The simultaneous effect of water supply and radiation on tomato flowering and setting

The main season for forcing greenhouse-grown tomatoes begins in late winter or early spring in the northern Temperate Zone. During this period, solar radiation and other environmental factors determine the timing of flowering and fruit setting. A spring tomato-forcing trial tested the progression and dynamics of tomato flowering and fruit setting in relation to water supply. Four intermediate varieties were tested, and 24 randomly selected plants were examined. The ecological conditions (temperature, PAR, relative humidity) were also measured. We studied flowering and fruit setting of tomatoes irrigated with two different water supplies (180 and 90 l/plant during the entire season). We determined the beginning and end of flowering and fruit setting, and the number of flowers and fruits in each truss. With a higher water supply the beginning of flowering is later and intensity is slower than with a lower water supply. The correlations between the intensity of flowering and accumulated PAR in each truss were: y = 7E - 16x(2) - 6E-08x + 1.6874 R-2 = 0.5027 for the 180 l/plant irrigation treatment y = 1E-15x(2) - 1E-07x + 2.5429 R-2 = 0.8571 for the 90 l/plant irrigation treatment These correlations concerning fruit setting were: y = 7E - 16x(2) - 6E-08x + 1.5837 R-2 = 0.6348 for the 180 l/plant irrigation treatment y = 1E-15x(2) - 8E-08x + 1.9299 R-2 = 0.7447 for the 90 l/plant irrigation treatment We concluded that extra water retarded flowering and fruit setting. One flower required an average of 30 MJ of accumulated PAR.