Abstract

KRUGER, Hugo R; VENANZI, Santiago  and  DE SA PEREIRA, Eduardo. Impact of cattle grazing on soil mechanical resistance in production systems under continuous no-till. Cienc. suelo [online]. 2008, vol.26, n.2, pp.211-217. ISSN 1850-2067.

The objectives of this study, were: a) to characterize the soil mechanical penetration resistance (RST) variation in the 0 to 20 -cm depth of two rotation treatments with and without cattle grazing and b) to determine the RST relationship with soil water content (W). The experiment took place on a Typic Haplustoll in SW Buenos Aires province, on sunflower-wheat based rotations. Treatments included: a) 100 % cash-crop rotation with no cattle grazing and b) Mixed rotation, including an oat forage crop with direct grazing by 350 to 400 kg steer at a 25 head/ha stocking rate between wheat and sunflower crops. RST and W were determined on ten opportunities near planting dates. After oat grazing, RST was higher in the Mixed rotation compared to the crop rotation in the 0 to 20 cm soil layer, with greater differences in the 2.5-7.5 cm layer. Corrected to a W of 190 g kg^-1, the RST in the crop rotation showed an increasing linear trend over time. RST for the mixed rotation fitted a quadratic model which tended to stabilize at 2.5 MPa. In addition, the mixed rotation showed a second variation pattern related to sample dates: RST after grazed oats was higher than at the end of the oat-sunflower-wheat cycle. This decrease was attributed to a recovery of bioporosity due to the crop roots effect on the soil. Observed RST values were close or higher than those considered critical for root penetration in 20 and 50% of sampling dates for the crop and mixed rotations, respectively.

Keywords : Soil management; Compaction; Rotation; Soil physical properties; Cattle grazing; No-tillage; Mechanical resistance.

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