Environmental impact of pesticide runoff in irrigated agriculture: evidence from Gomoa West field, Ghana

Abstract

Pesticide use in irrigated agriculture presents growing environmental and public health concerns, particularly in low-resource settings where regulatory enforcement and best practices are limited. This study assessed the ecological risks of pesticide runoff in irrigated farming systems in the Gomoa West District of Ghana, with a focus on farmer practices and potential impacts on aquatic ecosystems. Primary data were collected through semi-structured surveys with 150 farmers, supported by key informant interviews with agricultural officers and community leaders. To estimate environmental risk, the study employed two established tools: the Environmental Impact Quotient (EIQ) and the U.S. EPA's ECOTOX Knowledgebase, offering a validated alternative to direct residue measurement in settings where laboratory testing is not feasible. Findings reveal widespread overuse and misuse of chemical pesticides. 84% of farmers did not adhere to recommended application rates and 79% cultivated fields within 5 m of irrigation water sources. Poor waste management practices, including on-site washing of pesticide applicators and burial of containers, further compound the risk of runoff. EIQ-based analysis showed that commonly used insecticides (e.g., Carbofuran, Chlorpyrifos) and herbicides (e.g., 2, 4-D, Paraquat) posed high ecological risks, with potential harm to fish, amphibians, and beneficial insects. While some farmers reported declines in aquatic species, these observations remain anecdotal and highlight the need for further monitoring. This study underscores the urgent need for integrated pest management (IPM), farmer training, improved regulatory oversight, and the establishment of vegetative buffer zones to mitigate runoff. Though limited by its reliance on proxy risk indicators, the study provides valuable insight into the environmental consequences of pesticide use in irrigated systems and offers policy-relevant recommendations for improving sustainability in Ghana and similar agro-ecological contexts.