Tomato cultivated in spring at a low plant density and then increasing the effective plant density by means of allowing side shoots to develop, when daily light integrals are high, appears a promising way of increasing spring-season tomato crop fruit number per square meter and to produce fruits of more uniform size; and has the added advantage that fewer plants have to be purchased per cropped area. The effects of side shoots on fruit uniformity and yield of tomato crop were evaluated in a trial carried out from March to July 1998 in a greenhouse in Almería (south-eastern Spain). The initial plant densities were 2.4 and 3.0 plants m-2, in the case of non-grafted plants, which had one main stem; and 1.2 plants m-2 in grafted plants, which had two main stems (2.4 shoots m-2) at setting. From April, by allowing side shoots to develop (when the treatment required), population densities of 2.4; 3.0 and 3.5 shoots m-2 (grafted and non-grafted plants) were raised; and 3.0 non-grafted plants m-2 without side shoots during all cropping-season treatment was maintained. The results showed that grafted tomato plants set with two main stems presented the same final yield but produced fruits of more uniform size than non-grafted plants set with one main stem and double initial plant density. In a range from 2.4 to 3.5 shoots m-2, increasing shoot density increased early yield and produced fruits of more uniform size but presented no effect on the mean fruit weight and the final yield. The addition of side shoots (3.0 shoots m-2) was accompanied by a 20% loss of final yield but from 21% and 39% fewer non-grafted and grafted plants, respectively, and produced fruits of more uniform size, relative to the high initial density treatment (3.0 plants m-2 without side shoots).
Lycopersicon esculentum; greenhouse; soilless cultivation; nutrient film technique
