André da Costa

Atributos físicos relacionados à compactação de solos sob vegetação nativa em região de altitude no Sul do Brasil

The compaction caused by anthropic activities alters the soil physical properties, decreasing productivity and affecting the environment. Many studies on this topic have been conducted in agricultural soils; however there is little information in areas with native vegetation, where, usually, organic matter levels are higher. Thus, it is essential to evaluate the relationship between physical properties related to compaction under these conditions to establish reference values for the revegetation of native grassland or riparian forests. The objective was to relate maximum bulk density (MaxBD), optimum water content for compaction (OWC) and relative density (DR) with the limits of consistency, particle size and organic carbon content of predominant soils on the Southern Plateau of the State of Santa Catarina, Brazil, under native vegetation of temperate climate. Samples of A-Horizon were collected from two Oxisols (Rhodic and Xanthic Kandiudox), two Entisols (Lithic Udorthents and Typic Udipsamments) and two Inceptisols (Pachic Humudepts). The particle size distribution, particle density, total organic carbon content, limits of liquid, plasticity (LP) and stickiness, plasticity index, maximum bulk density (MaxBD), optimum water content (OWC) for compaction, bulk density, and the degree of compactness were evaluated. The MaxBD increases in soils with higher sand and fine sand content, and decreases in soils with higher clay content and higher liquidity and stickiness limits. The OWC decreases in sandy soils, especially those with a predominance of fine sand, and increases in those with higher clay content, total organic carbon and Atterberg limits. The OWC was between 0.76 and 1.05 times the plastic limit, directly related with the silt content, indicating that the optimum moisture content for compaction cannot be measured only by the determination of the plastic limit of a soil. The OWC/LP ratio of soils at higher altitude in the Southern Plateau of Santa Catarina is different from that of soils in other places, as a consequence of the high levels of organic matter and silt in these soils.

Pedotransfer functions to estimate retention and availability of water in soils of the state of Santa Catarina, Brazil

Studies on water retention and availability are scarce for subtropical or humid temperate climate regions of the southern hemisphere. The aims of this study were to evaluate the relations of the soil physical, chemical, and mineralogical properties with water retention and availability for the generation and validation of continuous point pedotransfer functions (PTFs) for soils of the State of Santa Catarina (SC) in the South of Brazil. Horizons of 44 profiles were sampled in areas under different cover crops and regions of SC, to determine: field capacity (FC, 10 kPa), permanent wilting point (PWP, 1,500 kPa), available water content (AW, by difference), saturated hydraulic conductivity, bulk density, aggregate stability, particle size distribution (seven classes), organic matter content, and particle density. Chemical and mineralogical properties were obtained from the literature. Spearmans rank correlation analysis and path analysis were used in the statistical analyses. The point PTFs for estimation of FC, PWP and AW were generated for the soil surface and subsurface through multiple regression analysis, followed by robust regression analysis, using two sets of predictive variables. Soils with finer texture and/or greater organic matter content retain more moisture, and organic matter is the property that mainly controls the water availability to plants in soil surface horizons. Path analysis was useful in understanding the relationships between soil properties for FC, PWP and AW. The predictive power of the generated PTFs to estimate FC and PWP was good for all horizons, while AW was best estimated by more complex models with better prediction for the surface horizons of soils in Santa Catarina.

Aplicação de resíduo alcalino na superfície de Cambissolos

The cellulose industry produce a large amount of residues, and some have potential to improve the soil fertility. However, there is still lack of information about the viability of use and the doses to be applied to the soil. The aims of this study were to evaluate the use of an alkaline residue (dregs) as acidity corrective and measure the changes in the chemical and physical attributes of two Cambisols, one clay loam and another sandy loam. The experiment was performed in pots in a greenhouse, with superficial application of dregs in the proportion of 0%, 12%, 35%, 50% and 100% of the equivalent rate of CaCO3 required to increase the pH to 6.0. The maize crop was grown until 40 days after germination to quantify the dry matter of roots and shoots. In soil not cultivated with maize, samples were collected to evaluate the aggregate stability, clay dispersion, pH, and content of exchangeable cations. The addition of surface dregs increases the pH, Ca, K and Mg, and reduces the content of exchangeable Al, mainly in the soil layer of 0 to 5 cm. However, harmful effects are observed, as the increase in the content of Na, the Ca/Mg ratio and dispersion of clay. Changes in soil chemical properties favor the growth of roots and shoots of maize until the dose equivalent to the dregs from 40 to 47% of the need for lime to raise the water pH to 6.0. Above these doses plant development is constrained.

