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John Kruse
Graduate Teaching/Research Assistant
– Environmental Soil Chemistry
M.S. University of Georgia
B.S. University of Georgia
3111 Miller Plant
Sciences Building
Athens, GA 30602-7272
(706)542-0909; FAX (706)542-0914
jkruse@uga.edu
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Subsoils of the Georgia Piedmont are often quite acidic, sometimes leading to poor root growth below the topsoil layer. These acid soils can prevent or limit roots from obtaining water found deep in the soil from past rainfall, which would be available if roots could only get to it. This shallow-rooted condition makes the turf plant dependent on more frequent irrigation, and denies the plant nutrients that might be available deeper in the soil. Often, the recommendation for correcting acid soils is to add lime in various amounts. The problem with this approach is that lime does not dissolve very easily and moves down into the soil profile extremely slowly. Most of the lime that is applied on established turf can still be found within an inch or two of the thatch layer years later. A turf manager may not even be aware he has an acid-soil problem, since soils are typically tested from only 0-6 inches in depth.
One possible solution to correcting acid subsoils may be an application of gypsum. Gypsum, or calcium sulfate di-hydrate, looks and feels very similar to powdered lime, which is calcium carbonate. One big difference, however, is that gypsum is much more soluble than lime, and can move down through the soil profile as irrigation or rainfall percolates through the soil. As the gypsum moves deeper into the soil, it increases the amount of calcium (an essential turf nutrient, especially for new roots) available to plant roots in the subsoil. It may also have other potentially positive effects on soil chemistry, such as reducing aluminum toxicity, which could lead to more abundant roots.
An experiment was established in the fall of 2003 with different applications of gypsum, lime, gypsum plus lime together, and control plots (no gypsum or lime added). In the center of each plot is an access box that will allow researchers to take moisture readings of the soil at three different depths (5, 15, and 45 cm). As roots grow and plants respire, they pull water from the surrounding soil, making the soil drier than it would be if no roots were present. The objective is to determine if turf plots with gypsum are growing deeper roots and using water from deeper in the soil profile. Soil samples are also taken on a periodic basis to observe changes in soil chemistry. Since this is the first summer moisture readings are being taken, no data is available at this time. The experiment is expected to last through the summer of 2005, with results that could lead to less demand on irrigation and healthier, more resilient turf. Additional greenhouse experiments are planned in order to elucidate the roles of Al toxicity, Ca deficiency, and Al: organic matter interactions in their effects on turf rooting.
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