| Non-heading Chinese cabbage(Brassica rapa L.ssp.chinensis),originated from China,is widely cultivated in China,and accounts for 30%to 40%of the vegetable cultivating areas in the cities of middle and lower reaches of the Yangtze River.It is a common practice in the cabbage production to apply fertilizer excessively and blindly,This not only causes increased production costs,but also leads to compacted soil,soil acidification,water contamination and other issues.Nitrogen fertilizer reduction technology aims to find the balance between nitrogen requirement and soil nutrient supply in crops,and to improve the utilization of fertilizer on the basis of ensuring high yield and high quality of crops,in order to reach the balance of economic benefits,ecological benefits and social benefits.In this experiment,a non-heading Chinese cabbage cultivar 'Qinglan' was selected as the test material to carry out the following research:(1)A total of 8 nitrogen fertilizer concentrations were set at 0,1,2,4,6,8,10,12 kg/667m2 in this study.The effects of nitrogen fertilizer on the growth,yield and quality of non-heading Chinese cabbage were observed by reducing nitrogen fertilizer in spring,summer and autumn,constructing different nitrogen fertilizer-yield models in different seasons and further forecasting the appropriate amount of nitrogen in the corresponding season.(2)Continuous nitrogen fertilization experiment was carried out in the same field to explore the effect of continuous nitrogen fertilizer on the growth,yield and quality of non-heading Chinese cabbage,and to analyze the effectiveness of nitrogen fertilizer reduction in continuous production.(3)Based on the reduction of nitrogen fertilizer,the effects and results of three different soil conditioners on the field production of non-heading Chinese cabbage were studied,and eventually providing the gist for the application of soil conditioner in the application of nitrogen fertilizer reduction in non-heading Chinese cabbage.The main research findings are as follows:1 The results of nitrogen fertilizer reduction test in spring,summer and autumn indicate that the relationship between yield and nitrogen fertilizer application in different seasons can be described by the quadratic equation in the regression model,With the increase of nitrogen application,the yield will increase first and then decrease.Compared with the plant of N12(CK Nitrogen 0 reduction)treatment,the yield of N6(Nitrogen 50%reduction)did not change significantly,the content of nitrate decreased,the content of Vc increased,soluble sugar and soluble protein and organic acid content were non-significant.According to the simulation equation,it is predicted that the recommended amount of nitrogen fertilizer in spring and autumn can be reduced by 19.1%and 30.0%respectively compared with the conventional fertilization,summer regression model was poorly fitted.In terms of three sowing periods,the yield was positively correlated with the amount of nitrogen fertilizer,and nitrate was negatively correlated.2 Continuous nitrogen fertilizer reduction experiment was.carried.out in the same field,the result has shown that after the second continuous cropping of nitrogen fertilizer,the contents of soluble sugar,soluble protein,Vc and organic acid content decreased,the nitrate content significantly increased and the yield decreased significantly than the previous crop.Continuous nitrogen fertilizer reduction is not conducive to maintain high yield of vegetable crops and lead to quality decrease,which made it difficult to achieve the purpose of continuous high yield of production.3 Under the condition of nitrogen fertilizer reduction,the application of soil conditioner significantly increased the yield of non-heading Chinese cabbage and the content of soluble protein,decreased the content of organic acid and the content of nitrate,and contributed to the increase of economic benefit.When the soil conditioner application is 40 kg/667m2(C40),the economic benefits were optimal. |
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