Effects Of Different Controlled-release Urea Operation Modes On Winter Wheat Growth And Yield

Wheat is of great significance to ensuring national food security in China.The one-time fertilization for saving labor was common in winter wheat production in the North China Plain,which caused the excessive application of nitrogen(N)fertilizer generally.Controlled-release urea(CRU)has a good application effect in crops with short growth periods such as rice and maize.However,the applications of CRU on winter wheat with a longer growth period are fewer.In order to study on the N release characteristics of coated CRU under different soil temperature and water content conditions,soil incubation trials of coated CRU with five coating thicknesses(2.8%,3.4%,4.0%,5.0%,6.4%)under three soil water content and three soil temperature(-5℃,10℃,25℃)conditions were carried out.A total of 45 treatments were set up in the soil incubation trials to study of temperature and moisture on the release of CRU.After screening,the PK(pharmacokinetics)model was selected as the basic model of the soil incubation trials,and then multiple sets of data were fitted to the model to obtain multiple sets of models.Multiple sets of data were applied to multiple objects and the nonlinear relationship was considered.Finally,the PK model and the nonlinear mixed-effects model were used to fit the N release process of coated CRU.To investigate the appropriate dosage and blending proportion of CRU and urea in wheat production,the suitable release longevity CRU were selected from the CRUs used in soil incubation trials and the field experiment with 52 treatments was conducted in 2019～2021.This relationship among the N application rates,CRU release longevity and CRU proportions with winter wheat yield was systematically studied,and the correlation analysis,interaction effect and main effects tests were carried out.Based on the Response surface analysis the binary quadratic effect models between yield and CRU factors were established,the partial derivatives were performed and the measured yield of winter wheat in 2018 and 2022 were used as independent data sets to test the field suitability of the fitted model.The main conclusions are as follows:(1)The increase of soil temperature had a greater effect on the cumulative N release of CRU with thicker coating thickness than that of CRU with thinner coating thickness,and soil temperature had a greater effect on the release of CRU than soil water content.When the soil temperature increased from-5 ℃ to 10 ℃,the N cumulative release rate increased by 22.38%;and from 10 ℃ to 25 ℃,the cumulative N release rate increased by 30.46%.However,when the soil moisture increased from70 % of field capacity to 130 %,the nitrogen release rate increased by only 9.84%.(2)The standard error of the nonlinear mixed-effect model based on the PK model was 3.55,the coefficient of variation was 7.3%,and the goodness-of-fit was 96.5%.The dispersion degree was small and the fitting effect was good,which can be used to predict the release process of the coated CRU.(3)CRU3 was released more nutrients in the two key stages of wheat N requirement(Feekes 6 to 9and Feekes 10.5 to 11),especially in the Feekes 10.5 to 11 stage,which was more consistent with the N demand in the growth period of winter wheat than other CRUs.(4)The main effect test and correlation analysis showed that the N application rate,CRU proportion and the interaction effect of CRU release longevity and CRU proportion had the greatest effect on winter wheat yield.In the case of low CRU proportion(10%～40%),the wheat yield could be increased by applying the CRU with long-release longevity;when the CRU proportion was high(40%～100%),the yield increase effect of the CRU with short-release longevity was better.(5)The error between the measured winter wheat yield and the predicted value of the winter wheat yield model was-9.8%～4.0%,and the winter wheat yield could be predicted accurately by using the CRU proportion and the CRU release longevity through the F-test and the field applicability test of the model.(6)Comprehensive field production survey and Response surface methodology(RSM)partial derivative analysis,the conventional N application rates(225kg/ha)was reduced by 20%～30%,CRUs with controlled release longevity of 60d～150d and CRU proportion of 24%～64% were the best choices for increasing wheat yield and reducing N application rates to promote the ‘Reduction and Efficiency of Chemical Fertilizers’ policies and environmental protection.