A Survey of Spray Water Quality in Eastern South Carolina: The Importance of Greenhouse Float Water and Spray Water Sampling for Flue-Cured Tobacco Farmers
Applied Research
William Hardee
Area Agronomy Agent
Clemson Extension
Conway
Abstract
South Carolina tobacco producers spend approximately 17-18% (~$730.00 / acre) of their total direct costs on crop protection in the form of herbicide, insecticide, fungicide, and sucker control applications, and 5-6% on transplant production. We often overlook the ingredient that makes up 95% or more of our spray and greenhouse floatwater solutions, and that is water. Extension agents in the Pee Dee Region have noticed a delicate balance between water quantity and water quality. Shallow wells usually pump smaller amounts of good quality water, and deeper wells often supply large amounts of water with decreased quality. This reduced water quality could result from saltwater intrusion into groundwater near-coastal counties and the mineral composition of underground geological formations. When these water quality parameters are unsuitable, pesticide efficacy or greenhouse transplant production can be negatively impacted. For example, spray water with a pH of 8 doesn’t sound like a big deal, but the pH scale is logarithmic, meaning a pH of 8 is ten times more basic/alkaline than a pH of 7 and one-hundred times more basic than a pH of 6. Since many pesticides are weak acids (pH of 4-6.5), mixing them with a water source that has a higher pH (>6.5) could quickly break them down, making them less stable and, ultimately, not as effective. Poor water quality can be very costly to South Carolina tobacco producers since reduced crop protection and transplant production directly correlate with decreased yields and/or profits. Water hardness and pH are the main two water quality parameters that affect pesticide performance. Iron levels and salinity (EC or TDS) can also hinder pesticide performance. Total Bicarbonates, pH, Sodium, and Chloride in Greenhouse float water are the main parameters that affect transplant production. After completing a water quality survey of the 10 tobacco producing counties, we observed a wide range of results throughout the survey area and even within the same county. This indicated the need to encourage growers to test all water sources used for pesticide application and transplant production.
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Authors: William Hardee III, David DeWitt
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Hardee III, W. Area Agronomy Agent , Clemson University Cooperative Extension Service, South Carolina, 29526
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DeWitt, D. Area Agronomy Agent, Clemson University Cooperative Extension Service, South Carolina, 29010