Effects Of Nitrogen Supply On The Growth And Quality Of Muskmelon

With the rapid development and demonstration of protected cultivation, the production of muskmelon broke through the limit of cultivation area between the south and north China. Muskmelon now can be cultivated in south China, but the low quality of muskmelon is the biggest problem in the production owing to the irrational application of chemical fertilizers. The effects of nitrogen supply on the growth and quality of muskmelon (Cucumis.melo. var.reticulatus Naud. cv. Chunli and Milinglong) were investigated in this paper by using substrate culture. The research consisted of three experiments: different nitrogen concentration experiment; different nitrogen forms experiment and different nitrogen concentration irrigation according to the different plant growth stage. The main results were as follows:1. Effects of four nitrogen concentrations (4mmmol·L^-1, 8mmmol·L^-1, 12mmmol·L^-1, 16mmmol-L^-1) on the growth and quality of muskmelon (cv. Chunli) were investigated. The results showed that the highest dry matter percentage of muskmelon fruit was obtained by 8mmmol·L^-1 nitrogen treatment. The highest chlorophyll content and NR activity were obtained by 12mmmol·L^-1 nitrogen treatment. Diurnal changes of net photosynthetic rate (Pn), stomatal conductance(Gs) and transpiration rate (E) of muskmelon leaves were a single-apex curve, whereas diurnal change of intercellular CO₂ concentration(Ci) was a "V" style in all treatments. The heaviest single fruit was obtained by 8 mmmol·L^-1 nitrogen treatment. Fruit nitrate content and TSS content increased significantly with increasing concentration of N in the nutrient solution. The highest vitamin C concentration, soluble sugar and sugar/acid ratio were obtained by Smmol·L^-1 nitrogen treatment. N concentration in all parts of muskmelon plant increased with increasing concentration of N in the nutrient solution. The P and Kconcentration in Fruit and leaf decreased as nitrogen concentration increased. Leaf Ca was significantly higher than other organs. Fruit Ca concentration increased whereas fruit Mg concentration decreased as nitrogen concentration increased. Smmmol·L^-1 nitrogen treatment was the best nitrogen concentration for the growth and quality of muskmelon.2. Effects of four nitrogen forms (NO₃^--N/NH₄⁺-N were 100:0, 75:25, 50:50 and 25:75, respectively) on the muskmelon growth and quality were investigated in this experiment. The results showed that different nitrogen forms significantly affected the dry matter accumulation percentage in different plant organs. Leaf nitrate reductase activity,...