CRESCIMENTO INICIAL DA CULTURA DA SOJA EM LATOSSOLO BRUNO COM DIFERENTES GRAUS DE COMPACTAÇÃO

A compactacao do solo e um dos principais fatores que altera a qualidade do solo e o crescimento das culturas. O objetivo deste trabalho foi determinar o grau de compactacao que restringe o crescimento da cultura da soja num Latossolo Bruno aluminico tipico. O experimento foi realizado em casa de vegetacao. O solo utilizado foi coletado no municipio de Guarapuava, PR, na camada de 0-20 cm. Esse possuia 570 g kg-1 de argila, 370 g kg-1 de silte e 60 g kg-1 de areia. Foi compactado para obtencao das densidades do solo de 0,90; 0,96; 1,02; 1,08; 1,14; 1,20; e 1,27 kg dm-3, correspondendo a graus de compactacao entre 75 e 105 %, que foram determinados pela relacao entre a densidade do solo atual e a densidade do solo maxima, obtida pelo ensaio de Proctor Normal. Durante o periodo de cultivo da soja avaliaram-se o crescimento radicular e a parte aerea, alem da evapotranspiracao diaria. Aos 60 dias apos a emergencia, determinou-se a massa seca da parte aerea e das raizes. Qualquer aumento no grau de compactacao acima de 75 % reduz o crescimento das raizes na camada compactada; entretanto, as raizes nao crescem quando o grau de compactacao e igual ou superior a 105 %. Quando o grau de compactacao e superior a 82 %, a altura das plantas diminui e quando e superior a 87 e 93 % reduz respectivamente a massa da materia seca da parte aerea e a evapotranspiracao. Assim, o grau de compactacao restritivo a cultura da soja depende do atributo que esta sendo avaliado.

Semeadura direta com diferentes mecanismos sulcadores: alterações em propriedades de um Latossolo Bruno e produtividade das culturas

The mechanisms of seeding machines to cut the mulch, mobilize the topsoil and deposit the seeds in the furrows modify soil properties and interfere in crop growth. This study sought to evaluate the effects of furrow openers and scarification on the attributes of a South Brazilian latosol (Bruno – oxisol) and crop yields. The treatments were: double disc furrow opener (DD); shovel type furrow opener (S); shoe type furrow opener (SH); and scarification followed by double disc furrow opener (SC+DD). Samples were collected at 0-10, 10-20 and 20-40 cm and evaluated for soil physical (bulk density, total porosity, macro and microporosity), chemical (pH, Ca, Mg, K and P) and organic carbon content. The normality of data was tested, and the analysis of the variance was performed (F test, p<0.05), and the means was compared by Tukey’s test (p=0.05). Soil attributes were analyzed for each layer separately. After four years it was observed that the bulk density is still affected by scarification, which reduces it. The successive use of DD in the winter for the implantation of the crops caused the homogenization of the soil, although with no differences on the other physical and chemical properties. In general, grain yield and dry mass were higher in the treatment that used scarification and the double disc during the summer, and the shoe type when compared to shovel type.

Corrective Potential of Alkaline Residue (Dregs) from Cellulose Industry in an Acid Soil Cultivated Under No-tillage

ABSTRACT The use of alkaline residues from cellulose industry can increase soil fertility and crop productivity, but some of these residues, such as dregs, can also reduce soil physical quality. This study aimed to evaluate the effects of the dregs compared to lime as corrective for soil acidity applied on the surface under no-tillage. The treatments applied, half in 2004 and half in 2006, were: without corrective; dregs rates of 3.25, 6.5 and 13 Mg ha−1 and dolomitic lime rates of 5.25 and 10.5 Mg ha−1. After 5.5 years since the first application, soil chemical and physical attributes were determined, as well as soybean yield in 2010 and bean yield in 2011. Positive effects were observed on the soil chemical attributes with the application of dregs or lime, such as increased pH, calcium content, cation exchange capacity, and base saturation, and decreased the aluminum saturation. However, it was observed increase in sodium content and calcium/magnesium ratio with the application of dregs, however without impairing the soil physical quality. The soybean and bean yield increased in a similar way using dregs or lime. These results indicate the possibility of using dregs as corrective of soil acidity.