Geraldo César de Oliveira

Dinâmica da resistência à penetração de um Latossolo Vermelho da Microrregião de Goiânia, GO

This study aims to evaluate soil moisture and bulk density effects on penetration resistance dynamics of Dark Red Latosol, located in the Microregion of Goiânia, Goias. Area under rotating pasture were sampled 1) in lines and 2) between lines; 3) pasture renewal area; 4) area under Central Pivot; 5) area under no-tillage and 6) forest. Penetrometry tests were done for three different soil moistures, and six undisturbed soil samples were collected in layers of 0-5 and 20-30 cm for determination of bulk density, soil moisture at field capacity, total porosity, and micro and macro-porosity. Soil use and management affected in a differentiated way, all analyzed soil attributes; penetrometry diagnosis test was efficient when accompanied by bulk density and soil moisture analysis; the Dark Red Latosol studied appears to offer a restriction on types of crops cultivated in areas under central pivot and in rotating pasture when soil presents low moisture.

Pressão de preconsolidação e intervalo hídrico ótimo como indicadores de alterações estruturais de um latossolo e de um cambissolo sob cana-de-açúcar

A identificacao dos impactos da colheita mecanizada da cultura da cana-de-acucar sobre a estrutura do solo em diferentes classes pode-se tornar uma importante estrategia de manejo para a minimizacao dos efeitos da compactacao. O objetivo deste trabalho foi avaliar as alteracoes estruturais, a pressao de preconsolidacao e o intervalo hidrico otimo (IHO) em um Latossolo Vermelho-Amarelo (LVA) e um Cambissolo Haplico (CX), em consequencia das operacoes de colheita da cana-de-acucar em diferentes epocas de safra. Coletaram-se amostras indeformadas de solo na profundidade de 0 a 0,05 m para determinar a pressao de preconsolidacao, a densidade, a porosidade do solo, a agregacao e o IHO, bem como amostras deformadas para a caracterizacao quimica e fisica do solo. O CX apresentou maior resistencia a compactacao que o LVA. O conteudo de agua no solo durante a colheita da cana-de-acucar variou na ordem: agosto de 2006 LVA em cada epoca. A densidade do solo na pressao de preconsolidacao foi sensivel a ocorrencia de alteracoes estruturais no solo. A macroporosidade limitante apresentou restricoes ao crescimento das plantas em niveis de compactacao inferiores a densidade do solo critica do IHO. A colheita mecanizada da cana-de-acucar realizada em solo com 0,16 e 0,21 kg kg-1 de agua, para LVA e CX, respectivamente, nao promoveu compactacao excessiva.

Intervalo hídrico ótimo como indicador de melhoria da qualidade estrutural de latossolo degradado

Grass pastures, if well-established and managed, play an important environmental role as soil cover, for aggregate formation and stabilization and in the reduction of dense or compacted layers. The objectives of this study were to quantify the least limiting water range (LLWR) of a physically degraded Red-Yellow Latosol (Oxisol) on which bermudagrass (Cynodon spp., cultivar coastcross) was planted, and to use the LLWR as an indicator of changes in the soil structural quality. Undisturbed samples were collected in volumetric rings (height 0.025 m, diameter 0.065 m) from the layers 0-0.05, 0.20-0.25 and 0.80-0.85 m (Bo horizon), in areas without machine traffic, during the rainy season of 2008/2009 in november 2008, march 2009 and may 2009. Based on these samples, the water retention curve, penetration resistance curve, bulk density, LLWR, and soil critical density were determined. The LLWR proved to be an adequate indicator of changes in the Latosol structure. The grass cultivar coastcross is potentially suitable for improving the soil structural quality, and is suggested for this purpose, instead of agricultural implements. The soil critical density of 1.24 Mg m-3 restricts the adequate development of the studied grass root system.

