Development of an Effective Biocatalyzed Organic Fertilizer Derived from Gliricidia Sepium Stem Biochar

Abstract

Biochar biocatalyst action could improve quality and reduce costs in producing biochar fertilizer. Objective of this study was to develop a high-quality organic fertilizer using biochar biocatalyst action. To activate Gliricidia stem biochar (produced at 400-500oC and 2.5 hours residence time), aqueous biocatalysts were prepared in two separate aerobic reactors containing 4L of water, 12.5 g of rock phosphate, and Gliricidia biocatalyst (GBC) with 1 kg of Gliricidia leaves and market waste biocatalyst (MWBC) with 1 kg of market wastes. Intermittently total 377.5 g and 525 g of biochar were added respectively to the reactors until they reach neutral pH. GBC showed higher total nitrogen (243 mg/L) and available phosphorous (8,125 mg/L) contents. Four compost piles were prepared with fresh immature grass of 18 kg/pile and Gliricidia leaves of 2 kg/pile. Produced biocatalysts were added at the beginning to three piles as 6% GBC, 3% GBC, and 3% MWBC and the control with 6% biochar on dw basis. N, P, K levels of all the compost piles after 8 weeks were within the recommended levels of compost. The highest total nitrogen (20.3 g/kg) and available potassium (83.71 g/kg) remained in 6% GBC and the highest available phosphorous (3.41 g/kg) measured in 3% MWBC. pH values of all piles ranged between 8.8-9.2. The made fertilizer is very suitable and cost-effective for acidic soils to improve soil nutrient status unlike the addition of lime. Michaelis-Menten kinetics indicates that it is preferable to add market waste-like substances to GBC for optimizing the qualities.