Our high school football field has turfgrass discoloration localized to the places where the numbers and hash marks were painted during the season . Soil analysis from the painted and non-painted areas were similar except for pH and calcium levels . The non-painted areas had a pH of 5.8 and the painted area pH values ranged from 7.1 to 7.5 . Do you have any recommendations on how to deal with this issue ?

Q & A WITH DR . GRADY MILLER

The sample analysis provided great diagnostic data , so I ’ ll start by giving accolades for their sampling approach . In this case , they independently sampled multiple problem areas and collected a composite sample from non-problem areas . These were then analyzed so that results could be compared among sample locations . In this case , the sampling strategy employed provided an indicator of what was causing the symptoms .

Sampling strategy can be very important for proper diagnosis of problems . For example , consider a large dead patch of turfgrass that may have succumbed to a disease . A first reaction may be to sample from the middle of the dead patch and sample in a healthy area of turfgrass . But the fungi that caused the patch has already moved out of the dead grass , so sampling the middle would not be useful for diagnosis . The margin where the healthy and unhealthy turfgrass meet is the zone where pathogen activity is greatest , so it would be better to take a sample from the leading edge of the damage . In other scenarios , such as searching for immobile nutrients or pesticides , sampling depth in soil may be important .

Paints commonly contain calcium carbonate , the same base ingredient used to increase soil pH in agriculture lime . Even calcium carbonate applied within paint can have a liming effect on soil pH . But there are white athletic field paints formulated with alternative pigments ( e . g ., titanium dioxide ) that do not alter soil pH . As with most compound products , ingredients can influence short- and long-term performance of the product , but may also influence the cost of the end product .

In addition , there are paints designed for application to natural grass . “ House paints ” and paints for synthetic turf are more likely to contain ingredients at concentrations that may not be safe for turfgrasses . So be sure to select paints that are designed to be applied to natural grass .

Following application , ingredients in the paint may move into the soil profile . Some components of paint are more soluble than others ; whereas others may accumulate in the soil profile . I have seen the grass surface removed from a football field with all the lines and logos still visible on the bare soil . This build-up can have antagonistic effects in the soil , which can result in off-color turfgrass . The directed process used for painting numbers and hash marks often concentrates greater amounts of paint per unit area compared to yard lines . This is probably why the symptoms are showing up in these areas and not across all the painted areas .

If not managed appropriately , paint can build up and impede water infiltration or reduce the uptake of plant nutrients from physical and chemical reactions . A high soil pH can limit the availability of nutrients such as iron , manganese and phosphorus .

To help prevent issues , it is best to core aerify these painted areas to open up channels through the soil profile . It is also advantageous to backfill aerification holes with an appropriate sand or soil to keep these channels open and dilute paint residue . These practices address the chemical and physical problems associated with paint buildup in the soil . Managers at some facilities prefer to cut out and re-sod the numbers or logos every few years to remove paint build-up . I do not suggest field managers try to chemically reduce soil pH in these localized areas with products such as elemental sulfur . SFM

Grady Miller , Ph . D . Professor and Extension Turf Specialist North Carolina State University

Questions ? Send them to Grady Miller at North Carolina State University , Box 7620 , Raleigh , NC 27695-7620 , or e-mail grady _ miller @ ncsu . edu

Or , send your question to Pamela Sherratt at 202 Kottman Hall , 2001 Coffey Road , Columbus , OH 43210 or sherratt . 1 @ osu . edu

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