José Ronaldo de Macedo

Impacto do manejo convencional sobre propriedades físicas e substâncias húmicas de solos sob cerrado

The utilization of intensive conventional management system on soils under cerrado biome has caused modification in their properties, as well as, in the behavior and quality of the organic matter. The objective of this research was to evaluate the impact of conventional soil management practices upon physical properties, contents and qualities of humic substances of a Red-Yellow Oxisol, formerly, under cerrado (savana-like) natural vegetation. The study was accomplished on an private agricultural property in the municipal district of Sao Desiderio-BA. They were appraised four areas under different length of times of agricultural use and one area under native cerrado (savana-like). The length of time under agriculture use was one, two, three and six years, and after six years the studied area was left uncultivated for a period of three years. The soil has been prepared under traditional systems which consists of plowing the land twice with heavy disks followed by twice grading. It was also applied, during the seedling time, N-P-K fertilizer plus micronutrients and lime according to soil analysis. The areas have been cultivated with corn and soybeans in a rotation system. It was observed that the adopted management system was not sustainable, because, at the first three years under cultivation occurred a great deterioration of physical properties such as soil density, porosity and available water contents. The humification process and the quality of the organic matter were influenced by both utilization of lime and by the rotation system (corn/soybeans). The used system was more benefic for the process of stabilization of the humic substances than for the physical properties of the studied soils.

Gamma-ray-computed tomography to investigate compaction on sewage-sludge-treated soil.

Soil compaction is one of the fundamental parameters to evaluate the environmental impact of agricultural machinery traffic on soils. Compaction causes modifications on soil physical properties such as changes in porosity and structure that are related to soil water movement and gas exchange The objective of this work was to evaluate soil surface sealing after sewage-sludge application, and the influence of agricultural machinery traffic, through computed tomography. A first generation tomograph was used having a 137Cs source and a 3 in x 3 in NaI(Tl) scintillation crystal detector coupled to a photomultiplier tube. Image analysis and tomographic unit profiles could successfully be used for the detection of soil surface sealing and soil compaction due to machinery traffic associated to sewage-sludge application.

Gamma-ray computed tomography to characterize soil surface sealing

The application of sewage sludge as a fertilizer on soils may cause compacted surface layers (surface sealing), which can promote changes on soil physical properties. The objective of this work was to study the use of gamma-ray computed tomography, as a diagnostic tool for the evaluation of this sealing process through the measurement of soil bulk density distribution of the soil surface layer of samples subjected to sewage sludge application. Tomographic images were taken with a first generation tomograph with a resolution of 1 mm. The image analysis opened the possibility to obtain soil bulk density profiles and average soil bulk densities of the surface layer and to detect the presence of soil surface sealing. The sealing crust thickness was estimated to be in the range of 2-4 mm.

Estimation of field capacity and moisture retention based on regression analysis involving chemical and physical properties in Alfisols and Ultisols of the state of Rio de Janeiro

This work determines field capacity and moisture retention through correlation and regression analysis, based on physical and chemical properties in Alfisols and Ultisols in the State of Rio de Janeiro (Brazil). The field capacity was estimated “in situ” by the direct method. The other properties were obtained by laboratory methods. Studies were developed in accordance to different levels of data analysis: global or partial (local). The correlation study showed that microporosity and contents of clay, sand, organic matter and coarse sand were meaningfully correlated with field capacity and moisture retention. The results have shown that texture–organic matter–microporosity interactions are the prime factors in determining water retention of those soils. The multilinear regression equations relating clay, sand, organic matter, coarse sand and microporosity to field capacity and moisture retention variables at different tensions, fitted well to global and partial data. Similar performance was observed when the pedofunctions based on clay, sand, and organic matter contents were used, as well as the simpler pedofunctions with microporosity as the only independent variable.

