Os ecossistemas naturais e agropecuários dependem fundamentalmente do solo como recurso básico para sua funcionalidade. Neste contexto, a qualidade do solo tem tido uma crescente importância global. Os objetivos deste estudo consistiram em propor modificações metodológicas e/ou instrumentais visando determinações mais acuradas dos indicadores da qualidade física do solo mediante o desenvolvimento de (i) um sistema eletro-mecânico que permite a obtenção de amostras indeformadas de solos sem aplicação de golpes; (ii) um penetrômetro estático automatizado, de baixo custo e portátil, para medidas de resistência à penetração (RP) e resistência tênsil (RT) sob regime de velocidade constante de 1,55 mm s-1; (iii) um consolidômetro, de baixo custo e de maior portabilidade, para determinações da curva de compressão do solo, da RP e da RT utilizando propulsão pneumática e (iv) melhorias instrumentais em um permeâmetro de carga constante de ar pela redução de oscilações durante a medição do gradiente de pressão bem como a otimização da seleção de diferentes níveis de vazão mássica de ar. Os resultados obtidos mostraram que (i) o sistema eletromecânico garantiu a preservação da estrutura do solo em amostras coletadas comparado com a amostragem por golpes, principalmente no solo mais argiloso; (ii) a RP e a RT puderam ser determinadas com elevada acurácia à velocidade constante de 1,55 mm s-1; (iii) a curva de compressão do solo foi sensível às diferenças entre os tratamentos (linha e entrelinha da cultura) e a utilização de propulsão pneumática não influenciou os resultados da RP e da RT e (iv) a instrumentação utilizada no permeâmetro de carga constante de ar permitiu realizar determinações da permeabilidade do solo ao ar tanto em campo quanto em laboratório com rapidez e elevada acurácia. / Natural and agricultural ecosystems rely fundamentally on soil as a basic resource for their functionality. In this context, soil quality has had a growing global importance. The objectives of this study were based on proposing methodological and/or instrumental modifications aiming to obtain more accurate determinations of soil physical quality indicators by developing: (i) an electro-mechanical system that allows the extraction of undisturbed soil samples without mechanical impact (no-hammering); (ii) a low cost and portable static automatic penetrometer, for measuring soil penetration resistance (PR) and tensile strength (TS) at a constant speed of 1.55 mm s-1; (iii) a low cost and portable consolidometer, for determination of soil compression curve, PR and TS using pneumatic propulsion and (iv) instrumental improvements to a constant head air permeameter by reducing the oscillation during measuring the pressure head gradient and the optimization of the selection of different levels of air mass flow. The results showed that (i) the electro-mechanical system ensured the preservation of soil structure in undisturbed samples in comparison to samples extracted by hammering procedures, especially in clayey soil; (ii) PR and TS could be determined with high accuracy at the constant speed of 1.55 mm s-1; (iii) the soil compression curve was sensitive to differences between treatments (crop row and inter-row) and the use of pneumatic propulsion did not influence the results of PR and TS, and (iv) the instrumentation used in the constant head air permeameter allowed determination of soil air permeability either on the field or in the laboratory with high speed and accuracy.

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.

Made available in DSpace on 2017-07-10T17:31:22Z (GMT). No. of bitstreams: 1 Wagner_de_Aguiar.pdf: 11388693 bytes, checksum: 2d568f29c8d953e3f9cb683f0a508900 (MD5) Previous issue date: 2012-02-27 / The object of this paper is to estimate the mechanical denudation rates for the river basin Quatorze in the sectors of the upper valley and the mouth of the river. The basin is located in the municipality of Francisco Beltrão, in Paraná, draining the left bank of the middle valley of the river basin Marrecas. Monitoring the field began in august 2011, rising daily data of rainfall, flow and concentration of suspended solids in the sections of the channels drained the upper valley and the mouth of the river, to obtain the discharges suspended solids. Carrying out further surveys in ten soil