Effect Of Drip Fertigation On WUE In The Wheat-maize Rotation System In North China

The winter wheat-summer maize doublecropping system has been the dominant system in the North China Plain,accounting for approximately 50%of wheat?Triticum aestivum L.?and 35%of maize?Zea maysL.?production in China.More than 70%of irrigation water from groundwater are used for winter wheat.Nowadays,groundwater level decline,water resources efficiency,non-point source pollution and food production safety are becoming serious problems attributed to groundwater overexploiting and nitrogen fertilizer over-using.Many studies have shown that fertigation can improve water use efficiency?WUE?,fertilizer use efficiency and reduce groudwater contamination.To optimize the fertigation management in the North China Plain,the experiment were conducted to access the effects of fertigation on crop yield,?WUE?,N₂O emissions and nitrate leaching..The experiments were conducted from 2015 to 2017 at Dry-farming experiment station of Dry Farming Institute of Hebei province agriculture and forestry academy.The experiment using a randomized complete block split plot designed with three replications of three irrigation frequencies?0,1 and 2 for wheat;0,2 and 3 for maize?as the main-plot and three nitrogen levels(wheat:137,228,319kgN^?hm^-2;maize:135,225,315kgN^?hm^-2from 2015 to 2016 and wheat:0,137,228kgN^?hm^-2;maize:0,135,225kgN^?hm^-2 from 2016 to 2017 as the split-plot,respectively,using Farmer'practice treatment?FP?as control.In order to provide theoretical and technical guidance for the water and fertilizer management of wheat-maize rotation system in the north China plain,morphological and physiological indexes?plant height,leaf area,chlorophyll,dry matter?,yield and its components,N₂O emission and soil nitrogen residues has been measured periodically during wheat and maize growing seasons.The main conclusions of this study are as follows:1.The results of wheat experiment indicated that fertigation could promote the plant growth,chlorophyll content increased with the increase of N application.Moreover,fertigation during anthesis could slow down the declining rate of wheat leaf area index?LAI?,promote the increasing amount and rate of dry matter accumulation in reproductive stage.While different N application has no significantly impacted dry matter,so reducing 40%N fertilizer did not affect the dry matter accumulation under drip fertigation.The wheat yield significantly increased with increasing drip irrigation frequency,The effect of drip irrigation frequency on WUE between the two wheat growing seasons were different,while N application rate of drip fertigation has no significantly impacted on grain yield and WUE?except for N0?.Compared with FP,drip fertigation increased WUE by 14.8%and 19.6%in 2015-2016 and 2016-2017,respectively.Drip irrigation increased wheat yieldattibuting to higher 1000-kernel weight and spike numbers.2.The results of maize experiment indicated that fertigation could increase LAI and chlorophyll content in the vegetative stage,40%reduction of N could slow down leaf senescence and did not significantly affect chlorophyll content in reproductive stage.However,fertigation frequency had no significant influence on the aboveground dry matter accumulation.Yield increased with the increase of frequency of drip irrigation,while WUE of summer maize decreased with increasing drip frequency.WUE of D3 treatment significantly lower than D0,there were no significant differences between D2 and D3.Compared with FP,fertigation could increased WUE by 12.8%.N application has no significant effect on WUE?except N0?.Drip irrigation increased maize yield attributing for higher 1000-kernel weight.3.Rainfall,fertilization and fertigation could lead to fluctuations of N₂O emission The effect of rainfall was significant lower than nitrogen fertilization and fertigation.The N₂O emission characteristics of fertigation were almost consistent.Wheat and maize N₂O emission flux increased with the increase of N application rate.The N₂O emissions flux of wheat significantly lower than that of maize due to strong rainfall and high temperature during the summer maize season,.The influence of drip irrigation frequency of wheat and maize on N₂O emission was not consistent.For wheat,D2 has increased cumulative N₂O emissions and emission factors by 29.4%and 22.8%compared with D1,respectively.While for maize,cumulative N₂O emissions and emission factors of D2 has increased by more than 30.7%,compared with D3,respectively.4.The amount of residual nitrate nitrogen in wheat and maize was increased with the increase of nitrogen in 0-40cm.The 40%reduction of N in wheat and maize could significantly reduce the nitrate residue in 0-100cm.Moreover,the amount of residual nitrate nitrogen significantly declined with the increase of drip frequency under 40%reduction of N.