EFFECTS OF PLANT DENSITY, LEAF REMOVAL AND LIGHT INTENSITY ON TOMATO QUALITY AND YIELD

Tomato quality is becoming more and more important for the consumer’s willingness to pay and therefore for the economy for producers and wholesalers. The objective of this paper was to investigate whether a combination of increased plant density and leaf removal could improve tomato yield and quality. In addition, the effect of light intensity on fruit soluble solid content was studied while outside radiation was low. Two tomato (Lycopersicon esculentum Mill.) cultivars, one round tomato, ‘Dometica’, and one cherry tomato, ‘Susanne’, were planted 13 October 2008 in the research glasshouse at Bioforsk Vest Særheim and harvested until 16 February 2009. Plants were grown at a plant density of i) 4.0 plants per m², without deleafing or with removal of one of three leaves, ii) 6.0 plants per m², with removal of one of three or three of six leaves, or iii) 8.0 plants per m² with removal of three of six or two of three leaves. Plants were subjected to light (HPS SON-T 400W) with an intensity of 180 or 260 µmol m^-2 s^-1 PAR during 18 hours a day. Results showed that highest yields were obtained using 6.0 plants per m² with removal of one of three leaves. Also higher light intensity increased yield, due to an increase in the number of fruits, while fruit weight was unaffected. Soluble solid content of the fruits was not affected by light intensity, plant density and leaf removal. In conclusion, manipulation of plant density in combination with leaf removal can be used to increase yield. An increase in light intensity increases yield but not fruit quality in terms of fruit size and fruit soluble solid content. Allocation of soluble solids to tomato fruits per m² ground area is not affected by cultivar, light intensity or truss-leaf ratio.