A compactação do solo tem sido objeto de estudo devido a utilização mais freqüente e intensa da mecanização e devido a sua influência negativa na qualidade física do solo às culturas. Os efeitos da compactação sobre a deterioração da estrutura do solo dependem de vários fatores, como, a textura, o conteúdo de carbono orgânico, o conteúdo de água no solo durante as operações de campo e a freqüência e intensidade da carga aplicada pelas máquinas e implementos utilizados no campo. Estes fatores são os responsáveis pelos diferentes níveis de compactação encontrados nos solos agrícolas, sendo que a influência destes é de importância fundamental para o desenvolvimento de estratégias que evitem ou pelo menos amenizem a compactação no perfil do solo. Neste sentido, este trabalho teve por objetivos (i) analisar os efeitos de diferentes níveis de carga de máquinas aplicados no solo sobre as propriedades físicas do solo; (ii) determinar propriedades físicas do solo em camadas superficiais e subsuperficiais de um solo cultivado por longo prazo em sistema de plantio direto; (iii) avaliar a qualidade física do solo através do parâmetro S; (iv) comparar as predições da pressão de preconsolidação estimada por diferentes métodos de ajuste com uma ampla variação textural do solo. Para isso, foi realizado um estudo de campo, conduzido em quatro experimentos na Suécia com tráfego de máquinas, onde diferentes pressões foram detectadas por sensores colocados em diferentes profundidades no solo, assim como a análise da densidade do solo e da resistência à penetração. Em outro estudo, propriedades dinâmicas e estáticas foram determinadas em diferentes camadas de um solo cultivado sob sistema de plantio direto há 14 anos, analisando a qualidade física do solo. E por final, a análise comparando diferentes métodos de ajuste para pressão de preconsolidação foi realizada. As propriedades físicas do solo refletiram os efeitos das cargas aplicadas no solo, demonstrando aumento da densidade do solo e da resistência à penetração. As propriedades estáticas do solo demonstraram a existência de uma camada mais densa no perfil do solo, porém as propriedades dinâmicas apresentaram resultados satisfatórios na mesma camada. A qualidade do solo avaliada pelo parâmetro S indicou que o solo possui boa estrutura física em todas as camadas estudadas. As comparações entre métodos de ajuste para a pressão de preconsolidação indicaram que superestimativas e subestimativas podem ocorrer quando se usa métodos diferentes, tornando difícil o uso de um valor absoluto de pressão de preconsolidação como um limite para as pressões exercidas no solo a fim de evitar a compactação do mesmo. / Soil compaction has been the subject of study for many years due to its implications for crop yield. Its effect on the deterioration of the soil structure depend on several factors, such as, soil texture, organic carbon content, water content during the field operations as well, the frequency and intensity of the load applied by the machines and implements used in the field. These factors are the responsible for the different levels of compaction found in the soil agricultural, and their effects are very importance for the development of strategies to avoid or to ameliorate the soil compaction in the soil profile. In this sense, this work took as objectives (i) to analyse the effects of different levels of load machines applied on the soil physical properties; (ii) to determine soil physical properties on topsoil and subsoil layers cultivated under no-tillage system; (iii) to evaluate the soil physical quality by S parameter; (iv) to compare the predictions of the precompression stress fitted by different methods ranging several soil textural classes. Then, it was carried out a field study, performed in four experiments in Sweden with machine traffic. Different load pressures were detected by sensors put in different depths in the soil, and also the bulk density and penetration resistance were determined. Another study, dynamic and static properties were determined in different soil layers under no-tillage. Besides that the soil physical quality was verified. Finally, comparisons between precompression stress fitted by different methods was done. The soil physical properties reflected the effects of loads applied on soil, demonstrating increase of the soil bulk density and of the penetration resistance. The soil static properties demonstrated to exist a denser layer in the soil profile, however the dynamic properties presented satisfactory results in the same layer. Soil physcal quality evaluated by the S parameter indicated a good soil physical structure in all the studied layers. The comparisons showed that the choice of method had a significant influence on the precompression stress values, becoming difficult the use of an absolute value of it, as a limit for the load pressures applied on soil to avoid the soil compaction.

