| Abstract: In order to determine the nitrogen and potassium ratio in nutrient liquid suitable for high-quality tomatoes in plastic greenhouse in early spring in suburbs of Beijing, four nitrogen and potassium ratios (1 : 1.2, 1 : 1.5, 1 : 1.8, 1 : 2.1) were set up and their effects on tomato plant, fruit traits, quality and yield were analyzed. The results showed that with the increase of potassium content, plant height, daily average growth rate of plant height, number of leaves and daily average growth number of leaves all increased first and then decreased, and reached the peak value at the ratio of N : K＝1 : 1.5. The fruit transverse diameter, longitudinal diameter, soluble solid content, total sugar content and sugar-acid ratio all increased first and then decreased with the increase of potassium content, and reached the peak value at the ratio of N : K＝1 : 1.8, in which the peak value of soluble solid content, total sugar content and sugar-acid ratio were 7.47%, 7.03% and 7.96, respectively. The number of fruit per ear, plot yield, yield per 667 m2 and yield of commercial fruit per 667 m2 of different treatments were all significantly different, and reached peak value at the N : K＝1 : 1.5, of which the peak value were 2 984.3 kg and 2 583.5 kg, respectively. The proportion of navel rot fruit at N : K＝1 : 1.5 was the lowest (13%), which was 6-8 percentage points lower than that in other treatments. In production, it was necessary to adjust the nitrogen and potassium ratio of nutrient liquid according to the production purpose, the N : K＝1 : 1.5 could meet the needs of the pursuit of yield, and the N : K＝1 : 1.8 could take into account the demand of the pursuit of yield and quality. |