Study On The Effects Of Nitrogen And Potassium On Watermenlon In Plastic Geenhouse

In order to offer theoretical basis for reasonable and efficient fertilization on watermelon in plastic greenhouse this experiment using watermelon cultivar"JING XIN ER HAO"as material, with the combination of two factors and three levels experimental design, studied the effects of different nitrogen and potassium fertilizer on growth, development, yield and quality of watermelon in plastic greenhouse. The experiment got the following main results.1. With the conditions in experiment field, increasing nitrogen supply could improve vegetative growth, the main stem grew faster, but vegetative growth would impose restrictions on reproductive growth. The first female flower need more time for getting mature. The increase of potassium supply could also improve the vegetative growth of watermelon, but not the same obvious as the increase of nitrogen supply. And the increase of potassium could make the first female flower develop faster.2. With the same potassium supply, increasing nitrogen supply could improve the net photosynthetic rate of watermelon, but when the nitrogen supply got over129.68 kg/hm2, the net photosynthetic rate fell below. With the same nitrogen supply, increasing potassium supply could also improve the net photosynthetic rate. From the change of intercellucar CO2 contention and net photosynthetic rate, we can get the conclusion that the stomatal limitation is the main factor, which influence the net photosynthetic rate of watermelon. The nitrogen and potassium supply both could increase the chlorophyll content of watermelon leaves.3. The yields of all the treatments got 75.18%～89.94% of the target yield. And the yields of all the treatments applied fertilizer got 3.98%～19.63% more than CK treatment (N0K0). With the same potassium supply, the increase of nitrogen supply could improve the yield of watermelon. But when the nitrogen supply got over 129.68 kg/hm2, the effect on yield of nitrogen got mild. The potassium supply also had the effects on improving yield of watermelon, but not the same obvious as nitrogen supply.4. With the same nitrogen supply, the increase of potassium supply could increase the Vitamin C content, soluble protein content and soluble solids content of watermelon. And the increase of potassium supply can narrow the gap between the central soluble solids content and the limbic soluble solids content. With the same potassium supply, the increase of nitrogen supply could improve the quality characteristics above, but when the nitrogen supply was over 129.68 kg/hm2, the quality characteristics above became lower.5. In summary, with 129.68 kg/hm2 nitrogen supply and 158.55 kg/hm2or 237.83 kg/hm2 potassium supply, watermelon in plastic greenhouse could grow fast, get high yield and good quality. Considering the cost of fertilizer, it is appropriate to increase potassium supply properly in the basis of 158.55 kg/hm2potassium supply and 129.68 kg/hm2 nitrogen supply.