José Fernando Wanderley Fernandes Lima

Caracterização e gênese do caráter coeso em latossolos amarelos e argissolos dos tabuleiros costeiros do estado de Alagoas

The cohesive character is an attribute of subsurface soil horizons with hard to extremely hard consistency when dry, and friable or firm when wetted. Despite the agricultural importance, the formation of these horizons is not yet completely understood. The objective of this study was to characterize and assess the possible mechanisms involved in the formation of cohesive horizons in soils of the Coastal Tablelands of Northeast Brazil, in order to understand their pedogenesis and to identify physical and chemical parameters that can be used for the definition of the cohesive character in the Brazilian System of Soil Classification. Four soil profiles were morphologically characterized: a Yellow Argisol (Ultisol), a Gray Argisol (Ultisol) and two Yellow Latosols (Oxisols). Samples from cohesive and non-cohesive horizons were taken for physical and chemical analysis. The morphological description revealed the presence of the cohesive character both under forest as well as under cultivation, confirming its pedogenetic nature. Soil morphology and soil density, together with the specific surface area efficiently identified the cohesive character in the studied soils.

Mineralogy and micromorphology of cohesive horizons in oxisols and ultisols of the coastal tablelands of Alagoas, Brazil

The cohesive character is a property of subsurface soil horizons with hard to extremely hard consistency when dry, and friable or firm when wet. Despite the agricultural importance, the formation of these horizons has not been fully explained. The objective of this study was a chemical, mineralogical and micromorphological characterization of cohesive soils of the Coastal Tablelands in Northeast Brazil, to understand their pedogenesis and identify properties for the definition of the cohesive character by the Brazilian System of Soil Classification. The following four soil profiles were morphologically characterized: a Yellow Argisol (Ultisol), a Gray Argisol (Ultisol) and two Yellow Latosols (Oxisols). Samples from cohesive and non cohesive horizons were taken for chemical analysis of Fe, Al and Si extracted by DCD, oxalate, CaCl2 and hot water, mineralogy by X ray diffraction, and micromorphological characterization. The Fe contents in the soils were low and kaolinite with a moderate to high degree of structural disorder predominated in all studied soil horizons. No increase in Al and Si extracted by DCB and oxalate was observed in the cohesive horizons, indicating the absence of cementation in its genesis. Results of the mineralogical and micromorphological characterization suggest two distinct phases in the genesis of the cohesive character. The first step was determined by clay illuviation, clogging the soil pores, and later iron loss, destroying the soil structure and resulting in a direct adjustment with kaolinite particles.

Relações solo-vegetação em áreas sob processo de desertificação no município de Jataúba, PE

Land degradation in semiarid regions is a result of natural processes that can be induced or intensified by man through the inadequate use of natural resources, resulting in the degradation of vegetation, soil and water resources. Aiming to relate vegetation and soil degradation processes in the Agreste region of Pernambuco State, soil and vegetation in twelve representative plots were characterized as preserved, moderately degraded and degraded environments in the municipality of Jatauba. To study the vegetation, plants were stratified in three layers or height classes: 3 - plants taller than 3.0 m, sampled in the total plot area (200 m2); 2 - plants with a height between 0.51-3.0 m, sampled in an area of 100 m2; 1 - plants with height equal to or less than 0.50 m, sampled in 18 miniplots of 25 x 50 cm. Soils were morphologically characterized in each plot and samples collected from each horizon for physical, chemical and mineralogical analysis. The vegetation of the 2nd stratum showed a great decrease in absolute density as a result of soil degradation intensity. Species with highest relative densities were: Neoglaziovia variegata (caroa) and Cordia leucocephala (moleque-duro) in the preserved area; Bromelia laciniosa (macambira), Aspidosperma pyrifolium (pereiro) and Caesalpinia pyramidalis (catingueira), in the moderately degraded area; and C. pyramidalis and Sida galheirensis (malva branca), in the degraded area. The soil properties of the Planosols that were strongly correlated with the preserved vegetation were the gravel contents in surface horizons, thickness of A + E horizons, and the concentration of organic carbon. The occurrence of soil crusting and erosion, as well as high percentages of exchangeable sodium was observed with greater intensity at the degraded sites covered by more sparse vegetation.

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.

Caracterização de vertissolos da ilha de Fernando de Noronha, Pernambuco

O Arquipelago de Fernando de Noronha (FN) possui solos pouco desenvolvidos das classes dos Cambissolos, Vertissolos e Neossolos, com caracteristicas peculiares relacionadas ao material de origem vulcânico, clima tropical com franco dominio oceânico e relevo ondulado a forte ondulado. Os Vertissolos de FN sao formados a partir de rochas basicas, tufos vulcânicos e sedimentos aluvionares e estao associados as superficies rebaixadas com drenagem impedida do planalto central ou da baixada litorânea. Tendo em vista a necessidade de preservacao ambiental, uso agricola ou geotecnico e caracteristicas peculiares desse ambiente insular, os Vertissolos de FN precisam de melhor entendimento de seus atributos. O objetivo deste trabalho foi, portanto, caracterizar morfologica, fisica, quimica e mineralogicamente Vertissolos de ocorrencia comum na ilha de Fernando de Noronha. Tres perfis de Vertissolos derivados de diferentes materiais de origem, classes de drenagem e niveis de salinidade e sodicidade foram descritos e coletados para realizacao das analises de caracterizacao. Os solos estudados foram: Vertissolo Haplico ortico solodico (P01), Vertissolo Haplico salico gleissolico (P02) e Vertissolo Haplico sodico gleissolico (P03). Os Vertissolos de FN apresentam feicoes tipicas da ordem, como a textura argilosa a muito argilosa, as superficies de friccao (slickensides) e o fendilhamento horizontal e vertical quando secos. Esses solos sao imperfeitamente a maldrenados e sofrem alagamento temporario no periodo de maior concentracao das chuvas. Apresentam elevados valores de soma e saturacao por bases, alem de teores altos a muito altos de P extraivel, de distribuicao irregular entre perfis e com dominância de formas inorgânicas. Nao obstante, esses apresentam problemas de acumulacao de sais, o que restringe a utilizacao agricola ou geotecnica deles. Os principais minerais da fracao argila dos solos sao do grupo das esmectitas, seguidos por caulinitas e, ou, haloisitas. A fracao silte e constituida por hematita, goethita, magnetita/maghemita, ilmenita, mica e feldspato e por minerais pouco comuns em solos brasileiros como crandalita e holandita.