Small-scale farmers agrochemical use and effects on soil microbes in selected wetlands of Kampala

Abstract

Agrochemicals have been tremendously used in agriculture worldwide to increase crop yield. However, its misuse creates a negative impact on the environment and health hazards for human beings. Little information is available on the use of agrochemicals by smallholder farmers in urban wetland areas of Kampala and the associated effects on ecosystem health. This study i) determined farmers’ knowledge, practices, and perception of agrochemical application in crop production, ii) assessed the factors that influence perception and practices regarding agrochemical use, and iii) assessed the effects of selected pesticides on soil microbial population and activity in wetlands around Kampala. This study employed both qualitative and quantitative methods to determine knowledge, practices, and perception of agrochemicals and the factors that influence perception and practices regarding agrochemicals. Laboratory experiments were conducted to assess the effect of the two most commonly used pesticides on soil microbes. One hundred small-scale farmers and 6 key informants were randomly selected and subjected to a questionnaire and a key informant guide respectively. Twenty-four soil samples were collected from a pesticide-free wetland areas and taken to the laboratory to assess the effect of rocket and dudu acelamectin on actinomycetes, bacteria and fungi population, and microbial C, P, and N. A completely randomized design with 4 treatments of pesticide (0, 50, 100, and 200 ppm) and 3 replications were used for each pesticide type. The study revealed that 40.8% of farmers used agrochemicals in general and 34% used pesticides. Farmers relied on their own experiences when using agrochemicals and most of them did not read instructions on agrochemical bottles. Farmers wear one or two but not all the required protective gears. More than half of the farmers interviewed (60%) stored pesticides in their houses. The ability to read and write, income, control for pests and diseases, and the need to increase crop yield were significant factors that influenced farmers' decisions to use agrochemicals. Pesticide use was significantly dependent on reading instructions, training, household size, and selling crops at high prices. The experiment revealed that the bacteria, fungi, and actinomycetes population increased with the increasing concentration of pesticides. The increase in the concentration of rocket reduced linearly the microbial C in the soil. The effect of rocket on microbial phosphorous followed a quadratic curve with a maximum of 78.6 ppm. Similarly, the effect of rocket on microbial N followed a quadratic curve with a maximum at 100 ppm which is likely to cause negative effects on microbial activities and shifts in populations. There is need therefore to sensitize farmers to use the recommended pesticide rates to reduce its effect on the environment.