Banca de DEFESA: RAFAELA FELIX DA FRANÇA

Combination of phosphate solubilizing bacteria and biochars to increase soil phosphorus availability for corn plants

Biochar, Klebsiella sp., Organic phosphorus.

In the modern agriculture, the search for sustainable strategies has been including the use of soil bacteria capable of solubilizing phosphate and increasing efficiency of phosphorus (P) use by crops. Another technology is the use of biochar, which comes from the pyrolysis of solid organic material, and can act as a biofertilizer and a vehicle for inoculation of microorganisms. This study aimed to: (i) present a review on the viability of biochar as an inoculation vehicle for phosphate-solubilizing bacteria; (ii) evaluate bacteria of the genus Klebsiella sp. associated with different sources of biochar at controlled and field conditions, applied to maize seeds, and to evaluate the phytotechnical changes of the plant, and soil chemical and biochemical analysis. Two experiments were carried out. In experiment 1, in 16-kg pots with soil in a greenhouse, different combinations of inoculum and sources of biochars were applied to maize seeds of the Batité variety.  A 3x4 factorial design with 4 replications was adopted, combining 3 sources of biochar: without biochar, rice straw biochar and white grape biochar, and 4 bacterial strains: UAGC17 (Bac.1), UAGC19 (Bac.2), the mixture of the two bacteria (Bac.1 + Bac.2), and control without inoculation. Phytotechnical traits of the plant were evaluated after 45 days, and chemical and enzymatic activity and fractions of P were analyzed in the soil. Rice straw biochar, associated or not with UACG17 bacteria, increased the soil labile organic P, soluble organic P in basic medium, soluble organic P in acidic medium, soil basal respiration, and acid and alkaline phosphatase and β -glucosidase enzymes. The white grape biochar increased the available potassium in the soil. Rice straw and white grape biochars showed promise as inoculation vehicles.  In experiment 2, under field conditions in Jupi, Pernambuco, the same treatments mentioned above were evaluated, with 8 replications. In general, for the phytotechnical traits, the treatments that received inoculation were superior to those not inoculated, highlighting the treatment Bac.1+Bac.2 associated with Bio.2, which provided greater stem diameter and height of the first ear. The Bac.1 treatment associated with Bio.1, increased all soil P fractions evaluated, the activity of phosphatase enzymes and basal soil respiration. No gains were observed regarding corn yield variables (number of commercial ears, total number of ears and ear weight).