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Soil sampling, testing and amendment application

Gone is the day when the golf course superintendent had to be an expert in every field. Technology has made it impossible to be successful without the help of a few good experts. Just as I no longer feel comfortable sticking my hand into a pump station control cabinet containing fuses bigger than my arm, I’m not ready to make major soil chemistry decisions without the help of a good soil scientist … especially growing Bentgrass in the Deep South.

Working with an expert in soil science has several advantages. At The Shoals, we have worked with Steve Ninemire of the Ninemire Group since inception. Not only has working with the same person given us an invaluable history, it gives us another set of eyes to examine the data and draw conclusions based on what we see in the field and in the lab. Regardless of who processes your soil samples, consistency is the key to recognizing the trends. We have been sampling and tracking our greens since 2003, and have included saturated soil or paste tests every three weeks for the past three years. The saturated soil tests have given us a pretty fair window into the effects of our maintenance practices. The monthly addition of calcite calcium, gypsum, humic acid, phosphorus, magnesium and potassium can become very efficient and accurate with real time testing. An agronomic fertility plan is developed over the winter months based on the values found in the existing soil and the amount of nutrients required by the plant.

From these values we determine application rates and frequency of application by product used. Recommendations are generated from the soil samples on a yearly basis while adjustments are made based on the results from the saturated soil tests. This historical data, combined with current test results, has given us the ability to forecast plant needs based on soil conditions. We have also been able to see a direct correlation between plant health and CEC levels. Giving the plant an optimal growing environment has allowed an increase in organic matter, thus an increase in CEC. Studies have also shown that the use of humic acid appears to aid in this pursuit.

Monthly, and sometimes weekly, applications of various products can become a scheduling nightmare. Due to massive greens, skyrocketing labor costs and the constant need to apply some type of product at The Shoals, we parked the push spreaders years ago and opted for a faster and more efficient method. A small, cart-mounted spreader is used for low spread rate materials, while a truckster-mounted Dakota Topdresser is used for products requiring a high spread rate. We had some concern as to the accuracy of this method, but we are applying enough material over the course of a year that our spread rates have worked out in the end. Amendments are applied early in the morning to avoid any undue stress to the greens. Following fall and spring aerification, we apply the lion’s share of our amendments. We also use this opportunity to catch up on any missed applications. That being said, we have seen through constant testing just how important and timely these applications really are.

Paste test results clearly reflect missed applications and misapplications. Skip a calcium application when conditions are favorable and watch sodium go through the roof. We now have the ability to receive an email or text alarm from the Ninemire Group when the paste test shows a dangerous imbalance between calcium and sodium, or any parameters we choose, for that matter. The ability to act quickly can mean life or death to a Bentgrass green during the heat of summer. During construction, Steve noticed our phosphorus levels had become abnormally high. We had been using a complete fertilizer during grow-in and had failed to report these additional nutrients, two examples of how accurate and useful this type of testing can be. Our greens have shown remarkable heat and disease tolerance over the years. Chemical balance in the soil has played a major role in this success.

Let’s face it, soil sampling is not fun! The key to success lies in the sampling itself. It takes a motivated and precise type of person to embark on a task requiring this level of commitment. Our superintendent, Randy Gatlin is that type of person. Randy and Steve have taken the use of this data to a new level.

Samples must be taken in a timely manner. They must be taken at the correct depth and of a representative area. The results are most accurate when paste testing is carried out with on-site irrigation water. We always include several bottles from our irrigation source. The samples do not require overnight delivery, but avoid letting them sit on your desk for more than a couple of days. The quicker the samples are sent in, the quicker the results can be put to use. We paste-test several representative greens on our property. The saturated paste program tells us immediately what is in solution and is available to the plant root. This allows us to take corrective action to any imbalances detected before we see the visual signs of problems on the surface. This program could become cost-prohibitive if too many subject greens are chosen, not to mention the constant pulling of samples. The growing conditions at our course are similar from hole to hole. Sample numbers should be based on need and, of course, economics. Our yearly standard soil samples are taken from a much larger selection of greens. Thus far we have been able to acquire more information than necessary with our present sample group.
Soil testing isn’t just about lime anymore. Traditional soil testing only gives part of the picture. Paste-extract testing fills in the rest. Paste testing might appear expensive and unnecessary at first glance. That is why it is imperative to work with a soil scientist with the heart of a teacher. This data can be truly amazing, and when used in conjunction with temperature and rainfall, it is possible to accurately forecast problems and lessen their impact, if not avoid them. Developing a fertility plan based on agronomic facts and implemented on a consistent basis gives the superintendent the ability to be proactive to plant needs, while being as efficient as possible with the input dollars available for fertility.

Doug is the superintendent at The Shoals Golf Club at Muscle Shoals, Ala.and can be reached at DTinkham@rtjgolf.com

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