GROWTH AND TOMATO YIELD IN RESPONSE TO PLANT DENSITIES UNDER TWO PRODUCTION SYSTEMS

Abstract

The effect of plant density on the growth and fruit yield of tomato (Lycopersicon esculentum Mill.) was studied under greenhouse
and field conditions. Five plant densities were tested in greenhouse (1.7, 3.8, 6.8, 15.4 y 66.6 plants/m²) with plants pruned to leave only
three floral clusters and no lateral branches. In the field six plant densities were compared (1.1, 2.2, 4.4, 8.8, 17.7 y 35.5 plants/m²) with plants pruned when until they reached 1.90 m of hight, leaving two stems per plant. In both conditions water and nutrient restrictions were prevented by fertigation. In both production systems the accumulated biomass per m² increased with plant density, but maximum values required more heat units (HU) in the field than in the greenhouse. Under the greenhouse production system maximum biomass was 2.8 kg m^-2 with 66.6 plants/m² which was reached at 1885 HU, while under the field production system the maximum biomass
was 2.5 kg m^-2 with 35.5 plants/m² obtained at 2461 HU. In contrast, fruit yield showed an opposite response to plant density between the
two systems. In the greenhouse the highest amount of fruits (1620 fruits/m²) and fruit yield (80.2 kg m^-2) were attained at the highest
density of 66.6 plants/m² , although the best density for export quality fruits (equatorial diameter > 6.0 cm) was 6.8 plants/m², with 202 fruits/m² and 26.9 kg m^-2. Under field conditions, the maximum yield of exportable fruits (5.39 kg m^-2) was obtained in the lowest density
(1.1 plants/m²). Therefore the exportable yield in the greenhouse system with plants pruned to have a determinate growth, is five times
higher than that obtained under field conditions with tall plants having a nearly indeterminate growth habit.