Planted forests occupy more than 6.5 million ha in Brazil, where harvest and logging operations are performed with increasingly heavier machinery, increasing the risk of soil compaction. Soil compaction can be avoided if soil load bearing capacity is not exceeded, what makes it important to assess both the soil strength and the impact of different operations. The aim of this study was to evaluate the load bearing capacity of some coarse textured soils (two Hapludult and one Haplorthod) in two soil horizons (BA and B), from northeastern Brazil; and to assess the impact of harvest and logging operations performed with harvester and forwarder. Although the Haplorthod presented higher load bearing capacity in both the BA horizon (for the whole moisture range) and the B horizon (for higher water contents), it suffered the greatest soil compaction. Traffic with the harvester resulted in soil compaction in both the BA and the B horizons, but the increase in bulk density was higher on the later, reaching 18.7% in the Haplorthod. The forwarder traffic intensity and the presence of plant residue cover significantly affected the occurrence of soil compaction. In the BA horizon, the increase in soil bulk density for different forwarder traffic intensities was 3 passes ~ 6 passes < 12 passes ~ 16 passes. The increase in bulk density was higher in the Haplorthod, reaching 32% after 16 forwarder passes over bare soil. Significant linear regressions were obtained from the number of forwarder passes and the increase in bulk density. Index terms:Harvester; forwarder; precompression stress; soil load bearing capacity. RESUMOAs florestas plantadas ocupam mais de 6,5 milhões de ha no Brasil, nas quais as operações de colheita e baldeio são realizadas com maquinário cada vez mais robusto, o que aumenta o risco de compactação do solo. A compactação do solo pode ser evitada se a sua capacidade de suporte de carga não for excedida, o que torna importante a avaliação tanto da resistência mecânica do solo quanto o impacto de diferentes operações. O objetivo deste estudo foi avaliar a capacidade de suporte de carga de solos de textura grosseira (dois Hapludult e um Haplorthod) em dois horizontes (BA e B) do Nordeste do Brasil; além de avaliar o impacto das operações de colheita e baldeio de madeira realizadas com harvester e forwarder. Apesar de o Haplorthod ter apresentado a maior capacidade de suporte de carga no horizonte BA (para toda a faixa de umidade) e no horizonte B (para maiores umidades) ele foi a classe de solo que apresentou maior compactação. O tráfego com o harvester resultou em compactação tanto no horizonte BA quanto no B, mas o aumento da densidade do solo foi maior no último, chegando a 18,7% no Haplorthod. A intensidade de tráfego do forwarder e a presença de resíduos de plantas na superfície do solo afetaram significativamente a ocorrência de compactação do solo. No horizonte BA, o aumento da densidade do solo em decorrência da intensidade de tráfego do forwarder foi de 3 passadas ~ 6 passadas < 12 passadas ~ 1...

The main source of soil structure degradation in coffee plantation is the machinery traffic because these operations may cause soil compaction affecting the crop development. This study aimed to generate the load-bearing capacity models for a Red-Yellow Latosol and to determine through the use of these models the soil susceptibility to compaction of the coffee plantation due to the implantation time and the compaction caused by the machinery traffic on the traffic lines located at the top and bottom of the ground. This study was carried out in the EPAMIG Experimental Farm, located at Três Pontas, MG, in coffee plantations (Coffee arabica L.) with 2, 7, 18 and 33 years of establishment. To obtain the load-bearing capacity models, 12 undisturbed soil samples were randomly collected in the 0-3 cm and 15-18 cm layers in the position between the rows for each establishment time of the coffee plantation. It was also randomly collected 10 undisturbed soil samples for each establishment time of the coffee plantations along the tractor traffic lines located at the top and bottom of the ground. These undisturbed soil samples were used in the uniaxial compression tests. The use of the load-bearing capacity models allow to identify the soil susceptibility to compaction due to the implementation time of the coffee plantation and the compaction caused by the machinery traffic on the traffic lines located at the top and bottom of the ground. The percentage of compacted soil samples increases with the establishment time in the layer of 15-18 cm.Index terms: Precompression stress, structure degradation, soil physics. RESUMOA principal fonte de degradação da estrutura do solo na exploração cafeeira é o tráfego de máquinas, pois essas operações podem causar compactação do solo, afetando o desenvolvimento da cultura. Neste estudo, objetivou-se gerar os modelos de capacidade de suporte de carga para um Latossolo Vermelho-Amarelo e determinar por meio do uso desses modelos a suscetibilidade à compactação do solo, pelo tempo de implantação da lavoura cafeeira e os impactos causados pelo tráfego das operações mecanizadas nas linhas de tráfego localizadas na parte de cima e de baixo do terreno. Este estudo foi realizado na Fazenda Experimental da EPAMIG, situada em Três Pontas, MG, em lavouras cafeeiras (Coffee arabica L.) com 2, 7, 18 e 33 anos de implantação. Para a obtenção dos modelos de capacidade de suporte de carga, 12 amostras indeformadas de solo foram coletadas aleatoriamente nas camadas 0-3 e 15-18 cm no centro das entrelinhas, para cada tempo de implantação da lavoura cafeeira. Foram também coletadas aleatoriamente 10 amostras indeformadas para cada tempo de implantação da lavoura cafeeira ao longo das linhas de tráfego do trator situadas nas partes de cima e de baixo do terreno. Essas amostras foram usadas no ensaio de compressão uniaxial. O uso dos modelos de capacidade de suporte de carga permitiu identificar a suscetibilidade do solo à compactação, em razão do tempo de implantação da lavoura cafeeira e a compacta...

