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Soil tillage and agricultural traffic generate changes in soil physical attributes and affect the growth of the roots. This study evaluates the impact of system soil tillage on compaction and sugarcane root growth. The experiment was carried out on a Rhodic Kandiudox with two soil tillages (Deep Strip Tillage and Conventional Tillage) and two positions (beds or traffic lane and no traffic lane), totaling four treatments (DST-beds + no traffic lane, DST-traffic lane, CT-no traffic lane and CT-traffic lane). Soil penetration resistance (SPR), bulk density, dry mass, and root system lengths and volumes were evaluated. DST-beds presented lower values for SPR (1.45 MPa) compared to the other treatments (2.55 MPa). This lower SPR did not reflect significant increases in root growth in relation to the DST-traffic lane, meaning that the roots were not confined to the beds. The dry root mass for CT- traffic lane was 35% less than for DST- traffic lane, and CT-no traffic lane reduced of the root dry mass in the layers 0.0–0.2 and 0.2–0.4 m by 62% and 47%, respectively, compared to the DST-beds. Therefore, CT, although widely used, does not create adequate conditions for root development in the first sugarcane cycle, even in lanes with no traffic.

colheita mecanizada. As avaliações da CSC foram realizadas em amostras de solo indeformadas, coletadas na linha de plantio e no canteiro, em quatro camadas: 0,00-0,10, 0,10-0,20, 0,20-0,30 e 0,30-0,40 m. Determinou-se a área de contato dos rodados com o solo, para a estimativa da pressão exercida pelas máquinas agrícolas no solo. As pressões de preconsolidação foram usadas para determinar a CSC. O sistema com três ciclos apresentou maior CSC do que o sistema com apenas um ciclo. A capacidade de suporte de carga do solo avaliado na faixa de friabilidade é maior que as pressões de contato aplicadas ao solo pelos rodados das máquinas agrícolas estudadas.Termos para indexação: área de contato, compactação do solo, compressibilidade do solo, curva de compressão, pressão de contato, pressão de preconsolidação. Load support capacity of an Oxisol cultivated with sugarcane and mechanization effects on the soilAbstract -The objective of this work was to determine the load support capacity (LSC) of an Oxisol and, through compressibility models, relate it to wheel-soil interactions under management systems with one and three sugarcane crop cycles, with mechanized harvest. LSC evaluations were carried out on undisturbed soil samples, collected at planting row and bed, in four layers: 0.00-0.10, 0.10-0.20, 0.20-0.30, and 0.30-0.40 m. The contact area between wheels and soil was determined in order to estimate the contact pressure by agricultural machinery on the soil. Pre-consolidation pressures were used to determine LSC. The system with three cycles showed higher LSC than the system with only one cycle. The load support capacity of the soil evaluated in the range of friability is greater than the contact pressures applied to the soil by the wheels of the studied agricultural machines.

Mechanical sugarcane harvesting increases soil compaction due to the intense traffic of agricultural machinery, reducing longevity of sugarcane crops. In order to mitigate the harmful effects caused by agricultural traffic on the soil structure in sugarcane fields, this study evaluated impacts of mechanical sugarcane harvesting on traffic lane under two soil tillage systems based on load bearing capacity models. The experiment was carried out in the region of Piracicaba, state of São Paulo, Brazil, on a Rhodic Nitisol, under conventional tillage (CT) and deep strip-tillage (DST). For CT soil tillage was applied to the entire area with a heavy disk harrow, at operating depths from 0.20 to 0.30 m followed by a leveling harrow at a depth of 0.15 m. For DST, soil tillage was performed in part of the area at a depth of 0.80 m, forming strip beds for sugarcane planting, while the traffic lanes were not disturbed. Undisturbed soil samples from traffic lanes were used in the uniaxial compression test to quantify preconsolidation pressure and to model the soil load bearing capacity. The surface layer (0.00-0.10 m) was most susceptible to compaction, regardless of the tillage system (CT or DST) used. In the DST, the traffic lane maintained the previous soil stress history and presented higher load bearing capacity (LBC) than the traffic lane in the CT. As in CT the soil was tilled, the stress history was discontinued. This larger LBC in DTS minimized the impacts of the sugarcane harvest. Under CT, additional soil compaction due to mechanical sugarcane harvesting in the traffic lane was observed after the second sugarcane harvest. There was a reduction in load bearing capacity from 165 kPa to 68 kPa under CT and from 230 kPa to 108 kPa under DST, from the first to the second harvest at surface layer. Water content at mechanical harvesting was the most relevant factor to maximize impacts on the soil structure in traffic lanes, for both tillage systems.