Effect Of Chemical Nitrogen Fertilizer Application Rate And Organic-inorganic Compound Fertilizer On Yields And Quality Of Vegetables

In order to develop and popularize organic-inorganic compound fertilizer for vegetablecrops, the effects of chemical nitrogen fertilizer application rate on yield and quality (nitratecontent, protein content, soluble sugar content, rough fiber content and Vitamin C content) of 4vegetables(Water spinach, Asparagus lettuce, Pak-choi, Radish)and nitrogen fertilizerutilization ration have been studied by pot experiment using ¹⁵N trace technique. Underguaranteeing the vegetables high yield, and good quality and low pollution, the rationalchemical nitrogen application rate of 4 vegetables have been obtained. And the effects oforganic-inorganic compound fertilizer on the photosynthetic characteristic, key enzymeactivities (such as sucrose synthase, sucrose phosphate synthase and nitrate reductase) ofcarbon-nitrogen metabolism, yields and quality (such as the content of vitamin C, soluble sugar,nitrate, inferior nitrate, coarse fibred and amino acids) of lettuce and Pak-choi are studied byfield plot experiment on the basis of this research conclusion. The results are shown as follows:1. There is a significant correlation between vegetables yield y (kg/pot) and nitrogenfertilizer application rate x (kg urea/pot); the parabola model regression equation could beexpressed as:Water spinach, FW:(?)=-14816x²+85.496x+0.0149;Asparagus lettuce, FW:(?)=-25951x²+175.23x+0.1042;Brassica chinensis, FW:(?)=-16647x²+113.93x+0.0133;Pak-choi, FW:(?)=-41666x²+225.75x+0.0311.2. The yield of 4 vegetables will increase with the increasing of chemical nitrogenapplication rate, but if the chemical nitrogen application rate is exceeded, the yield of fourvegetables will decrease. Rational chemical nitrogen application rate could increase the yieldof the vegetables.3. Increasing the application rate of chemical nitrogen fertilizer could increase Vitamin Ccontent of the esculent part of four vegetables during certain chemical nitrogen application rate range; but increasing the nitrogen application rate would decrease Vitamin C content ofvegetables after exceeding certain nitrogen application rate. Rational chemical nitrogenapplication rate could promote the synthesis and accumulation of vegetables protein, increasethe content of soluble sugar of vegetables, and chlorophyll content in functional leaves ofvegetables, lengthen the function period of the vegetables function leaves, strengthen theactivities of vegetables, reduce the accumulation of the vegetables nitrate, increase inherentquality and mouth feel of the esculent part of vegetables.4. With the increasing of chemical nitrogen application rate, total nitrogen absorption and¹⁵N% of vegetables plant are increased. Rational chemical nitrogen application rate couldsignificantly improve the absorption from chemical nitrogen and from soil nitrogen. Thechemical nitrogen utilization ratio, residual ratio and recovery ratio in the vegetables soil woulddecrease with the increasing of chemical nitrogen application rate, while the loss rate willincrease. Rational chemical nitrogen rate could improve the utilization ratio of the chemicalnitrogen, and reduce the loss ratio of the chemical nitrogen.5. Under guaranteeing the vegetables high yield, good quality and low pollution, therational chemical nitrogen application rate of four kinds of vegetables is as follows:Water spinach: 0.1400～0.1700 gN/kg soil; Lettuce: 0.1750～0.2125 gN/kg soil;Pak-choi: 0.1750～0.2125 gN/kg soil; Radish: 0.1260～0.1530 gN/kg soil.6. Organic-inorganic compound fertilizer could increase the content of chlorophyll and netphotosynthetic rate in the function leaves during middle and late growth stages of lettuce andPak-choi. Organic-inorganic compound fertilizer could significantly enhance the activities ofsucrose synthase(SS), sucrose phosphate synthase(SPS) and nitrate reductase(NR) in thefunction leaves during middle and late growth stages of lettuce and Pak-choi as compared tothe treatments of chemical fertilizer and farmer fertilization practice.7. Organic-inorganic compound fertilizer could promote the growth of vegetables, andthus increase the yields and quality of lettuce and Pak-choi. There is not a significant differencefor the yield of lettuce and Pak-choi between the treatments with organic-inorganic compoundfertilizer and farmer fertilization practice; while there are significant differences at 1% levelbetween the treatments with organic-inorganic compound fertilizer and chemical fertilizer. Andorganic-inorganic compound fertilizer could significantly increase the content of Vc and soluble sugar, and decrease the accumulation of nitrate and inferior nitrate and remain adequatecoarse fibre content in esculent part of lettuce and Pak-choi. It could obviously promotenutrient and health quality of vegetable crops. Net incomes and output/input ratio from thetreatment of organic-inorganic compound fertilizer was the highest among three treatments.Organic-inorganic compound fertilizer could significantly increase economic profit ofvegetables production.8. Protein content in esculent part of lettuce with organic-inorganic compound fertilizerwill be increased as compared to the treatments with chemical fertilizer and farmer fertilizationpractice; but there isn't a significant effect on aspartic acid, phenylalanine, isoleucine andtyrosine. The content of total nitrogen and protein nitrogen in esculent part of Pak-choi fromthe treatment with farmer fertilization practice is the highest among these three treatments; thefollowing is the treatment with organic-inorganic compound fertilizer; the lowest is thetreatment with chemical fertilizer. The content of aspartic acid, alanine and isoleucine of thetreatment with organic-inorganic compound fertilizer is the highest in esculent part of Pak-choi;while there is not a significant difference between these three treatments.