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No abstract

O objetivo deste trabalho foi modelar um conjunto de dados de teores de carbono orgânico ao longo do perfil do solo, em diferentes sistemas de uso da terra, com base na teoria de modelos mistos. Os solos foram coletados nas camadas 0-10, 10-20, 20-30, 30-40, 40-60, 60-80, 80-100, 100-130 e 130-150 cm, em três áreas distintas. Uma alta variabilidade no teor de carbono foi verificada nas camadas superficiais, por conta da maior incorporação de matéria orgânica existente. Modificando a estrutura que contém o efeito fixo e a que contém o efeito aleatório foi possível gerar modelos e testados pelo método da máxima verossimilhança. Os dados de carbono no solo foram estimados com alta precisão ao longo do perfil do solo, conclui-se que o modelo misto foi eficiente para simular a dinâmica de carbono ao longo do perfil do solo em diferentes padrões de uso e cobertura.

The diagnosis of plant nutritional status was a tool to improve crop fertilization and thus ensure better productivity. This study aimed to evaluate the nutritional status of three sugarcane varieties (RB92579, RB98710 and RB961552) in the plant-cane and first regrowth cycles in the sub-humid region of the state of Alagoas, located in the Northeast of Brazil. The experiment consisted of a randomized complete block design with five replicates. Plant nutritional status was determined by chemical analysis of leaf +3 at the maximum growth phase of the crop. There was a varietal effect for macronutrient and micronutrient contents in both crop cycles, but no variety stood out in regards to leaf contents. However, all three varieties were deficient in Cu and Mn.

The aim of this work was to investigate the carbon stock and soil organic matter (MOS) quality after the conversion from forest-pasture and forest-soybean in Belterra-PA. The climate there is hot and humid, and the annual average temperature is 25.3 °C, while rainfall averages are 1943 mm, concentrated between January and June. The soil of the region is classified as very clayey yellow Latosol. In this research we investigated: (i) a soybean areas in minimum tillage with similar managements-18 years old; (ii) a soybean areas in minimum tillage with similar managements-8 years old; (iii) a nominal pasture (implanted four years ago, managed with fire, without soil fertility correction and managed with extensive livestock) and an improved pasture (implanted six years ago, managed with crop rotation and soil fertility correction by a period of three years. Subsequently, it only remained homogeneous pasture, where the beef cattle herd is managed in a rotational system); (iv) an area of dense ombrophylous forest, used as the reference. Soil samples were collected at six different equidistant points every 50 m. Deformed samples were collected from 0-10, 10-20, 20-30, 30-50, 50-80, 80-100 cm depths and undisturbed samples were collect until 50 cm depth. We estimated the carbon content, soil density, carbon stocks and the C:N ratio. Natural abundance of 13C:12C was used to estimate the amount of carbon from grasses incorporated into the soil. The quality of the MOS was evaluated by humification index and by its physical fractionation. The same soil layers from different areas were compared by analysis of variance and Tukey test (5%). Both pastures were compared between them and in relation to forest area and soybean crops were also compared between them and the forest area. Soil bulk density increased significantly after forest to pasture conversion and forest to soybean conversion. The carbon stock accumulated in the 0-50 cm layer and the degree of humification of the MOS did not differ between the areas. This similarity may be the result of the high clay content presented in this soil, which leads to organic matter slow decomposition, even after changes in vegetation cover. On the soybean areas, the carbon management index was lower in the longer cultivated area, indicating a loss of carbon in this soil. On pasture areas, improved pasture incorporated more carbon from C4 plants in the soil in relation to the nominal pasture, reflecting a positive effect of the rational management on this production system.