SUMMARYThe plant-available water capacity of the soil is defined as the water content between field capacity and wilting point, and has wide practical application in planning the land use. In a representative profile of the Cerrado Oxisol, methods for estimating the wilting point were studied and compared, using a WP4-T psychrometer and Richards chamber for undisturbed and disturbed samples. In addition, the field capacity was estimated by the water content at 6, 10, 33 kPa and by the inflection point of the water retention curve, calculated by the van Genuchten and cubic polynomial models. We found that the field capacity moisture determined at the inflection point was higher than by the other methods, and that even at the inflection point the estimates differed, according to the model used. By the WP4-T psychrometer, the water content was significantly lower found the estimate of the permanent wilting point. We concluded that the estimation of the available water holding capacity is markedly influenced by the estimation methods, which has to be taken into consideration because of the practical importance of this parameter.Index terms: field capacity, permanent wilting point, soil water retention curve modeling, Oxisol, land use planning.( RESUMO: CAPACIDADE DE ÁGUA DISPONÍVEL NO SOLO PARA AS PLANTAS: MÉTODOS DE ESTIMATIVA E IMPLICAÇÕESA capacidade de água disponível no solo para as plantas é definida como o conteúdo de água entre a capacidade de campo e o ponto de murcha permanente e tem vasta aplicação prática no planejamento do uso da terra. Em um perfil de Latossolo representativo da região do Cerrado, objetivaram-se estudar e comparar métodos de estimativa para o ponto de murcha permanente, empregando os aparelhos de psicrômetro WP4-T e a câmara de Richards, utilizando amostras com e sem preservação da estrutura, bem como para a capacidade de campo, estimando-a pela umidade do solo submetido às tensões 6, 10 e 33 kPa, e pelo ponto de inflexão da curva de retenção de água calculado nos modelos de van Genuchten e polinomial cúbico. Verificou-se que para o Latossolo em estudo a capacidade de campo determinada no ponto de inflexão apresenta maior valor de umidade em comparação aos demais métodos e que mesmo nesse ponto são encontradas diferenças na estimativa em razão do modelo utilizado. Pelo psicrômetro WP4-T, valores significativamente menores de umidade foram encontrados para a estimativa do ponto de murcha permanente. Concluiu-se que a capacidade de água disponível foi influenciada marcantemente pelo método utilizado na estimativa da capacidade de campo e do ponto de murcha permanente, o que precisa ser considerado em virtude da importância prática desse parâmetro.Termos de indexação: capacidade de campo, ponto de murcha permanente, modelagem da curva de retenção de água do solo, Latossolo, planejamento de uso terra.

The normalized dispersion index (NDI) and the b/a index are commonly used to express the stability of aggregates measured by ultrasound. However, few studies have used the critical energy (CE) extracted from modeling to explain the effects of soil use and management on soil aggregation. The objective of this study was to evaluate the influence of soil cover on the CE level required for dispersion of aggregates of a Typic Hapludalf. Soil samples collected from the 0.0-0.05 m depth were evaluated in five different managements with cover plants: perennial soybean (PS), peanuts (P), spontaneous vegetation (SV), black oat/forage turnip (BOFT), and black oat/hairy vetch (BOHV). Aggregates ≤ 2 mm of the treatments were exposed to ultrasonic irradiation during 0, 30, 60, 120 and 180 s. The specific

SUMMARYStudies testing the High Energy Moisture Characteristic (HEMC) technique in tropical soils are still incipient. By this method, the effects of different management systems can be evaluated. This study investigated the aggregation state of an Oxisol under coffee with Brachiaria between crop rows and surfaceapplied gypsum rates using HEMC. Soil in an experimental area in the Upper São Francisco region, Minas Gerais, was studied at depths of 0.05 and 0.20 m in coffee rows. The treatments consisted of 0, 7, and 28 Mg ha -1 of agricultural gypsum rates distributed on the soil surface of the coffee rows, between which Brachiaria was grown and periodically cut, and compared with a treatment without Brachiaria between coffee rows and no gypsum application. To determine the aggregation state using the HEMC method, soil aggregates were placed in a Büchner funnel (500 mL) and wetted using a peristaltic pump with a volumetric syringe. The wetting was applied increasingly at two pre-set speeds: slow (2 mm h -1 ) and fast (100 mm h -1 ). Once saturated, the aggregates were exposed to a gradually increasing tension by the displacement of a water column (varying from 0 to 30 cm) to obtain the moisture retention curve [M = f (Ψ Ψ Ψ Ψ Ψ)], underlying the calculation of the stability parameters: modal suction, volume of drainable pores (VDP), stability index (slow and fast), VDP ratio, and stability ratio. The HEMC method conferred sensitivity in quantifying the aggregate stability parameters, and independent of whether gypsum was used, the soil managed with Brachiaria between the coffee rows,

