Effects Of Water Regulation In Growth Season On Growth And Water-nitrogen Utilization Of Spring Wheat In The Hexi Region

Considering the water shortage and the low water and fertilizer use efficiency by crops in the Hexi Region,field plot experiments were carried out with the spring wheat species of Yongliang 4 and a nitrogen rate of 180 kg N/hm2 in Shiyang river basin.Five lower soil water limits(i.e.W1(55%?60%?55%?50%),W2(60%?65%?60%?55%),W3(65%?70%?65%?60%),W4(70%?75%?70%?65%)and sufficient irrigation(CK)(75%?80%?75%?70%))were applied at different growing stages(Emergence-Tillering,Jointing-Booting,Heading-Anthesis,Filling-Maturity)to study the effects of soil water regulation on spring wheat growth and water-nitrogen utilization.The following conclusions were obtained:(1)Effects of soil water regulation on growing period of spring wheat growth showed that at the same fertilizer level,the increase in lower soil water limits increased the plant height and LAI of spring wheat.Compared with the W4 treatment,the plant height and LAI of the sufficient irrigation treatment(CK)increased by 2.2% and 7.9%.However,compared with sufficient irrigation treatment(CK),total dry matter accumulation and its distribution amount to grain of W4 treatment had significantly increased respectively by 5.6% and 17.1%.(2)Effects of soil water regulation on physiological property of spring wheat growth showed that with the increased in illumination intensity,the diurnal variation of Pn in Jointing and the diurnal variation of Pn in Anthesis showed the tendency of singlet and doublet,and reached the best-performing in CK treatment.To some extent,the increased in irrigation amount was beneficial to enlarge transpiration rate.At Jointing and Anthesis,the transpiration rate of CK treatment was increased by 3.9%?2.6% compared with W4 treatment,the yield of W4 treatment was increased by 4.1% compared with CK treatment,while the difference was not significant between the W4 and CK treatments.(3)Effects of soil water regulation on changes of soil moisture content and irrigation amount of spring wheat growth showed that the increase in lower limit of soil wanter promoted the irrigation amount and water consumption amount.Compared with the CK treatment,the irrigation amount of the W1,W2,W3 and W4 treatments reduced significantly by 26.6%,15.0%,9.3% and 4.8%,while the difference was not significant between the W4 and CK treatments.At the same time,with the increase in lower soil water limits,the field and water use efficiency(WUE)in all treatments increased first and then decreased,the sufficient irrigation treatment(CK)made the soil water content was so high that it was bad for soil water consumption constantly.(4)Effects of soil water regulation on nitrogen assimilation ?distribution of nitrogen ?nitrogen translation and nitrogen uptake and use efficiency of spring wheat on spring wheat growth showed that the increase in irrigation amount promoted the soil nutrient assimilation by wheat plants.Compared with the W4 treatment,the nitrogen assimilation in wheat plants of the W1,W2 and W3 treatments reduced significantly by 29.3%,23.0% and15.5%,while the difference was not significant between the W4 and CK treatments.Compared with the W1,W2,W3 and W4 treatments,the nitrogen assimilation in vegetative organs of the CK treatment at maturity increased respectively,but the grain nitrogen assimilation of the CK treatment was significantly reduced by 10.4% compared with the W4 treatment.The W4 treatment had the highest nitrogen translocation amount and efficiency except for its decreasing contribution proportion(76.2%).With the increase in lower soil water limits,the nitrogen uptake efficiency,nitrogen productive efficiency and nitrogen harvest index in all treatments increased first and then decreased,where the W4 treatment had the most obvious changing trend.(5)Effects of soil water regulation on NO3--N distribution and accumulation amount in 0-100 cm soil layer of spring wheat growth showed that at the same fertilizer level,the increase in irrigation amount increased the soil NO3--N moved into the deeper soil,it was bad for NO3--N uptake and use of spring wheat.The soil water regulation at different growing stage had significant effects on soil NO3--N contents.At Maturity,the treatment W4 showed the lowest soil NO3--N accumulation in the 0-100 cm soil layer,which was reduced by 9.6%,7.2%,6.6% and 1.4%,respectively,compared with that of the W1,W2,W3 and CK treatments.In previous studies on water-fertilizer coupling and regulation,the researches of water-fertilizer coupling in dry agriculture were spread widely.However,according to the lower limit of soil water for irrigation was less studied.This paper studied the effects of soil water regulation at different growing stages on growth and water-nitrogen utilization of spring wheat in the Hexi Region.Comprehensively considering the nitrogen accumulation,distribution,and soil NO3--N contents,the treatment W4 is selected as the optimal mode for spring wheat in the Hexi Region under the present experimental conditions.