Revisiting Field Capacity (FC): variation of definition of FC and its estimation from pedotransfer functions

Taking into account the nature of the hydrological processes involved in in situ measurement of Field Capacity (FC), this study proposes a variation of the definition of FC aiming not only at minimizing the inadequacies of its determination, but also at maintaining its original, practical meaning. Analysis of FC data for 22 Brazilian soils and additional FC data from the literature, all measured according to the proposed definition, which is based on a 48-h drainage time after infiltration by shallow ponding, indicates a weak dependency on the amount of infiltrated water, antecedent moisture level, soil morphology, and the level of the groundwater table, but a strong dependency on basic soil properties. The dependence on basic soil properties allowed determination of FC of the 22 soil profiles by pedotransfer functions (PTFs) using the input variables usually adopted in prediction of soil water retention. Among the input variables, soil moisture content θ (6 kPa) had the greatest impact. Indeed, a linear PTF based only on it resulted in an FC with a root mean squared residue less than 0.04 m3 m-3 for most soils individually. Such a PTF proved to be a better FC predictor than the traditional method of using moisture content at an arbitrary suction. Our FC data were compatible with an equivalent and broader USA database found in the literature, mainly for medium-texture soil samples. One reason for differences between FCs of the two data sets of fine-textured soils is due to their different drainage times. Thus, a standardized procedure for in situ determination of FC is recommended.

Aplicação do Código Florestal Brasileiro como subsídio para o planejamento ambiental: um estudo de caso na região noroeste do estado do Rio de Janeiro

This studied verified the application of the Brazilian Forest Code (CFB) in the Santa Maria creek basin, in northwestern Rio de Janeiro, as a support to environmental planning. This basin is fully located in the county of Sao Jose de Uba, and it has been subject to different processes of soil use and occupation, resulting in water and erosion problems. In order to perform the study, a map of current soil use and occupation was designed through automatic supervised classification, using air photos of Companhia de Energia do Rio de Janeiro -CERJ (Rio de Janeiro Power Company) and Mineral Resources Department -DRM/RJ. In order to design the map of soil use and occupation in compliance with the scenario established in article 2 of the CFB, a surrounding belt (buffer zone) was created. The results show that there would be conflicts between the CFB application and the current use of areas for agriculture, animal husbandry, exposed soil and urban area. In agriculture and animal husbandry, the conflicting use could be softened with adequate handling and conservation practices. Applying the CFB would significantly contribute to increasing APP (forest), promoting increased water seepage in soil and water system recharge, and decreasing overland runoff and soil erosion.

Estimation of field capacity from ring infiltrometer-drainage data

A Capacidade de Campo (CC) e um parâmetro largamente adotado na Ciencia do Solo aplicada. Entretanto, seu metodo de determinacao in situ pode apresentar dificuldades, geralmente por conta da necessidade de grandes suprimentos de agua nos locais dos testes. Ottoni Filho et al. (2014) propuseram uma padronizacao da determinacao de campo da CC e evidenciaram que tal CC in situ pode ser estimada por uma funcao de pedotransferencia (FPT) linear com base na umidade volumetrica do solo ao potencial matricial de -6 kPa [θ(6)] para os mesmos solos usados neste estudo. O objetivo deste trabalho foi utilizar os dados de umidade do solo abaixo de um infiltrometro de duplo anel, medidos 48 h apos o termino do teste de infiltracao, a fim de desenvolver FPTs para a CC in situ padronizada. Verificou-se que tais dados de CC de anel foram em media 0,03 m3 m- 3 maiores que os de CC in situ padronizada. A FPT linear que foi desenvolvida com os dados de CC de anel com base apenas em θ(6) foi quase tγo precisa quanto a FPT equivalente reportada por Ottoni Filho et al. (2014), que foi desenvolvida para os dados de CC padronizada. As raizes quadradas de residuo quadratico medio da CC determinada a partir de ambas as FPTs foram aproximadamente 0,02 m3 m- 3. O metodo proposto tem a vantagem de estimar a CC in situ do solo pelo uso da agua aplicada no teste de infiltracao.