profiles distributed throughout the basin, allowing the identification of the main soil classes (Regolithic Entisols, Inceptisols, Oxisols and Nitossolos) and the measurement of laboratory parameters such as density and real, total porosity and fines content (silt and clay). In the monitored period was recorded daily rainfall, which occurred on august 19, 165 mm, resulting in large peak flows and discharge of suspended solids, contributing to the total rainfall for the month of august 2011, 343 mm, reached the highest monthly index for the month of august, the last 37 years, according to data provided by the Meteorological Station of Francisco Beltrão. Recognizing that the largest fraction pedological removed by the force of runoff is composed of mud (silt and clay), this parameter was quantified for soils of the basin, yielding an average of 91.87%. From the data of total suspended solid discharge (1,616.54 tons. in the upper valley and 5960.38 tons. at the mouth) and the average density (1.05 g.cm-³) of soil profiles were estimated denudation rates for the month of august 2011, 0.0419 mm in the sector of the basin drained by the upper valley and 0.0527 mm in the area drained by the mouth of the river. These results were extrapolated to annual estimates, based on the monitored period of rainfall and monthly average of the years 1974 to 2010. The standard deviations of the average monthly rainfall, for those years, enabled the establishment of maximum and minimum estimates for the annual rates of denudation. The sector of the upper valley had average estimate of 0.2458 mm.yr-¹ can vary over a range of 0.1069 mm.yr-¹ to 0.3848 mm.yr-¹, while the sector had the mouth of the river estimated annual average higher, 0.3092 mm.yr-¹ may, however, vary in a range of 0.1344 mm.yr-¹ to 0.4840 mm.yr-¹. / O objeto de estudo deste trabalho é estimar as taxas de denudação mecânica para a bacia hidrográfica do rio Quatorze, nos setores do Alto Vale e da Foz do rio. A bacia está localizada no município de Francisco Beltrão, no Sudoeste do Paraná, drenando a margem esquerda do médio vale da bacia do rio Marrecas. O monitoramento a campo iniciou-se no mês de agosto de 2011, levantando-se dados diários de pluviosidade, de vazão e de concentração de sólidos em suspensão, nas seções dos canais drenados pelo Alto Vale e pela Foz do rio, para a obtenção das descargas sólidas em suspensão. Realizando-se na sequência levantamentos de solos em dez perfis distribuídos pela bacia, possibilitando a identificação das principais classes de solo (Neossolos regolítico, Cambissolos, Nitossolos e Latossolos) e a quantificação laboratorial dos parâmetros como densidade aparente e real, porosidade total e teor de finos (silte e argila). No período monitorado foi registrada pluviosidade diária, ocorrida no dia 19 de agosto, de 165 mm, provocando grandes picos de vazão e descarga de sólidos em suspensão, contribuindo para que a pluviosidade total do mês de agosto de 2011, 343 mm, atingisse o maior índice mensal, para os meses de agosto, dos últimos 37 anos, de acordo com dados fornecidos pela Estação Meteorológica de Francisco Beltrão. Reconhecendo-se que a maior fração pedológica removida pela força do escoamento superficial é composta pela lama (silte e argila), quantificou-se este parâmetro para os solos da bacia, obtendo-se um valor médio de 91,87%. A partir dos dados de descarga sólida em suspensão total (1.616,54 ton. no Alto Vale e 5.960,38 ton. na Foz) e da densidade aparente média (1,05 g.cm-³) dos perfis de solo, foram estimadas as taxas de denudação, para o mês de agosto de 2011, em 0,0419 mm no setor da bacia drenado pelo Alto Vale e 0,0527 mm no setor drenado pela Foz do rio. Resultados estes extrapolados para estimativas anuais, tendo como base as pluviosidades do período monitorado e das médias mensais dos anos de 1974 a 2010. Os desvios padrões das pluviosidades médias mensais, dos referidos anos, possibilitaram o estabelecimento de estimativas máximas e mínimas para as taxas de denudação anual. O setor do Alto Vale apresentou estimativa média de 0,2458 mm.ano-¹ podendo variar em uma faixa de 0,1069 mm.ano-¹ a 0,3848 mm.ano-¹, enquanto que o setor da Foz do rio apresentou estimativa média anual, mais elevada, de 0,3092 mm.ano-¹, podendo, no entanto, variar em uma faixa de 0,1344 mm.ano-¹ a 0,4840 mm.ano-¹.