Made available in DSpace on 2017-07-21T19:26:00Z (GMT). No. of bitstreams: 1 Jonathan Costa.pdf: 3369485 bytes, checksum: 2b63c545ac05b578cd30088e73371def (MD5) Previous issue date: 2011-04-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The gamma-ray attenuation technique is based on the interaction of radiation with matter. In soil physics the technique is mainly used to determine the soil bulk density, porosity, and soil moisture. The mass attenuation coefficient ) is defined as the probability of interaction per unit of volume of a photon with a given energy with the matter. An accurate measurement of is important for evaluation of representative soil physical parameters. Usually,is considered constant during evaluations of soil physical properties, even for different sample sizes or nuclear system geometry. The main objective of this study was to analyze the effect of sample size and collimator diameter in evaluations of for a heterogeneous porous medium (soil). The radioactive sources of 241Am (59,4keV) and 137Cs (661,6 keV) were used. These sources are chosen because they are the most commonly used for soil physical properties measurements. Sample thickness and solid angle variations were obtained using acrylic boxes with sizes from 2 to 15 cm and four circular collimators (1-4 mm). Two different soil textures (sandy-loam and silty-clay) were also used, besides the different sample sizes and collimator diameters. The results obtained show that the influence of collimator size and sample thickness in the variations of is less than 5% (relative deviation considering each value for each thickness and the average value calculated for all thicknesses) for both soils and radioactive sources. However, for the 241Am only specific sample thicknesses (2-12 cm) can be used when collimators with small diameters (1 and 2 mm) are used. This occurs due to problems in the photopeak evaluation after determined soil thickness. In order to compare the obtained experimental results of with theoretical ones, theoretical values were generated via XCOM for water and soils. A good agreement was found for water (3,8% - 241Am and 6,3% - 137Cs, relative deviation considering the theoretical value as reference), which represents a good gamma-ray system operation. However, for the soil samples the same was not observed. A possible explanation for this result is the qualitative soil chemical composition evaluation used to generate the via XCOM. To conclude, the results of this work show that even small changes in the value with the collimator size and sample thickness can cause important changes in measurements of soil physical properties such its bulk density. / A técnica de atenuação de raios gama se baseia na interação da radiação com a matéria, abrangendo diversos objetivos, dentre eles, a determinação de parâmetros físicos do solo, tais como sua densidade, umidade e porosidade. O coeficiente de atenuação de massa pode ser definido como a probabilidade de interação por unidade de volume entre um meio material (absorvedor) e o fóton a uma dada energia. Uma medida precisa desse coeficiente é importante para determinações representativas de parâmetros físicos do solo. Normalmente, em determinações destes parâmetros, mede-se o coeficiente de atenuação do meio que fica considerado como constante, mesmo para diferentes tamanhos de amostras ou geometria do sistema nuclear. No presente trabalho, procurou-se analisar a variação do com o aumento da espessura da amostra e também com o tamanho do colimador para um meio poroso heterogêneo como é o caso do solo. Foram usadas duas fontes de radiação gama emitindo fótons de diferentes energias, sendo elas 241Am (59,4 keV) e 137Cs (661,6 keV). Essas duas fontes são as mais comuns usadas para medidas de propriedades físicas do solo. As variações nas espessuras das amostras foram obtidas utilizando-se caixas de acrílico com tamanhos de 2 a 15 cm. Para a variação na espessura do feixe foram usados quatro colimadores circulares com diâmetros de 1 a 4 mm. Foram utilizados nesse estudo dois solos de diferentes texturas, sendo elas, franco-arenosa e argilo-siltosa. Os resultados obtidos mostram que, embora exista influência do tamanho do colimador e espessura da amostra nas medidas de essas são menores do que 5% (desvio relativo considerando cada valor de para cada espessura e o valor médio para todas as espessuras) para ambos os solos e fontes radioativas. Para a fonte de 241Am somente espessuras definidas de amostra (2-12 cm) podem ser usadas na medida do para o solo quando os colimadores menores (1 e 2 mm) estão sendo usados. Isso ocorre devido a problemas no levantamento do fotopico após determinada espessura de amostra para essa fonte radioativa. Na comparação dos valores experimentais de obtidos e valores teóricos gerados via XCOM foi observada uma boa concordância entre os dados experimentais e teóricos para a água (3,8% - 241Am e 6,3% - 137Cs de desvio relativo considerando o valor teórico como referência) o que representa um bom funcionamento do sistema nuclear. No entanto, o mesmo não foi observado para o solo devido ao levantamento da composição química desse meio poroso ter sido somente qualitativo. Porém, nesse trabalho foi verificado que, mesmo pequenas modificações no valor de com o tamanho do colimador e espessura da amostra, podem influenciar de maneira significativa medidas de propriedades físicas do solo como a sua densidade.

