Effect Of Nitrogen Fertilizer Amount On Soil Inorganic Nitrogen And Winter Rape Growth

Rape is a crop that requires a lot of nitrogen,and the application of nitrogen fertilizer has an important impact on the growth and development of rape and its yield and quality.Too low application rate of nitrogen fertilizer will affect the yield potential of rape varieties;too high application rate will have a negative impact on rapeseed yield,nitrogen utilization efficiency and soil inorganic nitrogen residues.Therefore,studying the effects of nitrogen fertilizer rates on winter rapeseed yield and soil inorganic nitrogen content can provide a basis for research on rapeseed high-yield and high-efficiency nitrogen fertilizer management strategies and nitrogen fertilizer environmental thresholds.This study carried out direct-seeded winter rape field trials in Hengyang County and Anren County,Hunan Province,and analyzed the growth and development,yield and yield composition of two new varieties,Dadi 199 and Fengyou 823,as well as the effects of nitrogen utilization efficiency and soil inorganic nitrogen content.The response differences of different nitrogen fertilizer rates（0,90,180,270,360 kg N/hm²）provide a reference for nutrient management of winter rape under current production conditions.The main results are as follows:1.The research results of soil inorganic nitrogen residues showed that with the increase of nitrogen fertilizer dosage,the soil ammonium and nitrate nitrogen residues also increased,with N360 treatment being the highest,and the Hengyang test site was significantly larger than the Anren test site.Compared with N0,the residual ammonium nitrogen in the four different nitrogen application rates increased by0.5-3.0mg/kg in Anren area,0-6.3mg/kg in Hengyang area,and 0.1-4.5mg/kg in Anren area,Hengyang area increased by 1.9-6.3mg/kg;the increase in nitrogen application also led to an increase in the apparent loss of nitrogen fertilizer,with N360treatment being the highest,Dadi 199 and Fengyou 823 in Anren area,and Dadi 199and Fengyou 823 in Hengyang area respectively.169 mg/kg,134 mg/kg,207 mg/kg and 223 mg/kg;compared with N0,Four different nitrogen application rates increased by-20-171 mg/kg in Anren area and 0-252 mg/kg in Hengyang area.2.The research results of rapeseed yield and yield component factors show that the yield of Fengyou 823 continued to increase with the increase of nitrogen fertilizer,and reached the maximum under N₃₆₀treatment,which was 2350kg/hm²and2670kg/hm²in Anren and Hengyang,respectively;Yield first increased and then decreased,reaching the maximum value under N₁₈₀treatment,2283kg/hm²and2487kg/hm²in Anren and Hengyang,respectively.It can be seen that Fengyou 823responds better to nitrogen fertilizer;calculated according to the relationship between nitrogen application rate and yield In Chuanren and Hengyang areas,the recommended nitrogen fertilizer dosage for Dadi 199 is 246kg/hm²and 243kg/hm²,and Fengyou 823 is 412kg/hm²and 267kg/hm²,respectively.With the increase in the amount of nitrogen fertilizer,the number of siliques per plant,the number of grains per silique,and the thousand-grain weight continued to increase.The number of siliques per plant increased most obviously,followed by the number of grains per silique,but the nitrogen application rate exceeded 180 kg N/hm²,the increase is significantly reduced,so the difference between N₂₇₀and N₃₆₀treatments or between N₁₈₀and N₂₇₀treatments is mostly not significant.3.The research results of rapeseed oil and protein accumulation show that with the increase of nitrogen application,the rapeseed oil content decreases and the protein content increases.However,due to the increase in yield,both oil yield and protein yield increase,and the change trend is the same as the yield.According to the relationship between nitrogen application rate and oil yield,it is calculated that the recommended nitrogen fertilizer rates for Anren and Hengyang areas are 240kg/hm²and 238kg/hm²for Dadi 199,and 256kg/hm²and 350kg/hm²for Fengyou 823,respectively.4.The research results of the production-to-investment ratio show that the output-to-input ratio of the application of nitrogen fertilizer increased,but only the output-to-input ratio of Anren Fengyou 823 increased with the increase of nitrogen level.The N₃₆₀treatment was the highest,and the rest were the largest under the N₁₈₀treatment.The ratios are respectively,Anren Dadi 199(N₁₈₀)205%,Anren Fengyou823(N₃₆₀)200%,Hengyang Dadi 199(N₁₈₀)219%,and Fengyou 823(N₁₈₀)210%.According to the relationship between nitrogen application rate and production-input ratio,the recommended nitrogen fertilizer rates in Anren and Hengyang regions are calculated to be 226kg/hm²and 313kg/hm².5.The research results of rape nitrogen accumulation and nitrogen utilization efficiency show that the increase of nitrogen fertilizer application can significantly increase the nitrogen content in the shoots and the nitrogen accumulation in the shoots.With the increase of nitrogen fertilizer,the nitrogen content in the shoots continues However,the nitrogen accumulation first increased and then decreased,and most of them reached the highest value under the N₁₈₀treatment;with the increase of the nitrogen application rate,the nitrogen harvest index showed a decreasing trend,and the partial productivity of nitrogen fertilizer,the agronomic utilization rate of nitrogen and the nitrogen absorption rate decreased.However,the decline was not large.The partial productivity of nitrogen fertilizer decreased within 10%,and the agronomic utilization rate of nitrogen fertilizer decreased about 13kg;the surplus of nitrogen fertilizer also decreased significantly with the increase of the amount of nitrogen fertilizer,and the surplus of nitrogen fertilizer for N₀and N₉₀treatments was lower,N₂₇₀The nitrogen fertilizer surplus of N₃₆₀treatment is relatively high,mostly exceeding 100 kg/hm².