A greenhouse experiment was conducted to study the effect of boron in dry bean plants (Phaseolus vulgaris L.) grown in pots. The treatments consisted of 0, 1, 2, 4, 8, and 16 kg.ha-1 of boron in the form of borax. Two identical experiments were carried out during the winter (June/July) and the spring (September/October) seasons. In the winter experiment, the boron deficiency symptoms were shown only by the control plants. In those conditions, the high concentrations of Ca and Mg and the low temperatures affected the boron absorption of the plants. The application of 1 kg.ha-1 of boron was sufficient to reduce the visible symptoms of B deficiency, and increased the dry weight of the shoots. At the rate of the 2 kg.ha-1 B or above there was excess of boron in the dry matter of the shoots. In the spring experiment there was no deficiency symptoms in the plants and the boron concentration was adequate in the shoots. Also, the application of 2 kg.ha-1 of B or more increased the B concentration to excess. The results suggest that boron deficiency is relevant only in the winter and that excess of boron is a problem, causing toxicity, independent of the season.
boron deficiency; boron excess; dry beans; sazonal effect
