Effects of combined top application of inorganic nitrogen and potassium on the yield and quality of overwintering tomato in greenhouse

Proper application of inorganic N and K fertilizer was important for overwintering tomato cultivation. Urea and potassium sulfate were dominant fertilizers used in local. Effects of top application of inorganic nitrogen-potassium fertilizer with different formulas on the growth, yield and quality of an overwintering tomato cultivars were studied in this paper. Results showed that proper nitrogen-potassium fertilization could maintain the balance of vegetative and reproductive growth of tomato. Balance application of N and K could promote the growth of tomato, increase the trusses number, fruit number and fruit weight effectively as well. In addition, contents of Vc, reducible sugar and organic acid of tomato were raised, which resulted in a better quality. From the point of view of whole cultivating process of overwintering tomato, the most appropriate formula of nitrogen-potassium fertilizer(N∶K2O) for the purpose of top addressing should be 1∶1.2～1.3; However, since the demanding of N and K varied with different growth durations, batching fertilization management differed with different growth durations should be adopted. At the incipient stage of vegetative growth, both the vegetative and reproductive growth are vigorous, the appreciate ratio of N and K2O should be 1∶1; at the middle stage, as a great deal of K was removed with the harvest of fruit, the dosage of K application should be increased therefore, thus the appreciate ratio of N and K2O should range from 1∶1.2 to 1∶1.4; at the late stage, vegetative growth declined and balanced application of fertilizer should be paid more attention, the ratio of N and K2O should be around 1∶1.2.