Orientador: Marlene Cristina Alves / Banca: Hélio Ricardo Silva / Banca: Carlos Roberto Espindola / Resumo: O biossólido é um composto passível de utilização agronômica, sendo fonte de nutrientes para as culturas e condicionador de solo. Neste sentido, desenvolveu-se um trabalho que teve por escopo estudar a influência da reaplicação de doses de biossólido na recuperação de atributos físicos e químicos do solo e no desenvolvimento da cultura do eucalipto e da braquiária, num Latossolo Vermelho degradado. O estudo foi realizado cinco meses após a reaplicação do biossólido, numa área em recuperação cultivada há seis anos com eucalipto e braquiária. O delineamento experimental foi em blocos casualizados com seis tratamentos e quatro repetições, sendo: Solo cultivado com eucalipto e braquiária sem adição de insumos; Solo cultivado com eucalipto e braquiária com adubação mineral; Solo cultivado com eucalipto e braquiária com reaplicação de 4,64 Mg ha-1 (base seca) de biossólido; Solo cultivado com eucalipto e braquiária com reaplicação de 9,28 Mg ha-1 (base seca) de biossólido; Solo exposto (sem qualquer cultivo ou adubação); Solo com vegetação natural de Cerrado. Estudou-se nas camadas do solo de 0,00- 0,05; 0,05-0,10; 0,10-0,20 e de 0,20-0,40 m, os atributos físicos: macroporosidade; microporosidade; porosidade total e a densidade do solo. Para os atributos químicos nas mesmas camadas os teores de: P, MO, pH, K, Ca, Mg, H+Al, SB, CTC e V%. Já para a cultura do eucalipto estudou-se a altura média de plantas e o diâmetro a altura do Peito (DAP) e na braquiária a massa fresca e seca. Verificou-se que a replicação do biossólido está recuperando o solo tanto em relação aos atributos físicos como químicos, sobretudo nas camadas mais superficiais, e que a maior dose influencia no desenvolvimento do eucalipto. Não foi constatada diferença significativa entre médias dos tratamentos para recuperação do solo da matéria... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The sludge is a compound capable of agricultural use, a source of nutrients for crops and soil conditioner. In this sense, has developed a work which objective on studying the influence of reapplication of biosolids in the recovery of physical and chemical properties of soil and the development of culture of eucalyptus and grass in a degraded Oxisol. The work was conducted five months after the biosolids re-application in a recovery area cultivated for six years under eucalyptus and pasture. The experimental design was randomized blocks with six treatments and four replications, with: Solo under eucalyptus and pasture with no added inputs, soil under eucalyptus and pasture with mineral fertilization, soil under eucalyptus and pasture with reapplication of 4.64 Mg ha-1 (on dry basis) of sludge, soil under eucalyptus and pasture with reapplication of 9.28 Mg ha-1 (on dry basis) of sludge, soil exposed (without any cultivation or fertilization), soil with Savannah vegetation. Was studied in soil layers of 0.00-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m, the physical attributes: macroporosity, microporosity; porosity and soil bulk density. For the chemical in the same layers of levels: P, organic matter, pH, K, Ca,Mg, H+Al, SB, CEC and V%. As for the cultivation of eucalyptus studied the average plant height and diameter at breast height (DBH) and the grass fresh and dry. It was found that replication of the sludge is regaining ground in relation to both physical and chemical properties, especially in the surface layers, and the highest dose influences the plantations development. There was no significant difference between treatment means for soil recovery of fresh and dry grass, after reapplication of biosolids / Mestre

