Herbicidal efficacy of spiny pigweed (Amaranthus spinosus L.) leaf extract for weed management in eggplant (Solanum melongena L.)

Abstract

Weed management in vegetable production increasingly requires environmentally friendly alternatives to synthetic herbicides. This study evaluated the potential of aqueous leaf extract of Amaranthus spinosus L. as a botanical weed-suppression agent and its effects on eggplant growth and yield. Four treatments were tested: control (no herbicide) and extract concentrations of 200, 400, and 600 g L^-1. Weed cover, weed dry weight, crop growth parameters, yield attributes, and species-specific weed responses were assessed. Results showed that A. spinosus extract reduced weed cover (77.13–85.83%) and weed dry weight (183.28–216.63 g plot^-1) compared with the control (87.37% and 284.93 g plot^-1), although differences were not statistically significant. The highest concentration (600 g L^-1) consistently produced the lowest weed biomass. Eggplant growth and yield parameters, including plant height, number of leaves, number of fruits, and fruit weight, were not significantly affected by the treatments, indicating no phytotoxic effects on the crop. Fruit weight increased from 447.35 g plant^-1 in the control to 669.05 g plant^-1 at the highest extract concentration, likely due to reduced weed competition. However, responses varied among weed species, with some showing reduced cover while others exhibited non-linear or increased responses, highlighting species-specific sensitivity to the extract. In conclusion, A. spinosus leaf extract demonstrated moderate, non-significant weed suppression without harming eggplant growth, suggesting potential as a component of integrated weed management. However, its efficacy remains limited and requires further validation through detailed dose–response studies, chemical characterization, and field-scale evaluations before practical application.