FERMENTATION DIGESTATES FROM MANURE: CONSIDERATIONS FOR THEIR RECOMMENDATION IN BACKYARD AGRICULTURE

Abstract

Making and using fermentation digestates or “biols” as liquid organic fertilizers (LOFs) is recommended in backyard agriculture without any control; however, these can contain microorganisms that are harmful to human health and cause phytotoxicity, so that quality parameters should be measured before their use. A physical-chemical, microbiological and phytotoxic characterization was performed (through germination bioassays) with rabbit, equine, bovine and ovine manure digestates from backyards, processed during 45 days in Batch type digestors of 70 L capacity. In compound samples, eleven physical-chemical parameters were determined by triplicate, and four microbiological variables 45 days after the process started. The digestates reached acid pH (5.38-5.55) and a C/N relation of 1.37-1.77. Coliforms were observed in the amount of 4 to 7/10 mL, with a higher content in bovine manure. The levels of phytotoxicity were high to moderate, depending on the manure, which suggests a longer period of fermentation should be used to recommend their use as FOL safely for crop production.