Effects Of Water And Nitrogen Application On Crop Yield And Water And Nitrogen Utilization In Controlled Release Fertilizers At Different Release Period

Water shortage and overuse of fertilizer were two major factors restricting agricultural production in the arid areas of Northwest China.The controlled-release fertilizer,serving as a promising new fertilizer,could be used to improve nutrient use efficiency and crop yields via adjusting the stage of nutrient release.It was very important for agricultural production to propose a suitable rate of water and nitrogen in the arid region.Therefore,the aim of this study was to explore the impacts of controlled-release fertilizers,irrigation amount,and application nitrogen rates on winter wheat yield.A field experiment was carried out in Wugong Town,Xianyang City,Shaanxi Province,China.The optimum combinations of water and fertilizer inputs were determined for both single-objective and multi-objective optimizations through the frequency and multiple regression analysis method.The main,sub,and sub-sub plots were designed in the field experiments.In the main treatments,three irrigation levels were set as W₁（30 mm）,W₂（60 mm）,and W₃（90 mm）.The sub treatments comprised of four nitrogen fertilization levels in the winter wheat and summer maize growing season,including winter wheat[N₀(0 kg·hm^-2),N₁(75 kg·hm^-2),N₂(150 kg·hm^-2),and N₃(225 kg·hm^-2)]and summer maize[N₀(0 kg·hm^-2),N₁(90 kg·hm^-2),N₂(180kg·hm^-2),and N₃(270 kg·hm^-2)].The sub-sub plots included three different nitrogen fertilizer types,namely PCU₆₀（a controlled-release fertilizer with a release periods of 60days）,PCU₁₂₀（a controlled-release fertilizer with a release periods of 120 days）,and CO（traditional urea）.A controlled release fertilizer was applied at one time during planting,where the application mode of traditional nitrogen fertilizer（winter wheat:basic application:topdressing during winter irrigation:top dressing at jointing stage=6:2:2,CO;summer maize:basic application:top dressing at jointing stage=5:5,CO）as a control（CO）.This study showed that the following results:（1）Clarify the release period of controlled-release fertilizer and the amount of water and nitrogen used for winter wheat/summer maize to obtain higher yields.When the types of controlled-release fertilizers were PCU₁₂₀and PCU₉₀,winter wheat and summer maize could obtain the best crop yields,respectively.Irrigation amount,application nitrogen rates,and types of controlled-release fertilizer had significant effects on crop yield in winter wheat and summer maize seasons.Under different controlled-release fertilizer conditions,crop yields first increased and then decreased with increasing levels of irrigation and application nitrogen.Under the conditions of applying PCU₁₂₀and PCU₉₀,the appropriate water and fertilizer application intervals are respectively:winter wheat season(PCU₁₂₀):47.72～52.28 mm and 159.23～199.47 kg·hm^-2,summer maize season(PCU₉₀):48.45～55.98 mm and 176.81～195.99 kg·hm^-2.The highest yield ranges that can be obtained for the two are:7744～7906 kg·hm^-2(PCU₁₂₀);9834～10075 kg·hm^-2(PCU₉₀).（2）Investigating the effects of controlled-release fertilizer release period and water and nitrogen levels on water use efficiency of winter wheat/summer maize.When the types of controlled-release fertilizers were PCU₁₂₀and PCU₉₀,winter wheat and summer maize could obtain the best water use efficiency（WUE）,respectively.Irrigation amount,application nitrogen rate,and type of controlled-release fertilizer had significant effects on WUE of winter wheat and summer maize.Under different types of fertilizers in winter wheat season,WUE decreased with increasing irrigation,and it first increased and then decreased with increasing rate of application nitrogen.Under the different types of fertilizers in summer maize season,WUE first increased and then decreased with increasing amount of irrigation and application nitrogen.Under PCU₁₂₀and PCU₉₀,their respective suitable water and fertilizer dosage ranges are:winter wheat season(PCU₁₂₀):23.79～31.31mm,129.98～174.71 kg·hm^-2;summer corn season(PCU₉₀):46.50～54.02 mm,178.73～197.39 kg·hm^-2.The highest water use efficiency ranges corresponding to PCU₁₂₀and PCU₉₀could be following as:2.14～2.19 kg·m^-3(PCU₁₂₀);2.45～2.66 kg·m^-3(PCU₉₀).（3）Clarify the release period of controlled-release fertilizer and its water and nitrogen dosage for winter wheat/summer maize to obtain higher apparent utilization rate of nitrogen fertilizer.Irrigation amount,application nitrogen rate,and controlled-release fertilizer had significant effects on apparent nitrogen utilization efficiency（ARE）in winter wheat and summer maize seasons.The ARE first increased and then decreased with increasing irrigation amount and nitrogen application rate.Therefore,the apparent nitrogen utilization efficiency of winter wheat and summer maize could reach the highest value in the middle water level.Compared with the CO,the application of controlled-release fertilizer could significantly increase the nitrogen utilization efficiency of crops.Considering high yield and water and fertilizer use efficiency,PCU₁₂₀and PCU₉₀should be recommended as suitable type of controlled release fertilizer in winter wheat and summer corn season,respectively.The respective suitable water and fertilizer application ranges are:(PCU₁₂₀):46.80～54.33mm and 123.71～146.29 kg·hm^-2in winter wheat season;(PCU₉₀):47.85～55.37 mm and 119.96～136.30 kg·hm^-2in summer corn season.The highest fertilizer utilization rates of PCU₁₂₀and PCU₉₀were 48.28～51.17%and 49.70～51.22%,respectively.（4）Investigating the effects of controlled-release fertilizer release period and water and nitrogen levels on the reduction of soil NO₃^--N residues by winter wheat/summer maize.The irrigation amount,nitrogen application rate,and controlled-release fertilizer type had significant effects on soil NO₃^--N residues in the mature period of winter wheat and summer maize.The residual NO₃^--N first decreased and then increased with increasing irrigation amount,and soil NO₃^--N residues were lowest when the irrigation amount was medium level.Moreover,soil NO₃^--N residues increased with increasing nitrogen application rate,and it was lowest value when the amount of nitrogen application was low level.Compared with the CO,the application of controlled-release fertilizer could significantly reduce soil NO₃^--N residues in the mature stage.Compared with the CK,the residual amount of NO₃^--N in the PCU₆₀and PCU₁₂₀treatments reduced by 41.6%and54.4%in winter wheat season,respectively.Compared with the CO,the residual amount of NO₃^--N in the PCU₆₀and PCU₉₀treatments reduced by 29.8%and 39.4%in summer maize season.Therefore,using PCU₁₂₀and PCU₉₀had better effect on the decrease of soil nitrate residue in winter wheat and summer maize seasons.（5）Clarify the release period of controlled-release fertilizer for winter wheat/summer maize with high yield and high efficiency and its water and nitrogen dosage.According to analyzing production function of water and nitrogen and using frequency analysis method,we found PCU₁₂₀in winter wheat season and PCU₉₀in summer maize season should be recommended as the optimal controlled-release fertilizer type.The suitable water and nitrogen application rates corresponding to PCU₁₂₀and PCU₉₀were following as:47.72～54.33mm and 159.23～174.71 kg·hm^-2(PCU₁₂₀);48.45～54.02 mm,178.73～195.99 kg·hm^-2(PCU₉₀).Therefore,this study concluded that PCU₁₂₀in winter wheat season,PCU₉₀in summer maize season,and application range of water and nitrogen was optimal water and nitrogen management strategy in winter wheat/summer maize rotation system in the Guanzhong Plain.