Atividade microbiana do solo, promoção de crescimento e controle da murcha de Fusarium em tomateiro influenciados por finos de carvão

Abstract

The use of carbonized biomass (biochar) as a means to improve physical and chemical quality of soils has been extensively studied in the last twenty years. However, the effects of biochar on soil biota and its impacts on plant diseases, especially soilborne plant pathogens, have not received due attention and are still poorly understood. In the present work we evaluated the impacts of biochar (BC) on soil microbial activity, on plant growth promotion and biocontrol to Fusarium oxysporum f. sp. lycopersici race 3 (fol), in tomato. In the experimental field, the incorporation of BC (0-20 cm deep) in the concentrations of 0, 10, 20, 30, 40 and 50 t ha -1 was carried out followed by the corn planting; after harvesting the soil was sampled and evaluated for its microbial activity (microbial respiration, C and N microbial, FDA, phosphatase and urease activity). In addition to this soil, another one was collected at Embrapa Meio Ambiente, which was mixed with BC at concentrations of 0, 1, 2, 3, 4 and 5% (v/v), being the soils infested with fol (1x10 6 conidia mL -1 ) and one tomato seedling per pot was transplanted. The progress of the disease was evaluated with a diagrammatic scale and at the end the fresh and dry weight of the root and aerial systems, stem diameter, number of leaves and plant height were determined. For the growth promoting assay, BC was mixed at concentrations of 0, 2.5, 5, 7.5, 10, 12.5 and 15% (v/v), one tomato seedling per pot, was transplanted and plant development was evaluated weekly. Thirty days after transplanting, four leaves were collected and enzymes (peroxidase, polyphenoloxidase, phenylalanine ammonia-lyase and total proteins) were evaluated. Biochar at doses of 20 t ha -1 has potential to increase soil microbial biomass and from 20 to 50 t ha -1 in reducing the symptoms of tomato Fusarium wilt, being an induction of systemic resistance the most probable due to an increase in the polyphenoloxidase activity. BC increased aerial and root biomass in tomato plants from the concentration of 7.5%. The increase of the concentration of BC in the soil reduces the severity of Fusarium wilt in tomato.