Nos últimos anos o interesse pelo estudo da Terra Preta de Índio (TPI) tem aumentado em razão das suas características únicas em relação aos solos normalmente encontrados na região, como sua maior fertilidade natural. Diversos estudos relatam que a presença do chamado carbono pirogênico na composição das TPIs é a responsável por esta superioridade, entretanto ainda não se sabe se este afeta as propriedades físicas dos solos de TPI. Esta pesquisa tem como objetivo comparar o comportamento de propriedades físico-hídricas de solos antrópicos (Terra Preta de Índio) com um solo adjacente por meio da determinação de suas propriedades físicas, e verificar a distribuição do carbono pirogênico entre os diferentes compartimentos da matéria orgânica em solos de TPI e adjacentes. Para este estudo foram coletadas amostras indeformadas em anéis volumétricos e blocos em uma área de TPI e adjacente. As áreas estão localizadas na Floresta Nacional de Caxiuanã, estado do Pará. As propriedades físicas analisadas foram textura, porosidade total, macro e microporosidade, curva de retenção da água no solo, condutividade hidráulica saturada, permeabilidade do solo ao ar e estabilidade de agregados. Para verificar o comportamento da matéria orgânica foi realizado o fracionamento físico, onde foram analisados a distribuição do carbono total e pirogênico nas diferentes frações da matéria orgânica. Verificou-se diferença nas duas áreas quanto às propriedades físicas porosidade total, macro e microporosidade, condutividade hidráulica do solo (Ksat), permeabilidade do solo ao ar (Ka), e retenção de água no solo, entretanto não foi possível verificar diferenças na estabilidade de agregados entre as duas áreas. A distribuição da matéria orgânica nas diferentes frações do solo foi distinta nas duas áreas, onde verificou-se que na área de TPI o C no solo foi predominante na fração macroagregados, enquanto que na área adjacente o carbono se localizou em maior quantidade na fração microagregados. Os valores de carbono pirogênico foram maiores na área de TPI do que na área adjacente, demostrando que a matéria orgânica das TPIs apresenta uma composição diferenciada, modificando o comportamento das propriedades físicas dos solos. / In recent years the interest in the study of Terra Preta de Indio or Amazonian Dark Earths (TPI) has increased, especially because of its unique characteristics when related to typical soils of the region, as its higher natural fertility. Several studies have reported that the presence of so-called pyrogenic carbon in its composition is responsible for this superiority, however it is not known if it affects the physical properties of TPI soils. This research aims to compare the behavior of physical and hydraulic properties of anthropic soils (Terra Preta de Indio) to an adjacent soil by determining its physical properties, and evaluating the distribution of the pyrogenic carbon between the different compartments of organic matter for both soils. For this study, undisturbed soil samples were collected in volumetric cylinders and blocks from a TPI and adjacent area. The areas are located in Caxiuanã National Forest, state of Pará, Brazil. The analyzed physical properties were texture, porosity, macro and microporosity, soil water retention curve, soil saturated hydraulic conductivity, soil permeability to air and aggregate stability. A physical fractionation was performed to verify the behavior of organic matter, which analyzed the distribution of the total and pyrogenic carbon in the different fractions of organic matter. There were difference in the two areas regarding the physical properties as total porosity, macro and microporosity, soil hydraulic conductivity (Ksat), air permeability to soil (Ka), and soil water retention, however it was not possible to see differences in stability aggregates between the two areas. The distribution of organic matter in different soil fractions was different in the two areas, where it was found that in the TPI area, soil carbon was prevalent in the macroaggregates fraction, while the adjacent area had larger amounts in the microaggregates fraction. The values for pyrogenic carbon were higher in the TPI area, showing that the organic matter of TPIs has a different composition which modifies the behavior of physical properties in the soil.

