Location: Southeast Watershed ResearchTitle: Sediment loss and runoff from cropland in a Southeast Atlantic Coastal Plain landscape Author
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2014
Publication Date: 12/18/2014
Publication URL: http://DOI: 10.13031/trans.57.10554
Citation: Endale, D.M., Bosch, D.D., Potter, T.L., Strickland, T.C. 2014. Sediment loss and runoff from cropland in a Southeast Atlantic Coastal Plain landscape. Transactions of the ASABE. 57(6):1611-1626. doi:10.13031/trans.57.10554.
Interpretive Summary: Proven environmental benefits of conservation tillage cropping systems are being threatened by weather shifts that include more occurrences of high rainfall rates, policies that encourage the removal of crop residues from fields for energy production, and increased herbicide resistance in weeds. Long-term integrated studies are needed to quantify potential impacts. Scientists at the USDA-ARS Southeast Watershed Research Laboratory in Tifton, GA, monitored 6 fields over ten years for runoff and sediment loss differences arising from landscape and management differences among fields. Half the blocks, containing 3 fields at the upper, middle and lower landscape position, were managed under strip tillage, a form of conservation tillage cropping system. Three fields in the other block on corresponding landscape positions were managed under conventional tillage. Cotton was grown in 2000, 2001, 2003, 2005, 2007, and 2009, and peanuts grown in 2002, 2004, 2006, and 2008. Rye was used as cover crop. Results showed that conventional tillage yields greater runoff and sediment loss than does strip tillage. Fields at the upper landscape position produced more runoff and sediment than those in the lower position. The 10-yr annual average sediment loss from the conventional tillage was 0.81 ton per acre per year, whereas it was 0.11 ton per acre per year for strip tillage fields. The soil loss tolerance value of 1.0 ton per acre per year was exceeded in 3 out 10 years and almost matched in one in the conventional tillage but never exceeded in the strip tillage. Such scientifically-based information, generated from long-term research, helps us make wise management decisions that sustain the integrity of our natural resources. Local, state and federal agencies involved in protection of natural resources would find these results useful in guiding their efforts.
Technical Abstract: Widespread implementation of conservation-tillage (CsT) systems during cotton and peanut production in the Atlantic Coastal Plain region (USA) has substantially reduced erosion and sediment loss. However, benefits of CsT in these cropping systems are being threatened by weather shifts that include increased frequencies of high rainfall rates; policies that encourage the removal of crop residues as cellulosic feedstocks for energy production; and increased herbicide resistance in weeds. Long-term integrated studies are needed to quantify potential impacts. We evaluated sediment loss from six 0.2-ha fields located on a gently sloping hill slope in a Southern Atlantic Coastal Plain landscape over ten years during rotational cotton (Gossypium hirsutum L.)-peanut (Arachis hypogea L.) production, with rye (Secale cearale) cover crop in all. Half of the fields were in conventional tillage (CT) and half in strip tillage (ST), a commonly used CsT practice in the region, and irrigated when needed. Fields were laid out as contrasting tillage-pairs at upper, middle, and lower landscape positions. Sediment load from CT was significantly greater than from ST at each landscape position. Over the 10 yrs of the study, mean total sediment load was 18.2 Mg ha-1 from CT and 2.4 Mg ha-1 from ST-fields. The T value of 2.2 Mg ha-1 yr-1 was exceeded in 3 out 10 yrs and almost matched in one in the CT. In ST, sediment loss was much lower than the T value each year. On monthly basis, extreme events (>90th percentile; 10%) accounted for 61 to 72% of the CT (467 to 2828 kg ha-1 month-1) and 73 to 8% the ST (49 to 593 kg ha-1 month-1) system 10-yr total sediment load. Rainfall plus irrigation was above the normal monthly rainfall in approximately 83% of these extreme monthly periods (mean 179 mm, range 81 to 316 mm). Summer, spring and cotton cropping posed the most risk for sediment loss. These results improve estimates of the increase in rainfall event size tolerated by ST versus CT cropping systems, and demonstrate the benefits of CsT management during cotton and peanut production. They are expected to guide management decisions that focus on reducing sediment loss in this landscape and in so doing sustain the region’s natural resource base.