João Tavares Filho

Physical properties of dystrophic Red Latosol (Oxisol) under different agricultural uses

Obtaining information about soil properties under different agricultural uses to plan soil management is very important with a view to sustainability in the different agricultural systems. The aim of this study was to evaluate changes in certain indicators of the physical quality of a dystrophic Red Latosol (Oxisol) under different agricultural uses. The study was conducted in an agricultural area located in northern Parana State. Dystrophic Red Latosol samples were taken from four sites featuring different types of land use typical of the region: pasture of Brachiaria decumbens (P); sugarcane (CN); annual crops under no-tillage (CAPD); and native forest (permanent conservation area) (control (C)). For each land use, 20 completely randomized, disturbed and undisturbed soil samples were collected from the 0– 20 cm soil layer, to determine soil texture, volume of water-dispersible clay, soil flocculation (FD), particle density, quantity of organic matter (OM), soil bulk density (Ds), soil macroporosity (Ma) and microporosity (Mi), total soil porosity (TSP), mean geometric diameter of soil aggregates (MGD), and penetration resistance (PR). The results showed differences in OM, FD, MGD, Ds, PR, and Ma between the control (soil under forest) and the areas used for agriculture (P, CN and CAPD). The soils of the lowest physical quality were those used for CN and CAPD, although only the former presented a Ma level very close to that representing unfavorable conditions for plant growth. For the purposes of this study, the physical properties studied were found to perform well as indicators of soil quality.

Soil aggregation under different management systems

Considering that the soil aggregation reflects the interaction of chemical, physical and biological soil factors, the aim of this study was evaluate alterations in aggregation, in an Oxisol under no-tillage (NT) and conventional tillage (CT), since over 20 years, using as reference a native forest soil in natural state. After analysis of the soil profile (cultural profile) in areas under forest management, samples were collected from the layers 0-5, 5-10, 10-20 and 20-40 cm, with six repetitions. These samples were analyzed for the aggregate stability index (ASI), mean weighted diameter (MWD), mean geometric diameter (MGD) in the classes > 8, 8-4, 4-2, 2-1, 1-0.5, 0.5-0.25, and < 0.25 mm, and for physical properties (soil texture, water dispersible clay (WDC), flocculation index (FI) and bulk density (Bd)) and chemical properties (total organic carbon - COT, total nitrogen - N, exchangeable calcium - Ca2+, and pH). The results indicated that more intense soil preparation (M < NT < PC) resulted in a decrease in soil stability, confirmed by all stability indicators analyzed: MWD, MGD, ASI, aggregate class distribution, WDC and FI, indicating the validity of these indicators in aggregation analyses of the studied soil.

Soil physical properties and sugarcane root growth in a red oxiso

Sugarcane, which involves the use of agricultural machinery in all crop stages, from soil preparation to harvest, is currently one of the most relevant crops for agribusiness in Brazil. The purpose of this study was to investigate soil physical properties and root growth in a eutroferric red Oxisol (Latossolo Vermelho eutroferrico) after different periods under sugarcane. The study was carried out in a cane plantation in Rolândia, Parana State, where treatments consisted of a number of cuts (1, 3, 8, 10 and 16), harvested as green and burned sugarcane, at which soil bulk density, macro and microporosity, penetration resistance, as well as root length, density and area were determined. Results showed that sugarcane management practices lead to alterations in soil penetration resistance, bulk density and porosity, compared to native forest soil. These alterations in soil physical characteristics impede the full growth of the sugarcane root system beneath 10 cm, in all growing seasons analyzed.

Characterization of soil structure and porosity under long-term conventional tillage and no-tillage systems

Os diferentes manejos do solo tendem a modificar a sua estrutura e porosidade ao longo dos anos de manejo. Dessa forma, este trabalho teve por objetivo estudar as alteracoes morfoestruturais e da porosidade de Latossolo Vermelho distroferrico sob preparo convencional e semeadura direta por 31 anos. O estudo baseou-se inicialmente na descricao dos perfis de solo, a partir do metodo do perfil cultural, para qualificar as estruturas mais compactas e definir os locais de coleta de amostras para as analises fisicas e quimicas e obtencao da curva de retencao de agua. Um perfil de solo sob mata foi descrito e usado como referencia. Os resultados permitiram concluir que, no preparo convencional, a estrutura microagregada do Latossolo Vermelho tornou-se fragmentada entre 0 e 0,20 m e compacta (densidade do solo de 1,52 Mg m-3) em subsuperficie, entre 0,20 e 0,50 m. Na semeadura direta, a estrutura tornou-se tambem compactada (densidade do solo de 1,40 Mg m-3) entre 0 e 0,60 m, porem, com a presenca de fissuras e bioporos e a classe de poros com diâmetro > 100 µm, apresentou volume limitado, tendo desaparecido no preparo convencional, enquanto as classes de poros com diâmetro < 100 µm nao foram alterados pelo tempo de manejo do solo.

Models for the estimation of the physical quality of a Yellow Red Latosol (Oxisol) under pasture

Models were developed considering the physical parameters penetration resistance (RP), bulk density (Ds), gravimetric moisture (U), clay content (Ag), sand content (Ar) and organic matter (MO) collected from a Yellow Red Latosol (Oxissol) medium texture under pasture from Rondonopolis county district, Mato Grosso State. Sampling was carried out in 34 fully randomized points in a 1 ha area to the depth of 0-20cm. The models were created using the Statistical Analysis System program (SAS) through which linear multiple regressions and correlations were made. Using the determination coefficient the following model was selected: RP=-12.134+0.004MO+7.6187Ds+0.131AG (R2=0.78). The evaluation of the organic matter and the soil clay content were important tools to evaluate the physical quality of the soils, along with other physical soil properties that indicate soil compaction.

