Grazing Winter Rye Cover Crop In A Cotton No-Till System: Soil Strength And Runoff

Grazing cover crops (CC) could provide an economic incentive to increase adoption rates in the southeastern United States. However, understanding grazing effects on soil properties is lacking for most soils of the region. Effects of grazing or rolling a cereal rye (Secale cereale L.) CC prior to no-till planting cotton (Gossypium hirsutum L.) were determined in 2009 after 4 yr on Cecil soil, in the Southern Piedmont near Watkinsville, GA. The four catchments had a previous long history of no-till cropping with CC. Wet spring conditions in 2009 resulted in visible surface roughness from cattle hooves. Average soil penetration resistance (PR) for the 0- to 30-cm profile was 14% greater following rye CC grazing than rolling (1.95 vs. 1.53 MPa) and was still apparent the following February (1.86 vs. 1.58 MPa) after cotton harvest. Increases in PR at 2.5- to 7.5- and 7.5- to 15-cm soil depths were observed following CC grazing but not rolling. Depth to 2 MPa resistance, considered sufficient to impede root growth, was similar for CC grazing and rolling treatments in March prior to grazing but decreased in the grazed treatment to 10.7 cm in May and 15.6 cm in February. Seasonal runoff data for 2006-2009 indicated no differences between grazed and rolled CC management. We concluded that grazing CC for short periods under wet conditions presents a risk of short-term negative effects even for Southern Piedmont soils where a long history of conservation tillage and CC has improved soil quality.