Assessment of the effects of selected agrochemicals on soil macro-invertebrates in sugar cane (Saccharum officinarum L.) plantations in Masindi district, Uganda

Abstract

The increasing demand for sugar has intensified sugarcane cultivation, leading to extensive use of agrochemicals such as herbicides and fertilizers. This study aimed to evaluate the effects of 2,4-D herbicide and NPK fertilizer on soil macro-invertebrates in sugarcane plantations in Masindi District, Uganda. Using a completely randomized block design over eight weeks, sugarcane was planted in 12 plots subjected to four different treatments, including a control. Soil samples were collected using the core sampler method to assess soil properties and the presence of soil-dwelling macro-invertebrates. Data were analyseds using IBM SPSS version 26, applying one-way ANOVA at a 0.05 significance level. Results showed that 2,4-D and NPK significantly altered soil properties. Specifically, 2,4-D increased soil alkalinity, while NPK reduced pH due to nitrification. Both treatments also influenced soil texture—NPK increased clay content, while chemical applications raised silt levels. Biologically, short-term application of these agrochemicals did not significantly affect the abundance or morphology (length, segment number, coloration) of soil macro-invertebrates such as earthworms and centipedes. However, biodiversity and ecological stability were highest in untreated control plots. Notably, 2,4-D alone suppressed macro-invertebrate diversity, whereas the combined application with NPK moderated this effect. The study concludes that short-term agrochemical use alters soil chemistry but not macro-invertebrate morphology, while still negatively impacting biodiversity. It recommends reduced herbicide use, promotion of agro-ecological practices, long-term environmental monitoring, and farmer education on the ecological risks of agrochemicals to support sustainable soil health and biodiversity conservation.