Los sistemas productivos agrícolas presentan altos niveles de mecanización con tractores y máquinas cada vez más pesados. Como consecuencia, la compactación de los suelos es un problema emergente, dando como resultado el deterioro de la estructura de muchos suelos y la baja de los rendimientos productivos. El objetivo del presente trabajo fue evaluar el efecto de distintas intensidades de tráfico sobre dos condiciones de suelo: con labranza y bajo siembra directa, sometidos a diferentes intensidades de tráfico. Se compararon dos sistemas de siembra: suelo bajo siembra directa y suelo con labranza. Como subtratamientos se estudió la incidencia del pasaje repetido sobre la misma senda de un tractor de 6,4 Mg resultando en una, cinco y diez pasadas. Para cuantificar la compactación inducida se evaluaron la resistencia a la penetración, la densidad aparente y la profundidad de huella. Además se evaluó la compactación máxima resultante a través del test Proctor (1933). El suelo labrado resultó ser más compactable, presentando mayor profundidad de huella y menos resistencia a la penetración luego del tráfico. El suelo bajo siembra directa presentó una menor compactabilidad Proctor y una menor humedad óptima. Además, se encontró que este suelo tenía un mayor porcentaje de carbono total y de carbono particulado y mayor estabilidad estructural. El suelo bajo siembra directa fue capaz de almacenar más agua durante un periodo más prolongado. Hubo un comportamiento reológico diferente según el sistema de labranza. Los cambios en las propiedades físicas mesuradas resultaron más evidentes en el suelo labrado.

Agricultural farm systems show high levels of mechanization using tractors and machines weighing more than formers. As a consequence, soil compaction is an emerging problem, resulting in the deterioration of the structure of many soils and low yields. The aim of this study was to evaluate the effect of different intensities of traffic on two conditions of soil: low tillage and direct seeding, under different traffic intensities. Two sowing systems were compared: direct seeding and tilled soil sowing. As subtreatments, multiple traffic intensities were applied using one, five and ten passes of a 6.4 Mg tractor. Induced soil compaction was assessed by penetration resistance, bulk density and rut depth. In addition the resulting maximum compaction was evaluated using Proctor Test (1933). Tilled soil was more compactable, showing more important rut depths and less penetration resistance after the traffic. The soil under reduced tillage presented lower Proctor compactness and lower optimum moisture. Furthermore, it was found that this soil had a higher percentage of total carbon and particulate carbon, and greater structural stability. The soil under no tillage was able to store more water for a longer period. There was a different rheological behavior under tillage system. The changes in physical properties were more evident in the tilled soil.

O tráfego necessário à exploração de pomar frutícola tem características que se denominam "tráfego controlado", já que se realiza sempre sobre os mesmos caminhos do espaço entrelinhas. No alto Valle do Rio Negro, Argentina, a essa situação deve ser agregado, como fator de predisposição das sobrecompactações, o fato de que ocorre com freqüência um excesso de irrigação, que obriga ao tráfego sobre um solo úmido e, portanto, com baixa capacidade de suporte e alta predisposição à compactação. O presente trabalho teve o objetivo de estabelecer a possibilidade de sustentabilidade do sistema produtivo, que se conseguiria com a redução do tráfego resultante das mudanças das aplicações fitossanitárias de calendário fixo, pelas propostas no Projeto Frutícola Integrado (PFI) do INTA (Instituto Nacional de Tecnologia Agropecuária). Em um pomar de macieiras, foi simulado, sobre duas condições de solo, com e sem cobertura vegetal, o tráfego correspondente ao somatório de um ano para cada sistema. Para os tratamentos de tráfego, foi utilizado um conjunto trator-pulverizador padrão. O parâmetro que se vinculou à compactação, foi a resistência à penetração. O estado do solo anteriormente à aplicação do tráfego foi tomado como testemunha. A medição de sobrecompactações sobre o solo nu testemunha foi mais freqüente que sobre o coberto por vegetação. Depois dos tratamentos, a reologia dos solos foi diferente. Concluiu-se que as diminuições do tráfego, como as que foram propostas no PFI, são de significativa importância na busca da sustentabilidade do sistema produtivo.

