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United States Department of Agriculture

Agricultural Research Service

Research Project: SOIL RESPONSE TO CONSERVATION TILLAGE IN A COTTON-PEANUT ROTATION

Location: Southeast Watershed Research

Title: Antecedent Water Content Effects on Runoff and Sediment Yields From Two Coastal Plain Utisols

Authors
item Truman, Clinton
item Potter, Thomas
item Nuti, Russell
item Franklin, Dorcas
item Bosch, David

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2011
Publication Date: April 9, 2011
Citation: Truman, C.C., Potter, T.L., Nuti, R.C., Franklin, D.H., Bosch, D.D. 2011. Antecedent Water Content Effects on Runoff and Sediment Yields From Two Coastal Plain Utisols. Agricultural Water Management. 98:1189-1196.

Interpretive Summary: The low-carbon, intensively cropped, drought-prone Coastal Plain soils of Georgia are susceptible to runoff and soil loss, especially at certain times of the year when soil water contents are elevated. We evaluated the effects of antecedent water content (AWC) on runoff (R) and sediment (E) losses from two Coastal Plain soils managed under conventional- (CT), strip- (ST), and/or no-till (NT) systems. Two AWCs were evaluated: field moist (FM) and pre-wet (PW), each created with and without post pesticide application irrigations (~0.5 in of water added over 30 min) for incorporation. Treatments evaluated were: CT+FM, CT+PW, ST+FM, ST+PW, and NT+PW. Field plots, each 6x10-ft, received simulated rainfall at a variable rainfall intensity (Iv) pattern for 70 min or a constant rainfall intensity (Ic) pattern for 60 min (target I=2 in/h). Pre-wetting with ~0.5 in of water increased AWCs of the 0-1 and 1-6 in soil depths 3-9 fold and 23-117% compared to existing field moist (FM) conditions. Increase in AWC increased R 8-60% and decreased E at least 59%. Compared to CT, ST and NT decreased R at least 2.6-fold and decreased E at least 2.8-fold. R and E curves had similar shapes as the Iv pattern. Peak R and E occurred 5-10 min after the 20 min Iv peak. Rmax values for CT+PW and ST+PW plots were 96% and 23% higher than those for corresponding FM plots; Rmax values for CT+FM and CT+PW plots were 1.9 and 3 times higher than those for corresponding ST plots. Emax values for CT+FM and ST+FM plots were 10% and 44% higher than those for corresponding PW plots; Emax values for CT+FM and CT+PW plots were 3.1 and 3.8 times higher than those for corresponding ST plots. Runoff curves for CT+PW and ST+PW plots were always higher than corresponding FM curves; whereas E curves for CT+FM and ST+FM plots were always higher than corresponding PW curves. For the Ic pattern, Rmax for CT+PW plots was 9% higher than that for CT+FM plots; Emax for CT+FM plots was 1.8 times higher than that for CT+PW plots. Changes in AWC and tillage affected R and E losses and the size of sediment being transported. A more accurate measure and better understanding of infiltration, runoff, and sediment delivery was obtained when creating field conditions (increased AWC with irrigation; Iv pattern derived from natural rainfall; commonly used tillage systems) were utilized in rainfall simulation studies.

Technical Abstract: The highly-weathered, low-carbon, intensively cropped, drought-prone Coastal Plain soils of Georgia are susceptible to runoff and soil loss, especially at certain times of the year when soil water contents are elevated. Our objective was to quantify the effects of antecedent water content (AWC) on runoff (R) and sediment (E) losses from two loamy sands managed under conventional- (CT), strip- (ST), and/or no-till (NT) systems. Two AWC treatments were evaluated: field moist (FM) and pre-wet (PW). AWC treatments were created with and without post pesticide application irrigations (~12 mm of water added with the rainfall simulated over 30 min) for incorporation. Treatments (5) evaluated were: CT+FM, CT+PW, ST+FM, ST+PW, and NT+PW. Field plots, each 2x3-m, received simulated rainfall at a variable rainfall intensity (Iv) pattern for 70 min (ave Iv=1227 mL, CV=4%) or a constant rainfall intensity (Ic) pattern for 60 min (ave Ic=50.8 mm h-1, CV=1%). Pre-wetting with ~12 mm of water increased AWCs of the 0-2 and 2-15 cm soil depths 3-9 fold and 23-117% compared to existing field moist (FM) conditions. Increase in AWC increased R 8-60% and decreased E at least 59% for corresponding tillage treatments. Compared to CT, ST and NT decreased R at least 2.6-fold and decreased E at least 2.8-fold. R and E curves had similar shapes as the Iv pattern. Peak R and E occurred 5-10 min after the 20 min Iv peak. Rmax values for CT+PW and ST+PW plots were 96% and 23% higher than those for corresponding FM plots; Rmax values for CT+FM and CT+PW plots were 1.9 and 3 times higher than those for corresponding ST plots. Emax values for CT+FM and ST+FM plots were 10% and 44% higher than those for corresponding PW plots; Emax values for CT+FM and CT+PW plots were 3.1 and 3.8 times higher than those for corresponding ST plots. Runoff curves for CT+PW and ST+PW plots were always higher than corresponding FM curves; whereas E curves for CT+FM and ST+FM plots were always higher than corresponding PW curves. For the Ic pattern, Rmax for CT+PW plots was 9% higher than that for CT+FM plots; Emax for CT+FM plots was 1.8 times higher than that for CT+PW plots. Changes in AWC and tillage affected detachment and transport processes controlling R and E losses and the size of sediment being transported and/or delivered. A more accurate measure and better understanding of rainfall partitioning, and detachment and transport processes affecting R and E losses was obtained when creating field conditions (increased AWC with irrigation; Iv pattern derived from natural rainfall; commonly used tillage systems) were utilized in rainfall simulation studies.

Last Modified: 9/21/2014
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