Fall Lawn Feeding
I just had a MSU soil test (#FLC4DA) done that indicated I need to add potassium. My local feed store carries Anderson 0-0-62 granular potash (K2O). Is this acceptable? What is the maximum application rate? I can only buy a 50 lb bag for ~ 18,500 sqft (1.88 lbs per 1,000 sqft) and would like to throw it all down at once.
For the last fall feeding in November, is it better to use a quick release soluable Nitrogen fertilizer or a controlled release insoluable Nitrogen fertilizer?
Livingston County Michigan
Thank you for using the Ask an Expert service. Sorry for the slow reply.
You can use the 0-0-62 granular potash to apply only potassium (K2O) (i.e. it is acceptable). However, this type of product can potentially burn turf at high application rates. As it says in the recommendations in the soil test report you received, to minimize burning potential, the maximum single application rate is 1.0 lb K2O or 0.83 lb. K/1000 ft.². Also, irrigation should be applied following application. If you use the fertilizer calculator on the homesoiltest.msu.edu website (under “Tools”), it tells you to use 1.61 lbs of 0-0-62 (N-P-K) fertilizer to apply 1 lb. K2O/1000 ft.²
It’s not the best idea to throw the entire recommended amount of potassium all down at once. Consider splitting the recommended annual amount of potassium into two applications. Since your recommended annual application of potassium is 1.4 lb per 1,000 sq. feet, half would be 0.7 lbs per 1000 sq ft. Use about 1.13 lbs of 0-0-62 (N-P-K) fertilizer to apply 0.7 lb. K2O/1000 ft.²
I would still suggest a controlled or slow-release nitrogen fertilizer for the final fall application. As it mentions in the article by Kevin Frank, applying fast-release nitrogen fertilizers in the fall can force too much top-growth that results in more mowing and reduced rooting. Although, he is discussing applying fertilizer in September.
Below are a couple of articles I would suggest reading. In addition to reviewing your personalized soil test recommendations on the website:
Timing for fall fertilization and rust on turf from MSU Extension
Fertilizing Home Lawns to Protect Water Quality (E0001TURF) from MSU Extension
Please let me know if you have any further questions!
I wanted to let you know that I received new input regarding your second question, about using slow- or quick-release nitrogen fertilizer in November in particular.
I asked someone even more knowledgeable about turf if he would still recommend a November or fall fertilizer application, because I had thought I heard something to the contrary recently. I also asked if it depended on the nutrient. Also, if you’re applying N, whether September or November, should it be slow-release?
This was his response:
"This is an area where recommendations have evolved recently based on some new research - in a nutshell I tend to encourage folks to fertilize earlier in the fall (Sept-Oct) as opposed to waiting until Nov. As you get later in the fall it probably makes more sense to use faster release fertilizers rather than slow release - I’d rather get the fertilizer into the plant at this time than have it overwinter. Most of the traditional ‘winterizer’ fertilizers have a mix of slow and fast release but probably more fast release. Hopefully I didn’t cause more confusion…"
Hopefully that was helpful and not more confusing, as he said. That's why research is done, to test our assumptions and refine techniques. Let me know if you have further questions!