Acúmulo de biomassa, acidez ativa e fracionamento de carbono orgânico em solo cultivado com plantas de cobertura nas entrelinhas do cajueiro anão

Abstract

The use of vegetation cover is a soil and water conservation practice with the potential to increase soil organic matter content, promote nutrient cycling in the soil, reduce solar radiation incidence, and enhance the biological activity of microfauna. The cultivation of dwarf cashew (Anacardium occidentale L.) is of great economic importance in the Northeast region of Brazil. However, few studies have been conducted to determine which cover crops are most suitable for the semiarid region. Therefore, the objective of this study was to evaluate the effect of different cover crop species on soil organic matter accumulation and active acidity in a red-yellow Argisol cultivated with dwarf cashew. The experiment was carried out from 2019 to 2021/2022 at the Experimental Area of Embrapa Agroindústria Tropical in Pacajus. Three soil samples and three samples of remaining plant residues were collected at the end of each cycle. The experimental design used was randomized blocks, with 5 treatments and 4 replicates. Four cover crop species were evaluated, in addition to the control treatment: T1: control (spontaneous vegetation); T2: 1st cycle - Cajanus cajan cv. BRS Mandarim and from the 2nd cycle onwards - Brachiaria humidicola; T3: Panicum maximum cv. Massai; T4: Brachiaria ruziziensis; and T5: Brachiaria brizantha cv. Xaraés. The grasses were broadcast seeded, while the legume was planted in holes. The remaining biomass collections were conducted at the end of the year (November/December), and soil samples were taken at the beginning of the year (February to April). pH analysis in water, determination of soil organic matter, and organic carbon fractionation were performed. Capim Xaraés and Capim Ruziziensis stood out in terms of the amount of remaining biomass. It was observed that even maintaining native vegetation in the Control treatment resulted in increased soil organic matter content compared to previous years. Regarding carbon fractionation, all treatments contributed to an increase in organically associated mineral carbon, which is the fraction with the greatest adherence to the soil. In conclusion, Capim Ruziziensis and Capim Xaraés are the most suitable plants for maintaining residual biomass in the soil, as well as for increasing organic carbon content. Capim Xaraés proved to be the most consistent treatment in terms of accumulating biomass on the soil surface among all the evaluated species.