Sequestro de carbono e supressão de plantas invasoras por cobertura vegetal

Abstract

Soil is a dynamic compartment in its composition and it is important for the development of plants. The use of cover crops contributes to the maintenance and improvement of soil quality and nutrient cycling. The accumulated biomass of these plants promotes soil cover, suppresses the growth and development of invasive plants. Also the decomposition of these vegetal residues allows the accumulation of organic matter in the soil, in addition to the increment in the C stock of the soil. The aim of this study was to evaluate the effect of the use of different species of cover plants on the chemical properties of the soil and to evaluate the storage potential of organic carbon of these species, besides the suppression of invasive plants. The study was conducted at Fazenda Santa Rosa, located on AM 70 highway, Km 12, in Iranduba town, State of Amazonas-AM. The species of cover plants used in the treatments were: Brachiaria decumbens; Brachiaria ruziziensis; jack bean; Calopogonium and Millet. In addition to the cover crops, another treatment were the invasive plants as natural cover and non-vegetation treatment. The phytosociological survey of the invasive plants was in the area of the treatments, as well as the dry matter production of the cover plants and the invasive plants suppression. Fractions of organic matter were collected from soil samples at depths from 0-20 to 20-40 cm. In each plot, three replicates per depth were collected and the following variables were evaluated: total organic carbon (TOC), particulate organic carbon (COP), organic carbon associated with minerals (COAm), labile carbon (CL). The indexes of the neighborhood effect (RNE), carbon management index (BMI) and stratification index (SI). Ten invasive plant species distributed into 8 botanical families were identified. The plants of jack Bean of pig and Calopogônio were those that provided greater coverage of the soil and the main suppressors of the invasive plants. Also accumulated high amounts of dry matter were B. decumbens and B. ruziziensis with 12 t ha-1 and 11.5 t ha-1, respectively. There was no difference in soil carbon content among the different depths and species of cover plants. The cover plants sequestrated carbon and with superior quality of the organic matter, when compared without vegetal cover. These plants were efficient in maintaining and increasing the stocks of organic matter in the soil.