SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/517437
www.stma.org June 2015 | SportsTurf 15 managers, considering recent weather events, thinking about diseases that have been a problem in the past are all good initial actions at the outset of diagnosis. APPEARANCE CATEGORIES In the overall context of trying to figure out the cause of the yel- lowish appearance, a basic set of appearance categories to work through can be useful. Category 1. Turf is dry, bluish green, wilts, brown on leaf blade edges; possibilities include drought, wilt, uneven watering Category 2. Turf is pale, yellow, thin or grows slowly; pos- sibilities include nutrient deficiency, over-application of growth regulators Category 3. Turf suddenly appears scorched; possibilities include fertilizer burn, pesticide burning, mower injury Category 4. Turf is bare and/or thinned, often in trafficked areas and shade; possibilities include algae, moss, compaction Category 5. Regular or irregular patches of dead and dying turf; possibilities include thick thatch or buried debris, sod webworms, anthracnose In the case of maybe, where there aren't obvious other causes, the best place to start is with a soil test. SOIL TEST The best way to get a handle on the current level of various nutrients is by conducting a soil test. However, even though a soil test can provide great insights, a report is best thought of as a snapshot of results, not a solid guarantee of what is in the soil. This is especially true for nitrogen, which is a mobile nutrient, one that can leave the rootzone quickly or change from unavail- able to available in a relatively short period of time. The best soil test is a representative one. The key word in the last sentence is representative. The soil sample must mirror the entire affected area as closely as possible. In order for that to be the case, many subsamples must be taken. On a given area that is suspected of nutrient deficiency, an average of 10 soil cores should be taken and mixed together before submission. In order to gain better insights as to the cause of the decline, a set of samples should be taken from the non-affected areas and then compared to the ones from the area of concern. Consider making a soil test when your turf is growing at its optimum, this may give you a baseline to compare against when condi- tions aren't so good. When sampling, keep in mind the rootzone for the turf plants; this is generally the upper 8 inches of soil profile. Use a soil probe to extract a sufficient number of cores, then cut off the upper 2 inches of the extracted soil plug. The reason for the removal of the upper portion is that it usually contains a fair amount of thatch and old turf crowns, which can skew the results of the soil test. Soil testing can be greatly affected by the nature of the soil substrate, namely a native soil vs. a sand based field. Generally, deficiencies are more likely to occur on sand based fields, in that the particles have fewer attachment sites due to the greater glazing of the surfaces. The Cation Exchange Capacity (CEC) is a good measure of this, and will be noted on the soil test report. As such, sand-based fields often lend themselves to the application of light and frequent doses of nutrients as opposed to native soil fields, which are usually best maintained with three or four applications of moderately concentrated fertilizer applications. Also keep an eye on pH. Since nutrient availability is closely related to soil pH, make sure you know the optimum availabil- ity ranges for your turfgrass areas. Interestingly, plant nutrient availability normally decreases when a soil's pH starts to exceed 7.5; however, Molybdenum's availability starts to reach its maximum at that point. CLASSIC SYMPTOMS OF DEFICIENCY Visual clues are useful for determining if the lack of nutrients is the cause of a turfgrass malady as well as the amount(s) indicated in a soil test report. Another consideration to keep in mind is nutrient mobility within the plant. Under deficient conditions, the more mobile nutrients will be moved to the younger, upper leaves, causing the older, lower leaves to exhibit Example of iron deficiency, courtesy of Dr. Andy McNitt, Penn State.