Modelagem da curva de retenção de água de Latossolos utilizando a Equação Duplo Van Genuchten

SUMMARY : MODELING THE WATER RETENTION CURVE IN OXISOLSUSING THE DOUBLE VAN GENUCHTEN EQUATION The clay fraction mineralogy and the granular structure of Oxisols in the Cerrado(Brazilian savanna) are the reason for the great volume of large pores as well as of extremelysmall pores, but no significant medium pore volume, resulting in low available water forplants. This study aimed to characterize and model the behavior of water retention in Oxisolswith different texture classes of the Cerrado region. Samples were collected from the Bwhorizon of 10 Oxisols under native vegetation. Water retention was measured at matric potentialsof 1, 2, 4, 6, 8, 10 kPa using a Richards plate, and the water retained in potentials of 1.500 and300.000 kPa determined by a thermocouple psychrometer model WP4-T Dewpoint PotentiaMeter. The double van Genuchten model was proposed to fit the experimental water retentiondata by non-linear fitting using software R 2.10.1. The relationship between the estimatedmodel parameters and the inflection point with soil texture properties was evaluated also bythe Pearson correlation test. Results indicated good fitting of the model and great predictionpower and correlation between the soil clay content and equation parameters (U

Loosening potential of an Argisol promoted by tifton 85 grass

The production of conserved forages using an intense traffic of machinery under inadequate conditions of water content in the soil has caused soil compaction and the degradation of pastures. In order to face this serious problem it is necessary to know the potential of soil loosening by some forage plants. The objective of the present study was to evaluate the loosening of an Argisol cultivated with Tifton 85 grass, as well as its production. The experiment was conducted at the Federal University of Lavras, from February to June 2007, using a completely randomized design, cultivating the Tifton 85 grass under the following compaction degrees: 66, 83, 88, 92 and 98%. The physical attributes, the compressive behavior of soil and the production of dry mass of grass were evaluated. The loosening was quantified by the reduction of the preconsolidation pressure after cultivation. The bearing capacity models reflected the changes in soil macroporosity. Under study conditions, the Tifton 85 grass promoted the soil loosening proportional to the initial compression degree. The production of forage increased as the soil is loosened.

Compactação de solos cultivados com cana-de-açúcar: II -quantificação das restrições às funções edáficas do solo em decorrência da compactação prejudicial

A reducao do periodo de entressafra canavieiro pode levar a disseminacao da compactacao do solo, em decorrencia da colheita mecanizada da cana-de-acucar na estacao chuvosa. Dessa forma, faz-se necessario definir estrategias que visem a minimizar a esse processo. O presente estudo objetivou modelar o processo de compressao do solo com base na pressao critica. Avaliou tambem os efeitos da colheita mecanizada da cana-de-acucar em diferentes epocas da safra em um Latossolo Vermelho-Amarelo (LVA) e em um Cambissolo Haplico (CX). Determinaram-se em amostras indeformadas a macroporosidade do solo, a pressao de preconsolidacao em diferentes conteudos de agua no solo e a densidade do solo. A partir da incorporacao da densidade do solo critica na modelagem do comportamento compressivo do solo, foi possivel estimar a pressao critica. A pressao critica superestima a capacidade de suporte de carga dos solos. A colheita mecanizada da cana-de-acucar, realizada na zona de friabilidade do solo, nao provocou compactacao prejudicial a cultura. A cana-de-acucar pode ser colhida mecanicamente sem causar a degradacao estrutural no LVA e no CX, respectivamente, sob conteudos de agua de ate 0,16 e 0,21 kg kg-1.

Compaction of soils cultivated with sugarcane: I - modeling and quantification of the additional soil compaction after harvest operations

The mechanized harvesting of sugarcane when accomplished in times of crop where the soil meets the inappropriate water contents has been responsible for soil compaction and reduction of yield in subsequent cycles of the crop. This study aimed to evaluate the effect of the harvesting operations of sugarcane at different times of the crop on preconsolidation pressure in a Red-Yellow Latosol (LVA) and in a Haplic Cambisol (CX). Mechanized harvesting traffic consisted of two passes of a sugarcane harvester and tractor + sugarcane transfer in each interrow of the culture. Undisturbed soil samples were used to determine the soil bearing capacity models and quantification of soil compaction due to mechanical harvesting in the months of November 2005, March and August 2006, and manual harvesting without traffic, in March 2006, because it is a time of greater rainfall intensity. The percentage of soil samples, in the region where additional soil compaction occurs, indicated that the CX was more resistant to compaction than the LVA. A mechanized harvesting of sugarcane being held in the friability zone caused soil compaction while the harvest accomplished manually did not cause the same effect.

