Comparative evaluation of different organic fertilizer on the soil fertility, leaf mineral composition and growth performance of mango seedlings (Magnifera indica L.)

An investigation was carried out at Akure in the rainforest of Nigeria to determine the effectiveness of sole and amended oil palm bunch ash and spent grain with poultry and turkey manures as sources of fertilizers on the growth of mango seedlings (Magnifera indica L) in the nursery. Eight organic fertilizer treatments, spent grain, oil palm bunch ash, poultry manure, turkey manures (sole forms), oil palm bunch ash + poultry manure, oil palm bunch ash + turkey manure, spent grain + poultry manure, spent grain + turkey manure, were applied at 8t/ha (40g per 10kg soil filled poly bag) with an NPK fertilizer 400kg/ha (2g per bag) treatment as a reference and a control (no fertilizer; no manure), replicated three times and arranged in a completely randomized design. The results showed that the organic fertilizers increased significantly (P 0.05) plant height, leaf area, stem girth, number of leaves of mango seedlings and root length, soil and leafN, P, K, Ca and Mg, soil pH and organic matter contents relative to the control treatment. Oil palm bunch ash + poultry manure treatment increased the plant height, stem girth, leaf area, leaf number and root length of mango seedlings by 22%, 24%, 10/0, 270/0 and 10% respectively, compared to NPK 15-15-15 fertilizer treatment. Amended oil palm bunch ash + poultry manure treatment also increased the soil pH (H20 ), O.M., N, P, Ca and Mg by 27%, 79%, 30%, 26%, 99% and 99.2% respectively compared to NPK fertilizer treatment. In addition, it also increased the leafN, P, K, Ca and Mg by 37%,45%, 180/0,35%, and 15% respectively compared to the oil palm bunch ash (sole) treatment, However, NPK 1515- 15 fertilizers increased only soil K by 10% compared to the oil palm bunch ash (sole) treatment. The highest soil K/Ca, K/Mg and P/Mg ratios in NPK fertilizer treatment led to imbalance in the supply of P, K, Ca and Mg nutrients to mango. Oil palm bunch ash + poultry manure treatment applied at 8t/ha was the most effective treatment in improving mango growth parameters, leaf mineral composition, and soil fertility.