Which cover or green manure crop you plant can only be determined by the condition of your soil. Alfalfa grows best only in pretty good soils, a good soil pH and well balanced in nutrients. Some clovers also need a pretty good soil while a few will do well on soils that do need improvement. White Dutch Clover, a good, natural Nitrogen source, is considered by many to be a "weed" instead of a desireable plant and it is not terribly fussy about the soil, except that it does not grow well in soils with adequate N levels.
Start with a good, reliable soil test. Contact your county office of the University of Missouri USDA Cooperative Extension Service about having that done and also dig in with these simple soil tests

1. Structure. 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. 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 more your soil needs.

Here is a link that might be useful: University of Missouri CES

kimmsr,
thanks for the reply, glad to see this board is active. when I did the reno on the front part of the property a friend got me into reading banned*lawn.info(good board, some organic info).
yes, going to get the soil tests, mailed off this week. have an older one for the front from UofMo. org. material=2.3%, low on P, high on K, CEC=11.2meq.
thru years of neglect, suspect the back part of the property is worse.

notice at various places the top of the soil is cracked and crusty in the summer(surface hardpan?).

anyway, I'm just getting started, not in a big hurry and have no fantasies about growing pristine KBG.

I'll post the soil test results. go from there.
thanks.
*got an error message and can't post the name of the other site, wonder whats with that?

Look into Microclover...as the name implies, it's a smaller, lower-growing form of DWC. Last I checked, however, it could only be purchased in seed blends (with PRG, TTTF, etc) and not as a stand-alone seed.

*got an error message and can't post the name of the other site, wonder whats with that?

What's up with that is the namesake of that other forum was banned from Gardenweb for differing in a personal opinion with one of the GW owners. It was in a non-gardening forum. The vendetta seems to linger on. I have known several excellent gardening contributors who have been banned from GW for very arbitrary reasons. And as a matter of fact all of them are on that other forum.

I think I replied to you on the other forum but for the people here, alfalfa is a special plant. I would find someone growing it and see if that is what you want in your yard. Dutch white clover used to be a staple in every grass seed up until the end of WWII when modern defoliants came to the home owner. Since they kill weeds and clover, clover was declared a weed. It does make a very lush ground cover, though. Look around at Google Images for clover lawns.

Hi David,
some interesting reading over here in the organic lawn and organic garden forums.
here's a few links I found, interesting reading--
http://www.uvm.edu/vtvegandberry/factsheets/organicN.html
http://attra.ncat.org/attra-pub/PDF/covercrop.pdf

I'm planning on taking a driving tour of the country side, have some feed/seed stores, co-ops on a list. yes, I need to get out and talk to people that do this. also, going to look for sources of manure.

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Here is a link that might be useful: Seed list