Structural changes in latosols of the cerrado region: I - relationships between soil physical properties and least limiting water range

Apesar do elevado potencial agricola dos Latossolos da regiao do Cerrado brasileiro, quando inseridos no processo produtivo sob sistemas de manejo inadequados, o seu espaco poroso pode ser seriamente alterado, levando a sua rapida degradacao. Como consequencia, tem-se observado aceleracao do processo erosivo e assoreamento dos mananciais associados na paisagem. Dessa forma, o presente trabalho teve por objetivo avaliar as alteracoes estruturais de Latossolos do municipio de Rio Verde, GO, por meio da caracterizacao do intervalo hidrico otimo (IHO), e as relacoes entre IHO e demais propriedades fisicas desses solos. O estudo foi conduzido utilizando-se amostras coletadas no horizonte Bw de cinco Latossolos oxidicos representativos da variabilidade textural observada nos Latossolos ocorrentes no bioma Cerrado. Foram determinados o IHO e os atributos fisico-hidricos dos solos em diversos estados de compactacao induzidos por compressao uniaxial. Os resultados indicaram que a compactacao do solo resultou desde beneficios ao crescimento das plantas, relacionados ao aumento na retencao de agua, ate condicoes de severas restricoes as suas funcoes edaficas, sendo observadas relacoes inversas entre o conteudo de argila e os valores de densidade do solo (Ds) nas diversas condicoes estruturais. A Ds correspondente a macroporosidade critica do solo (DscMAC) foi mais restritiva ao manejo sustentavel dos Latossolos estudados que a Ds critica correspondente ao IHO (DscIHO). A maior compactacao permissivel observada nesses Latossolos oxidicos deve-se a elevada porosidade de aeracao conferida pela estrutura do tipo granular.

Preconsolidation pressure, soil water retention characteristics, and texture of Latosols in the Brazilian Cerrado

In the Brazilian Cerrado Biome, Latosols (Oxisols) predominate on gently sloping areas and are highly suitable for the development of mechanised agriculture. However, inappropriate management may lead to reduced crop yields and environmental degradation. We examined the relationships between compression behaviour and texture of Latosols to support decisions on the sustainable use and management of agricultural land. We collected soil samples in 10 Latosols with variable textures under native vegetation and determined the oxide content, bulk and particle density, total porosity, water retention curves, and preconsolidation pressure at different water potentials to develop preconsolidation pressure models. Our results showed that soil texture influenced soil physical properties, that is, an increase in the clay content enhanced the total porosity and water retention and decreased bulk density. Consequently, the susceptibility of these soils to compaction increased with an increase in the clay content. Considering the characteristics of the machinery used in intensive Brazilian agriculture, the compaction risk of these soils was considered high, despite the differences in resistance of the soils. In clayey and very clayey soils, some additional compaction is almost inevitable, even when the water content is low. Thus, caution is required in the evaluation of structural changes after mechanised field operations.

Disponibilidade hídrica e distinção de ambientes para cultivo de cafeeiros

This study was conducted in the districts of Sao Roque de Minas and Vargem Bonita, MG, with the aim to distinguish landscapes for coffee growing, with higher water available to the crop. Soil moisture was monitored in eight plots of coffee, and in five of them being also determined water availability for plants and soil bulk density. The plots are located in areas of Latosols and Cambisols. In one plot of each soil class, the distribution of the root system of coffee in the soil profile was studied. Soil moisture was monitored from April 2008 to February 2009, in the interval of 30 to 40 days. The soil depths of 0.2, 0.4, 0.8, 1.2 and 1.6 m were sampled, in line and between the lines of the coffee. The combination of the five plots, two sampling positions (line and between the lines) and five depths, formed the 50 Treatments used in the multivariate analysis. It was observed that soil moisture is lower in the line of coffee compared to between lines. The class of soil and plant age influence soil moisture and water availability to plants. The root system of coffee reached the depth of 1.5 to 1.7 m, in both studied soil classes. The 50 Treatments were grouped into 4, by means of the principal component analysis, according to the soil class and management.