Agronomic and economic evaluation of commercial organic manure doses in watermelon (Citrullus lanatus L.) cultivation

Abstract

This study evaluated the agronomic and economic effects of different organic manure doses recommended by commercial producers on watermelon (Citrullus lanatus L.) cultivation. Five treatments - chemical fertilization without organic manure (control), vermicompost, ovine manure, poultry manure, and bovine manure - were applied with three replications. Among the treatments, the company-recommended dose of ovine manure resulted in the highest yield (65.38 tons ha⁻¹) and net income (3,334.0 USD ha⁻¹), making it the most effective option. On average, organic manures increased fruit yield by 17.71% and rind thickness by 31.61%, the latter potentially reducing consumer satisfaction. Flesh firmness was lowest in the ovine manure treatment, while other manures showed no significant difference. Farmers should pay attention to the shelf life of watermelon fruit, especially if they prefer ovine manure due to the increase in yield and net income, taking into account that the intra-fruit hardness decreases. Bovine manure led to excessive nitrogen accumulation in leaves, and all treatments except poultry manure showed reduced phosphorus levels in the second season. Organic fertilization also decreased calcium content in leaves, and vermicompost-treated plants showed manganese deficiency, unlike the other treatments. Overall, the dose recommended by the ovine manure producer provided the most favorable balance between productivity, nutrient sufficiency, and economic return in watermelon cultivation