Precompression stress is an important property for assessment of tropical soil structure sustainability and is often determined in laboratory tests. The objective of this study was to compare the load bearing capacity models obtained with controlled moisture in laboratory and those obtained with natural field moistures determined a long one year. The evaluation of soil structural sustainability follows four distinct steps: soil sampling in the field, uniaxial compression test of the samples in the laboratory, determination of precompression stress and estimation of the load bearing capacity models. Laboratory estimates of precompression stress were obtained from moisture controlled in laboratory and from natural moisture determined in a field a long one year. In this process, the soil samples were saturated by capillarity with distilled water in laboratory, and after 48 hours, the samples were air dried to obtain the different moisture contents. Then, the precompression stress was determined for this both conditions. To verify if the load bearing capacity models obtained with controlled moisture in laboratory may represent the load bearing models obtained with natural field moisture, these models were compared using the homogeneity test procedure. It was observed that 75% of field models analyzed were similar to the laboratory models. Thus, due to the similarity on the load-bearing capacity models obtained using natural (field) or controlled (laboratory) moisture contents, the assessment of the soil structure sustainability can be done using both methods.Index terms: Agricultural traffic, Coffea Arabica L., homogeneity test, precompression stress. RESUMOPressão de pré-consolidação é uma importante propriedade na avaliação da sustentabilidade estrutural do solo e é determinada em testes de laboratório. Neste estudo, objetivou-se comparar modelos de capacidade de suporte de carga obtidos com umidade controlada em laboratório e com umidade natural de campo ao longo de um ano. A avaliação da sustentabilidade estrutural do solo ocorreu em quatro etapas: coleta de amostras de solo indeformado, ensaio de compressão uniaxial das amostras em laboratório, estimativa da pressão de pré-consolidação e obtenção dos modelos de capacidade de suporte de carga. As estimativas da pressão de pré-consolidação de laboratório e de campo foram obtidas com umidades controladas em laboratório e com umidade de campo, respectivamente, ao longo de um ano. No laboratório, a saturaçaõ das amostras se deu por capilaridade, com água destilada e depois de 48 horas, essas amostras foram secas ao ar para obter diferentes valores de umidade. Em seguida, realizou-se o ensaio de compressão uniaxial dessas amostras e a pressão de pré-consolidação foi determinada para as duas condições aqui proposta. Para verificar se os modelos de capacidade de suporte de carga com umidade controlada em laboratório podem representar os modelos de capacidade de suporte de carga de umidade natural, esses modelos foram comparados utilizando o teste de homogeneida...

Eucalyptus forests play a major role in the world economy, providing raw materials for different purposes. In planted forests, harvest operations performed by heavy machinery may cause severe soil compaction. This study aimed to evaluate the impact of a full‐tree harvesting system in planted eucalyptus forests from Northeastern Brazil. Different soils were evaluated (two Hapludults and one Haplorthod) in two horizons (BA and Bt). We tested different equipment, namely feller buncher, skidder (with traffic intensities of 3, 6, 12 and 16 passes), flail (at different ground‐contact points), grapple saw and loader. The soil physical attributes reflected not only the impact of equipment traffic but also the intrinsic differences between the soils. Bulk density (ranging from 1.36 to 1.80 t m−3 after trafficking) related well to soil class and horizon. Precompression stress (ranging from 203 to 430 kPa) and degree of compaction (76%–94%) following trafficking were well correlated, while increase in bulk density (reaching a maximum of 20%) related more strongly to soil moisture. A contingency table was constructed with the number of compacted samples and further examined by correspondence analysis. Compaction varied according to soil, horizon and equipment, indicating that machine–soil interactions are very specific and demand detailed research under different conditions. The Haplorthod experienced the greatest amount of compaction, whereas the Hapludult‐2 was more resistant (60% and 25% of compacted samples, respectively). The grapple saw and the skidder at higher traffic intensities (12 and 16 passes) exerted the highest mechanical impacts (81% and 67% of compacted samples, respectively).

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