Effect of selective herbicides on yield of soybean and management of weeds

Abstract

Weeds remain a major constrain to soybean production, contributing up to 96% yield reduction of the soybean. The major weeds that have been reported to infest soybean fields include Cynodon dactylon, Cyperus rotundus, Commelina benghalensis, Bidens pilosa, Sorghum halepense, Eleusine indica, Digera arvensis, Amaranthus spinosus among others. Different methods of weed control have been used in the management of weeds in the soybean fields and they include; hand hoe weeding, use of chemical herbicides and integrated weed management. Different herbicides have been used in the management of weeds in soybean but no comprehensive study has been done to ascertain the effect of selective herbicides on the Maksoy varieties. The objective of this study was to improve weed management practices and soybean productivity in Uganda. The experiment was planted in Split plot design, five Maksoy varieties were used (Maksoy 1N, Maksoy 2N, Maksoy 3N, Maksoy 4N and Maksoy 5N) and the treatments were the two selective herbicides which included Quizalofop + Fomesafen 16% EC and Bentazon 14.5% EC, and were replicated twice. Through physical measurements, observation, and Genstat used as analysis tool, data on the two selective herbicides, yield, agronomic attributes of the five varieties Maksoy and weed management was obtained, analyzed and interpreted. There was significant difference (P<0.01) for the two parameters that is to say Number of branches per plant and weed diversity in regard to the treatments applied. Quizalofop + Fomesafen 16% EC showed significant influence on the number of branches and excellent weed management. The weed flora that was observed in the experimental area (field) included Cynodon dactylon, Eleusine indica, Bidens pilosa, Cyperus rotundus, Commelina benghalensis, Ageratum conyzoides (goat weed), Euphorbia heterophylla (Wild poinsettia), Amaranthus species, standing leaf desmodium. The study showed that, Commelina benghalensis and standing leaf desmodium were not fully managed by the selective herbicides. Basing on this study, the two selective herbicides (Quizalofop + Fomesafen 16% EC and Bentazon 14.5% EC) showed better weed management and did not affect the yield attributes of the five Maksoy varieties hence can be recommended for use by farmers for weed management.