During the period 1996–2005, experiments were carried out at the Joniškėlis Research Station of the Lithuanian Institute of Agriculture on an Endocalcari-Endohypogleyic Cambisol. The experiment was set up in 1956 in the ten - field crop rotation: 1) mixture of vetch and oat, 2) winter wheat, 3) spring barley, 4) fodder beet, 5)spring barley with under sowing, 6) 1-st year perennial grasses (red clover and timothy), 7) 2-nd year perennial grasses, 8) winter wheat, 9) fodder beet, 10) spring barley. Scheme of the soil tillage: 1) Conventional soil tillage with ploughing 22-25 cm, 2) permanent shallow ploughing 12-15 cm, 3) soil tillage with an inconstant ploughing depth: 25 cm in fallow, 20 cm after perennial grasses, 15 cm after spring barley, 10 cm after fodder beet, 20-25 cm after winter wheat, 4) soil ploughing depth according to necessity, 5) deep loosening with chisel cultivator PČ-2,5 25 cm. The aim of this investigation was to evaluate the influence of conventional and permanent shallow soil tillage, its alternation, and no-shell board deep loosening on humous, soil physical properties, the productivity of crop rotation and energy efficiency. During the fifth crop rotation, conventional soil tillage alternated with permanent shallow soil tillage or with deep loosening with an inconstant ploughing depth according to necessity had no significantly influence on soil humous. The most increase (0,19 percentage units) of soil humous was determined in soil tillage with an... [to full text]

Agricultural management practices including tillage and irrigation have a considerable effect on soil physical and hydraulic properties in space and time. Tillage practices initially alter the soil physical and hydraulic properties depending on the type and depth of tillage. These changes are reverted back to original conditions due to reconsolidation during cycles of wetting and drying. Irrigation techniques can manipulate the reversion process dynamically due to different modes of wetting. The combined effects of tillage and irrigation have rarely been investigated. Therefore, two experiments were conducted to investigate the effect of different tillage practices and irrigation techniques on soil physical properties and temporal variations in soil hydraulic properties, one on wheat and second on the following maize crop grown on the same plots. The tillage and irrigation treatments implemented for the wheat crop were repeated for the subsequent maize crop restoring the same treatment layout plan. Intact soil core samples were collected, in the middle of the wheat crop before irrigation and the end of the maize crop season, for the determination of soil physical and hydraulic properties. Field saturated hydraulic conductivity (K_fs) was determined using the Guelph pressure infiltrometer method and volumetric soil water content (θ_v) and potential (ψ_m) was measured in the field using water content sensors and tensiometers, respectively. The wheat crop received rain showers from time to time, while in maize, a heavy spell of monsoon rains following tillage caused most of the soil reconsolidation. So, the greater intensity of rains, rather than the cycles of wetting and drying, became primarily responsible for the differences in soil physical and hydraulic properties between the two crops. Moldboard plow resulted in an increase in yield and improvement of soil hydraulic properties during both crop seasons. Flood irrigation reverted back the effects of tillage on soil hydraulic properties greater than sprinkler irrigation, while it did not affect the yield significantly. The dynamics of volumetric soil water content (θ_v) differed, depending on tillage type, irrigation technique and crop season. Moldboard plow was the wettest after rain or irrigation events but it dried quicker than other tillage treatments. Flood irrigation caused higher wetting than sprinkler irrigation. These wetting effects were greater in wheat as compared to maize crop. Temporal variability calculated as time averaged relative difference in θ_v was greater during wheat as compared to maize, while temporal stability calculated as standard deviation of temporal stability decreased with flood irrigation in both crops. Soil bulk density (ρ_b) and water retention characteristics (θ_v (ψ_m )) measured on the intact soil cores and total porosity (φ), plant available water capacity (θ_PAWC) and pore size distribution calculated from water retention data depended on the time of sampling. During wheat, the ρ_b was lower resulting in a higher φ than after maize. Moldboard plow decreased ρ_b increasing φ, while the effect of flood irrigation was opposite in both crops with greater magnitude in wheat. Similarly, the effects of tillage on θ_v (ψ_m ) were observed in both crops, while those of irrigation were observed in maize only. Cultivator treatment retained higher θ_v at higher ψ_m (−30 and −100 kPa), followed by chisel and moldboard plow. Plant available water capacity (θ_PAWC) was greater in maize as compared to the wheat crop. Cultivator had higher θ_PAWC than chisel and moldboard plow in both crops. Wheat had greater volume of larger pores (> 10 μm, φ_(>10)), whereas extraordinary rains as well as irrigations after tillage caused these larger pores to decrease in maize. Moldboard plow had higher φ_(>10) at 10 cm depth in both crops with greater magnitude in wheat. Field saturated hydraulic conductivity (K_fs) determined before irrigations and at the end of both crop seasons was greater in wheat than in maize especially in the first determination. Moldboard plow exhibited greater K_fs followed by chisel plow and cultivator in both crops and it decreased significantly with time in wheat but not in maize. Flood irrigation was responsible for a reduction in K_fs and the effect was greater in wheat as compared to maize. It was concluded that a greater intensity of water application in the form of rains or irrigations can revert the changes in soil physical and hydraulic properties induced by tillage more effectively than the cycles of wetting and drying. Soil hydraulic properties may be optimized with the combination of suitable tillage and irrigation for efficient utilization of water resources.

