What do you have against Milorganite?

I don't have a problem with Milorganite. The deer in my neighborhood have a problem with Milorganite.

Milorganite is used by many to keep deer, and others, away from plants, so in addition to feeding plants it would be useful here too.
Iron is a micro nutrient. Plants need it in very small quantities and most often it is not available to plants because of the soil pH.
The nutrients that things such as Greensand have become available to plants because the Soil Food Web converts them and the Soil Food Web needs organic matter in the soil to function. Most often if adequate amounts of organic matter are in the soil so will the nutrients plants need to grow strong and healthy.
A study, done at Texas A & M, seemed to indicate that corn meal could aid in controlling some types of fungi. However, others have not been able to replicate that.
Corn Gluten Meal needs to be applied about 6 weeks before the unwanted seeds will be germinating. For many that might mean applying it about the time Forsythia are beginning to blossom.
Michigan has severely restricted the use of Phosphorus in lawn fertilizers because of the build up of toxic algae in lakes because of the vast amounts of P that enter the water. I know the Ohio legislature was looking to do the same but do not know if they have. Check with the people at your local Ohio State Universities Cooperative Extension Service. The only way to know if your lawn needs any nutrients is by having a good reliable soil test done.
Granite meal must be worked on by the Soil Food Web for the nutrients to become available to the plants. The Soil Food Web needs adequate levels of organic matter in the soil to properly function and adequate levels of organic matter In the soil will supply the nutrients needed without adding materials mined from far away.
Soybeans are one of the most Genetically Engineered crops out there today and should be unacceptable to any organic grower. I would use soybean meal only if I could find some organically grown.

You will be hard pressed to find quantitative answers. Amounts of nutrients and their resulting effects are commonly identified, even in research, as sufficient, insufficient, low, high, excessive, etc. Likely this is due to the variety of variables involved: type of turf, soil, rainfall, Edit: temperaturel End Edit and the highly transient characteristics of some nutrients like nitrogen. However, somehow, or maybe consequently, recommendations based on soil analysis are made to adjust to a specific range.

Anyway, phosphorus is necessary for production of DNA, plant cells and plant metabolism.

Optimal nitrogen is one of my favorite questions. Anytime I have asked degreed turf horticulturalist and turf managers that question, the answer is that it is determined by Edit:"maximum growth rate model" The model is location and turf dependent. Basically it is just a "guide" based on collected data by the individual user. google Micah Wood End Edit. LoL Hope that helps in some way. Edit: For us pedestrians, the only quantitative recommendations for nitrogen are those supplied by university turf programs for home lawns. e.g. one pound of nitrogen applied in the months of X, Y and Z. End Edit

You are accurate that potassium in "sufficient" levels improves root growth, water retention, and turf tolerance to heat and cold.
Higher levels of nitrogen have also been shown to be an important part of winterization resulting in increased root mass and earlier spring green up, possibly due to greater carbohydrate reserves. Edit: This increase in nitrogen for winterization benefits are totally unrelated to and in addition to the "maximum growth rate" model for determination of nitrogen requirements.

This post was edited by yardtractor1 on Sat, May 24, 14 at 2:54

Excess Nitrogen and Phosphorus are known, and have been shown, to flow out of soils with the excess water and not only enter our ground water where they pollute, Nitrates in our drinking water and toxic algae growth in our lakes and ponds, slowly poisoning us.
The only means to know what the soil under your feet need to grow a good healthy turf is to have periodic soil tests done and look at the soil so you can adjust what you are doing to provide that soil with what it needs. That also makes economic sense since you are not spending your money on what you do not need.

"The only means to know what the soil under your feet need to grow a good healthy turf is to have periodic soil tests done and look at the soil so you can adjust what you are doing to provide that soil with what it needs. That also makes economic sense since you are not spending your money on what you do not need."

All good, but the OP asks: " is there an optimal Nitrogen level I should shoot for and how often should I test for it? "

Because Nitrogen availability to plants is very dependent on the activity of the Soil Food Web, which is dependent on soil temperature, few soil test labs today test for Nitrogen.
Work at making the soil into a good healthy soil and there will be adequate, but not in excess, amounts of all nutrients in balance available to those plants.