Impact of Humic Acid on Growth, Yield, and Nitrogen, Phosphorus, and Potassium Uptake of Eggplant (Solanum melongena L.) in Coarse-texture Soils

Abstract

To study how coarse-textured soils affect plant growth, yield, and Nitrogen (N), Phosphorus (P), and Potassium (K) content in eggplant (Solanum melongena L.), this study was carried out in pots using a factorial completely randomized design with three replications, and five different levels of humic acid (HA) (0, 40, 60, 80, and 120 kg/ha) was used during the 2024–2025 growing season. Field validation is recommended before making broad agronomic recommendations. Growth parameters, fruit yield components, N, P, and K concentrations in soil and plant organs were determined based on dry weight. Generally, plant height, leaf number, fruit diameter, and fruit weight increased significantly with HA application; the highest values were recorded at 80–120 kg/ha. Studied parameters were significantly affected by soil texture, loamy sand, and sandy loam, responding more strongly to HA than to loam. Most growth, yield, and nutrient concentrations recorded significant interaction effects between HA and soil texture. The availability of N, P, and K in soil increased with an increase in HA, as well as their accumulation in roots, shoots, and fruits. These results show that HA is effective as a soil improver and bio-stimulant for increasing eggplant productivity in coarse-textured soils; an ideal approach is the application of 80–120 kg/ha, which represents an optimal management strategy.