Start with a good, reliable soil test. Contact your local OSU Cooperative Extension Service office for assistance about this. They will send your samples to either Penn State or the University of Kentucky since the soil testing lab at the university has been closed, but the results you get will be good. This soil test will tell you about your soils pH (for a lawn that should be in the 6.0 to 7.0 range) and the levels of Phosphorus, Potash, Calcium, and Magnesium. Then you can dig in with these simple soil tests,
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains� too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
to see what else your soil might need to become a good healthy soil that will grow strong and healthy plants. Once you know what the soil you have is now then you can begin to plant what you will need to do.

Search the Organic Gardening forum FAQs for the Organic Lawn Care FAQ. That will get you started.

And yes, do the entire lawn at once. No need to wait or to mix chemicals with organics.

Here is a picture from a GW member back in 2011. He applied a handful of alfalfa pellets to his zoysia lawn in mid May. The picture was taken in mid June. Note the improved color, density, and growth.

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