Foliar Fertilization with Boron on the Growth, Physiology, and Yield of Snap Beans

The snap bean is a vegetable of great worldwide economic importance. However, tropical soils have low amounts of nutrients, especially boron, a micronutrient essential for plant nutrition. The objective of this work is to verify the effects of foliar application of boron on the growth, physiology, nutrition, and productivity of snap beans. The experiment was carried out in a greenhouse in a completely randomized design, with five treatments comprising boron doses (0 – control, 1350, 2700, 4050, and 5400 ppm) and four replicates. Foliar application of boron was carried out at the V3 vegetative stage (third mature trifoliate). Growth, physiological, nutritional, and productivity variables were evaluated at the reproductive stages R5 (flowering) and R8 (harvest). Data were subjected to analysis of variance and F test at a 5% significance level. When significant, data was submitted to Student t, Scott-Knott, and regression analysis. Doses above than 2700 ppm affected significantly foliar temperature, transpiration, stomatal conductance, photosynthesis, and internal carbon concentration of bean pods. Foliar fertilization with boron influenced significantly the content and accumulation of boron in the shoot (868%) and the root system (105%), but it did not change the contents in pods. However, although they affect the physiology of snap bean plants, the tested doses did not influence significantly the growth variables and productivity. Boron doses from 2700 ppm caused symptoms of phytotoxicity on snap bean crops. Therefore, we do not recommend foliar application of boron at the stage V3 in snap bean crops even with a low boron content in the soil.