Comparative analysis of good agronomic practices (GAP) and conventional methods in Sri Lankan vegetable farming

The agricultural sector in Sri Lanka faces persistent challenges in optimizing crop yields, reducing production costs, and enhancing farmers’ incomes. This study evaluates the economic viability of Good Agronomic Practices (GAP) compared with conventional farming practices across four vegetable crops (tomato, pole bean, cabbage, and carrot) cultivated in two agroecologically distinct vegetable production areas: Balangoda and Boralanda. Using a participatory field trial design, we assessed crop yield, cultivation costs, and net income over two growing seasons. The results indicate that the GAP plots produced agronomic and economic improvements or no losses compared to conventional plots, though effects varied by crop and season. For cabbage, no significant differences were observed in season one; however, in season two, GAP recorded a 35% higher cultivation costs (p < 0.001), an 18% higher yield (p < 0.05), and a 31% increase in gross returns (p < 0.05), without significant improvements in net returns or benefit–cost ratio (BCR). For carrots, season one showed 10% lower cultivation costs (p < 0.001) and 33.9% higher yields (p < 0.05) under the GAP, although net returns were not significantly different. In season two, GAP achieved significantly higher net returns (an 83.2% increase; p < 0.05) and BCR (a 50.3% improvement; p < 0.05). For pole beans, season one recorded 20% lower cultivation costs (p < 0.001) and a 53.1% higher BCR (p < 0.05) under the GAP. In contrast, in season two, GAP production costs were 43% higher (p < 0.001) but achieved statistically non-significant increase in net returns and the BCR. Importantly, GAP consistently used fewer chemical inputs than the control, suggesting its potential for safer, more sustainable production. These findings highlight the importance of context-specific GAP packages to inform policy and guide farmers toward profitable, sustainable vegetable production.