Red clover growing naturally is generally a good sign that the soil has some merit already. Probably Ph at least close to 6.0. Red clover will grow a little more easily than most white clovers on soils 5.5 - 6.0 ph.

Sometimes you can tell by the plants growing, what parts of a field might be better suited for plots. Use existing weed vegetation as soil indicators.

Acidic loving plants include: Queen Anne Lace, Daiseys,Paintbrushes, plantain .

On "less acidic soils" - you will see more: Milkweed, lambsquarters, chickory, clovers.

I like clovers above all else for "pasture type" plots.Use lime to "up" your Ph.
I like White clover mixes best since they grow lower to the ground - and my deer seem to prefer white clovers. Once established - I mow 2-3 times per year and leave the clippings lay.

FH