Influence of Triiodobenzoic Acid on Growth, Nodulation and Yields of Inoculated Soybeans¹

Abstract

Abstract In field studies with two lines of inoculated soybeans, a spray application of 1 ounce per acre of triiodobenzoic acid (TIBA) during the early blossom period reduced plant height by 16%, increased branching, shortened leaf petioles, and produced a conical‐shaped row profile. Pod numbers were increased by 4 to 15% and were concentrated on the lower branches; lodging was minimal. With 36‐inch rows, TIBA had no effect on yield. Nodulation of the TIBA treated plants was equal to that of untreated plants. No adverse effect on symbiotic nitrogen fixation was noted. Inoculation produced significant yield increases on both untreated and TIBA treated plants. With TIBA, inoculation increased yield only when plants received a side‐dressing of fertilizer nitrogen in mid‐August. Apparently the nodules were unable to supply the demand of TIBA treated plants for nitrogen during the heavy podding stage.