Evaluating the efficacy of different selective herbicides for weed management among six Maksoy Soybean varieties.

Abstract

Weeds are the most economically important biotic stressor in soybean production in Uganda and Sub-Saharan Africa as a whole. Several selective chemical herbicides provide control over a wide range of weed species however, there is limited information regarding their effectiveness in the control of these weeds amongst the Maksoy soybean varieties. Therefore, a field experimental study was conducted to assess the efficacy of three different post- emergence selective herbicides in the management of weeds amongst the six Maksoy soybean varieties at Makerere University Agricultural Research Institute Kabanyolo. The main objective of the study was to determine the effect of new selective herbicides on weed management and performance of soybean. The experiment was laid out in a completely randomized block design in split plot arrangement with two replications. Six Maksoy varieties were used (Maksoy 1N, 2N, 3N, 4N, 5N and 6N) and the treatments were the three post-emergence selective herbicides which included; Quizalofop + Fomasafen 16% EC, Bentazon 15.5% EC and Haloxyfop-R methyl ester 108g/l. Two controls (both hand hoe and no weeding) were used. Data collected through physical measurement, counting and careful observation of the parameters of interest was analysed using R analytical tool. The treatments applied showed significant difference (P<0.05) in several parameters that included plot yield, number of days to physiological maturity, number of seeds per pods, plant height, number of branches, number of pods per plant, weed density and weed diversity. Amongst the three herbicides used during the study, Haloxyfop-R methyl ester 108g/l is the most effective in the control of weeds of grass family only. The results further indicated that Bentazon 15.5% EC, exhibited the most effective and excellent control over both grass and broadleaf weed species and therefore created the most conducive environment for the performances of the six Maksoy varieties. Therefore, Bentazon can be recommended for the management of both grasses and broadleaf weed species. There is need to conduct this study in multiple environments to validate these results obtained in this study. Furthermore, there is need to identify the most critical stage of herbicide application during the different growth stages of the weeds.