Coupling Effects Of Supplemental Irrigation And Nitrogen Application On Winter Wheat Field In Sandy Barren Soil

To study the effects of supplemental irrigation, nitrogen application rates as well as thecoupling effects of the two on the growth, grain yield, grain quality of winter wheat, theabsorption and utilization of water and nitrogen, and the distribution and accumulation ofnitrate nitrogen in soil profile, field experiment was conducted in the meadow soil region atthe experimental station in north China, with the experimental breed of Zhoumai17. Theresults showed:1. Compared with treatment with no nitrogen application, treatments of differentnitrogen applications all increased the tillering ability and plant height of winter wheat inmaturity remarkably, but there were no remarkable difference during different nitrogenapplications under equal irrigation rates. Under equal nitrogen application rates, the plantheight of winter wheat increased with higher irrigation rate, but there was a limit of60%offield capacity. Comparison of dry matter accumulation in different growing periods showedthat within limits, while higher irrigation rate could achieve higher dry matter accumulationafter jointing, nitrogen application could increase the dry matter accumulation of winterwheat before jointing, but nitrogen application of more than195kg/ha went against the drymatter accumulation of winter wheat after jointing.2. Under equal irrigation rates, treatments of different nitrogen applications allincreased the grain yield, ears per mu and grains per ear of winter wheat remarkably, butthere were no remarkable difference during different nitrogen applications, which wasrelated to the decrease of thousand seed weight. In order to bring the yield-improving effectsof nitrogen into full play, higher supplemental irrigation amount should be applied. Of allcombination of nitrogen and irrigation, the highest grain yield of winter wheat was achievedunder W4N195, which was8187.41kg/ha.3. Under equal irrigation rates, the nitrogen uptake of winter wheat and the percentageof nitrogen translocated into grains increased remarkably with the increase of nitrogenfertilization, but if applied over the amount of195kg/ha, the improving effect of fertilizer onN absorption was not remarkable; under equal nitrogen application rates, the improvingeffect of irrigation on N absorption could be seen under relatively lower supplementalirrigation rates. The N uptake of winter wheat increased when soil water content was kept at60%of field capacity before jointing, and at70%of field capacity after anthesis. The highest nitrogen uptake was achieved under W3N195, W4N195.Under equal irrigation rates, compared with treatment with no nitrogen application,treatments of different nitrogen applications all decreased the nitrogen dry matter productionefficiency remarkably; while under equal nitrogen application rates, appropriate amount ofirrigation was of great benefit to the improve of the nitrogen dry matter productionefficiency, which attained the maximum under W3N0, and the soil water content should notexceed70%of field capacity. Higher nitrogen use efficiency was obtained when thenitrogen application rate was less than120kg/ha under equal irrigation rates; the improve ofnitrogen use efficiency and water conservation were both achieved when soil water contentwas kept at50%of field capacity, and the highest nitrogen use efficiency was achievedunder W1N0, which was29.00%.4. Both nitrogen application and the increase of supplemental irrigation could increasethe water consumption of winter wheat in the whole growth stage, however, the increaseeffect of nitrogen applied was not significant when nitrogen application exceeded theamount of120kg/ha. The irrigation water use efficiency and water use efficiency bothincreased notably with the treatment of nitrogen applied, while both declined with theincrease of irrigation rates. The efficiency would declined when the nitrogen applicationamount exceed195kg/ha. Under lower supplemental irrigation levels, appropriate reductionof nitrogen applied was of great benefit to the improve of water use efficiency. The highestirrigation water use efficiency and water use efficiency were both obtained under W1N120,which were42.25%and19.39%respectively.5. Under equal irrigation levels, the nitrate nitrogen content in soil layer of0-80cmincreased with more nitrogen application, and no significant effects on soil layer below80cm. The nitrogen application amount had a significant increase effect on0-200cm soilnitrate content, while irrigation did not. Under different amounts of nitrogen applicationcondition, supplemental irrigation would increase soil nitrate content under100cm, and thenitrate would move down more as the increase of supplemental irrigation amount. When thenitrogen application amount was120kg/ha,195kg/ha and270kg/ha, combined with thesupplemental irrigation level than70%of the field water capacity, we could decrease nitratecontent in lower soil effectively.6.Under equal irrigation rates, Zn content of grain yield increased with the increase ofnitrogen application; while under equal nitrogen application rates, Fe, Mn and Zn contentdecreased with the increase of irrigation amount, but the effect of irrigation weakened withthe increase of nitrogen application. The highest Fe and Mn content of grain yield wereachieved under W1N0, which were147.18mg/kg,36.23mg/kg, and under W1N270, the highest Zn content of grain yield was achieved, which was35.51mg/kg.To sum up, under the current soil condition, taking the growth of winter wheat, yield,quality and water and fertilizer utilization efficiencies, soil nitrate residual accumulation,and leaching loss into consideration, a recommendation of195kg/ha nitrogen applicationand70%of the field capacity supplemental irrigation could be obtained as a suitable ratio ofwater and nitrogen.