Effect Of Irrigation And Nitrogen Coupling On Nitrogen Flow And Utilization Of Winter Wheat Under Wheat-Maize Cropping System

On the North China Plain (NCP), excessive application of nitrogen (N) fertilizer coupledwith unreasonable irrigation has produced high levels of nitrate concentration in surface andgroundwater in agricultural areas, which lowered nitrogen and water use efficiencies (NUEand WUE), and seriously confines the balancing increasement of its economic benefit, socialbenefit and ecological benefit. It is in need of establishing an effective irrigation and nitrogenfertilizer management system conducive to the sustainable development of agriculturalproduction. Based on the wheat-maize cropping system, a lysimeter-rain shelter researchfacility was used to quantitatively study the influence of the rate of N fertilization, type of Nfertilizer, and irrigation level on nitrogen and water use characterastics of different NUEgenetype winter wheat varieties (high NUE genetype variety, shimai15and low NUEgenetype variety, jimai19), water and nitrogen balance in winter wheat production system, toreference for the rational use of nitrogen fertilizer and irrigation. The main results of thisstudy are shown as follows:1Effects of nitrogen and irrigation coupling on grain yieldThe grain yield and dry matter of JM19and SM15were increased with the rate of Nfertilizer and level of irrigation. The interaction of irrigation and N fertilizer has significantlyimpact on grain yield and dry matter of winter wheat. The variance of grain yield and drymatter between high and low rate of N fertilizer under W2irrigation level was smaller thanthat under W1irrigation level. In terms of grain yield and dry matter, values for the manuretreatment were lower than for the urea treatment in season1yet were otherwise higher thanurea treatment in season3. Grain yield of SM15was significantly higher than JM19underW1irrigation, whereas opposite trend under W2irrigation. Dry matter of SM15under both W1and W2irrigation were higher than JM19. This indicates that harvest index of JM19washigher than SM15under W2irrigation. The grain yield of SM15and JM19under W1irrigation level were41.0%and77.2%higher than that under W2irrigation level, thus thenegative effect of water deficit on grain yield of SM15was stronger than JM19. From whichit can be indicated that the drought resistance of SM15was weaker than JM19.The spike number, kernel number and1000grain weight of JM19and SM15wereelevated when the level of irrigation amount increased, and kernel number and1000grainweight of JM19and SM15were elevated obviously when the rate of N fertilizer increased.1000grain weight of both winter wheat varieties of manure treatment was higher than ureatreatment with the same rate of N fertilizer. The effect of N fertilizer type N fertilizer rate onspike number was indistinct. The spike number of JM19was lower than than of SM15.2. EffectS of nitrogen and irrigation coupling on nitrogen flow in wheat fieldCrop uptake, ammonia volatilization, nitrate leaching loss, taking up to54.1~199.9%、2.7~36.5%and2.5~12.6%of imput N, are the main components of N flow after fertilizationapplication in wheat field. With the increasing of level of irrigation and rate of N fertilizer, Nuptake by crop and N accumulation in kernel were increased significantly. However, droughtand N fertilizer deficit promoted the N transportation from stem and leaf to grain.From90to180kg N ha-1urea N applied, the accumulation of AV loss was increasedfrom34.5to38.3kg N ha-1with11.1%improvement, but its proportion of fertilizer appliedwas declined from41.5%to23.0%with44.5%debase. The rate of AV and accumulation ofAV loss under W2irrigation level were18.5%and15.4%higher than that of W1irrigationlevel, respectively. The accumulation of AV loss for urea treatment is approximately2.8-3.1times higher than theat from manure treatment. Among the different treatments, theaccumulation of AV loss of W2U1treatement was the highest one, and reached to43.8~45.6kg N ha-1, taking up to24.4~25.4%of fertilizer N. The proportion of AV loss of W2U2treatement was the highest, and reached to24.4~25.4%of fertilizer N. Rate of AV is directlyrelated to surface soil NH4+-N concentration and average daily temperature. NH4+-Nconcentration in surface soil layer was influenced by type of N fertilizer, rate of N fertilizerand level of irrigation amount.No leaching was observed during three wheat seasons in the W2irrigation treatment, inseason1and after irrigation on anthesis and filling stages in seasons2and3. Most of leachatewas observed during the earlier wheat growth stage, which accounted for91.1and56.1%ofthe total leachate volume in seasons2and3, respectively. Under W1irrigation, the nitrate leaching for different treatments were3.4~9.1kg N ha–1in wheat season2and4.9~12.6kg Nha–1in wheat season3, taking up to2.5~7.6%and4.9~12.6%in season2and3, respectively.The nitrate concentration in soil solution and leachate was elevated with the increasing of rateof N fertilizer, otherwise for the ratio of leached nitrate in the input N. The