Qualidade do solo e crescimento inicial de plantas do cerrado após adubação com resíduos de cana-de-açúcar e biochar de torta de filtro

Abstract

Due to the increase in sugarcane production in Brazil, the proper handling of residues from processing in the sugar and alcohol industry has become a major challenge. The objective of this work was to evaluate the effect of sugarcane by­products and filter cake biochar on the initial growth of Cerrado species and soil quality. Two experiments were implemented. The first was carried out in an area undergoing recovery with the planting of seedlings fertilized with sugarcane by­products with the treatments: (T1) without addition of by­product or fertilizer; (T2) filter cake; (T3) sugarcane bagasse; (T4) filter cake + sugarcane bagasse and (T5) mineral fertilizer NPK 4:14:8. To follow the growth of the seedlings, three evaluations (40, 200 and 400 days after planting) of total height and diameter at ground height of the plants were carried out. Soil quality was evaluated at depths 0­10 and 10­20 cm, with the determination of carbon and total nitrogen and microbial contents, C:N ratio, soil basal respiration, metabolic quotient and microbial quotient, after one year of planting the seedlings. The second experiment was carried out in a greenhouse, where the effect of four doses of filter cake biochar (1%, 2%, 4% and 8% v/v) and two control treatments (with soil correction and fertilization and without fertilization), on the physiology and growth of three Cerrado species: Acrocomia aculeata, Psidium firmum and Anacardium humile, and on the chemical and microbiological attributes of the soil. Physiological variables were evaluated: photosynthesis, transpiration, stomatal conductance, consumed CO2, internal carbon and electron transport rate; and morphological: height and diameter of the plants. The evaluated soil attributes were pH, Ca, Mg, P, K, CEC, organic carbon, total and microbial nitrogen. In experiment 1, for the species A. humile, T2 favored its growth in diameter, and for H. courbaril, T3 provided greater plant growth. For H. impetiginosus, T1, T2 and T5 provided greater height growth. A. humile, B. capitata and H.courbaril had greater growth in height with the addition of filter cake and bagasse (T2, T3 and T4). As for soil attributes, from 0­10 cm, organic carbon, total and microbial nitrogen were the ones that most correlated with T2. From 10­20 cm, the variables responded well to treatments T1, T2 and T3. In experiment 2, for A. aculeata, the application of 2% biochar favored photosynthesis. For P. firmum, 30 days after transplanting, the treatment without fertilization obtained the highest averages for the physiological variables. A. humile responded positively to the application of biochar. In terms of soil attributes, the 1% dose of biochar and fertilization were the treatments that best conditioned the soil. Thus, the use of sugarcane residues and filter cake biochar promoted good growth and physiological responses of native Cerrado seedlings, as well as improvements in soil attributes, and are therefore indicated for use in projects of recovery of degraded areas.