Orchard production traffic demands have characteristics that is called controlled traffic. Tractors and its machines, always use the same tracks in each of their passage. Not only this negative condition, but the fact that the irrigation used is usually excessive, it leads to a highly potential condition to enhance over-compaction in Alto Valle region in Argentina. This paper is part of a thesis refered to the possibility of introducing changes in the manner of the phytosanitary applications are done. These changes consist in leaving the fixed calendar method to the one proposed by the Integrated Orchard Production program of the INTA. In an apple orchard field, on two soil conditions, with and without grass, traffic corresponding to a whole year management passages of a tractor and it sprayer were simulated for both systems. Penetration resistance was assessed before and after traffic, and related to induced compaction. Over-compaction values were measured more frequently on non-grassed soil if control plot was considered. Edaphic reology was different for each soil condition after traffic was applied. Traffic decreases due to Integrated Orchard Production management and were of significant importance if a sustainable system is the target.

With the aim to evaluate the soil mechanic reaction-traffic relationship to different tillage systems, penetration resistance and soil bulk density measurements were made. Four traffic conditions (6, 8, 10 and 12 passes of a 2WD, 52.25 kW tractor) were evaluated in a typic Argiudol soil with six years of wheat-soybean rotation under no-tillage and conventional tillage. Bulk density and penetration resistance were used to evaluate the traffic effects on soil compaction. After the six-year rotation, no-tillage system showed significant higher penetration resistance values with respect to conventional tillage system in the topsoil layer. The bulk density values recorded in the non tillage system determine root growth limitation at low number of passes and at shallow depth. The greater the number of passes, lower the depth at which the penetration resistance can reach potential root growth limiting values.

El objetivo del presente trabajo fue cuantificar la reacción mecánica del suelo al tránsito, a través de la resistencia a la penetración y la densidad aparente para visualizar posibles diferencias debido al sistema de labranza utilizado. El ensayo se instaló sobre un suelo Argiudol típico, sobre dos lotes, provenientes cada uno de seis años de cultivo trigo-soja bajo dos formas de labranza: siembra directa (SD) y labranza convencional (LC). Se establecieron 4 tratamientos de tránsito, correspondientes a 6, 8, 10 y 12 pasadas de un tractor de diseño convencional (2WD) Massey Fergusson 1175 de 52,25 kW (71 CV) en el motor. Para determinar los efectos del tránsito sobre la compactación inducida, se determinaron la densidad global (DA) y la resistencia a la penetración (RP). Luego de 6 años de rotación trigo-soja bajo estas dos formas de cultivo (siembra directa y labranza convencional) la condición mecánica de los suelos resultó ser significativamente diferente, al menos en las capas más superficiales, resultando el suelo trabajado con SD mayores valores de RP que la condición de LC. La siembra directa registró valores de DA limitantes para el normal desarrollo radicular a menores intensidades de tráfico y desde menores profundidades. A medida que aumentó la intensidad de tráfico disminuyó la profundidad donde se alcanzaron valores de resistencia a la penetración potencialmente determinantes de la detención en el crecimiento radicular.

Os solos submetidos a sistemas de produção que não incluem o preparo do solo, estão condicionados, em sua sustentabilidade, a um manejo que priorize o acompanhamento da compactação que o tráfego de máquinas provoca. Foram realizados ensaios de campo com o objetivo de avaliar a reologia de um solo Typic Hapludert, submetido ao tráfego de veículos em dois sistemas de preparo do solo (preparo convencional - LC, e semeadura direta - SD). Os subtratamentos foram quatro intensidades de tráfego (0; 80; 160 e 240 Mg km ha-1). As variáveis experimentais dependentes foram: índice de cone (IC) e densidade aparente a seco (DA). Para 160 e 240 Mg km ha-1, encontraram-se diferenças estatísticas significativas no IC em relação à testemunha. Para o LC, com as maiores intensidades de tráfego, encontraram-se valores de DA superiores a 1,83 Mg m-3. O comportamento mecânico do solo sob tráfego é mais diferente em SD que em LC. Existe uma relação direta entre o número de passadas e a profundidade onde se localiza a camada de maior resistência à penetração nos solos sob tratamento com LC.