Made available in DSpace on 2017-05-12T14:42:51Z (GMT). No. of bitstreams: 1 Wagner_de_Aguiar.pdf: 11388693 bytes, checksum: 2d568f29c8d953e3f9cb683f0a508900 (MD5) Previous issue date: 2012-02-27 / The object of this paper is to estimate the mechanical denudation rates for the river basin Quatorze in the sectors of the upper valley and the mouth of the river. The basin is located in the municipality of Francisco Beltrão, in Paraná, draining the left bank of the middle valley of the river basin Marrecas. Monitoring the field began in august 2011, rising daily data of rainfall, flow and concentration of suspended solids in the sections of the channels drained the upper valley and the mouth of the river, to obtain the discharges suspended solids. Carrying out further surveys in ten soil profiles distributed throughout the basin, allowing the identification of the main soil classes (Regolithic Entisols, Inceptisols, Oxisols and Nitossolos) and the measurement of laboratory parameters such as density and real, total porosity and fines content (silt and clay). In the monitored period was recorded daily rainfall, which occurred on august 19, 165 mm, resulting in large peak flows and discharge of suspended solids, contributing to the total rainfall for the month of august 2011, 343 mm, reached the highest monthly index for the month of august, the last 37 years, according to data provided by the Meteorological Station of Francisco Beltrão. Recognizing that the largest fraction pedological removed by the force of runoff is composed of mud (silt and clay), this parameter was quantified for soils of the basin, yielding an average of 91.87%. From the data of total suspended solid discharge (1,616.54 tons. in the upper valley and 5960.38 tons. at the mouth) and the average density (1.05 g.cm-³) of soil profiles were estimated denudation rates for the month of august 2011, 0.0419 mm in the sector of the basin drained by the upper valley and 0.0527 mm in the area drained by the mouth of the river. These results were extrapolated to annual estimates, based on the monitored period of rainfall and monthly average of the years 1974 to 2010. The standard deviations of the average monthly rainfall, for those years, enabled the establishment of maximum and minimum estimates for the annual rates of denudation. The sector of the upper valley had average estimate of 0.2458 mm.yr-¹ can vary over a range of 0.1069 mm.yr-¹ to 0.3848 mm.yr-¹, while the sector had the mouth of the river estimated annual average higher, 0.3092 mm.yr-¹ may, however, vary in a range of 0.1344 mm.yr-¹ to 0.4840 mm.yr-¹. / O objeto de estudo deste trabalho é estimar as taxas de denudação mecânica para a bacia hidrográfica do rio Quatorze, nos setores do Alto Vale e da Foz do rio. A bacia está localizada no município de Francisco Beltrão, no Sudoeste do Paraná, drenando a margem esquerda do médio vale da bacia do rio Marrecas. O monitoramento a campo iniciou-se no mês de agosto de 2011, levantando-se dados diários de pluviosidade, de vazão e de concentração de sólidos em suspensão, nas seções dos canais drenados pelo Alto Vale e pela Foz do rio, para a obtenção das descargas sólidas em suspensão. Realizando-se na sequência levantamentos de solos em dez perfis distribuídos pela bacia, possibilitando a identificação das principais classes de solo (Neossolos regolítico, Cambissolos, Nitossolos e Latossolos) e a quantificação laboratorial dos parâmetros como densidade aparente e real, porosidade total e teor de finos (silte e argila). No período monitorado foi registrada pluviosidade diária, ocorrida no dia 19 de agosto, de 165 mm, provocando grandes picos de vazão e descarga de sólidos em suspensão, contribuindo para que a pluviosidade total do mês de agosto de 2011, 343 mm, atingisse o maior índice mensal, para os meses de agosto, dos últimos 37 anos, de acordo com dados fornecidos pela Estação Meteorológica de Francisco Beltrão. Reconhecendo-se que a maior fração pedológica removida pela força do escoamento superficial é composta pela lama (silte e argila), quantificou-se este parâmetro para os solos da bacia, obtendo-se um valor médio de 91,87%. A partir dos dados de descarga sólida em suspensão total (1.616,54 ton. no Alto Vale e 5.960,38 ton. na Foz) e da densidade aparente média (1,05 g.cm-³) dos perfis de solo, foram estimadas as taxas de denudação, para o mês de agosto de 2011, em 0,0419 mm no setor da bacia drenado pelo Alto Vale e 0,0527 mm no setor drenado pela Foz do rio. Resultados estes extrapolados para estimativas anuais, tendo como base as pluviosidades do período monitorado e das médias mensais dos anos de 1974 a 2010. Os desvios padrões das pluviosidades médias mensais, dos referidos anos, possibilitaram o estabelecimento de estimativas máximas e mínimas para as taxas de denudação anual. O setor do Alto Vale apresentou estimativa média de 0,2458 mm.ano-¹ podendo variar em uma faixa de 0,1069 mm.ano-¹ a 0,3848 mm.ano-¹, enquanto que o setor da Foz do rio apresentou estimativa média anual, mais elevada, de 0,3092 mm.ano-¹, podendo, no entanto, variar em uma faixa de 0,1344 mm.ano-¹ a 0,4840 mm.ano-¹.

