| In this paper,annual field experimentsunder the winter wheat-summer maize rotation were conducted to study soil nutrient changes,nutrient accumulation characteristics,photosynthetic physiological characteristics,crop yield,annual nutrient balance and nitrogen use efficiency under different fertilization lsuch as once or twice application of common urea,once application of special fertilizer and nitrogen reduction in Hebi(high-yield areas)and Yuanyang(middle-yield areas).This study clearly defined the nutrient characteristics and the appropriate fertilization mode of the wheat–maize rotation system,which provides basis for scientific fertilization of winter wheat-summer maize rotation system.The results of this study are as follows:1.Annual N,P and K accumulation in winter wheat and summer maize in high-yielding areas were 342.40~548.47,105.72~151.42 and 346.30~453.63 kg/hm2,respectively,in which winter wheat accounted for 52.99%,73.81% and 53.36% approximately.The accumulation of N,P and K in middle-yield arear were 197.96~358.86,90.66~ 129.33 and 200.71~288.22 kg/hm2,respectively,in which winter wheat accounted for 58.75%,62.09% and 61.21%.2.In the high-yield areas,the fastest accumulation period of nitrogen in winter wheat was about 160~180 days after sowing;The accumulation of phosphorus and potassium was mainly concentrated in 180 days and 105~160 days,meanwhile,the fastest period of N P K absorption in summer corn was 61~76 days,.60-90 days and 27~76 days,respectively.In the mid-yield areas,the rapid absorption period of nitrogen and phosphorus for the winter wheat is 201-229 days,and the potassium is mainly 134-178 days.The rapid accumulation period of nitrogen in summer maize was before 70-th day and from 100-th dayto maturity.The alkali hydrolysable nitrogen of soil decreased rapidly with the crop absorption,and the available P and available K gradually decreased with time,and remained stable during the period of rapid crop absorption.The N,AP,and AK concentrations of soil under special fertilizer once application maintained a high level all the time.3.Fertilization could significantly increase the photosynthetic rate,stomatal conductance,transpiration rate and SPAD value of key growth stages in winter wheat and summer maize,and e effectively reduce the intercellular CO2 concentration of leaves at the same tim.Compared to the management of once application of common urea,the annual yields under the special fertilizer applied once in high yield and middle yield areas were increased by 9.51% and 17.29%,respectively.the yield under Nitrogen application of 210 kg/hm2(75% coated urea +25% common urea)in winter wheat was increased by 5.60%~35.63% and 5.64%~37.47%,respectively ascompared to other fertilization treatments,and the yield under 750 kg/hm2(28-10-12)of special release fertilizer for summer maize was increased 5.42%~30.15%,with no significant difference beteewn N reduced treatments,however,the NUE was increased by 16.41% and 9.10% compared with the once application,respectively.4.Comprehensive consideration of yield and nitrogen use efficiency,the application of 180 kg/hm2 nitrogen(75% coated urea + 25% normal urea)for winter wheat and application of special slow-release fertilizer(26-10-12)750 kg/ hm2 for summer maize in high-yield area and middle area were recommended,which could meet the annual nutrient demand of crops and achieve high yield and efficiency simultaneously. |
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