不同水氮组合对冬小麦产量及水氮利用效率的调控效应

Optimal water and nitrogen rate combination for winter wheat yield and water-nitrogen efficiency in Guanzhong area of Shaanxi

【目的】探明喷灌条件下水氮调控对冬小麦产量、土壤养分及水氮吸收利用的影响,以期为关中地区小麦生产提供科学合理的水肥一体化施肥方案。【方法】采用喷灌施肥技术,在陕西扶风进行了小麦田间区域试验。试验采用裂区设计,主区为4个灌溉水平:30、60、90、120 mm,记为W1、W2、W3、W4;副区为4个施氮(N)水平:150.0、187.5、225.0、262.5 kg/hm^(2),记为N1、N2、N3、N4,共16个水肥组合。小麦收获期,采集0—20 cm土层土样测定土壤理化性质及微生物生物量碳、氮、磷含量,采集小麦植株样品测定干物质、氮素积累量,并调查产量及构成因素。【结果】小麦产量随灌溉、施氮水平的提高呈先上升后下降趋势,W3N2处理下产量最高,为9053 kg/hm^(2),较W1N1处理增产1973 kg/hm^(2);拟合曲面最高产量达8848 kg/hm^(2),此时灌溉量为98 mm,施氮量为212 kg/hm^(2)。提高灌溉量有利于小麦干物质与氮素积累,W3灌溉下平均干物质积累量和平均氮素积累量均最高,分别达20306 kg/hm^(2)和221 kg/hm^(2),干物质、氮素积累量均在W3N2处理达最高值,分别为21252、237 kg/hm^(2)。过量施氮不利于小麦氮素利用,N4处理下的氮肥偏生产力、氮素利用效率分别较N1处理降低34.5%~40.4%、2.5%~6.9%。各处理小麦水分利用效率处于15.1~21.6 kg/(hm^(2)·mm),施氮量控制在217~228 kg/hm^(2)时小麦的水分利用效率较高。W3灌溉条件下土壤理化性质最优,W4灌溉造成土壤硝态氮、微生物生物量碳、氮含量同步下降。路径分析表明,干物质及氮素积累量、水氮投入、土壤养分、产量构成因素对产量的总效应值分别为0.716、0.642、0.522、0.400,以干物质及氮素积累量的效应值最高;干物质及氮素积累量、产量构成要素以直接路径调控小麦产量,直接效应值分别为0.555、0.400;水氮投入、土壤养分主要以间接路径调控小麦产量,间接效应值分别为0.554、0.544。【结论】干物质及氮素积累量对小麦产量的直接影响最强,灌溉施氮水平对小麦产量的间接影响最强,二者是实现小麦增产的重要因素。过量灌溉、施氮反而降低产量、水氮利用效率和土壤理化指标。在关中地区采用喷灌方法条件下,冬小麦灌溉80~100 mm、施氮210~230 kg/hm^(2)时可以协同小麦高产与水氮高效。

【Objectives】We explored the effects of water and nitrogen rate on regulating winter wheat yield,and soil nutrient availability,to provide an efficient water and nitrogen coupling management scheme for wheat production in the Guanzhong region.【Methods】A field split plot experiment on winter wheat was conducted in Fufeng County,Shaanxi Province.Four sprinkling irrigation levels of 30 mm(W1),60 mm(W2),90 mm(W3),120 mm(W4)were used as the main zone,and four nitrogen(N)fertilization levels of 150.0 kg/hm^(2)(N1),187.5 kg/hm^(2)(N2),225.0 kg/hm^(2)(N3),262.5 kg/hm^(2)(N4)were used as the subzones.After harvest,0−20 cm soil samples were collected to determine soil physicochemical properties and microbial biomass of carbon(MBC),nitrogen(MBN),and phosphorus(MBP)contents.Plant samples were collected to determine dry matter,N content,yield and yield components.【Results】The wheat yield increased first and then decreased with the increase of irrigation and N application level.The highest(9053 kg/hm^(2))was recorded under W3N2 treatment,which was 1973 kg/hm^(2)higher than W1N1 treatment.And the maximum yield fitted by the Curved surface model was 8848 kg/hm^(2),corresponding to irrigation amount 98 mm and N application rate 212 kg/hm^(2).Increasing irrigation amount benefited wheat dry matter and N accumulation,with the highest average dry matter accumulation(20306 kg/hm^(2))and the highest average N accumulation(221 kg/hm^(2))under W3 treatments.The highest dry matter and N accumulation were recorded in the combination of W3 and N2,which was 21252 and 237 kg/hm^(2),respectively.Increasing N application was not conducive to N use by wheat,the N partial productivity and N use efficiency of N4 treatments were 34.5%−40.4%and 2.5%−6.9%lower than those of N1 treatment,respectively.The water use efficiency in all the treatments were in range of 15.1−21.6 kg/(hm^(2)·mm),and controlling N application rate within 217−228 kg/hm^(2)could maintain water use efficiency at a high level.Under W3 irrigation treatments,soil physical and chemical properties were optimal,and W4 led to a synchronous decrease in soil NO3−-N,MBC and MBN content.According to the path analysis,the total effects on yield by dry matter and N accumulation,water and N input,soil nutrient content,and yield components were 0.716,0.642,0.522,and 0.400,in turn,the dry matter and N accumulation exhibited the highest effect on yield.In addition,the dry matter and N accumulation and yield components regulated wheat yield mainly through direct path,with direct effect size of 0.555 and 0.400,respectively,water and N input and soil nutrients regulated wheat yield mainly through indirect path,with indirect effect size of 0.554 and 0.544,respectively.【Conclusions】The dry matter and N accumulation shows strongest direct effect,and irrigation and N application rate show strongest indirect effect on wheat yield.They are important factors in achieving wheat yield increase.Excessive irrigation and N application will deteriorate soil physicochemical properties,resulting in lower yield and water and N efficiencies.In winter wheat production under sprinkling irrigation in the Guanzhong region,irrigation amount 80−100 mm and N rate of 210−230 kg/hm^(2)show synergistically effect on wheat yield and water and N efficiency.