Planting density and training in grafted indeterminate tomato plants grown under plastic cover

ABSTRACT Grafting in tomato is a regular production practice aimed to control vascular diseases. Even though grafted plants are more expensive, when a vigorous rootstock is used the plants can be trained using multiple leading shoots, reducing the number of plants per hectare. Seeking to reduce direct labor cost and the cost of the plants, this experiment tested 29,000, 26,000, 23,000 and 20,000 leading shoots/ha, training the plants with either 3 or 4 leading shoots each. Plants were grown in a polyethylene-covered greenhouse, transplanting at the end of January; the harvest was done from May until August, quantifying yield, fruit size and leaf area, analyzing the data with quadratic regression. Yield increased from 81 to 103 t/ha when comparing the lowest and the highest density of shoots/ha, but the difference between the training systems was only 4 t/ha. When the two extremes of the density were compared (29,000 vs 20,000 shoots/ha), leaf area increase by 2%, the equatorial fruit diameter increased from 7.4 to 7.8 cm, and the weight increased from 178 to 199 g/fruit. The training system showed difference of 0.1 cm in fruit diameter, while the leaf area and fruit weight were not affected. While the lowest density of shoots per hectare had a 30% reduction in direct labor cost, the largest net profit margin was observed when using 3 shoots/plant and 29,000 shoots/ha.