Do ponto de vista agronômico, a irrigação com efluente tem a grande vantagem de permitir a economia de água e adubos, uma vez que o efluente é naturalmente rico em nutrientes e matéria orgânica; no entanto, é também neste ponto que surgem as preocupações relacionadas ao ambiente. Se mal planejada esta aplicação, o excesso de nutrientes e matéria orgânica pode causar poluição e provocar alterações nas propriedades do solo, tanto químicas quanto físicas e hídricas. Tendo em vista a problemática acima exposta, o presente trabalho teve como objetivo estudar o efeito da irrigação com efluentes de esgoto tratado nas propriedades físicas e hídricas de um latossolo. A área experimental situa-se no município de Lins-SP e é composta de três parcelas: parcela Água (A), parcela Efluente (E) e parcela Testemunha (T), numa vertente imediatamente ao lado das lagoas. Todo o estudo foi realizado em 8 profundidades, até 1,875m. Determinou-se, em campo, através do método do perfil instantâneo, a condutividade hidráulica do solo em meio não saturado, K(&#952;); da mesma forma, determinou-se em laboratório através do método da carga decrescente, a condutividade hidráulica do solo saturado, Ksat. Avaliou-se também K(&#952;) em laboratório pelo sistema Wind (baseado na evaporação), comparando-o ao método do perfil instantâneo (baseado na drenagem). Analisou-se a porosidade do solo, através da distribuição do diâmetro dos poros obtida a partir das curvas de retenção de água. Os resultados mostraram que houve alterações da condutividade hidráulica do solo em ambas as parcelas irrigadas, com água e com efluente, em relação à parcela tomada como referência. Isto demonstra que, não só o efluente, mas também a irrigação convencional deve ser planejada com precauções na região em estudo, uma vez que a própria água de abastecimento utilizada é rica em sódio. As parcelas irrigadas apresentaram diminuição significativa de K(&#952;) em relação à parcela Testemunha nas umidades elevadas; por outro lado, o K(&#952;) aumentou nas parcelas irrigadas nas umidades baixas, o que sugere uma mudança na estrutura e na porosidade do solo. Em relação à Ksat, identificou-se um decréscimo nas parcelas irrigadas em relação à Testemunha ao longo de todo o perfil de solo. O sistema de laboratório Wind, mostrou-se mais adaptado a solos irrigados com águas sódicas do que o método do perfil instantâneo. A irrigação com efluente e com água (águas sódicas) levou à diminuição da microporosidade, isto é, a classe de poros de diâmetro entre 0,2 µm e 50 µm. Por outro lado o aumento significativo da criptoporosidade (<0,2 µm) foi identificado em todo o perfil de solo estudado. Houve correlações significativas entre os volumes de microporos e criptoporos, a porcentagem de argila dispersa em água e o Na+, o que resultou da ocorrência dos processos de dispersão e expansão dos agregados. / From the agronomic point of view, irrigation using treated sewage effluent has a great advantage in saving water and fertilizers, once effluent is naturally rich in nutrients and organic matter. However, some concerns related to the environment are raised regarding this aspect. The excess of nutrients and organic matter can cause pollution and provoke changes in the soil chemical, physical and hydraulic properties, in case this application is not well planned. The present work aimed to study the effect of irrigation using sewage treated effluent on the physical and hydraulic properties of an Oxisol. The experimental area is located in Lins-SP, and it is composed of three plots: Water plot, Effluent plot and Control plot located on a slope beside the ponds. All the study was carried out in 8 depths up to 1,875 m. The unsaturated soil hydraulic conductivity K(&#952;) was determined under field conditions using the instantaneous profile method. Similarly, saturated soil hydraulic conductivity, Ksat, was determined by using the falling head method. K(&#952;) was also evaluated, under laboratory conditions, by using the Wind system (based on evaporation), which was compared afterwards to the instantaneous profile method (based on drainage). The soil porosity was analyzed by means of the pores diameter distribution obtained from the water retention curve. The results showed that there were changes in the soil hydraulic conductivity in both plots irrigated with water and effluent, in relation to the reference one. This fact demonstrates that not only the irrigation with effluent, but also the conventional one must be managed with precautions in the studied area, once the water supplied to the city is rich in sodium. The irrigated plots presented a significant decrease in K(&#952;) in relation to the Control plot with higher water contents. On the other hand, K(&#952;) increased in the irrigated plots with lower water content, suggesting a change in the soil porosity. In relation to Ksat, a decrease in the irrigated plots in relation to the Control was identified along the whole soil profile. The Wind system showed to be more adapted to soils irrigated with sodium-rich water when compared to the instantaneous profile method. The irrigation with effluent and with water (sodium-rich waters) induced a decrease in the microporosity, that is, the pores class with diameter comprising between 0,2 µm and 50 µm. On the other hand, a significant increase in criptoporosity (<0,2 µm) was identified in the whole soil profile. Significant correlations among micropores and criptopores volumes, water clay dispersion, and Na+, which resulted from the aggregates dispersion and expansion processes.