NH4+-Nconcentration in leachate was very low, and NO3--N was the dominant form of N in leachate,which account from95.3~97.9%of the mineral N. Under W1irrigation, nitrate in soilsolution increased after fertilizer application. The depth of nitrate in surgace soil layer afterirrigation was related to wheat growth season. It could move to200cm during planting stageto jointing stage, and move to100cm during flowering stage to filling stage. Compared tourea, manure fertilization can cause nitrate to leach through2m of soil although the leachingnitrate amount for manure application was lower than that for urea fertilization.3Effect of nitrogen and irrigation coupling on nitrogen balance and useefficiencies of winter wheatAfter three winter wheat-summer maize growth seasons, the change of organic mattercontent of different treatments was varied from wheat variety, irrigation amount, type and rateof N fertilizer. Organic matter content in surface soil was declined for most urea fertilizationtreatments and the declining amount of U1treatment was higher than U2treatment. Organicmatter content in surface soil was improved for all manure fertilization, and the improvedamount and improved ratio for M1and M2treatments were0.56~2.43g kg-1and5.13~22.35%,0.06~0.96g kg-1and0.52~8.70%, respectively. Moreover, these were higherunder W1irrigation condition then W2irrigation. Compared to urea fertilization, manurefertilization increased organic matter content and soil fertility in surface soil. Sufficient watersupply promote the increased of organic matter content in surface soil.When priming effect of nitrogen fertilizer on soil nitrogen and denitrification wereirrespective, and soil mineralization amount was equal to the difference between N output andN input for no fertilizer application treatment, the N input was higher than N output for alltreatments except SW1U1and SW1U2. The imput N was109.0~107.7kg N ha-1higher thanthat output N of M1treatment, taking up to30.1~30.2%of input N. During the three wheatseasons, the mineral N content in2.0m soil profile was increased for treatments of W1M1,W2M1and W2U1. Among which, the increase of W2M1treatment was highest. The mineralN content in2.0m soil profile was decreased for other treatments during3wheat season.Nitrogen and water coupling have an significant impact on nitrogen use efficiency(Nit-UE), nitrogen uptake efficiency (NUpE), nitrogen utilization efficiency (NUtE) and nitrogen harvest index (NHI). Compared to stress irrigation, normal irrigation couldeffectively improve wheat Nit-UE, NUpE, NUtE, however stress irrigation enhanced NHI.Nit-UE, NUpE, NUtE and NHI were decreased when N application evalaved from90to180kg N ha-1. Nit-UE and NUpE of urea were higher than manure treatment, whereas NUtE ofmanure were higher than urea. Although Nit-UE of Jimai19was higher than Shimai15, thecrop nitrogen uptake, NUpE and Nit-UE of Shimai15were higher than Jimai19.Using high N use efficiency wheat variety, substitute urea for manure fertilizer, andreducing the fertilizer and irrigation input on planting stage, are the efficient ways to decreasesoil N losses through leaching and ammonia volatilization, increases crop N uptake, andsynchronously improve wheat yield and N use efficiency.4Effect of nitrogen and irrigation coupling on water use characteristic ofwinter wheatSoil water content changed actively in the surface soil layer, which were0–105cm forW1and0–75cm for W2. Higher variance occurred in the0–75cm layer for W1and in the0–35cm layer for W2. The leaching water amount, extracted soil solution amount, soil waterdepletion (SWD) and wheat evaportranspiration (ET) for W2irrigation treatment weresignificantly lower than W1irrigation treatment. The water use efficiency of grain yield(WUEg) and water use efficiency of dry matter (WUEd) under W2irrigation treatment washigher than W1in wheat season1, but otherwise in wheat seasons2and3. With theincreasing of rate of N fertilizer from90to180kg N ha-1, WUEgand WUEdwas increased.The variance of WUEgand WUEdbetween90and180kg N ha-1was higher under W1irrigation than under W2irrigation. Water deficit could inhibit the positive effect of higher Nfertilizer on grain yield and reduce N use efficiencies. Also, increasing rate of N fertilizercould mitigate the negative impact of water deficit on water use efficiency.5Effect of nitrogen and irrigation coupling on photosynthesis and agingproperties characteristicCompared to urea fertilization, the aging enzyme activity and soluble protein content offlag leaf could maintain at higher level on late winter growth stage for manure fertilization,thus manure fertilization could delay leaf senescence process. In this study, increasing rate ofN fertilizer from90to180kg N·ha-2could ease membrane lipid peroxidation in flag leafduring late wheat growth stage, increased photosynthetic rate, photosynthate and winter wheatgrain yield. Water deficit significantly declined leaf area index, photosynthetic rate, photosynthate and aging enzyme activity, which result in leaf premature aging, early maturityof wheat and obviously lower grain yield.