Volume 25, Number 2, 2001

This experiment was carried out in pots containing a Dark Red Latosol (Acrortox, loamy sand), to evaluate the effect of sub-soil compaction on root growth of six cover crop species (black oats, pigeonpea, pearl millet, black mucuna, sorghum and blue lupin). The treatments consisted of three sub-soil compaction rates at a 15 cm depth, where bulk densities of 1,12, 1,36 and 1,60 Mg m-3 were established. Cover crop species were grown for a period of 37 to 39 days after emergence, when they were […]

Phosphate sorption can cause particle dispersion, changing soil porosity, and affecting soil-water relationships, mainly in oxidic soils. Therefore, it can also affect water-related parameters, such as consistence limits and response to soil compaction. The objective of this study was to test the effect of phosphate sorption on consistence limits and compression indexes of undisturbed samples from 0-0.03 and 0.27-0.3 m-layers of a Dark Red Latosol from Campos das Vertentes, Minas Gerais, Brazil. Phosphate was added to half of the samples, during […]

Adsorption-desorption reactions of lead in soils are affected by surface chemistry and solution composition. This study evaluated the effect of pH upon lead adsorption-desorption by A-horizon samples of Brazilian Oxisols. Soil suspension was previously titrated with either 7 mmol HNO3 or saturated Ca(OH)2 to determine the amount of acid or base necessary for pH adjustment. The effect of pH on Pb adsorption was evaluated after a 72 h-reaction of the soil samples with 0.15 mmol L-1 Pb(NO3)2 at pH 4.5, 5.5, and 6.5, using […]

Total soil lead (Pb) content along with the sorption capacity of Pb in soils are important parameters for risk assessment studies of Pb in the environment. This experiment used A-horizon samples of 17 Oxisols from all Brazilian regions to evaluate their total Pb content as well as their Pb maximum adsorption capacities (PbMAC). The total soil Pb content varied from 6.14 to 30.55 mg kg-1, averaging 18.00 mg kg-1. The highest total soil Pb contents were found for soils of the southern and southeastern regions, […]

Carbon and nutrients released from the mineralization of organic materials can interact with mineral components changing their dynamics in the soil. In this study, mixtures of corn straw, kaolinite, synthetic goethite, and quartz sand were leached with water after 7, 15, 33, 68 and 113 days of incubation at room temperature. Concentrations of soluble carbon, calcium, magnesium, and potassium were measured and accumulated over time. After 200 days, the total carbon remaining in the mixture was quantified. Total calcium, magnesium, and potassium […]

Cadmium may be added to the soils through tire residues, oils, urban waste, sewage sludge and phosphated fertilizers. It is easily absorbed and translocated by plants and can potentially harm human health. The objectives of this work were to study cadmium adsorption in surface and subsurface horizons of two highly weathered soils with different textures: Anionic “Rhodic” Acrudox (RA) and Anionic “Xanthic” Acrudox (XA), representing extreme conditions in the scale of weathering and exhibiting a predominant balance of positive charge […]

Two experiments were carried out at the Soil Science Department of the Federal University of Lavras (MG), to assess the tolerance to heavy metals “in vitro” of inoculant strains (I), and isolates from both heavy metals contaminated soil (ICS) and uncontaminated soil (IUS) of Bradyrhizobium from Enterolobium contortisiliquum and Acacia mangium and of Azorhizobium from Sesbania virgata. In the first experiment ten strains and, or, isolates of each plant species, were tested in YMA media modified by addition of biological […]

Nitrogen top dressing period affects wheat grain yields and should occur at the stages when yield potential is established. In order to determine the critical stages related to N needs, field experiments were conducted at Estação Experimental Agronômica/UFRGS, Eldorado do Sul (RS), Brazil, in 1993, 1994 and 1995. Wheat cultivars BR 23 (1993 and 1994) and Embrapa 16 (1995) were sown by the end of June at 300 seeds m-2. Nitrogen treatments (40 kg ha-1) were applied at the following stages: (a) plant emergence, (b) […]

In Brazil, upland rice is cultivated mainly on cerrado soils, which, due to their highly weathered degree, present low pH, low base saturation and low ratio of Si oxides of Fe and Al. A greenhouse experiment was conducted to evaluate the response of upland rice to calcium silicate as well as its effect on correcting soil acidity. The treatments consisted of six levels of SiO2 (0; 125; 250; 375; 500 and 625 mg kg-1 of soil) as of wallastonite, Wansil-10 (50% of […]

Black oats and common vetch are the main winter cover crops in southern Brazil. Grass-legume bicultures grown as winter cover crops are rarely used by farmers, although they can provide a more balanced biomass C/N ratio than single crops, besides erosion control and N supply to corn. In order to evaluate this hypothesis, this work was carried out on a Hapludalf with a sandy-loam texture, located at the Federal University of Santa Maria (RS). The treatments comprised different seeding density […]