REDUCED ATRAZINE DOSES COMBINED WITH SORGHUM AQUEOUS EXTRACTS INHIBIT EMERGENCE AND GROWTH OF WEEDS

C1ombining low doses of herbicides with allelopathic plant extracts subject weeds to different mechanisms of action, which reduces herbicide resistance. The effects of reduced atrazine doses combined with sorghum aqueous extracts (sorgaab) from sorghum accessions IS9456, IS22320 and Mahube on emergence and growth of Bidens pilosa and Eleusine indica were evaluated in a greenhouse experiment at the University of Zimbabwe in 2017. Two experiments were set up as a 3 * 5 factorial arrangement in a completely randomized design testing sorghum varieties as sources of sorgaab, and five atrazine-sorgaab mixtures (100% sorgaab, 10% of the label recommended dosage (LRD) of atrazine for maize + 90% sorgaab, 30% LRD atrazine + 70% sorgaab, 100% LRD atrazine, and untreated check). Percent emergence, height, and total chlorophyll content in leaves significantly decreased (PMahube>IS9456, for B. pilosa and E. indica. Sorghum variety significantly (P0.05) affect dry weight of E. indica. Percent emergence, height, total chlorophyll content and plant dry weight significantly (P100% sorgaab>10% LRD atrazine + 90% sorgaab>30% LRD atrazine + 70% sorgaab>100% LRD atrazine. There were significant (P Key words: Herbicides, reduced dose, sorghum, allelopathy, Eleusine indica, Bidens pilosa
INTRODUCTION Herbicides are an integral part of weed management [1]. Their usage is reported to be increasing worldwide, including in Africa owing to rising rural-urban migration, which is causing scarcity [...]