The consequences of land use choices on soil water and gas transport properties are significant for gas and water flux in agricultural environments. Spatial and temporal patterns and associations of soil water and soil gas characteristics and processes in different land uses are not well understood. The objectives of this study were to 1) characterize soil structure under crop and grass systems, 2) quantify spatial patterns and associations of soil physical characteristics in crop and grass systems, and 3) quantify spatial and temporal patterns and associations of CO2 and N2O fluxes. The research was conducted in a 60 by 80 m field divided into grass and crop systems. Sixty sampling points were distributed in four transects with 5- and 1-m spatial intervals between measurement points. Gas fluxes were measured, at two-week time intervals, 22 times during a year. Pore size distribution was more homogeneous and more continuous pores were found in the grass than in the crop system. The spatial variability of most selected soil physical characteristics was more structured in the crop than in the grass system, which reflected the impact of land use and soil structure on their spatial patterns. CO2 flux was dependent for a longer distance in the grass than in the crop system, however, the two land-use systems exhibited similar spatial ranges of N2O flux. Gas fluxes were temporally dependent for a longer period in the grass than in the crop system. The spatial associations between CO2 and N2O fluxes and selected biochemical and physical factors depended on the flux sampling season and land use. Soil temperature was the dominant controlling factor on the temporal variability of CO2 and N2O fluxes but not on the spatial behavior. Considering the spatial and temporal ranges and dependency strength of soil variables helps identify efficient sampling designs that can result in better time and resource management. Spatial and temporal relationships between the selected soil variables also improve understanding soil management and sampling soil variables. This study provides the baseline and recommendations for future investigations specifically for sampling designs, soil management, and predictions of different soil processes related to gas fluxes.

A região amazônica possui extensas áreas que foram desmatadas e convertidas em sistemas de pastagens. A falta de técnicas na implantação e no manejo destes sistemas resultou em inúmeras áreas de pastagens degradadas. A condução de experimentos de campo visando a reversão deste quadro está sendo avaliada no presente estudo. A área em estudo está localizada na Fazenda Nova Vida, município de Ariquemes, Estado de Rondônia/RO. O solo da fazenda foi classificado como Latossolo Vermelho Amarelo. Os tratamentos utilizados consistiram em dois sistemas de plantio direto (arroz e soja), aplicação de herbicida no controle de invasoras, operação de gradagem e a pastagem controle. O Intervalo Hídrico Ótimo (IHO), a densidade do solo, resistência à penetração, macroporosidade, microporosidade, porosidade total e permeabilidade do solo ao ar foram determinadas. Não foi verificada diferença significativa entre os tratamentos utilizados. O solo estudado não apresentou restrições físicas ao crescimento de plantas. As variações na estrutura do solo são melhor avaliadas quando os fatores que afetam diretamente o crescimento de plantas são integrados em um único parâmetro. As propriedades físicas determinadas foram menos sensíveis que o IHO às alterações provocadas pelos sistemas de manejo. O IHO possui um grande potencial como índice de qualidade física do solo na avaliação de experimentos que visam a recuperação de pastagens degradadas, pois integra em um único parâmetro os fatores diretamente relacionados ao crescimento de plantas. / The Brazilian Amazon region has extensive areas that had been deforested and converted into pasture systems. The absence of adequate techniques in implementation and management of these pastures resulted in pasture degradation in several areas. Field experiments with objective of reverting the degradation process are being evaluated in this study. The field site was located at the Nova Vida farm, Ariquemes county, Rondonia State, Brazil. The soil at the farm was classified as “Latossolo Vermelho Amarelo” in agreement with Brazilian classification system. The treatments consisted of two no-tillage systems (rice and soybeans), weed control using herbicides, harrowing and control pasture. The Least Limiting Water Range (LLWR), soil bulk density, soil penetration resistance, macroporosity, microporosity, total porosity and soil air permeability were also evaluated. There was no significant difference between treatments under evaluation. The soil estudied did not show physical restrictions to plants growth. Soil structure variations are better evaluated when the factors that affect directly plant growth are integrated in a single parameter. The soil physical properties evaluated were less sensitive than the LLWR to alterations caused by the management systems. The LLWR has a great potential as a soil physical quality index in the evaluation of experiments designed to recover degraded pastures because it integrates in a single parameter the factors directly related to plant growth.

