SOURCES OF BORON FOR FOLIAR FERTILIZATION OF COTTON AND SOYBEAN

Recent introduction of new boron (B) fertilizer materials prompted an examination of the efficacy of B uptake by cotton (Gossypium hirsutum L.) and soybean (Glycine max L.) from foliar-applied B originating fro m various sources. Conducted as a greenhouse study at four participati ng universities, cotton (Deltapineland 90) and soybean (Pioneer 9761) were sprayed at a rate equivalent to 0.22 kg . ha(-1) B when plants we re 6 weeks old. Sources of B were: 1) boric acid (17.5% B), 2) sodium berate (Solubor(R) 20.5% B), 3) Solubor(R) at the pH of boric acid, 4) Trace Liquid B (10% B), and, 5) Smith and Ardussi Liquid B (10% B). C ontrol plants that did not receive B were sprayed with water. Four pla nts were grown in each pot in sandy loam soils with a pH greater than 6.0. Plants were harvested during the eighth week. To determine if the solvents used to prepare the foliar liquids affected B absorption, tw o of the harvested plants per pot were washed with distilled water and two plants were left unwashed. All plants were oven dried and analyze d for B. All B sources produced significantly more tissue boron than t he water-sprayed check. Within a state, there were variations in tissu e B responses to the sources of B in cotton and soybean. Combined data for ail states showed no differences in tissue B due to source of B i n cotton or soybean. In cotton, the average tissue concentration incre ase from the foliar B applications ranged from 8 to 11 mg . kg(-1). In soybean, the average increase ranged from 16 to 22 mg . kg(-1) B. Was hing created a significant decrease in tissue B in cotton. but not soy bean.