Volume 21, Number 3, 1997

The application of a surface complexation model to determine the effect of the pH and the phosphate concentration in the soil solution on the adsorption of phosphorus in two acric soils, was evaluated. Surface and subsurface samples were collected from two Oxisols of Ribeirão Preto and Guaíra, northern of the State of São Paulo, Brazil, in 1993. The samples were incubated with increasing amounts of calcium carbonate and hydrochloric acid to change the pH. The adsorption curves were obtained by […]

The fumigation-extraction method was used for measuring soil microbial biomass of C (BM-C) and N (BM-N) in a red-yellow latosol under different forest types. Soil samples from eucalypt and pine plantations presented higher values of BM-C (223.72 and 207.39 mg kg-1 of C in the soil, respectively) than samples from Piptadenia rigida and regenerating secondary forest (82.94 and 79.47 mg kg-1 of C in the soil, respectively). Similar results were obtained for the litter layer. On the other hand, the […]

With the objective of assisting sampling systems and planning orange experiments, soil variability was assessed in a twelve-year-old orange orchard, cv. Pera, grown on a dystrophic Yellow Latosol of medium texture plain relief, in Governador Mangabeira, State of Bahia, Brazil, 1990. A transect consisting of 50 trees, spaced 4 m apart, was sampled. Soil samples were taken from a fixed point under the tree drip line on the successively fertilized strip. Results showed that only phosphorus and gravimetric soil moisture […]

The variability of leaf nutrient concentrations (nitrogen, phosphorus, potassium, calcium, magnesium, zinc, copper, manganese, and iron) was assessed in a twelve-year-old orange orchard, cv. Pêra, grown on a dystrophic Yellow Latosol of medium texture plain relief, in Governador Mangabeira, State of Bahia, Brazil, 1990. A transect consisting of 50 trees, spaced four meters apart, was sampled. Twenty leaves were collected from each tree. The leaves were taken from four different points of the crown, opposite two by two, and from […]

The efficiency of two nitrogen fertilizers, ammonium sulphate and urea, labelled with 15N, in two major Central-Amazonian soils (Yellow Latosol – an Oxisol and Red-Yellow Podzolic – an Ultisol), was studied in greenhouse experiments in Nancy, France, 1992. Italian rye-grass (Lolium multiflorum L.) was used as the test plant. Rye-grass nitrogen uptake of ammonium sulphate ranged from 44 to 49%, and of urea from 60 to 70%. Immobilization and losses of nitrogen were dependent on the fertilizer type. Microbial nitrogen […]

This study was carried out under laboratory conditions from September to December, 1992. The objective was to evaluate the mineralization of nitrogen in cowpea (Vigna unguiculata L.) green manure, using 15N as tracer, in three major soils of Central Amazon: an Oxisol, an Ultisol and a Low-Humic Gley. The variation in amount and form of the mineral N from cowpea residues was related to the chemical characteristics of each soil. In the Oxisol and Ultisol the incorporation of green manure […]

The spatial variability of the soil characteristics colour, clay content, pH and penetrometer resistance was evaluated in seven areas on which strongly weathered and intensively cropped soils occur, in the Planalto Médio region, State of Rio Grande do Sul, Brazil. Nested analysis of variance was performed with the objective of assessing their homogeneity and optimal soil sampling density. Representative soil profiles were characterized and classified in these areas. Field work was performed from August to November, 1989. Kandiudox, Hapludox and […]

The spatial variability of soil characteristics in the Planalto Médio region, State of Rio Grande do Sul, Brazil, was studied in six areas cultivated with soybean. Semivariance and variance analyses were applied to the data obtained by systematic soil sampling to confirm and detail results obtained by nested analysis of variance, and to estimate the variance of characteristics within soil mapping units and the range of its application for land evaluation. Field work was performed from December, 1989 to March, […]

A rotating-boom rainfall simulator, operating at a constant rainfall intensity of 64 mm h-1 for sufficient time to runoff reaches steady-rate, was used to investigate water erosion and other related parameters in three tillage systems. The experiments were carried out immediately following corn and wheat harvesting, in a sandy loam Red-Yellow Podzolic soil (Paleudult) with a 0.066 m m-1 average slope, in Eldorado do Sul, State of Rio Grande do Sul, Brazil, from 1992 to 1994. No-tillage, chiselling and disk-plowing […]

A cartographic simulation in a Geographical Information System (GIS) was used to evaluate the environmental impacts of different forest management strategies on a watershed scale. The project was conducted in a small (2 km2) watershed located at northern coast of the State of Espírito Santo, Brazil, which is inserted in an area of eucalypt-clone plantation comprised by the agro-industrial complex Aracruz Celulose S.A. Potential impacts were assessed by applying the Universal Soil Loss Equation (USLE) in a GIS, where different […]