Propriedades físicas de solo e crescimento de batata-doce em diferentes sistemas de preparo

Trabalhos sobre preparo reduzido em solos cultivados com raizes e tuberculos sao escassos e controversos. Assim, este trabalho teve por objetivo avaliar o impacto de sistemas de preparo em propriedades fisicas de um Argissolo Vermelho-Amarelo e no crescimento de raizes tuberosas de batata-doce. Para avaliacao das propriedades fisicas do solo, foi instalado experimento em blocos ao acaso, esquema de parcelas subdivididas. As parcelas corresponderam aos tratamentos: preparo convencional, com confeccao de leiras, e preparo reduzido, com manutencao de palhada superficial e as subparcelas, as epocas de coleta: 120 e 180 dias apos o plantio (DAP) da cultura de batata-doce. Foram avaliados os atributos fisicos densidade do solo, porosidade total, macro e microporosidade, resistencia do solo a penetracao e umidade gravimetrica do solo. Para avaliacao do crescimento de raizes tuberosas de batata-doce, montou-se experimento em que as parcelas corresponderam as formas de manejo do solo, e as subparcelas as quatro epocas de colheita: 90, 120, 150 e 180 DAP. Avaliaram-se as relacoes comprimento/diâmetro e massa fresca individual/comprimento de raizes tuberosas. O preparo convencional do solo com confeccao de leiras, em oposicao ao preparo reduzido, promoveu menores valores de densidade do solo, resistencia do solo a penetracao e microporosidade, maiores valores de porosidade total e macroporosidade; proporcionou menor manutencao de agua na camada superior do solo (0-0,15 m); e permitiu maior crescimento vertical de raizes tuberosas de plantas de batata-doce.

Effects of different management systems on porosity of oxisols in Paraná, Brazil

SUMMARY Soils play a fundamental role in the production of human foods. The Oxisols inthe state of Parana are among the richest and most productive soils in Brazil, butdegradation and low porosity are frequently documented, due to intensive farminginvolving various management strategies and the application of high-tech solutions.This study aims to investigate changes in the porosity of two Red Oxisols (LatossolosVermelhos), denoted LVef (eutroferric) and LVdf (dystroferric) under conventionaland no-tillage soil management, with a succession of annual crops of soybean,maize and wheat over a continuous period of more than 20 years. After describingthe soil profiles under native forest, no-tillage management and conventional tillageusing the crop profile method, deformed and non-deformed soil samples werecollected from the volumes most compacted by human intervention and thephysical, chemical and mineralogical properties analyzed. The various porosityclasses (total pore volume, inter-aggregate porosity between channels andbiological cavities) and intra-aggregate porosity (determined in 10 cm

Sistema radicular de plantas cítricas e atributos físicos do solo em um Latossolo argiloso submetido à escarificação

The work had as objective to evaluate the influence of the scarification on physical attributes of the soil and on the distribution of the root system of Rangpur lemon budded with the ‘Pera’ orange. Four trenches were digged for each treatment (inter-row scarified and inter-row not scarified) The distribution of the roots in the row and inter-row were evaluated down to 1.0 m depth with the SIARCS 3.0 software (Sistema Integrado de Analise de Raizes e Cobertura do Solo). The total porosity and soil bulk density were evaluated in three depths (0.000-0.125; 0.125-0.250 and 0.25-0.375 m) in three sites: row, inter-row and limit of the tree canopy in the interrow. Three years after scarification there were no differences among treatments for soil total porosity and bulk density on inter-rows and for the amount of roots of all depths and sites.

Structural changes and degradation of Red Latosols under different management systems for 20 years

Soils are the foundation of terrestrial ecosystems and their role in food production is fundamental, although physical degradation has been observed in recent years, caused by different cultural practices that modify structures and consequently the functioning of soils. The objective of this study was to evaluate possible structural changes and degradation in an Oxisol under different managements for 20 years: no-tillage cultivation with and without crop rotation, perennial crop and conventional tillage, plus a forested area (reference). Initially, the crop profile was described and subsequently, 10 samples per management system and forest soil were collected to quantify soil organic matter, flocculation degree, bulk density, and macroporosity. The results indicated structural changes down to a soil depth of 50 cm, with predominance of structural units ∆μ (intermediate compaction level) under perennial crop and no-tillage crop rotation, and of structural units ∆ (compacted) under conventional tillage and no-tillage. The soil was increasingly degraded in the increasing order: forest => no-tillage crop rotation => perennial crop => no-tillage without crop rotation => conventional tillage. In all managements, the values of organic matter and macroporosity were always below and bulk density always above those of the reference area (forest) and, under no-tillage crop rotation and perennial crop, the flocculation degree was proportionally equal to that of the reference area.

Influence of Soil Management and Crop Rotation on Physical Properties in a Long-Term Experiment in Paraná, Brazil

This work aims to evaluate the soil physical properties affected by cover crop rotation and soil management in a long-term experiment in southern Brazil. The experiment was established in 1986, with treatments combining six winter treatments and two tillage systems (conventional and no tillage). Bulk density, porosity, aggregate-size class distribution, and organic carbon content of the aggregates were determined at six depths. Bulk density was not affected by tillage systems and winter treatments. The soil disturbance by plowing enhanced the macroporosity, decreased the microporosity, and promoted the formation of smaller aggregate size, in comparison to no tillage. Apart from the soil management, all winter species increased the greater aggregate-size classes, mean weight diameter, geometric mean diameter, and aggregate stability index compared to the fallow treatments. At the no-till treatments, the greater part of sequestered carbon into the soil was stored into the lower and bigger soil aggregates.