ABSTRACT. Biochar is a carbon-rich material produced during organic waste pyrolysis. In this context, two experiments were performed to evaluate the effect of biochar produced from rice husks and cattle manure on soil fertility and common bean production, as well as to identify the optimal dose of cattle manure biochar to be applied. The first experiment (Experiment I) was conducted according to a completely randomized design (factorial scheme 2 × 2 × 2 + 1) with six replicates: two types of biochar (cattle manure biochar and rice husk biochar), with and without acidity correction [addition of calcium carbonate and magnesium carbonate (PA) in a proportion of 4:1 (Ca:Mg) to raise the soil base saturation to 60%], with or without the addition of 120 mg dm-3 of phosphorus (P) as ammonium phosphate, and a control treatment (without biochar, acidity correction, and P). Based on the results of Experiment I, a second experiment was conducted according to a completely randomized design, with five treatments (doses of biochar from cattle manure) and four replications. Rice husk biochar, as a conditioner of soil chemical properties, had less prominent effects than cattle manure biochar. Cattle manure biochar functioned as a corrective for soil acidity and a source of nutrients (mainly phosphorus). The dose corresponding to 5.46% of the soil volume led to the maximum grain production by common bean plants.

RESUMO Os solos do Cerrado Brasileiro são geralmente ácidos e com baixa disponibilidade de nutrientes, portanto, o uso de insumos alternativos para melhorar fertilidade deve ser investigado. Os objetivos deste estudo foram avaliar o potencial dos biochars de casca de arroz (BHR) e de esterco bovino (BCM) no aumento da disponibilidade de fósforo e seus efeitos nas propriedades químicas do solo e nas plantas de feijoeiro. Os experimentos foram conduzidos em delineamento inteiramente casualizado, em esquema fatorial 4x2+3, com quatro repetições. Os tratamentos foram quatro doses de biochar (1, 2, 3 e 4% m / v), dois biochars (BRH e BCM) e três tratamentos adicionais (C1, sem calagem e sem fertilização; C2, adição de carbonato de Ca e Mg e Fertilizantes NPK e; C3, adição de silicato de Ca e Mg e fertilizantes NK). Nas maiores doses de BRH houve aumento de 2,7, 5,3 e 2,5 vezes no teor de P extraído por Mehlich 1 e quantificado por colorimentria, por Mehlich 1 e quantificado por espectroscopia e por resina de troca iônica e quantificado por espectroscopia, respectivamente. Para as doses mais altas de BCM, os aumentos no conteúdo de P foram 51,3, 289,2 e 88,4 vezes maiores que em C1, respectivamente, de acordo com os métodos descritos para o BRH. Os biochars aumentaram o pH do solo, a CEC, os teores nutrientes e o crescimento do feijoeiro em relação ao C1, especialmente o BCM. No entanto, a produção de matéria seca foi significativamente menor do que a no C2.

ABSTRACT The soils of the Brazilian Savanna are generally acidic and have low availability of nutrients, so the use of alternative inputs to improve their fertility should be investigated. The objectives of this study were to evaluate the potential of biochars from rice husk (BHR) and from bovine manure (BCM) in increasing phosphorus availability and their effects on soil chemical properties and in common beans plants. The experiments were carried out in a completely randomized design, in a 4x2+3 factorial scheme with four replicates. The treatments were four biochar doses (1, 2, 3 and 4% m/v), two biochars (BRH and BCM) and three additional treatments (C1, no liming and no fertilization; C2, addition of Ca and Mg carbonate and NPK fertilizers and; C3, addition of Ca and Mg silicate and NK fertilizers). In the highest doses of BRH there was an increase of 2.7, 5.3 and 2.5 times in the P content extracted by Mehlich 1 and quantified by colorimentria, by Mehlich 1 and quantified by spectroscopy and by ion exchange resin and quantified by spectroscopy, respectively. For the highest doses of BCM, the increases in P content were 51.3, 289.2 and 88.4 times greater than in C1, respectively, according to the methods described for BRH. The biochars increased soil pH, CEC, nutrient content and the growth of bean plants compared to C1, especially BCM. However, the production of dry matter was significantly lower than that obtained in C2.