Bromacil Interactions in Plant Bioassay, Fungi Cultures, and Nitrification

Abstract

Rates and magnitude for phytotoxic diminuation of 5-bromo-3-sec-butyl-6-methyluracil (bromacil) at 0.25, 0.5, and 1 ppm for oats (Avena sativa L.) and 1, 2, and 4 ppm for sorghum (Sorghum vulgare Pers.) plants were related to increased nitrogenous composition of organic and inorganic amendments with a Psammentic paleustalf, Eufaula sand. Soil isolates not inhibited by bromacil concentrations up to 2,000 ppm in defined broth media sans presynthesized growth factors included Aspergillus tamarii Kita, A. flavus Link ex Fries, A. oryzae (Ahlburg) Cohn, Penicillium funiculosum Thorn. P. brevicompactum Dierckx. Curvularia lunata (Wakker) Boedijn, Mucor pusillus Lindt, Trichoderma viride Persoon ex Fries, and Myrothecium verucaria Ditmar. A. niger van Tieghem was inhibited with bromacil levels less than 1500 ppm. This substituted uracil fungitoxicity was offset with increasing inorganic N levels to 500 ppm as NH4NO3 and/or 1,000 ppm of presynthesized growth factor additive as cyanocobalamin, yeast extract, and peptone. Bromacil levels to 100 ppm reduced nitrification temporarily for only 5 days in contrast to sustained inhibition of nitrification for 15 days by equivalent levels of 2-amino-4-chloro-6-methylpyrimidine (Toyo Koatsu AM).