Application Of A Modified Solution Method Of Response Model On The Nitrogen Recommendation Of Corn

The variability of nutrients' recommendation rates consists of a puzzle for the crop scientist for a long time,and study on the gap between the two benefits further understanding the principle and optimization of fertilization.The objectives of this study are to establish the nutrient response models by using data from a field experiment,and to solve the function in order to obtain the site-specific recommendation rates of nitrogen,and four response models,the linear-plus-plateau model,ternary quadratic model,binary quadratic model and quadratic model have been used at the same time,soil nutrients are monitored and analyzed to investigate the suitability of fertilization.The study investigate the effect of response models on the nitrogen recommendation based on the response models recommended by the Ministry of Agriculture and Rural Affairs of the PRC(Method Recommended by Ministry,MRM),and evaluated the appropriateness of the N recommendation judged by the soil residual nitrogen(SRN).The experiment was conducted in Harbin with�3414�design,meaning three factors and four levels for nitrogen,phosphorus and potassium(N: 0,93.75,187.5,281.25 kg/ha;P2O5: 0,22.5,45,67.5 kg/ha;K2O: 0,37.5,75?112.5 kg/ha)respectively and 14 treatments in total.The experiment was a Randomized Complete Block(RCB)Design with four replicates.The experiment was conducted in 2017 located in Xiangfang district of Harbin City,China.The results are as follows:(1)The ANOVA results and multi-comparison results showed that the significant difference happened between N1(93.75 kg/ha)and N2(187.5 kg/ha).Based on this,nitrogen recommendations from different response models(three out of nine in total)were screened and chosen averaging the final nitrogen recommendation which was 156.65 kg/ha,while nitrogen recommendations was 207.27 kg/ha by traditional methods which involved nine nitrogen recommendations without screening.The gap between the two was 50.65 kg/ha,being 32.3% relatively.(2)Nitrogen recommendation by new method differs significantly from the nitrogen recommendations beyond the appropriate range indicated by ANOVA results,the gap is qualitative and huge,and mathematically averaging all nitrogen recommendations results in higher nitrogen recommendations.(3)The modified nitrogen recommendation,the provincially regional nitrogen recommendations and traditional nitrogen recommendation are respectively 156.65 kg/ha,180 kg/ha,207.27 kg/ha,and their corresponding corn yield are respectively 10700 kg/ha,10998 kg/ha,11174 kg/ha,with a range of 474 kg/ha in which the positive effect of nitrogen on corn yield,while the nitrogen recovery efficiencies(REN)are respectively 59.4%,56.2%,51.8%,which decreased by 7.6%.(4)Both NH4-N and NO3-N decreased from the top soil to the depth of soil profile,but the change in NO3-N was much obvious than that of NH4-N in the growth stages of corn.At the mature stage,this trend was the most obvious in the high nitrogen rates treatments,while this trend weakened in other nitrogen treatments.(5)Though soil NO3-N increased with nitrogen rate at the mature stage of corn,a sharp increase in soil NO3-N residual nitrogen was postulated from 147.45 kg/ha by solving a cubic regression equation,less than the N recommendation rate 156.56 kg/ha,supplying evidence for the latter.Thus,it was concluded that nitrogen recommendations by new method sacrificed a small level of yield,but decreased significantly the nitrogen rate and significantly increased the nitrogen use efficiency(expressed by nitrogen recovery)and soil residual nitrogen.