The effects of cluster pruning and the K:N ratio on greenhouse tomato yield and quality

Both the number of fruit in a cluster and the K:N ratio in the nutrient solution can affect the yield and quality of greenhouse-grown tomatoes (Solanum lycopersicum L.). To prevent the loss of photoassimilates to fruit at the end of clusters, which rarely mature and ripen, it is necessary to know the optimal number of fruit in a cluster under different nutritional conditions. In this study, we investigated the effects of cluster pruning and the K:N ratio in the nutrient solution on yield, yield components, and quality of tomato fruit grown in a greenhouse. The treatments consisted of five levels of cluster pruning (control or unpruned, and retaining 4, 6, 8, and 10 fruit per cluster), and two levels of the K:N ratio in the nutrient solution (2:1 and 4:1). Under both K:N ratios, the unpruned and ten-fruit cluster treatments had the highest yield. These treatments also had the highest unripe fruit weight. The highest ripe fruit dimensions and weight were found in four-fruit clusters fed by the solution with a K:N ratio of 2:1. Fruit firmness was higher than in other treatments in four-fruit clusters when the K:N ratio was 4:1. Fruit harvested from the four-fruit cluster treatment had the highest titratable acidity compared to the other treatments, while the K:N ratio did not have a significant effect on this trait. The highest total soluble solids were found in fruit obtained from four-fruit clusters grown with the 2:1 K:N solution. In general, we concluded that under our growing conditions, keeping ten fruit in a cluster and adjusting the K:N ratio to 2:1 in the nutrient solution is advisable for the cultivar of cherry tomato used in this study, although some fruit quality factors may be improved when the number of fruit in clusters is manipulated.