Characteristics Of Winter Wheat Growth And Soil Moisture Utilization In Root Zone Under Different Precipitation Years In Guanzhong Area

Soil moisture is an important factor in agricultural production.Precipitation and irrigation are the main ways to supplement soil moisture in farmland.The Guanzhong area is a transitional zone of semi-humid and semi-arid climates,with precipitation exceeding 200 mm during the growing season of winter wheat in more precipitation years.And the precipitation time is concentrated in the peak period of crop water consumption(jointing–maturity period),and precipitation accounts for a large proportion of crop water consumption.Studies have shown that high soil moisture in winter wheat seedling stage can promote production and income,improve water use efficiency,and save irrigation water resources.However,it is unknown whether the soil moisture management model can harvest high yield and high water use efficiency under different precipitation years.Based on this,this study carried out a winter wheat barrel experiment under different precipitation years in the greenhouse,setting the initial soil water content to the field water holding capacity to ensure sufficient soil moisture during the seedling stage,and simulating different precipitation years(drought,normal and wet years)by regulating the irrigation water volume and irrigation time,and use a full water treatment as a control(CK).The characteristics of winter wheat growth and soil water use in the root zone under different precipitation years and CK were analyzed to investigate whether high soil moisture in seeding stage under different precipitation stages could get high yield and WUE.The conclusions are as follows:(1)Under the various precipitation years,the soil moisture content in winter wheat root zone decreased with the growth of crops,and the growth period was: drought < normal < wet.The difference in soil moisture content in the root zone between precipitation years mainly occurs in heading-mature period.The large difference in soil moisture occurs in the top layer of root zone(0-20 cm).The high initial water content can ensure that the winter wheat in each precipitation years is not affected by water stress in the pre-growth stage(before the middle of jointing).After the jointing,the winter wheat under wet years is still not affected by water stress,while the drought and normal years are subject to different degrees of water stress,and worse of drought years.(2)The soil water deficit will lead to a shortened growth cycle of winter wheat,which is reduced compared three kinds of precipitation years with CK.There was no significant difference in plant height of winter wheat under different precipitation years,and not significantly reduced by CK.The maximum leaf area(MLA)of winter wheat and the dry matter(DM)of mature wheat under each precipitation year were significantly lower than CK.The content of chlorophyll a was higher under high precipitation.There was no significant difference in chlorophyll b content between different precipitation years.The chlorophyll a/b value increased first and then decreased with crop growth.The average photosynthetic rate of winter wheat in wet,normal and drought years during the filling period was 13.7 %,20.5 % and 29.5 % lower than CK.(3)The total root length / weight density of winter wheat under different precipitation years increased first and then decreased with the growth of the crop,and reached the maximum at the heading-filling stage.The total root length / weight density of different precipitation years were as flows: drought < normal < wet,and 26.0 % / 33.6 %?22.7 % / 28.0 %?16.4 % / 22.9 % lower compared with CK.The greater the total amount of precipitation during the growth period,the greater the root length / weight density in the upper soil,and the lower layer was opposite.The root water consumption of winter wheat under three kinds of precipitation years increased significantly in the jointing-mature period.The water consumption in the root zone was the most significant during the heading and filling stage,and the heading and filling stage was the key period of winter wheat root-water mutual feeding.The soil moisture condition is essential for harvesting high yields.(4)The water consumption during the growth period of winter wheat in drought,normal and wet years was reduced by 47.8 %,40.0 % and 27.4 %,but the yield was reduced by 41.7 %,32.4 % and 19.2 % compared with CK.High water consumption makes higher yields and single-ear kernels,but will reduce 1000-grain weight.There was no significant difference in WUE of winter wheat under different precipitation years,which was about 11.5 % higher than CK.Through the comprehensive benefit evaluation of winter wheat yield and WUE under different water consumption,it is considered that the yield and WUE of winter wheat can be harvested under the wet years,and the suitable water consumption of winter wheat is about 320 mm.For adequate irrigation,the appropriate supplementary irrigation amounts for drought,normal and wet years are 110.3 mm,77.0 mm and 25.5 mm in Guanzhong area,respectively.