Compost tea and bioslurry as plant biostimulants. Part 1: characterization and phytotoxicity testing

Abstract

In the present study, the quality of aerated (A), non-aerated (NA) and bioslurry (B) as potential bio-fertilizers were evaluated. Aerated and non-aerated compost teas were brewed from two different compost: exhausted grape marc (G); and a mixture of residues (M): goat manure, grape marc, garden raking leaves and alfalfa cutting hay. Bioslurry was prepared from fresh organic material in anaerobic digestion, according to FAO. Aeration, with shorter extraction time, resulted in higher pH (8.25 and 7.44 regarding 7.32 and 6.98, respectively for AM, NAM, AG and NAG), but in general with lower nutrient concentration than non-aerated. B presented higher nitrogen content (7.86 mg L-1 N-NO3- and 40.77 mg L-1 N-NH4+). No pathogens or phytotoxic effects were detected. To our knowledge, this is the first time that B has been evaluated, and our results suggest that the use of fresh organic matter may generate a high-quality product to be used as a biostimulant. Agricultural bio-inputs, elaborated from organic residues, represent a cheaper and safer alternative to traditional fertilizers, while residues are reduced and reused.