ABSTRACT In the Prata watershed there are units corresponding to the Pleistocene Terraces and the Fluvium-Lagoon Sediments. This watershed is inserted almost entirely in the area of plateaus (Tabuleiros) with altitudes of 10 to 100 meters, and in areas with altitudes of 2 to 10 meters in the area of floodplains and fluvio-lagoon terraces. The present work aimed to characterize and classify soils in the Brazilian Soil Classification System - SiBCS and correlate them with the IUSS Working Group WRB-FAO (in parentheses), besides evidence some soil-landscape relations, that occur in Pleistocene terraces and fluvium-lagoon sediments in the Prata watershed, located in the ecological reserve of Dois Irmãos State Park in Recife – PE, Brazil. Soil samples were used to perform physical, chemical and mineralogical analysis in laboratory. Watershed delimitation, Digital Elevation Model (DEM), slope map, soil map and slope x soil map were obtained and studied. The soils are quite acidic and have a very low natural fertility, with the Latossolos (Ferralsols) predominating in the landscape. The silt and clay fractions of the studied Argissolos (Acrisols) and Latossolos (Ferralsols) presented quartz and kaolinite as the main component. In the profile of Neossolo Quartzarênico (Arenosols) only quartz was identified as a component of the silt and clay fractions. The kaolinitic mineralogy of the clay fraction is consistent with the environment of its formation, that is, hot and humid. There is no relationship between the colors of soils and their exposure to the sun on the slopes where they occur. The occurrence of a sandy and whitish horizon between the litter and the A horizon, is not foreseen in the norms and criteria adopted in the Brazilian Soil Classification System - SiBCS.

Abstract: One of the most serious problems in areas indicated for irrigation projects in the Brazilian Northeast region is the occurrence of sandy soils, known to have low moisture retention, but occurring in strategic locations in terms of water supply and geographical situation, and which can be used for agricultural purposes. The objective of this study was to evaluate the influence of particle size distribution and porosity on the water retention capacity of sandy soils in the semiarid area of the Northeast region. Soil bulk and particle densities, total porosity (macro, meso and microporosity), field capacity, permanent wilting point and soil-water retention curve were determined in samples of surface (A) and subsurface (C or Bw) horizons of ten sandy soil profiles. Particle size was determined subdividing the sand fraction into five classes. Higher amounts of the medium and fine sand fractions of the studied soils oriented their physical and hydric characteristics, being responsible for their great water retention. The arrangement of the fine silt, clay, fine sand and very fine sand particles may have provided a diversity of pore sizes and a good pore distribution, being responsible for the large proportion of micropores in the soils, allowing great water retention capacities.

RESUMO A cana-de-açúcar é uma espécie de grande importância econômica para o Brasil. O estudo da atividade enzimática tem ajudado a identificar variedades de cana-de-açúcar tolerantes ao estresse salino para plantio nas regiões semiáridas brasileiras nas quais ocorre incidência de solos salinizados. Objetivou-se, neste estudo, avaliar a atividade enzimática de três variedades de cana-de-açúcar submetidas ao estresse causado pela salinidade. O experimento foi conduzido em casa de vegetação na Universidade Federal Rural de Pernambuco. Foi feito um delineamento inteiramente casualizado, com quatro repetições. Foram coletadas amostras do limbo foliar para análise das proteínas solúveis e determinação da atividade das enzimas catálase e ascorbato peroxidase. O teor de proteínas foi maior para a variedade RB962962 and menor para as variedades RB92579 e RB867515; entretanto se percebeu, na variedade RB867515, aumento da atividade da ascorbato peroxidase e da catálase enquanto que nas variedades RB92579 e RB962962 ocorreu uma redução da atividade dessas enzimas cujos resultados indicam que a variedade RB867515 apresenta um mecanismo mais eficiente na proteção da planta contra a ação de espécies reativas de oxigênio.

ABSTRACT Sugarcane is a species of great economic importance to Brazil. The study of enzymatic activity has helped to identify varieties of sugarcane tolerant to salt stress, for planting in Brazilian semiarid regions, where there is the occurrence of saline soils. The objective of this study was to evaluate the enzymatic activity of three varieties of sugarcane subjected to stress caused by salinity. The experiment was conducted in a greenhouse at the Federal Rural University of Pernambuco, in a completely randomized design with four replicates. The leaf blade samples were collected for analysis of soluble proteins and determination of the activity of catalase and ascorbate peroxidase. The protein content was higher for RB962962 and lower for the varieties RB92579 and RB867515. However, in RB867515, there was an increase in the activity of ascorbate peroxidase and catalase, while the varieties RB92579 and RB962962 showed a reduction in the activity of these enzymes. These results indicate that the variety RB867515 has a more efficient mechanism in plant protection against the action of reactive oxygen species.