Effect of water source on efficacy of glyphosate in weed control in Lwampanga sub-county, Nakasongola district

Abstract

The study of the quality of water used in the spray tanks is important because it can affect herbicide efficacy. Thus, this study was aimed at contributing to effective weed control in farmers’ fields through elucidating on the possible positive and negative interactions of glyphosate herbicides with water sourced from the varied available reservoirs. The five water samples were collected and analyzed in the laboratory using different types of standard analytical techniques. The parameters analyzed include; pH, total alkalinity (CO3 2- or HCO3 -), calcium hardness, Magnesium hardness, total hardness, Na+, K+ and total suspended solids (turbidity). The field experiment was laid out in a randomized complete block design with six treatments and three replications. There were three villages (Kisaalizi, Kimole and Podya), in which three field plots with weed species (predominantly Sodom apple (Solanum incanum), Spear grass (Imperata cylindrica) and Couch grass (Digitaria scalarum), that were broadly differing from one field to another were randomly selected. Data was collected on different water quality parameters in the laboratory and scorching effect and analyzed using GenStat software program. Results on water quality parameters indicated that bore hole 2 (near Lake Kyoga) had the highest pH (7.15), Mg2+ (19.899 ppm), Ca2+ (367 ppm), Na+ (412 mgl-1) and total alkalinity (547.5 ppm); yet dam water had the highest K+ (75 mgl-1) and rain water had the lowest K+ (6 mgl-1). The scorching effect was significant (P < 0.001) between the different water sources. The scorching effect of glyphosate herbicide was highest with control (4.33) and lowest with borehole 2 (2.22). The mean scorching effect of glyphosate herbicide was also highest in Podya village (3.72) followed by Kimole village (3.44) and Kisaalizi village (3.33) with the least. In conclusion, in the context of effect of water source on efficacy of glyphosate herbicide in weed control in Lwampanga subcounty, Nakasongola District farmers should not use Borehole water (B2) to mix with glyphosate to form spray solution. However, if optimum scorching effect is to be obtained in farmers’ fields, they should use Rain water, Lake Water, Dam water and Borehole water (B1). It was recommended that farmers in order to realize the full benefits of glyphosate in weed control, it is essential that adjuvants are added to the solution before use, to enhance its effectiveness in farmers’ fields. It was suggested that more research should be done to assess the synergistic or antagonistic interactions of glyphosate anion and water cations.