No abstract

Root system growth and soil structure are interdependent and the threshold of separation between both of them is complex. However, by the evaluation of soil pore space, it is possible to characterize the root system growth environment. The aim of this study was to evaluate the effect of conservation management system over time on pore distribution and on root system development of coffee plantation in Cerrado Oxisol, located in the state of Minas Gerais, Brazil. Two coffee plantation areas were sampled (3 or 6 years old). Trenches were dug lengthwise along the planting row to expose the root system and the vertical profiles were divided into 0.05 × 0.05 m grid cells (0.70 × 1.50 m grid), totaling 420 sample sites. Digital images were taken and using the computer software Safira, it was measured layers along the soil profile, which was spaced 0.10 m apart. Disturbed and undisturbed soil cores the length, the surface area and the volume of the root system were sampled at 0.20 to 0.34, 0.80 to 0.94, and 1.50 to 1.64 m depths layers, in order to determine particle size, total porosity, and pore size distribution. The 3-years coffee stand had the greatest volume of macropores and the largest number of absorbent roots, besides a noticeable root system growth below 1 m depth. The 6-years old coffee stand presented pores reconfiguration due to increase in the intermediate-sized pores and to the uniform root distribution in both horizontal and vertical directions up to 0.9 m depth.

Morphological characteristics of the soil aggregates are important tools to analyzing and monitoring the structural quality. The present study aimed to characterize morphometrically aggregates of a Inceptisol, originated from pelitic rocks, after 1.5 years of the implementation of a management system that adopts conservation tillage practices in the coffee cultivation. The aggregates were collected at the depths of 0.0-0.05; 0. 05-0.20; 0.20-0.40; 0.40-0.80 m, both at row and interrow position in a coffee field, and also a natural environment of native vegetation that was used as a reference for the study. The analyzes of the aggregates were carried through 2D images obtained by scanning at 300 dpi spatial resolution. Each image contained 60 households and were processed using the software QUANTPORO. The morphometric variables were obtained: area, perimeter, compactness, roughness, appearance and Ferret diameter. For validation, the correlations among morphometric variables determined by image analysis and pattern aggregation indices (GMD, MWD and aggregates retained in the class > 2.00 mm) obtained by wet sieving were studied. After 1.5 years of implantation increased the dimensions of the aggregates on the natural environment have been detected, as well as better structural quality Inceptisol. Key words: Image analysis. Morphometric characteristics of the aggregates. Structural quality. ResumoAs características morfológicas dos agregados são importantes indicadores da qualidade estrutural do solo. O presente trabalho teve por objetivo caracterizar morfometricamente os agregados de um Cambissolo originado de rochas pelíticas (siltito) após 1,5 anos da implantação de um sistema de manejo que adota práticas conservacionistas do solo no cultivo do cafeeiro. Os agregados foram coletados nas profundidades de 0,0-0,05; 0,05-0,20; 0,20-0,40; 0,40-0,80 m, nas posições linha e entrelinha do cafeeiro e também em um ambiente natural Cerrado Nativo tomado como referência para o estudo. As análises dos agregados foram realizadas por meio de imagens 2D obtidas por escaneamento, em 300 dpi de resolução espacial. Cada imagem continha 60 agregados e foram processadas utilizando o software Quantporo. As variáveis morfométricas obtidas foram: área, perímetro, compacidade, rugosidade, aspecto e diâmetro de Ferret. Para validação, foram estudadas as correlações entre as variáveis 1 Parte da Dissertação do primeiro autor. Trabalho financiado pelos órgãos CNPq e FAPEMIG.

