Effect of rate surfactant application on herbicide phytotoxicity.

Abstract

In Uganda the use of surfactants has not been explored. There is limited understanding of the surfactant application including rate of application. Therefore, there is need to know the effect of rate of application of surfactants during weed control on efficacy of weed management. The objectives of this study were; to determine the effect of rate of surfactant application on time taken for the herbicides to act and; to determine the effect of rate of surfactant application on the mortality rate of different weeds. The study was carried out from Nandagi Central Forest Reserve under Lwankiima Sector in Lakeshore Range. The forest is located in Namawojjolo Parish in Nama Sub- County, Nama County in Mukono District Uganda. A total of 15 plots of 10m×10m were established alternately 5m equidistant along 3 transects with 5 plots each transect and quadrant sampling method was used in data collection. The results revealed that if the rate of surfactant application is high, it would increase the coverage on the foliage of the weeds, increase its ability to penetrate the leaf membranes and also increase the rain resistance of the herbicide to being washed away. Mortality rate of the weeds differs between the annual grass weeds, annual broadleaved weeds and perennial grass weeds. The results showed that time taken for the herbicides to start acting was reduced with increased rate of surfactant application. This was attributed to increased spreading and penetration of the spray solution into the leaves of weeds. Furthermore, the study showed that mortality rates of AG; AB; PB increased with increase in surfactant application rates whereas there was no effect of rate of surfactant application on mortality rate of PG. This was attributed to the high growth cycle, deep roots as well as high genetic diversity within the weeds. On the other hand, annual grass weeds and annual broadleaved weeds have a less cycle of growth, less genetic diversity and not deeply rooted, hence have high mortality. It was recommended that field trials should be conducted to determine the most effective herbicide and surfactant rates.