Pollination and yield of winter-grown greenhouse tomatoes as affected by boron nutrition, cluster vibration and relative humidity

Abstract

Problems with reduced yields owing to poor pollination where tomatoes are grown out-of-season in low cost greenhouses, motivated this study. Greenhouse tomatoes were planted in acid washed river sand. Four balanced nutrient solutions, with different boron (B) levels (0.02; 0.16; 0.32 and 0.64 mg l−1), were applied. The second flower cluster was covered with a transparent plastic bag and three relative humidity (RH) levels were applied to the isolated clusters. Dry (<10% RH) normal (60–75% RH) and moist (85–97% RH) air was constantly blown into the bags at ± 50 ml min−1. As a third factor at two levels, some of the clusters were vibrated daily with an electric vibrator (Poli-bee) and the controls not. The number of flowers per cluster, fruits per cluster, fruit set, weight of the cluster (yield), average fruit weight, seed production, fruit weight per number of seeds formed and fruits with blossom-end-rot (BER) were evaluated. Higher B-levels improved fruit set where trusses were not vibrated. A high RH reduced the number of seeds that developed per cluster, lowered cluster weights and the number of fruits per cluster and increased the incidence of BER. More BER developed on bigger fruit. Fruit set improved with cluster vibration, associated with more seeds and bigger fruit, especially under less humid con- ditions.