Study On The Appropriate Nitrogen Application Rate For Vegetable Rapeseed

The development of vegetable rapeseed is an important way to expand the multi-functional use of rape and is important for enriching the variety of edible vegetables,providing higher nutritional value food for the population and increasing farmers’income.As a new agricultural industry,the lack of scientific application techniques and the problem of nitrogen(N)application are prominent.Currently,most of the production is managed with reference to conventional rapeseed application resulting in failure to achieve yield potential,or with reference to vegetable application resulting in over-application,both of which are detrimental to the development of a high quality vegetable rapeseed industry.In order to clarify the appropriate N application rates for vegetable rapeseed,a field experiment of N application rates for autumn-sown vegetable rapeseed was conducted in Wuhan,Hubei Province,in 2021 and 2022,and a field experiment of N application rates for summer-sown vegetable rapeseed was conducted in Dali,Yunnan Province,in 2022,to investigate the effects of N application rates on vegetable rapeseed yield,quality and economic efficiency,and to compare the differences in fertility and yield of vegetable rapeseed in different seasons.The study was conducted to determine the appropriate N fertilizer application rates and application principles for vegetable rapeseed,with a view to providing a basis for scientific N application to vegetable rapeseed.The main results of the study are as follows:(1)N fertilization significantly increased the yield of vegetable rapeseed,and the application rates of N fertilizer could regulate the yield structure ratio.The maximum yield of vegetable rapeseed in autumn and summer sown was 135 kg/hm~2 and 180 kg/hm~2respectively,with yields of 24.85 t/hm~2 and 16.98 t/hm~2 respectively.The appropriate N application rates resulted in a more harmonious yield distribution and increased the yield of first and second stage vegetable rapeseed.The fertility period of autumn-sown vegetable rapeseed was longer than that of summer-sown vegetable rapeseed,and the harvest interval was 11～41 d.The temperature productivity of summer-sown vegetable rapeseed was lower than that of autumn-sown vegetable rapeseed,with a decrease of 15.6%～48.9%compared to autumn-sown vegetable rapeseed.(2)The appropriate application rates of N fertilizer significantly improved the quality of vegetable rapeseed.The quality of vegetable rapeseed was significantly improved at 135kg/hm~2 and 180 kg/hm~2 of N fertilizer for autumn and summer sown vegetable rapeseed respectively.In the autumn-sown vegetable rapeseed experiment,compared with the treatment without N fertilization,each N fertilization treatment increased shoots weight,shoots thickness,number of leaves,leaf width and leaf length by 56.1%to 236.2%,33.3%to 83.3%,39.5%to 57.9%,12.2%to 98.0%and 8.9%to 96.2%,respectively,and each N application treatment decreased soluble sugar content by 28.6%to 37.3%.each N application treatment increased Protein,nitrate and vitamin C content by 3.4%～99.2%,0.9%～11.9%and 17.2%～26.0%,respectively;each N application treatment decreased phosphorus content by 2.6%～21.3%and each N application treatment increased potassium,calcium,zinc and iron content by 0%～28.7%,8.7%～49.4%,11.4%～63.0%and 5.2%～53.1%,respectively.In the summer sown vegetable rapeseed experiment,compared to the treatment without N fertilization,each N fertilization treatment increased single shoots weight by 11.2%～47.0%,shoots length by 11.9%～32.4%,shoots thickness by 2.8%～7.6%,soluble sugar content by 16.4%～18.4%,protein content by 50.0%～64.2%,phosphorus content by 15.3%～28.5%,potassium,calcium,magnesium,zinc,iron calcium,magnesium,zinc and iron content increased by 4.3%～24.9%,18.2%～34.8%,28.9%～48.4%,27.1%～102.4%and 4.0%～50.7%.(3)N application rates significantly influenced the N utilization efficiency of vegetable rapeseed.The appropriate N application rates had a significant effect on the N uptake rate,N agronomic utilization rate and N contribution rate of vegetable rapeseed.The N use efficiency indexes in the autumn and summer sown vegetable rapeseed experiments reached the maximum values at 135 kg/hm~2 and 180 kg/hm~2 of N application rates,respectively,and decreased when the N application rate continued to increase.In the autumn sowing vegetable rapeseed,N fertilizer bias productivity decreased gradually with increasing N fertilizer use,with 25.0%to 90.9%and 48.3%to 97.0%decrease in each treatment compared with 45 kg/hm~2.(4)N fertilizer use significantly influenced the efficiency of rape cultivation for vegetable rapeseed.Appropriate N application rates have a significant effect on N fertilization uptake and utilization,N fertilization agronomic utilization and N fertilization contribution in vegetable rapeseed.The N use efficiency index reached a maximum at 135kg/hm~2 and 180 kg/hm~2 of N fertilization in the autumn and summer sown vegetable rapeseed experiment respectively,with net incomes of 76,212 yuan/hm~2 and 39,672yuan/hm~2,2.3 and 2.8 times higher than those for the treatment without N fertilization.The maximum yield to production ratio was 2.26 and 2.09 for autumn and summer sowing at135 kg/hm~2 and 180 kg/hm~2 of N application respectively.In summary,by fitting yield,production value and important quality indicators,the appropriate N application rate for maximum yield was 110 kg/hm~2,for maximum production value was 135 kg/hm~2 and for major quality was 135 kg/hm~2 in the autumn-sown vegetable rapeseed trial in Wuhan,Hubei.Under the experimental conditions,the appropriate N application rate was 210 kg/hm~2 for maximum yield,155 kg/hm~2 for vegetable rapeseed with maximum production value,and 160 kg/hm~2 for major quality.