Effects Of Nitrogen Reduction On Rapeseed Fertilizer With Organic Fertilizer And Controlled-release Urea

As an important oil crop in China,rapeseed has a large demand for fertilizers（especially nitrogen fertilizers）.Excessive fertilization has no positive effect on the growth of rape,and it will bring a series of environmental problems while increasing the cost of fertilization.Therefore,it is necessary to study the nitrogen application rate of rape,under the premise of not increasing yield,reducing the number of fertilization,improving fertilizer utilization,and providing a theoretical basis for chemical fertilizer reduction application technology.By applying common urea,controlled-release urea and organic fertilizer to rape,the effects of different fertilizers on rape yield,nitrogen accumulation,nitrogen fertilizer utilization,economic benefit,soil nutrients and soil enzyme activity were studied.It provides a theoretical basis for the organic substitution of chemical fertilizers and the application of new fertilizers.The main findings are as follows:1.With the growth of rapeseed,the nitrogen accumulation in the seedling stage and the flowering stage of rapeseed increased continuously,reaching the highest between the flowering stage and the podding stage,and then began to decrease.Between the podding stage and the mature stage,the nitrogen accumulation in the stems and leaves of rapeseeds decreased drastically.With the increase of nitrogen application rate,the nitrogen accumulation of rape shot with common urea and organic fertilizer increased continuously.When the nitrogen application rate of organic fertilizer treatment exceeded180 kg/hm²,its nitrogen accumulation began to decrease.The accumulation of nitrogen in all parts of rapeseed treated with organic fertilizer was higher than that of urea treatment;compared with that without nitrogen fertilizer,the accumulation of nitrogen in the stalks,pods,and grains of organic fertilizer at the mature stage increased by 16.4%-54.81%,18.86%-40.66%,21.6%-59.68%;under the same nitrogen application rate,the nitrogen accumulation of rapeseed grains treated with organic fertilizer was 16.7%-149.3%higher than that of ordinary urea.2.Appropriate amount of nitrogen and organic fertilizer can increase rapeseed yield.Increasing the amount of nitrogen applied greatly increased the yield of rape.The nitrogen application rate of common urea is 135-180 kg/hm²,and the optimal yield of rapeseed is3146 kg/hm².When the nitrogen application rate of common urea is 135-180 kg/hm²,the rapeseed reaches the best yield（3146 kg/hm²）,and when the organic fertilizer nitrogen application rate is 135 kg/hm²,the rapeseed output also reaches the maximum（3833kg/hm²）.Continue to increase the amount of nitrogen applied,increasing rate began to decline,rapeseed production decreased due to excessive fertilization.The utilization rate of rapeseed with organic fertilizer was higher than that of rapeseed with ordinary urea,and the output was about 351-1510 kg/hm² higher than that with ordinary fertilizer.The effect of increasing yield was obvious.The linear and platform equation fitting results showed that the optimal dosage of nitrogen fertilizer was 147 kg/hm² without applying organic fertilizer,at which time the platform yield（3052 kg/hm²）was reached;when applying organic fertilizer 2250 kg/hm²,nitrogen application was 90kg/hm²,the output of rape had reached 3277 kg/hm²,which was higher than the platform output.This showed that,relating to the recommended amount of nitrogen fertilizer（141 kg/hm²）,the application of organic fertilizer 2250 kg/hm² can replace 36.17%nitrogen fertilizer.3.The results of field trials indicated that the controlled-release urea was not completely released early in the growth of rape,so the effect was not obvious.From the beginning of the flowering period,the cumulative amount of nitrogen,phosphorus and potassium nutrients treated with CRU_180-1 was significantly higher than that of N_180-1,which was the same as that of N_180-3.The application of controlled-release urea increased the accumulation of nutrients in various parts of the aerial part of rape during different growth stages,and achieved the effect of ordinary urea fertilization.The nutrient release of controlled-release urea is basically consistent with the nutrient requirements of rape during the growth period,and it can make up for the labor cost caused by fractional fertilization.The yield of rapeseed treated with CRU_180-1 was 3313 kg/hm²,which was1152 kg/hm² higher than the single basal application,the yield increased by 53.31%,and the economic benefit increased by 5270 yuan/hm².There was no significant difference from the treatment with N_180-3.The effect of organic fertilizer application was better than that of controlled-release urea,and the yield was 634 kg/hm² higher than that of controlled-release urea.4.Appropriate amount of fertilization can increase soil nutrient content and soil enzyme activity.Compared with ordinary urea,the application of organic fertilizer and controlled-release urea can significantly improve soil nutrients and enzyme activity.The soil nutrient content of organic fertilizer treatment was higher than that of ordinary urea treatment,and the contents of organic matter,total nitrogen,available phosphorus and available potassium were higher by 1.7%-7.9%,1.2%-7.5%,7.5%-19.2%and 1.8%-9.3%.Soil invertase,urease and catalase activities were higher than ordinary urea treatment too.Controlled-release urea CRU_180-1 treatment was 24%,13.66%,37.66%,and 10.17%higher in organic matter.The activities of soil invertase,urease and catalase in seedling stage,flowering stage,podding stage and the mature stage were 5.17%-21.84%,4.06%-17.43%,2.41%-4.33% higher..