Granulated organomineral fertilizers from by-products of the agricultural and forestry sector

ABSTRACT The present study evaluated the granular properties of organomineral fertilizers produced from charcoal fines (biochar) and natural phosphate with three distinct binders: cassava wastewater (CW), pyroligneous extract (PE), and bio-oil (BO). The objective was to ascertain the potential of these fertilizers to increase common bean production. To form the granules, a 3:1 ratio of biochar to natural phosphate was employed, along with five binder doses (50, 75, 100, 125, and 150 % of the biochar-phosphate mixture weight). The granules were evaluated based on their crushing strength, water absorption ratio (WAR), granule density, impact resistance index (IRI), salinity index (SI), and pH. The most optimal granules were selected for the experiment with the common bean, using a completely randomized design in a 3 × 4 + 4 factorial scheme with three replications. The treatments comprised three binders (CW, PE, and BO), four binder doses (75, 100, 125, and 150 %), and four controls: unfertilized soil (NS), natural phosphate (NP), biochar mixed with natural phosphate (B + NP), and biochar (B). Compared to the CW or PE granules, the BO granules exhibited superior crushing resistance, density, and IRI, accompanied by a reduced WAR. The PE granules exhibited a higher SI and a lower pH. The application of CW, PE, or BO granules resulted in a significant increase in shoot dry matter (SDM), with values of 98.31, 123.73, and 47.46 %, respectively, compared to the NS. Similarly, root dry matter (RDM) notably increased, with values of 331.03, 755.17 and 141.38 %, respectively. The physicochemical properties of organomineral fertilizers are influenced by the type of binder used, affecting common bean production. Further research is needed to ascertain the long-term effects of these slow-release fertilizers.