Made available in DSpace on 2014-06-11T19:31:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-05-23Bitstream added on 2014-06-13T20:02:21Z : No. of bitstreams: 1 silva_jr_dr_botfca.pdf: 1243112 bytes, checksum: a6ff73d1d32431a4754520748d549e85 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Foram avaliados os efeitos causados ao solo pelo tráfego de máquinas florestais de corte e baldeio de madeira, com ênfase à compactação, em floresta de Eucalyptus grandis Hill ex Maiden, de 91 meses de idade, através do comportamento de parâmetros físicos e mecânicos de um Latossolo Vermelho Amarelo, com 480 g.kg-1 de areia total e 430 g.kg-1 de argila. Os tratamentos avaliados foram o trânsito anterior ao experimento, a fase de corte e processamento de madeira, efetuada por colhedora (harvester) sobre esteiras e a fase de extração, por trator transportador autocarregável (forwarder) com rodado de pneus, considerando-se as condições de presença ou ausência de cobertura de galhada. Os parâmetros físicos empregados na avaliação foram: densidade do solo, porosidade total, macroporosidade, microporosidade, água disponível no solo, taxa de infiltração de água, temperatura do solo e estabilidade de agregados a seco. Os parâmetros mecânicos avaliados foram resistência do solo à penetração e ao cisalhamento, densidade máxima do solo, teor de água crítico para compactação e grau de compactação. Também foram avaliadas a área de contato rodado-solo e a pressão de rodados sobre o solo. Adotou-se o delineamento inteiramente casualizado, sendo os resultados obtidos submetidos à análise de variância pelo Statistical Analysis System (SAS), com aplicação do teste Tukey a 5% e 10% de significância. Comparativamente, a densidade do solo, a resistência mecânica ao cisalhamento e a pressão de rodados sobre o solo foram maiores após o tráfego do trator transportador em relação ao conferido pela colhedora de madeira. Os parâmetros porosidade total, macroporosidade, microporosidade, água disponível e estabilidade de agregados a seco foram maiores na fase de corte de madeira do que na fase de baldeio... / A study of soil compaction was carried out on a Red-Yellow Latosol with 43% of clay and 48% of sand, according to some soil physical and mechanical parameters in a harvester of a 91-month-old Eucalyptus grandis Hill ex-Maiden forest. The aim was to evaluate the influence caused by the traffic of a 100 kWa-tracked harvester followed by a 190 kWa-wheeled-forwarder, over and without slash, in comparison to the soil conditions before the harvesting operations. The physical parameters used were soil dry bulk density, total porosity, air-filled porosity, micro porosity, soil water availability and infiltration rate, temperature and soil mean aggregate sizes. The mechanical parameters were soil penetrometer resistance, shear strength, Proctor test and machine ground pressure. A randomized-block trial with 15 replicates was used, applying Statistical Analysis System (SAS) and Tukey test at 5% and 10% significance levels. Results showed that wheeled-forwarder increased soil dry bulk density, soil shear strength and soil machine pressure in relation to the tracked-harvester. Thus, the parameters total porosity, air-filled porosity, micro porosity, soil water availability and soil mean aggregate sizes were higher on harvesting than on wood hauling. The wheeled-forwarder operating without slash produced a higher soil dry bulk density, temperature and soil compaction degree. Also, this work condition decreased total porosity and air-filled porosity in relation to the same operation accomplished over slash. Micro porosity, water availability, soil infiltration rate, soil penetrometer resistance and the maximum soil dry bulk density were not affected by both machines working on both slash conditions. All the soil mechanized operations evaluated were rated higher than 2 MPa on soil penetrometer resistance parameter, looked like a soil limit to allow the root growing... (Complete abstract, click eletronic address below)

