Fabíola Gomes de Carvalho

Matéria orgânica e propriedades físicas de um Argissolo Amarelo Coeso sob sistemas de manejo com cana-de-açúcar

The continuous cultivation of the sugar cane for long-term under different management systems in soils of Coastal Tablelands can cause alterations in the organic matter and in the physical properties of the soil. The effects of different management systems with sugar cane on the properties of a Cohesive Yellow Argisol, in the Triunfo Sugar Cane Mill, in the State of Alagoas, Brazil, were studied. The management systems consisted of an irrigated area, an area not irrigated, an area with vinasse application and an area under native forest in original condition. Samples were collected from each area at 0-0.2, 0.2-0.4 and 0.4-0.8 m depths to determine the modification in the consistence limits, compaction parameters, stability of aggregates and physical fractions of the organic matter of the soil. The results indicated that the cultivation of sugar cane under not irrigated and irrigated systems promoted a more expressive reduction in the plasticity limit, optimum moisture for compaction and aggregate mean weight diameter, in relation to soil under native forest, due to reduction in the contents of total organic carbon and of particulate organic matter. The management system with vinasse application promoted smaller degradation in physical and chemical properties of the soil in relation to soil under native forest.

Alterações físicas e químicas de um Argissolo amarelo sob diferentes sistemas de uso e manejo

Alterations in the chemical conditions of the soil due to different soil management systems with sugarcane can cause modifications in clay dispersion and in the state of aggregation of the soil. The effects of different soil management systems with sugarcane on the physical and chemical properties of a cohesive Yellow Argisol were studied, being selected four different use and management systems, constituted of a site with irrigated cultivation, a site with not irrigated cultivation, a site with vinasse application and a site under native forest as original condition. Samples of each site were collected at 0-0,2, 0,2-0,4 and 0,4-0,8 m depths to determine the alterations in the chemical and physical properties of soil. The management systems with sugarcane affected the chemical properties of the soil, resulting in reduction of cation exchange capacity and increase of the electrical conductivity, pH in water and critical flocculation concentration. These chemical alterations resulted in larger clay dispersion in the soil cultivated with sugarcane, reducing the stability of the aggregates in water.

Coesão e resistência ao cisalhamento relacionadas a atributos físicos e químicos de um Latossolo Amarelo de tabuleiro costeiro

The cohesive soils of Brazilian coastal plain have subsurface horizon with a peculiar characteristic - when wet the consistency is friablet, but of hard, very hard or extremely hard consistency when dry. The objective of this study was to evaluate the mechanical characteristics of cohesive and non-cohesive horizons of a Yellow Latosol of coastal tableland based on shear parameters related with soil physical and chemical properties and moisture. The results showed that soil cohesion and shear strength increased substantially with the reduction of the water content in the cohesive horizon. The cohesive horizon presented the highest values of bulk density, microporosity and Fe, Si and Al oxides, resulting in higher values of soil cohesion and shear strength as compared to the non-cohesive horizons. The highest values of soil cohesion resulted in greater resistance to penetration in the cohesive horizon in comparison to the non-cohesive horizons. The shear parameters (soil cohesion, internal friction angle and shear strength) proved sensitive for the identification of cohesive horizons in soils of coastal plains.