Biochar de açaí e Bacillus safensis como estratégia sustentável para a promoção do crescimento do feijoeiro

Abstract

The common bean (Phaseolus vulgaris L.) is an essential food in the Brazilian diet, with a high protein and mineral content. In light of the demand for sustainable agricultural practices, biochar, a byproduct of the pyrolysis of agro-industrial waste, stands out for its ability to improve the chemical, physical, and biological properties of the soil. At the same time, plant growth-promoting bacteria (PGPBs) are emerging as a complementary strategy in sustainable agriculture and plant tolerance to climate change. In this context, bacteria isolated from different conservation areas (Campos Ferruginosos de Carajás National Park (PA), Guartelá State Park (PR), and Iguaçu National Park (PR)) were subjected to in vitro assays to select elite strains with growth-promoting potential and tolerance to abiotic stresses (temperature, salinity, and water deficit). Following selection, greenhouse experiments were conducted with common beans under ideal and water-deficient conditions, combining inoculation with different doses (0, 4, 8, 16, and 20 t ha⁻¹) of açaí biochar (Euterpe oleracea Mart.). Five strains of the genus Bacillus (Bacillus safensis (LMB 414), B. thuringiensis (LMB 372), B. cereus (PEG 156), and B. velezensis (LMB 314 and LMB 398)) exhibited all mechanisms of plant growth promotion (indole-3-acetic acid (IAA) production, siderophore synthesis, phosphorus solubilization, and biological oxygen fixation). In a greenhouse, under ideal water conditions, increasing doses of biochar led to a progressive increase in shoot length 14 and 21 days after sowing and at the final assessment. Under water stress, treatments with biochar and inoculation with B. safensis (LMB 414) promoted a progressive increase in root length and root dry weight, contributing to the mitigation of water stress. The results indicate that the integration of açaí biochar and B. safensis constitutes a promising strategy for the development of agricultural bio-inputs, promoting common bean growth, tolerance to water deficit, and the sustainability of agricultural systems.