Feature Story
Q&A Q&A on on
Potassium
Nutrition in in Golf Golf Turf Turf Management Management By Mike Goatley, Jr., Ph.D., Professor and Extension Turfgrass Specialist, Virginia Tech
When should (or what agronomic signs indicate) a superintendent test for potassium levels in his course’s turf? It is very difficult, if not impossible, to visually identify potassium deficiency since the symptoms are not clearly defined as they can be for other nutrients. A general thinning of the turf, poor recovery, perhaps an increased tendency to show wilt—these are all things that happen over extended time periods, and not over a matter of days.
How is this best accomplished? Soil testing is a logical way to monitor potassium levels, but the strategy that really works best for getting the best handle on potassium in the turfgrass is regular tissue testing. Tissue testing is a snapshot in time of nutrient levels in the plant, and it is necessary to pair the information with that of a soil test. But tissue testing on sand-based soils is about the only way to really monitor what is going on inside the plant re: potassium nutrition because of how mobile potassium can be in those soils.
Is there a best time of the year to do the testing? I usually think of potassium much like I do lime – if it is needed, it should be applied. The only way to really know
if you need it is to soil and/or tissue test. In particular, I think it is important to know your potassium levels prior to the logical stress periods of summer or winter. I think of potassium as the “anti-freeze” or “coolant” of the plant world, and you need to have adequate amounts in the turfgrass tissues before the stress period arrives.
Are there any steps to make sure a superintendent does not miss along the way in terms of proper testing? Establish a good working relationship with a testing firm for either (or both) soil and tissue testing, and then stick with that firm if you are getting what you feel are solid, reliable and timely results. Avoid the temptation of comparing the values between labs, since one can really make this very confusing when comparing values between labs.
Should all areas of the course be tested? Why? Yes, but the areas that must be most carefully monitored are sand-based soils, particularly modified putting greens. While potassium is held in the soils by Cation Exchange Capacity reactions, it is still a fairly mobile nutrient that can leach, and that is logically more likely to happen in sandy soils.
18 | Virginia Turfgrass Journal March/April 2016 www.vaturf.org