Studies On Effects Of The Application Rate Of Chemical Nitrogen Fertilizer On Yield And Quality And Nitrogen Fertilizer Utilization Ratio Of Vegetables

In order to provide the rational application rate of chemical nitrogen for rational culture of vegetables. The trace technique of l5N-labelled nitrogen was used to study; and effects of the application rate of chemical nitrogen fertilizer on yield and quality (nitrate content, protein content, soluble sugar content, rough fiber content and Vitamin C content) nitrogen fertilizer utilization ration of four vegetables(Water spinach; Asparagus lettuce; Brassica chinensis; Radish) have been studied by pot experiment. The results were shown as follows:There was significantly correlation between vegetables yield y (g/pot) and nitrogen fertilizer application rate x (gN/kg soil); the parabola model regression equation could be expressed as:Water spinach, FW:y= 14.81 +1208.60x-2959.52x2, DW: y = 3.10 +H6.38x-277.78x2; Asparagus lettuce, FW:y= 104.21 +2476.31x-5181.97x2, DW:y = 0.95 +179.58x-390.60x2; Brassica chinensis, FW: y= 13.23 +1610.10x-3324.44x2, DW: y = 1.35 +94.59x- 193.52x2; Radish, FW: y = 31.07 +3190.47x - 8320.60x2, DW: y = 3.85 +228.28x - 591.81 x2.The yield of four kinds of vegetables increased with increasing of chemical nitrogen application rate. While exceeding certain chemical nitrogen application rate, the yield of four vegetables decreased. Rational chemical nitrogen application rate could increase the yield of the vegetables.Increasing the application rate of chemical nitrogen fertilizer could increase Vitamin C content of the esculent part of four vegetables in certain chemical nitrogen application rate range; but increasing the nitrogen application rate would decrease Vitamin C content of vegetables after exceeding certain nitrogen application rate. Suitable chemical nitrogen application rate could promote the synthesis and accumulation of vegetables protein, increase the content of soluble sugar of vegetables, and chlorophyll content in functional leaves of vegetables, lengthen the function period of the vegetables function leaves, strengthen the activation of vegetables NR, reduce the accumulation of the vegetables nitrate, change inherent quality and mouthfeel of the esculent part of vegetables.With the increasing of chemical nitrogen application rate, total nitrogen absorptionand 15N% of vegetables plant were increased. Rational using the chemical nitrogen could expectively improve the absorption from chemical nitrogen and from soil nitrogen. The chemical nitrogen utilization ratio and the residual ratio and recovery ratio in the vegetables soil would decrease with the increasing of chemical nitrogen application rate, while the loss rate increased. Rational chemical nitrogen rate could improve the utilization ratio of the chemical nitrogen, reduce the loss ratio of the chemical nitrogen.Under guaranteeing the vegetables high yield and good quality and low pollution, the rational chemical nitrogen application rate of four kinds of vegetables is, Water spinach: 0.1400-0.1700gN/kg soil; Lettuce: 0.1750-0.2125gN/kg soil;Brassica chinensis: 0.1750-0.2125gN/kg soil; Radish: 0.1260-0.1530gN/kg soil.