Comparative evaluation of different organic fertilizers on the soil fertility, leaf mineral composition and growth of bitter kola seedlings

E MoyinJesu,C Adeofun

doi:10.9755/ejfa.v12i1.5179

Abstract

The effect of oil palm bunch ash, spent grain, poultry and turkey manures applied solely and their supplemented forms, as sources of fertilizer on soil fertility, leaf mineral composition and growth of bitter kola (Garnicia colae) seedlings was investigated at Akure in the rainforest zone of Nigeria. The eight organic fertilizer treatments: spent grain, oil palm bunch ash, poultry manure, turkey manure, spent grain + poultry manure, spent grain + turkey manure, oil palm bunch ash + poultry manure and oil palm bunch ash + turkey manure were applied at 40g per 10kg soil filled polybag (8t/ha dry weight) with a reference treatment 400kg/ha NPK 15-15-15 fertilizer (2g per bag) and arranged in a completely randomized design (CRD) and replicated three times. The supplemented or amended treatments were applied at a 50:50% by weight (20g each). The results showed that these organic fertilizers increased the growth parameters, soil and leaf N, P, K, Ca and Mg, soil pH and organic matter significantly (P<0.05) compared to the control treatment. The supplements of oil palm bunch ash and wood ash with poultry and turkey manures increased consistently the growth, soil and leaf mineral compared to their sole forms. Oil pal bunch ash + poultry manure increased the leaf N (52%), P (27%), K (44%), Ca (39%) and Mg (51%) compared to the sole application of poultry manure. When compared with NPK 15-15-15 fertilizer, the oil palm bunch ash + poultry manure treatment increased the plant height (40%) leaf area (50%), stem girth (45%) number of leaves (53%), and fresh shoot weight (29%). For soil chemical composition, the oil palm bunch ash + poultry manure treatment increased the soil pH (28%), O.M. (92%), P (26.3%), Ca (99%), Mg (98%) and Na (93%) compared to the NPK 15-15-15 fertilizer. However, the NPK 15-15-15 fertilizer increased the soil K by 11% compared to the former. The high soil K/Ca, K/Mg and P/Mg ratios in the NPK 15-15-15 fertilizer treatment led to an imbalance in the supply of P, K, Ca and Mg nutrient to bitter kola seedlings. In these experiments, oil palm bunch ash + poultry manure applied at 8t/ha was most effective treatment in improving bitter kola growth parameters, soil and leaf mineral composition.

Highlights

Bitter kola (Garnicia colae) belongs to the family sterculiaceae and it is an important tree species occurring in the humid rainforest zones of West Africa
In spite of the medicinal and economic importance of the crop, it is rapidly moving towards extinction because of the difficulty in raising it from seeds in the nursery and the situation is worsened by continued decline in soil fertility levels
Based on the established critical levels for soils in Southwest Nigeria, the soil was acidic with pH 5.3 and low in organic matter compared to the critical level of 3% O.M. (Agboola and Corey, 1973)

Summary

Introduction

Bitter kola (Garnicia colae) belongs to the family sterculiaceae and it is an important tree species occurring in the humid rainforest zones of West Africa (elevation 10m, lat 4o N and 201 N, 5o1 W 181 E while the annual precipitation is 1444mm). Olapade (2000) reported that bitter kola is very high in Fe, beta carotene and antioxidant, which help to prevent high blood pressure and anemia in the human body. The bitter component of the crop is the medicinal property which helps the breakdown of glycogen (liver sugar level) to reduce sugar accumulation in the body. In spite of the medicinal and economic importance of the crop, it is rapidly moving towards extinction because of the difficulty in raising it from seeds in the nursery (i.e. long germination period) and the situation is worsened by continued decline in soil fertility levels. Efforts to supplement the soil nutrient status with inorganic fertilizers are limited by the high cost of purchasing fertilizers especially for the poor resource farmers and acute scarcity at time of planting (Aduayi, 1980, Agbede and Kalu 1990, Obi and Ofoduru, 1997)

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Conclusion