A former concern related to agricultural soil, under no tillage systems, might be the state of compaction due to farm machinary traffic. Two treatments corresponding to two different tillage systems (disk plowed, LC, and no tillage, SD) included four traffic subtreatmets (0; 80; 160, and 240 Mg km ha-1) on a Typic Hapludert. Cone index (IC) and dry bulk density (DA) were the experimental dependent variables asessed. Soil reology under traffic had a different behaviour in both treatments. In both treatments for the higher traffic intensities (160 and 240 Mg km ha-1) statistical significant difference (P < 0,05) were measured when compared with the control plots, when the IC was considered. Considering LC treatment and the higher traffic intensities, the dry bulk densities values measured arised to 1.83 Mg m-3, the disk plowed, and no tillage under traffic soils reologies are different. If the depth of the maximum response in terms of IC measurements is considered, a direct relationship between traffic intensities and depth, could be stablished.

The main objectives of this research were: to determine the responsability of weight, number of passes and independent variables, on the vertical distribution of subsoil compaction and to obtain evidence to decide upon the convenience of matching equipments with light or heavy tractors, according to their differences in passes on the field. Field tests were carried out on grassland, on a typic Argiudol with a soil moisture below, but near to field capacity. The dependent experimental variable was the induced soil compaction and was related to bulk density (assessed with gamma probe), penetration resistance (measured with an electronic cone penetrometer), and remaining grassland yield, six and eight months after traffic treatments were applied. Data from two tests, with two phases of data logging were analysed, totalizing a three year period of assessment pursuit. Results did not show differences between heavy and light treatments in the shallower depth range. Nevertheless, highly significant differences were shown if the deepest range is considered. Decrease in grassland yields ranging from 7 to 25% were measured in out-of-track areas, and 52 to 76% in intrack areas. It was concluded that the number of repeated passes on the same tramlines of a light tractor, can do as much or even greater damage than the heavier tractor with fewer passes. Ten is the critical number of passes, beyond it, advantages taken from the use of a light tractor are lost.

Han sido objetivos principales de este trabajo, tanto el discriminar la responsabilidad de las variables independientes, peso y número de pasadas, en la distribución vertical de la compactación inducida, como obtener evidencia que permita decidir la conveniencia entre conjuntos ligeros que rueden muchas veces sobre la superficie trabajada, o conjuntos más grandes y pesados que resuelvan la tarea con menos pasajes. Se trabajó sobre un suelo de textura fina, con alta humedad presente. Las variables experimentales independientes configuraron dos tratamientos, tractor pesado y ligero, y tres diferentes número de pasadas, 1, 5 y 10, resultaron en seis subtratamientos de diferente intensidad de tráfico, más una parcela testigo sin tráfico. Los resultados no mostraron diferencias entre los tratamientos pesado y ligero, en el rango más superficial evaluado, sin embargo siempre fueron muy significativas las diferencias si se considera el rango de mayor profundidad. Disminuciones del rendimiento del pastizal del orden de 7 a 25% fueron medidas en las zonas adyacentes a las huellas, mientras que esas pérdidas ascendieron al rango de 52 a 76% dentro de la impronta dejada por las huellas del tráfico. Se pudo concluir que, el número de pasadas reiteradas sobre la misma senda, puede emular, e incluso reemplazar, al factor peso sobre el eje, en la responsabilidad principal de inducir compactaciones en el subsuelo. Diez pasadas, es el número crítico de rodadas, a partir del cual se pierden las ventajas de traficar con un tractor ligero, como alternativa a uno pesado con menos pasadas.