowing has the decisive effect on the yield of Winter Wheat.Under the condition of keeping water storage during summer fallow period,the yield of Winter Wheat under dry water can reach about 88%-90% of the yield under the condition of sufficient water supply in Loess Plateau.(4)The water requirement of Winter Wheat at jointing or booting stage is more,if precipitation is not enough,a certain amount of supplementary water can be supplied;The same water supply increased by soil water storage before sowing or irrigation in growing period have the same effect of increasing production under the condition of no severe water stress.Under a high soil water storage before sowing and irrigation on the jointing and booting stage,the yield of WT7 reached a higher level in the experimental year,and WUE was improved at the same time.(5)The yield of Winter Wheat and ET showed Logistic curve relationship,with the increase of ET,the yield of Winter Wheat increased rapidly and then slowly and the marginal water use efficiency(MWUE)continues to decrease but not turn negative.Logistic curve model can better express the relationship between Winter Wheat yield and water consumption,and analysis of the relationship between yield,water consumption and WUE.The WUE with the water consumption appeared three stages of rise rapidly,steadily and rapidly declined,and the WUE reached the highest before yield.