No abstract

Fruticulture in the Amazonian Rainforest is one of the main causes of deforestation, biodiversity loss, and soil erosion. Fruticulture plays a key role in the soil traits and soil organic matter (SOM) compartments by altering the soil ecosystem. Our aim was to assess the influence of Forest–Fruticulture conversion on soil traits, and SOM fractions in Brazil’s Legal Amazon. The experiment was carried out in field conditions using four land uses as main treatments: Bixa orellana, Theobroma grandiflorum, Paullinia cupana, and the Amazon Rainforest. The soil physicochemical traits were analyzed using samples that were collected from 0–5, 5–10, and 10–20 cm soil depth by using grids (10 × 10 m) with 36 sampling points. Our results showed that the Fruticulture promoted an increase in bulk density, GMD, aggregate diameter, soil porosity, gravimetric moisture, sand, clay, carbon associated with humic acid, and, the sum of bases (K+, Ca2+, and Mg2+), while the Amazon Rainforest showed the highest values of silt, soil P content, SOC, p-SOC, m-SOC, carbon associated with fulvic acid, humine, and soil C stock. Overall, the fruticulture farming systems have negative effects on SOM compartments. The results of our study highlight the importance of considering fruticulture with endemic plant species by promoting soil fertility and soil aggregation.

O objetivo desse estudo foi determinar os teores de fósforo total (PT) e de suas formas e frações (Pt-bic, Pi-bic, Po-bic, Pt-H+ , Pi-H+ , Po-H+ , Pt-OH- , Pi-OH- e Po-OH- ), em agregados biogênicos e fisiogênicos sob diferentes sistemas de manejo agroecológico, no município de Seropédica-RJ. Foram abertas trincheiras com dimensões aproximadas de 0,25 x 0,20 m, em seguida foram coletados blocos de solos nas áreas amsotrais: sistema agroflorestal (SAF); café em pleno sol (C-SOL); café sombreado (C-SOM); cultivo em aleias de flemíngia/vagem (AL-FLE) e plantio direto com milho/ (PD) com 6 anos de cultivo; em 3 camadas (0,00-0,05; 0,05-0,10 e 0,10-0,20 m) com 4 pseudorepetições em delineamento inteiramente casualizado. Após a coleta, as amostras foram submetidas a tamisação em conjunto de peneiras de 9,7 - 8,0 mm. Foram utilizados para a identificação das vias de formação os agregados retidos neste único intervalo. Estes foram examinados sob lupa e separados manualmente e classificados em: biogênicos – aqueles que apresentaram formas arredondadas; e fisiogênicos – definidos com formas angulares. O PT foi determinado via digestão sulfúrica, e as formas e frações de P foram extraídas em sequência com NaHCO3, H2SO4 e NaOH. O PT e as suas formas e frações foram determinadas por colorimetria após a redução do complexo fosfomolibídico com ácido ascórbico. Os resultados foram submetidos à análise de variância com aplicação do teste de agrupamento de médias de Scott Knott (p<0,05). Nos agregados fisiogênicos foram verificados os maiores teores de Pt-bic, Po-bic, Pt-H+ , Pi-H+ , Po-H+ e Po-OH- em comparação aos agregados da via biogênica na maioria das áreas estudadas. As concentrações de P encontradas nos diferentes tipos de agregados evidenciaram o importante papel das vias de formação na avaliação da qualidade do solo e que todas as áreas avaliadas possuíam capacidade de se auto sustentar em relação à nutrição fosfatada.

Histosols provide several ecosystem services, related mainly to their reserves of carbon and nitrogen. Management practices in these soils can increase the mineralization of organic matter and contribute to the emission of greenhouse gases. This study aimed to investigate the effect of tillage with plowing and drainage on Histosol properties in three land use systems located in the municipality of Rio de Janeiro, Brazil. Three areas subjected to different land use systems over the last twenty years were chosen: Area 1, secondary forest with natural regeneration; Area 2, conventional tillage of cassava with plowing; and Area 3, intercropped coconut + cassava with an artificial drainage system. The chemical characterization, von Post scale of organic matter decomposition, percentage of rubbed fiber, organic matter, percentage of mineral material, bulk density, electrical conductivity, soluble phosphate, total organic carbon (TOC) and nitrogen (NT), organic carbon fractions, and C and N stocks were analyzed. Our results showed the critical, nearly irreversible effects of agricultural practices comprising drainage and plowing of the soil. Over twenty years, in Area 2, the TOC and NT values decreased by 33 and 20 %, respectively in the histic horizon, and by about 17 and 8 %, respectively in the gley horizon. In Area 3, the TOC and NT values decreased by 31 and 18 %, respectively, in the histic horizon, and by 27 and 21 % in the gley horizon. Our findings also showed that the loss of C is related to the labile organic carbon, which is more sensitive to environmental changes, even at deeper depths. The plowing of the soil decreases the organic matter content due to the accelerated oxidation of organic matter, increasing the bulk density. Drainage, besides the loss of organic matter by subsidence, promotes the sulfidization of the soil with a high content of SO 4 2-, due to the oxidation of soil materials containing sulfides.

The objective of this study was to evaluate the bulk density, total pore volume, carbon stock and natural abundance of 13C in Rhodic Ferralsol in no-tillage system (NTS) areas under different succession and rotation of cultures in the Cerrado of Goiás State, Brazil. In order to do so, NTS areas were selected in Montividiu, Goiás, under the same soil and climatic conditions as the following rotations: soybean-corn succession, soybean-millet succession, soybean-corn-millet-beans-cotton rotation, soybean-corn-brachiaria succession and a pasture area (PA), used as a control. In each area, samples were collected at depths of 0.0–0.05, 0.05–0.10, 0.10–0.20, and 0.20–0.40 m. The lowest levels of carbon content and stocks were verified in PA in comparison to the other areas evaluated. The NTS with soybean-corn-millet-beans-cotton crop rotation followed by NTS with soybean-corn-brachiaria succession were those that presented greater potential for carbon stock increase and total soil pore volume, as well as bulk density reduction. The origin of the soil organic matter in the NTS areas is related to plants employing the C4 photosynthetic cycle; however, for mixed C3 and C4 plant systems, the isotopic signature of 13C is reduced, mainly in areas with crop rotation.