The predominant production system in North central Uruguay is based on the combined beef cattle and sheep cattle grazing of native grasslands. Soils include an important area of Pelluderts, with high content of expansible clays and high organic matter in the surface horizon. At the beginning of the 90 s there was a rapid expansion in rice production in this part of the country, increasing soil use intensity. Rice is grown in rotations with seeded pastures. Due to variations in annual forage production because variations of the hydric regime, irrigation technology was studied as an alternative to achieve greater inter-annual production stability. The effect of soil compaction, is to be considered when managing Vertisols especially in low soil use intensity situations, like natural pastures improved by overseeding and fertilization, or the more intense rice pastures rotation. The objectives of this research were to quantify the effects of animal trampling, as compared with rice harvesting, on the physical quality of the Vertisols and to obtain a quantitative relationship between rain plus irrigation water input and forrage production. Two experiments were conducted in the basaltic experimental field of INIA-Tacuarembó-Uruguay, to evaluate the effects of irrigation and animal compaction on the improved natural pasture. Another on farm experiment was also conducted to evaluate soil compaction due to rice cropping and harvesting. Physical quality results, showed animal trampling compaction effect in the surface layer (0-3 cm), but not in subsurface (9-12 cm), due animal trampling on bulk density, total porosity, macroporosity, microporosity, compressibility, and penetration resistance. In the rice field, effects of soil deformation by harvesting-combine traffic were evident to 20 cm depth under of high soil moisture conditions.Forage production did not show differences between the irrigation frequencies used in a rainy year (2003). Meanwhile in a dry year (2004), the irrigation treatments produced more (425 %) than the non irrigated, and the one irrigated more frequently produced more (35 %) between the two irrigated ones. General response to water was 8.95 kg MS ha-1 mm-1. Red clover showed greater response than white clover. The effect of animal trampling was significant on forage yield production of red clover, but there was no effect on white clover production. The botanical composition, in a dry year, showed loss of legume presence without irrigation. / O sistema de produção de forma extensiva em campo nativo predominante na região Centro-Norte da República Oriental do Uruguai inclui o pastejo de bovinos e ovinos. Entre os solos encontrados estão os Vertissolos com argilas expansivas e alto teor de matéria orgânica no horizonte mais superficial. A partir dos primeiros anos na década de 90, houve forte expansão da cultura de arroz na região, com aumento da intensidade de uso do solo, e adoção de sistemas de produção arroz gado de corte. Devido a variações da produção forrageira anual relacionada com as variações do regime hídrico, o trabalho teve como objetivo avaliar o uso da tecnologia de irrigação como alternativa para alcançar uma maior estabilidade na produção. Os efeitos sobre as características físicas dos Vertissolos foram avaliados em situações de baixa intensidade de uso, campo natural melhorado sob pastejo ou maior intensidade na rotação arroz-pecuária. Mais especificamente o trabalho procurou quantificar os efeitos do pisoteio animal em comparação com a pressão das máquinas de colheita de arroz na qualidade física de Vertissolos e encontrar uma relação quantitativa entre lâmina de água de chuva mais irrigação e produção de forragem. No campo experimental de basalto de INIA-Tacuarembó-Uruguai, foram realizados dois experimentos para avaliar os efeitos da compactação animal e a irrigação num campo natural melhorado, e noutro campo no departamento de Tacuarembó-Uruguai foi realizado um experimento para avaliar os efeitos da compactação durante a cultura e colheita de arroz. Do ponto de vista da qualidade física do solo, em geral, os resultados dos experimentos mostraram efeito da compactação superficial (0-3 cm), mas não subsuperficial (9-12 cm), devido ao pisoteio animal nos parâmetros densidade do solo, porosidade total, macroporosidade, compressibilidade e resistência do solo à penetração. Na colheita do arroz, foram evidenciados os efeitos de deformação do solo pelo tráfego de colheitadeiras em condições de alto conteúdo de água no solo. A produção forrageira não apresentou diferença para as freqüências de irrigação usadas no ano chuvoso (2003), enquanto que durante o ano seco (2004) os tratamentos irrigados produziram 425 % mais que o não irrigado e o irrigado mais freqüentemente produziu 35 % mais que o irrigado menos freqüentemente. A resposta da produção forrageira à água foi de 8,95 kg de MS ha-1 mm-1. O trevo vermelho apresentou maior resposta da produção forrageira à água do que o trevo branco, 11 kg de MS ha-1 mm-1 e 9 kg de MS ha-1 mm-1, respectivamente. O efeito do pisoteio animal na produção forrageira reduziu a produção do trevo vermelho, mas não do trevo branco. Com relação à composição botânica, no ano seco, houve redução na porcentagem de cobertura por leguminosas no melhoramento nas situações sem irrigação.