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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #220033
Title: Conservation Tillage to Effectively Reduce Interrill Erodibility of Highly-Weathered Ultisols

Author
item Truman, Clinton
item SHAW, J - AUBURN UNIVERSITY
item Flanagan, Dennis
item Reeves, Donald
item Ascough Ii, James

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2008
Publication Date: 8/1/2009
Citation: Truman, C.C., Shaw, J.N., Flanagan, D.C., Reeves, D.W., Ascough II, J.C. 2009. Conservation Tillage to Effectively Reduce Interrill Erodibility of Highly-Weathered Ultisols. Journal of Soil and Water Conservation. 64(4):265-275. doi:10.2489/jswc.64.4.265.

Interpretive Summary: Soils in the Southeast have traditionally been intensively cropped under conventional tillage systems, are drought-prone, and are susceptible to consolidation, runoff, and soil loss. Conservation tillage systems effectively reduce runoff and soil loss. We quantified differences in infiltration, runoff, soil loss, and interrill erodibilities (Ki) for the Compass, Decatur, and Tifton soils managed under conventional- (CT), strip- (ST), and/or no-till (NT) systems with and without a residue cover (+C/-C) and/or with and without paratilling (+P/-P). Interrill erosion plots on each tillage treatment received simulated rainfall (2 inches/h for 2 h). Runoff and soil losses were measured from flat, level-sloping plots (slopes=1-3%), and Ki values were calculated from measured soil loss. The WEPP model was used to extend experimental data to long-term annual trends. NT-P+C or NT+P+C (surface cover) plots for the Compass loamy sand, NT+P+C (paratilling) plots for the Decatur silt loam, and ST-P+C (surface cover) plots for the Tifton loamy sand represented the best-case scenario; CT-P-C plots (all soils) represented the worst-case scenario. Surface residue cover decreased Ki values for all three soils; Paratilling decreased Ki values for the Compass and Decatur soils. NT and/or ST systems had lower calculated Ki values from corresponding CT-P-C treatments, indicating that NT and/or ST were effective in all three soils. Converting from a CT to a NT or ST system reduced predicted runoff and soil losses. The most benefit of NT or ST in terms of runoff was for the Compass and Tifton soils; and in terms of soil loss was for the Compass and Decatur soils. Conservation tillage systems (NT, ST) coupled with surface residue cover and/or paratilling are effective in reducing runoff and sediment yields from highly-weathered soils by lowering effective Ki values.

Technical Abstract: Highly-weathered, Southeastern soils traditionally cropped under conventional tillage systems, are drought-prone and susceptible to consolidation, runoff, and soil loss. Conservation tillage systems reduce runoff and soil loss. We quantified differences in infiltration, runoff, soil loss, and interrill erodibilities (Ki) for the Compass loamy sand, Decatur silt loam, and Tifton loamy sand managed under conventional- (CT), strip- (ST), and/or no-till (NT) systems with and without a residue cover (+C/-C) and/or with and without paratilling (+P/-P). Duplicate plots (1-m x 1-m) on each tillage treatment received simulated rainfall (50 mm/h for 2 h). Runoff and soil losses were continuously measured from flat, level-sloping plots (slopes=1-3%), and Ki values were calculated from measured soil loss. The WEPP model was used to extend experimental data to long-term annual trends. NT-P+C or NT+P+C (surface cover) plots for the Compass loamy sand, NT+P+C (paratilling) plots for the Decatur silt loam, and ST-P+C (surface cover) plots for the Tifton loamy sand represented the best-case scenario; CT-P-C plots (all soils) represented the worst-case scenario. For the Compass loamy sand, NT-C plots increased runoff (decreased infiltration) by as much as 43% and soil loss by as much as 10-fold compared to NT+C plots. NT+P+C plots decreased runoff by as much as 70% and soil loss by 24-fold compared to CT-P-C. For the Decatur silt loam, NT+P plots decreased runoff by as much as 71% and soil loss by as much as 2.7-fold compared to NT-P plots. NT+P+C plots decreased runoff by as much as 73% and soil loss by as much as 11.8-fold compared to CT-P-C. For the Tifton loamy sand, ST+P+C plots decreased runoff by as much as 44% and soil loss by as much as 2.7-fold compared to CT-P-C plots. Calculated Ki values for the Compass, Decatur, and Tifton soils were 0.37, 0.40, and 0.24, respectively. Residue cover decreased effective Ki values by 11%, 2.0-fold, and 2.6-fold for the Decatur, Tifton, and Compass soils, respectively; Paratilling decreased effective Ki values by 3-fold for both the Compass and Decatur soils. NT and/or ST systems had lower calculated Ki values from corresponding CT-P-C treatments by 4- to 37-fold for the Compass loamy sand, 4-to 13-fold for the Decatur silt loam, and 2-fold for the Tifton loamy sand, indicating that NT and/or ST were effective in all three soils (most effective for the Compass loamy sand). Converting from a CT to a NT or ST system reduced predicted runoff (1.7-fold for Compass loamy sand; 10-17% for Decatur silt loam; 1.6- to 2.3-fold for Tifton loamy sand) and soil loss (10- to 12-fold for Compass loamy sand; 6- to 33-fold for Decatur silt loam; 7.3- to 12.1-fold for Tifton loamy sand). The most benefit of NT or ST, based on the maximum difference in 100-yr predicted runoff and soil losses, was for the Compass (78%) and Tifton (75%) loamy sands for runoff; and the Compass loamy sand (10.3-fold) and Decatur silt loam (9.7-fold) for sediment. Differences in predicted daily soil loss for selected return periods (2-50 yrs) between CT and NT or ST ranged from 6-to 35-fold , and were greatest for the Decatur silt loam (9- to 35-fold). Conservation tillage systems (NT, ST) coupled with surface residue cover and/or paratilling are effective in reducing runoff and soil loss from highly-weathered soils by lowering effective Ki values.