In environmental studies is important to know the adsorption process of heavy metals in clay minerals, since they are able to immobilize these metals. Knowing the cations adsorption is influenced for several factors, the objective of this research was to study the zinc adsorption process by bentonite clay and to evaluate the particle size of clay and pH influence on this process. In order to quantify the adsorbed zinc, 2 g of bentonite clay, dried at room temperature and sieved at 0.5 and 2-mm-mesh, were equilibrated for 24 hours with 20 mL of water containing different quantities of zinc (10, 15, 20, 30, 50, 100, 150 and 200 mg L-1) as background solutions of pH values 4 and 6. Langmuir's adsorption equation in its linearized form was applied and the values of the maximum capacity and those of the constant related to the bonding energy were obtained. The results showed that Langmuir equation was adequate to describe zinc adsorption at different pH values and particle size of bentonite clay. Zinc adsorption in bentonite clay depended on pH and particle size, decreasing as they increased. The maximum retention capacity, 3.24 mg g-1, was obtained in pH 4 using particle size of bentonite clay < 0,5 mm.

The work was developed in a greenhouse, with the objective to evaluate the behavior of Sudan sorghum in one normal and another saline-sodic soil treated with increasing concentration solutions of calcium chloride. Two samples of Alluvial Soil proceeding from the half-barren part of Paraíba, Brazil, with salinity and sodicity problems had been used. The physical and chemical characterization of soil samples was carried and was mounted an experiment in randomized block type, at 2 x 6 factorial arrangement, being two soils and six solutions of calcium chloride with increasing concentrations, in three replicates. The soil had been conditioned in polyethylene vases with 5,0 kg of capacity, being submitted to the ticket of the solutions during sixty days, being then made a sampling for determination of the exchangeable sodium and the calculation of ESP. After this period, was planted one sorghum tolerant cultivar to salinity, being continued the ticket of the solutions under daily irrigation. At 60 days of application of calcium chloride solutions, it was observed that it had a reduction of the ESP, which continued being reduced until the 120 days, mainly for the saline-sodic soil, correcting the sodicity partially. The effect of the salinity had been evident in sorghum cultivated in saline-sodic soil, with problems since the germination in the treatments of lesser calcium chloride concentration, with improvement in the growth of the plants in the intermediate levels and decrease in the last level, probably, for the raised saline concentration, reflecting in the height of the plants and the production of dry matter.

The pineapple in Paraíba, the fruitful of larger economical importance is considered, with an area planted with more 11.000 there are, and with one of the best productivities at national level, about 23 t/ha. This research was developed in six producing municipal districts in the State, located in the area of the Swamp and Zone of the Forest, in the months of May, June and July of 2006, with the objective to diagnose the process of production of the culture of the pineapple. The data were obtained through a structured questionnaire, approaching information on the productive and socioeconomic process of the culture, being 10 questionnaires for municipal district, which were maybe distributed to the and applied in a direct and individual way, approaching from the big to the small producer. The data were submitted to the analysis of frequency distribution and descriptive. It was verified that the pineapple of cultivating 'Pérola' was the favorite for the producing of small and big load, and most of the pineapple produced in the State he/she feels in the small production, the crop is made in a handmade way, and most of the time without application of powder-crop techniques. Good part of the producers doesn't receive technical attendance it publishes, nor matter.