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Sunflower (Helianthus annuus L.) harvest: Tractor and grain chaser traffic effects on soil compaction and crop yields

Previous studies have defined compaction as an important degradation process of agricultural soils. However, there is very little information (under field conditions) on the effects of tractor and grain chaser traffic during harvest operations on soil cropped for 15 years under no‐till cultivation methods. The aim of this study was to quantify the effects of two different total loads of tractor and grain chaser traffic on soil physical properties and sunflower (Helianthus annuus L.) yields. The treatments included a control plot with no tractor or grain chaser traffic (T1), a plot with tractor and grain chaser traffic with a total load of 275.8 kN (94.35 kN km−1 ha−1; T2), and a plot with tractor and grain chaser traffic with a load of 332.2 kN (123 kN km−1 ha−1; T3). Soil physical properties and sunflower yields were analysed over three growing seasons in the western part of the Pampa region, Argentina. In the topsoil (0 to 200 mm), the results showed that after one pass of T2 and T3, infiltration decreased significantly compared with that in T1; a similar trend was observed for total topsoil porosity. Cone index values in T3 were >2.5 MPa and between 3.33 and 4.90 MPa in the subsoil (200 to 600 mm). Dry bulk density values in T3 were >1.70 Mg m−3 in the topsoil and in the subsoil. This study also demonstrated that as the wheel load and ground contact pressure increase, sunflower yields decrease and subsoil compaction increases, even in soils with a high bearing capacity.