Changes in soil physical properties are inherent in land use, mainly in superficial layers. Structural alterations can directly influence distribution, stability and especially morphometry of soil aggregates, which hence will affect pore system and the dynamic process of water and air in soil. Among the methods used to measure these changes, morphometry is a complementary tool to the classic methods. The aim of this study was to evaluate structural quality of a Latosol (Oxisol), under different management systems, using morphometric techniques. Treatments consisted of soil under no-tillage (NT); pasture (P), in which both had been cultivated for ten years, and an area under native vegetation (NV -Savannah like vegetation). Aggregates were sampled at depths of 0-0.10 and 0.10-0.20 m, retained on sieves with 9.52 -4.76 mm, 4.76 -1.0mm, 1.0 -0.5mm diameter ranges. Aggregate morphometry was assessed by 2D images from scanner via QUANTPORO software. The analyzed variables were: area, perimeter, aspect, roughness, Ferret diameter and compactness. Moreover, disturbed samples were collected at the same depths to determine particle size, aggregate stability in water, water-dispersible clay, clay flocculation index and organic matter content. It was observed that different soil management systems have modified soil aggregate morphology as well as physical attributes; and management effects' magnitude increased from NT to P. Key words: Image analyses, soil structural quality, conservationist management systems ResumoAs alterações dos atributos físicos do solo, principalmente nas camadas superficiais, são inerentes ao uso do solo. Mudanças estruturais podem influenciar diretamente a distribuição, estabilidade e especialmente a morfometria dos agregados, o que afeta o sistema poroso e todo o processo dinâmico da água e ar no solo. Entre as metodologias que permitem mensurar estas alterações a morfometria apresenta-se como uma ferramenta complementar aos métodos tradicionais. Objetivou-se com esse trabalho avaliar a qualidade estrutural de um Latossolo Vermelho Distroférrico sob diferentes manejos do solo, empregando técnicas morfométricas. Os tratamentos deste estudo foram: o sistema plantio direto (PD), pastagem (P) ambos com dez anos de cultivo e área sob vegetação nativa (VN -Cerrado). Foram amostrados agregados nas camadas de 0-0,10 e 0,10-0,20 m retidos no intervalo de 9,52 -4,76 mm, 4,76 -1,0mm, 1,0 -0,5mm de diâmetro, obtidos por meio de um jogo de peneiras padrão. As análises dos agregados foram realizadas por meio de imagens 2D obtidas via scanner e analisadas com o programa QUANTPORO. As variáveis morfométricas avaliadas foram: Área, Perímetro, Aspecto, Rugosidade, Diâmetro de Ferret e Compacidade. Amostras com estrutura deformada foram coletadas nas mesmas profundidades para as seguintes determinações: granulometria, estabilidade de agregados em água, argila dispersa em água, grau de floculação e o conteúdo da matéria orgânica. Os diferentes sistemas de manejo do solo modificaram a morfometria dos agregado...

Abstract:The use of polymers is increasing at the agricultural area, however their effects on soil porosity have been little studied. The objective of this article is to analyze the effects of applied synthetic polymers on soil porosity and water retention of a Dystroferric Red Latosol. This study was conducted on undisturbed samples collected at a depth of 0.05 m in a Latosol beneath native forest. The samples were saturated with distilled water and polymers HyC, HyA, HyB diluted in water according to use recommendations for coffee plantations. These samples were then submitted to matric potentials of -2, -4, -6 and -10 kPa in the suction units and -33, -100, -500 and -1500 kPa in a Richards extractor. The models were fitted and pore size distribution estimates calculated. The data were subjected to variance analysis and the averages were compared using the Scott-knott test to a level of 5 %. Decreasing of large pores volume than 145 µm, was detected with the application of polymers HyA and B. However the HyB polymer promoted a reduction in the pore volume in the intermediate classes (2.9-0.6; 0.6-0.2 µm), that are responsible for water availability to plants. On the other hand the HyC polymer promoted an increase in the soil water retention.Keywords: soil porosity; synthetic polymers; soil water availability.RESUMO: O uso de polímeros é crescente no meio agrícola, porém seus efeitos na porosidade do solo são pouco estudados. O presente trabalho teve como objetivo analisar os efeitos da aplicação de polímeros sintéticos na porosidade e retenção de água de um Latossolo Vermelho Distroférrico muito argiloso. O estudo foi realizado em amostras indeformadas coletadas na profundidade de 0,05 m, em um Latossolo sob mata nativa. Amostras foram saturadas com água destilada e com os polímeros HyC, HyA, HyB diluídos em água conforme recomendações de uso para cultura do cafeeiro. Em seguida estas amostras de solos foram submetidas a potenciais matriciais de -2, -4, -6 e -10 kPa nas unidades de sucção e -33, -100, -500 e -1500 kPa nas câmaras de Richards. Foi realizada a modelagem de curvas de retenção de água e calculada a distribuição de poros por tamanho. Os dados foram submetidos a análises de variância e as médias comparadas pelo teste de Scott-knott ao nível de 5 %. Houve uma redução do volume de poros da classe de tamanho > 145 µm quando o solo foi saturado com os polímeros HyA e HyB. O polímero HyB promoveu uma redução do volume de poros das classes intermediárias (2,9-0,6; 0,6-0,2 µm), responsáveis pela disponibilidade de água para as plantas. Já o polímero HyC promoveu o aumento da retenção de água no solo.Palavras-chave: porosidade do solo; polímeros sintéticos; disponibilidade de água no solo.