The principle of testing is the same: know what you've got since looking at a bale of hay or an acre of ground doesn't tell all. Hay with a low proportion of leaves to stem can't provide the balance of energy, protein, minerals and fiber. Soils needing lime that test low in potassium and phosphorus will produce only a fraction of yield under drought or plant stress. When Mother Nature provides the rain and sun for plant growth then a fertile, productive soil responds to produce pastures of plenty. That reduces your hay purchases and gives you the best quality "hay": natural, selective grazing by your horse.