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.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The hypothesis that soil compaction in no-tillage affects crop production has been tested often, however, there is no regularity in the relationship between plant response and soil compaction indexes that has allowed generalization of research results. Therefore the objective of this study is to investigate these relationships. An experiment was conducted on an Oxisol under eight corn crops grown (Zea Mays L.) during the 2010/2011 and 2011/2012 growing seasons using no-tillage (NT), no-tillage + chiseling (CNT) and no-tillage + traffic (TNT) treatments. The aim of additional chiseling and traffic is to reduce and increase soil compaction, respectively. From the soil physical properties and daily sequential water balance, soil indexes were calculated over the entire corn cycle in NT, CNT and TNT, consisting of frequencies and accumulated resistance to penetration (RP), matric tension (ψ) and fraction of available water (FAW). Other soil indexes were calculated, including the frequency that the water content (θ) remained of the least limiting water range (LLWR) and the LLWR amplitude, using different values of ψ and RP in the lower limits of the LLWR. Agronomic parameters measured include: plant height (Ph), leaf area index (LAI), effective rooting depth (Rd) and grain yield. Correlation and regression analyzes were performed to assess the relationship between measures of corn and soil indexes. The soil indexes regularly indicated that the increase in compaction decreased Ph, LAI and Rd. Grain yield ranged from 1980 to 5738 kg ha-1 in the eight corn crops, but there was little statistical evidence that this variability was caused by compaction. The corn variables were weakly correlated with ψ and FAW. Alone, RP was more efficient than the IHO to relate response of corn to soil compaction, and the RP efficiency increased when RP was subject to decay with decreasing in θ. However, the most efficient RP index explained only 25, 24 and 6% of the variation in Ph, LAI and grain yield, respectively. Furthermore, the assumption that the LLWR indicates soil physical quality for crop production was statistically refuted by grain yield. The evidence from this study indicate that soil physical indexes such as LLWR, critical density and penetration resistance are inefficient to investigate the regularity of plant response to soil compaction. / A hipótese que a compactação do solo em plantio direto prejudica a produção das culturas vem sendo frequentemente testada, mas não há regularidade nas relações entre resposta das plantas e indicadores de compactação que possibilitam generalização de resultados das pesquisas. Investigar essas relações é o que constitui o objetivo deste trabalho. Para isso, um experimento foi conduzido num Latossolo Vermelho Distroférrico típico sob plantio direto (PD), que recebeu escarificação (PDE) e compactação adicional (PDC). Nesses tratamentos, foram medidos a altura de plantas (Ap), o índice de área foliar (IAF), a profundidade efetiva de raízes (Ze) e o rendimento de grãos (Rend), em oito cultivos de milho (Zea Mays L.) nas safras 2010/2011 e 2011/2012. A partir de propriedades físicas do solo e da execução de cálculos de balanço hídrico sequencial diário, índices físico-hídricos, consistindo de frequências e acumulados de resistência do solo à penetração (RP), tensão matricial (ψ) e fração de água disponível (FAD), foram calculados ao longo do ciclo do milho no PD, PDE e PDC. Também foram calculados índices obtidos pelas frequências que o conteúdo de água (θ) permaneceu fora do intervalo hídrico ótimo (IHO) e pela amplitude do IHO, adotando-se diferentes valores de RP e ψ para os limites inferiores do IHO. Análises de correlação e regressão foram utilizadas para verificar a relação entre as medidas da cultura do milho com índices de solo. Os índices de solo regularmente indicaram que o aumento da compactação diminuiu a Ap, o IAF e o Ze. O rendimento de grãos variou de 1980 kg ha-1 a 5738 kg ha-1 nos oito cultivos, mas houve pouca comprovação estatística que essa variabilidade foi causada pela variação da compactação. As variáveis da cultura estiveram pouco correlacionadas com a ψ e a FAD. Sozinha, a RP foi mais eficiente que o IHO para relacionar resposta da cultura do milho com compactação do solo, e sua eficiência aumentou quando a RP foi condicionada ao decaimento com o decréscimo de θ. Contudo, o índice de RP de maior eficiência explicou somente 25%, 24%, e 6% da variação da Ap, do IAF e do Rend, respectivamente. Além disso, a suposição de que o IHO indica qualidade física do solo para produção das culturas foi refutada estatisticamente pelo Rend. As evidências a partir deste trabalho indicam que índices físicos do solo como intervalo hídrico ótimo, densidade crítica e resistência à penetração são pouco eficientes para se investigar a regularidade da resposta das plantas à compactação do solo.

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.