How to Add Enough Potash to Lawn in a Year?

I am trying to figure out a general plan in applying the right amount of fertilizer into my lawn. Based on my 7500 sqft lawn size, I figure that I need to add 28.7 lb of nitrogen, 7.2 lbs of phosphate, and 14.4 lbs of potash into my lawn every year (assuming that soil test result is "average"). But I have a hard time in finding out a right plan to add enough potash without adding too much nitrogen and phosphate. For example, I have developed a plan like the following to apply commonly available store-bought fertilizers into my lawn:
Nitrogen Phosphate Potash -------- --------- -------- Late-Mar: Scotts Turf Builder With 6.0 lbs 0.6 lbs 0.8 lbs Halts Crabgrass Preventer
Mid-Apr: Milorganite Organic 6.9 lbs 2.3 lbs 0.0 lbs
Mid-May: Milorganite Organic 6.9 lbs 2.3 lbs 0.0 lbs (may not apply this)
Early-Sep: Scotts Starter Fertilizer 5.2 lbs 6.9 lbs 1.3 lbs
Early-Oct: Milorganite Organic 6.9 lbs 2.3 lbs 0.0 lbs
Early-Nov: Scotts Winterizer Fall 4.6 lbs 0.6 lbs 3.0 lbs Lawn Fertilizer -------- --------- -------- Total (with Mid-May Application): 36.5 lbs 15.0 lbs 5.1 lbs Total (without Mid-May Application): 29.6 lbs 12.7 lbs 5.1 lbs -------- --------- -------- Expected: 28.7 lbs 7.2 lbs 14.4 lbs
If I follow this plan, I will not add enough potash to my lawn (and will add too much phosphate).
My questions are:
- Is there a way to develop a plan in a way that I can add the recommended amounts of N/P/K without adding too much of any one component?
- I am hoping that I can avoid using Green Sand to increase potash because it is very expensive. Is there a way to increase potash without spending a lot of money?
- If I must use Green Sand to increase potash, I am wondering how I can apply it evenly? Do I need to mix it with the other fertilizer? How to set the proper setting in my broadcast spreader for Green Sand?
Thanks in advance for any help.
Note: - I will use 0.5 bags of Scotts Turf Builder With Halts Crabgrass Preventer fertilizer each time when I use it. - I will use 3.0 bags of Milorganite Organic fertilizer each time when I use it. - I will use 1.4 bags of Scotts Starter Fertilizer each time when I use it. - I will use 0.5 bags of Scotts Winterizer Fall Lawn Fertilizer each time when I use it.
Jay Chan
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Jay Chan said:

My sandy soil is well-supplied with phosphorous and deficient in potassium. So I have to look for lawn fertilizers which will give me N and K and avoid applying more P.
You might be able to find 'winterizer' formulas which contain more potash. I buy Vigoro winterizer (23-3-14) which is usually available briefly in the fall (at Home Depot) and may not be availalbe everywhere. I use that in the late fall, and usually use Restore (10-2-6) (Memorial Day and Labor Day) and either Restore or occasionally Milorganite in summer (4th of July). Restore should be available pretty widely (I've seen it under both the Ringer and Safer brand name).
Never use a pre-emergent. Occasionally spot-treat for weeds.
I generally use organic fertilizers (my soil is desperate for organic matter). I make an exception for Vigoro, which is a controlled-release fertilizer and comes recommended by the Healthy Lawn and Garden Technical Advisory Committee for Wayne and Oakland County (protecting the Rouge Watershed).
http://www.plymouthtwp.org/Community/RougeRiver/EarthDay.htm
<snip>

Greensand is generally something you apply heavily once and till in and then don't apply again for many, many years. It is an extremely slow and lasting source of potash and trace minerals. Doesn't leach away.
Sulfate of Potash is cheaper (in dollars per pound of potassium) but would be hard to spread. IMO you'd be better off paying a shipping premium to mail order a winterizer lawn fertilizer (if such weren't available to you locally) than trying to figure out how to distribute a small bag of Sulfate of potash thinly and evenly over you entire lawn...
Wood ashes can also supply potassium, but are very leachable and extremely alkaline, which can play havoc with the pH.

Measure a 100 square foot area. Measure 5 - 10 pound of greensand (the recommended amount for surface application on 100 square feet). Then experiment to find the setting that lets you spread the full measure of greensand on 100 square feet. (I would hazard a guess that the spreader would be set on one of its lowest settings.)
--
Pat K. ('someplace.net' is comcast)

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Thanks. This causes me to take a look on the use of Fertilizer with Halts Crabgrass Preventer and the use of Starter Fertilizer. I decide to replace both with Winterizing Fertilizer. This cuts down the annual amount of phosphate, while at the same time increase the annual amount of potash level. I also replace the use of one serving of organic fertilizer with Winterizing Fertilizer.
The revised plan is like this:
Nitrogen Phosphate Potash -------- --------- -------- Late-Mar: Scotts Winterizer Fall 4.6 lbs 0.6 lbs 3.0 lbs Lawn Fertilizer
Mid-Apr: Milorganite Organic 6.9 lbs 2.3 lbs 0.0 lbs
Mid-May: Scotts Winterizer Fall 4.6 lbs 0.6 lbs 3.0 lbs Lawn Fertilizer
Early-Sep: Scotts Winterizer Fall 4.6 lbs 0.6 lbs 3.0 lbs Lawn Fertilizer
Early-Oct: Milorganite Organic 6.9 lbs 2.3 lbs 0.0 lbs
Early-Nov: Scotts Winterizer Fall 4.6 lbs 0.6 lbs 3.0 lbs Lawn Fertilizer -------- --------- -------- Total: 32.2 lbs 7.0 lbs 12.0 lbs -------- --------- -------- Expected: 28.7 lbs 7.2 lbs 14.4 lbs
Seem like the annual amount becomes very reasonable. This means I can achieve what I need to do without the use of expensive Green Sand while still manage to use some organic fertilizer. The only thing that I don't like is that I will need to apply chemical fertilizer for 4 times instead of 3 times. Hopefully soil test tells me that the potash level in my soil is still OK; then I don't need to follow this plan that strictly. But this plan will probably be the general guideline of what I am going to do.
Obviously, I need to apply crabgrass preventer separately. This is OK.

Thanks for the instruction. I hope I don't need to do this because Green Sand is very expensive. But I never know. This info may come in handy.
Jay Chan
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