BORON UPTAKE AND CONCENTRATION IN COTTON AND SOYBEAN AS AFFECTED BY BORON SOURCE

Continued introduction of new boron (B) fertilizer materials prompted a second examination of the efficacy of foliar-applied B materials on B content, B uptake, and dry matter yield of cotton (Gossypium hirsutu m L.) and soybean (Glycine max: L.). Similar to a previous study, this greenhouse study was conducted at four participating universities usi ng 6-week-old cotton (Deltapineland 90) and soybean (Pioneer 9761) pla nts. Sources and rates of B were 1) boric acid (17.5% B) at 0.22 kg ha (-1), 2) sodium berate (Solubor(R) 20.5% B) at 0.22 kg ha(-1), 3) Smit h & Ardussi Liquid B (10% B) at 0.22 kg ha(-1), 4) Smith & Ardussi Liq uid B at 0.11 kg ha(-1), 5) Borosol 10 (10% B) at 0.22 kg ha(-1), 6) B orosol 10 at 0.11 kg ha(-1), and 7) an untreated control. Control plan ts that did not receive B were sprayed with water. Four giants were gr own in each 15-cm diam. pot in sandy loam soil. Plants were sprayed at 6 weeks of growth and top growth was harvested at eight weeks. Whole- plant samples were dried (70 degrees C), ground, and analyzed for B co ntent. Uptake of B, plant B concentration, and plant dry weight varied by state, so results were not combined over all states. In every stat e there were significant differences in B concentration and B uptake b y cotton and soybean as affected by B treatment, but effects were not consistent with any one B source. In two of four cases (Alabama and Ge orgia) cotton plants receiving any B treatment had greater B concentra tion and B uptake than the water-sprayed control. In Virginia and Nort h Carolina, application of B treatments rarely affected B uptake by co tton or soybean. No one B source produced consistently greater B uptak e than any other B source.