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Cropping System and Consolidation Effects on Rill Erosion in the Georgia Piedmont

Dep. of Agronomy, Univ. of Georgia, Athens, GA 30602

G. W. Langdale and R. R. Bruce

USDA-ARS Southern Piedmont Conservation Research Center, Watkinsville, GA 30677

J.M. Laflen

USDA-ARS National Soil Erosion Research Lab., West Lafayette, IN 47907

A. W. Thomas

USDA-ARS Southeast Watershed Research Lab., Tifton, GA 31793

*Corresponding author.

ABSTRACT

Consolidation and changes in surface horizon properties induced by no-tillage may reduce soil loss to levels beyond those attributable to surface residue alone. To evaluate effects of consolidation and surface horizon modification induced by long-term no-tillage on rill erodibility (K_r) and critical hydraulic shear (_c), simulated rainfall and inflow were applied to plots managed under conventionally tilled monocropped soybean [Glycine max (L.) Merr.], conventionally tilled monocropped grain sorghum [Sorghum bicolor (L.) Moench], and no till double cropped crimson clover (Trifolium incarnatum L.) and grain sorghum at three sites with differing surface horizon clay contents. All surface residue was removed prior to rainfall simulation, and conventionally tilled cropping systems were evaluated in both consolidated and freshly tilled conditions. Increases in organic C from 9.3 to 12.9 g kg^–1 and water-stable aggregates from 50 to 76% induced by no-tillage resulted in a 60 to 70% decrease in K_r for the no-till system, compared with conventionally tilled systems. No differences in K_r were observed for the two conventionally tilled systems. No differences in _c were observed among the tillage systems. Consolidation within the conventionally tilled treatments reduced K_r by 60% from that observed for freshly tilled soil. The reduction was attributed to greater resistance to detachment by flow associated with soil strength increases due to consolidation. Differences in K_r and _c among the sites were small and were not readily explained by any of the soil properties evaluated. These results indicate that consolidation and modification of surface soil properties under no-till cropping systems are important factors that contribute to reduced rill soil loss observed under no-tillage.

Received for publication May 8, 1990.