| Popis: |
The pyrolysis of agricultural wastes process in an environment with absence or deficiency of oxygen has drawn much attention for generating products such as biochar with potential to act as soil conditioners. Characteristics of biochar reinforce its performance as soil conditioner, such as high porosity, aromatic structure and presence of acid functional groups, which result in accumulation and persistence of carbon in the soil, generation of electrical charges, and retention and availability of nutrients. Considering that the time of adopting a management system can influence the quantity of total organic carbon (TOC) contents, but this may not indicate differences between the treatments evaluated, some authors have proposed to fractionate TOC according to four decreasing degrees of oxidation, through the use of different concentrations of sulfuric acid. This method, called TOC fractionation by degrees of oxidation, allows the classification of soil carbon into the fractions F1, F2, F3 and F4. Fractions F1 and F2 are more labile and are more related to the availability of nutrients and the formation and stabilization of macroaggregates, while fractions F3 and F4 are related to compounds with greater chemical stability and molecular weight. This work aimed to evaluate the influence of doses of eucalyptus bark biochar on TOC content and oxidizable organic carbon fractions in dry-separated soil aggregate classes. The study conducted in the field consisted of the application at a Eucaliptus urograndis plantation of five doses of eucalyptus bark biochar (0; 0.25; 0.5; 1 and 2% v v, equivalent to 0; 2.5; 5; 10; 20 t ha-1) produced at two pyrolysis temperatures (350 °C and 600 °C). Two soil samples were taken (365 days and 730 days) at depths of 0.0-0.10 m and 0.10-0.30 m. Through regression analysis of the biochar produced at 350 ºC, we observed a linear increase in the content of the fraction F2, in the classes of aggregates 4.00-2.00 mm (p |
