Plant spacing effects on yield of the greenhouse tomato

The effect of six equidistant spacings (23, 30, 38, 45, 53 and 60 cm, corresponding to 113 000, 74 000, 53 000, 40 000, 31 000 and 25 000 plants ha −1 , respectively) on fruit yield of four-row plantings of greenhouse tomato (Lycopersicon esculentum Mill. ’Jumbo’ and ’Ohio CR-6’) was studied over two spring and two fall seasons. Fruit was harvested and recorded separately from inside (shaded) and outside (exposed) plants of the four-row plantings. The total and marketable yield (g plant −1 ) of both inside and outside plants of both cultivars and in both seasons declined linearly with successive decreases in plant spacing. The rate of yield reduction of both cultivars was steeper in the spring, compared to the fall season. Also, the rate of yield reduction in the spring was steeper on inside compared to outside plants; but, in the fall, yield was similar for inside and outside plants. The response of the total and marketable yield (g m −2 ) of both inside and outside plants of both cultivars and in both seasons to decreasing plant spacing was described by a first or second degree polynomial. In the fall, the total and marketable yield of all plants increased (mostly) linearly with decreasing plant spacing; but, in the spring, yields were highest at intermediate spacings and declined with closer and wider spacings. We conclude that there is a greater potential for marketable yield increases, with any increase in plant density from a normal of 25 000 plants ha −1 to a maximum of 74 000 or 113 000 plants ha −1 for the cvs. Ohio CR-6 and Jumbo, respectively, in a fall greenhouse tomato crop than in a spring crop. However, with closer planting, a reduction in fruit size must be anticipated in both seasons.Key words: Lycopersicon esculentum Mill., plant spacing, greenhouse tomato