Effects of Bio- and Chemical Fertilizers on Growth and Soil Microbial Population of Cacao (Theobroma cacao L.) Seedlings

Abstract

A comparative study was done to determine the growth, microbial population, and physico- chemical properties on UF18 cacao (Theobroma cacao) seedlings when treated with chemical fertilizers and biofertilizers, either applied singly or in combination. The experimental design was randomized completely block design with five seedlings per treatment per block. Treatments used were: control, ½ recommended rate of chemical (RRC) fertilizer, RRC, MYKORICH®, MYKOCAP®, ½ RRC + MYKORICH®, ½ RRC + MYKOCAP®, RRC + MYKORICH®, and RRC + MYKOCAP®. MYKORICH® and MYKOCAP® contain 12 species of arbuscular mycorrhizal fungi isolated from stressed environments. The results showed that plant growth and physico-chemical properties were significantly improved by the application of biofertilizer than by chemical fertilizer. MYKORICH® treatment gave the highest spore count and is highly significant (p < 0.05) as compared to the other treatments with spore count ranging from 41–115.5/ 50 g soil. In terms of nitrogen-fixing bacteria count, ½ RRC treatment gave the highest (16.9 CFU x 10–5 g soil–1) bacterial count. RRC + MYKORICH® inoculation gave the highest values for most of the soil physico-chemical analysis (pH, P, K, and CEC). The positive response of cacao seedlings to mycorrhizal inoculation with or without chemical fertilizer provides a useful criterion in other agricultural lands throughout the country for crop production and sustainability.