Non-uniformly broadcast as well as row applied fertilizers under a no-tillage system increase the variability of soil chemical attributes. Therefore, to acomplish an appropriate fertility description of an area under no-tillage it is necessary to establish better sampling procedures, including number of subsamples. So, the main objective of this work was to measure the horizontal variability of soil fertility attributes, allowing, as a consequence, a definition of the number of subsamples needed to compose a whole and representative fertility sample. […]

In order to evaluate organic N availability to oats and corn, a microplot experiment was carried out using 20 types of soil from Rio Grande do Sul State, Brazil. Microplots consisted of 20 L soil plastic pots with free drainage, maintained in an open area, with supplemental irrigation when necessary. N taken up by oats (Avena strigosa) and three corn (Zea mays) crops grown in successions was evaluated. Soil total-N and organic matter contents were initially determined as well as […]

The semiquinone free radical concentration (SFRC), determined by electron paramagnetic resonance (EPR), is an index of degree of humification of soil organic matter. The objective of this study was to evaluate the possible interference of mineral fraction in the quantification of SFRC in organo-mineral aggregates 20-53, 2-20 and < 2 ∝m of three soils from southern Brazil: Paleudalf, Paleudult and Haplorthox. The SFRC was calculated by the semiquinone signal intensity (I, in cm) multiplied by its square line width (∆H2, […]

Growing corn and soybean in acid soils requires lime application to raise the soil pH to reduce the aluminum toxicity and to add the nutrients calcium and magnesium. The residual effect of liming may last for several years of successive cropping. To evaluate this effect, an experiment was carried out in a Low Humic Gley soil in the EMBRAPA Cerrados Research Center, with the broadcasting application of lime levels of 0, 2, 4, 6 and 8 t ha-1, beginning in […]

Soil is in a steady state under natural conditions, but an inadequate management can cause degradation, mainly of the organic matter, impairing the sustainability of agricultural systems. The present study was undertaken in a six-year-old field experiment on a typic Hapludalf (Red Yellow Podzolic Soil), at the Department of Soil Science, UFSM, Santa Maria, Rio Grande do Sul state, Brazil, to evaluate the effects of plant successions on soil nitrogen dynamics, under no tillage system. The plant successions used were […]

Farming and cattle-raising integrated system is an alternative to increase farmers’ yield in southern Brazil (29o 45´south and 53o 42´ west Greenwich). However, grazing and, or, soil tillage may cause soil compaction at levels that can affect root growth and crop yield. The effect of animal trampling in continuous grazing during winter/spring (cold season) and soil management system effects on soil compaction, chemical attributes and root distribution were studied. The soil used was a Red-Yellow Podzolic (Hapludalf), with a loam […]

The effect of rhizosphere soil addition on ametryn degradation rate was evaluated. The 14CO2 release rate from sterile and non-sterile samples of a sandy soil was compared with the same soil amended with 10% rhizosphere soil from a sugar-cane plantation, treated or not with ametryn. Sterilized soils showed very low 14CO2 release as compared with non-sterilized soil. When mineralization of non-amended soil was compared with rhizosphere soil amended from treated and non-treated fields, 3.5 and 1.7 fold increases of mineralization, […]

Corn requires a high uptake of nitrogen. Because soil has a limited capacity to supply this N demand, other N sources as legumes and mineral fertilizers are used. Potentially, the association of these sources of N can contribute to agricultural sustainability. This work was carried out to evaluate the impact of tillage and cropping systems on N availability. A long-term experiment established on a Paleudult at UFRGS (RS), Brazil was used. This experiment had three tillage systems: conventional, minimum and […]

Spontaneous plant species in agricultural areas have been regarded as weeds, invasive or unwanted plants, when considering the damages that they can bring to cultivated species. However, spontaneous species can bring about the same effects of soil protection and nutrient cycling that cultivated or introduced species used for green manure do. Biomass productivity and nutrient accumulation for the aerial part of spontaneous and leguminous plants used as green fertilizers were measured at the experimental station Embrapa Corn and Sorghum, in […]

Two systems of sugar cane harvesting were compared: 1-previous burning (burned cane) and 2-straw spreading over the soil surface (green cane), over an area of Linhares Agropecuária S.A. plantation, in Linhares, Espírito Santo, Brazil. The soil was classified as Yellow Podzolic sandy over medium texture, developed from Barreiras Formation sediments. After six years of sugar cane cultivation (1989-1994), nutrient distribution, humified fractions, and soil microbial biomass dynamics were determined. The green cane system showed an increasing of soil carbon content […]