Tillage-based water conservation on farms in southeastern United States

Authors: Endale, Dinku; Schomberg, Harry; Reeves, Donald; HOOK, J - UGA

Submitted to: Georgia Water Resources Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/28/2007
Publication Date: 3/27/2007
Citation: Endale, D.M., Schomberg, H.H., Reeves, D.W., Hook, J.E. 2007. Tillage-based water conservation on farms in southeastern United States. Georgia Water Resources Conference 2007, March 27-29, 2007, University of Georgia, Athens, Georgia.

Interpretive Summary: Water availability and use is a contentious issue among stakeholders in Georgia and neighboring states. Georgia has started putting together a statewide water management plan as mandated by The Comprehensive Statewide Water Management Planning Act of 2004. One of four main objectives of the plan is to minimize withdrawals of water by increasing conservation, reuse, and efficiency, which will affect the farming community, particularly in irrigated agriculture. Average irrigation water use in Georgia is about 1.1 billion gallons per day out of a total water withdrawal of 6.5 billion gallons per day. Conservation tillage has great potential for increasing water use efficiency and water conservation in irrigated and non-irrigated croplands. Soil disturbance by conventional tillage has led to serious problems of runoff and soil erosion in many areas. Conservation tillage minimizes soil disturbance and maintains residue on 30% or more of the field that ultimately leads to increased infiltration. Researchers at the USDA-ARS J. Phil Campbell Sr. Natural Resource Conservation Center near Watkinsville, GA, compared water infiltration from no-till and conventional tillage cotton with rye cover crop. They found an extra 6.9 inches of rainwater infiltrated with no-till over a period of one year, representing about 14% of the average annual rainfall. Over the three million or so acres of harvested croplands in Georgia this would amount to about 564 billion gallons of water annually. Conversely a 6.5-acre field lost 16% of annual rainfall to runoff under conventional tillage. Runoff was reduced to less than 2% of annual rainfall soon after conversion to no-till, and continued at an even less rate through 24 years of continuous no-till with winter cover cropping. Conventional cotton grown each year for 20 years lost an average of 20 tons of soil per acre and 21% of the rainfall annually. While Georgia’s current draft agricultural water conservation plan rightly targets potential waste in irrigated agriculture through retrofitting irrigation system components that waste water, conservation tillage offers water conservation both in irrigated and non-irrigated agriculture. For this potential to be realized, leadership and appropriate resources are needed across all government agencies and non government organizations involved in natural resources policy, formulation, research, education, extension, and outreach.

Technical Abstract: Conservation tillage, particularly no-till, has a significant role to play toward achieving agricultural water conservation goals envisaged in Georgia’s Comprehensive Statewide Water Management Planning Act of 2004. We base this on scientific evidence from across the country and our own research that show that conservation tillage allows substantially more of rain and/or irrigation water to infiltrate/percolate into the soil compared to conventional tillage methods, thus reducing much runoff waste. In one study spanning May 1, 1997 to May 5, 1998 near Watkinsville, GA, we found an extra 6.93 inches of rain water infiltrated into the soil profile in a no-till cotton/rye system compared to conventional tillage. This represents 14% of the average annual rainfall and is equivalent to more than 188 billion gallon of water from a one million acre cropland, which is about a third of the area of Georgia’s harvested cropland. Annual irrigation use in Georgia fluctuates between 100 and 300 billion gallons. Additionally, conservation tillage reduces sediment that alters critical habitat and stream flow and reduces non-point source contaminants that require additional assimilative capacity in those streams. While the current agricultural water conservation plan rightly targets potential waste in irrigated agriculture through retrofitting irrigation system components that waste water, conservation tillage offers water conservation both in irrigated and non-irrigated agriculture. For this potential to materialize, aggressive leadership that provides both political will and appropriate resources is needed across all government agencies and non-government organizations (NGOs) involved in natural resource policy formulation, research, education, extension, and outreach.