Utilisation of Compost-derived Humic Acid on Growth and Yield of Okra (Abelmoschus esculentus L. Moench)

Abstract

Humic acid (HA) is an important fraction of humic substances and plays a significant role in promoting plant growth and productivity. A pot culture experiment was conducted to evaluate the effects of compost-derived HA on the growth, root characteristics and yield of okra (Abelmoschus esculentus L. Moench). HA extracted from aerobic compost, farmyard manure, vermicompost and coir pith compost was applied as a foliar spray at 0.5 and 1.0% at 30 and 45 days after sowing. Nine treatments were arranged in a completely randomised design with three replications. Foliar HA application produced significant treatment effects on leaf area, leaf area index, number of fruits per plant, fruit length, root volume, root citric and malic acid contents, fruit yield and dry matter production. Farmyard-manure-derived HA at 1.0% produced 78 fruits per plant, a leaf area of 421.80 cm², a leaf area index of 6.858, a root volume of 95 cm³, the highest fruit yield of 2.34 kg plant⁻¹ and the maximum dry matter production of 4980.61 kg ha⁻¹. The highest fruit length (26.20 cm) occurred with aerobic-compost-derived HA at 0.5%, while the highest root citric acid content (12.96%) occurred with aerobic-compost-derived HA at 1.0%. Overall, okra responses varied with HA source and concentration under the conditions of this pot experiment, indicating that the agronomic effects of compost-derived HA were treatment dependent.