Grasses grown for hay or pasture often take a back seat to other crops in the area of soil fertility. That’s a mistake, says Maurice Watson, an Ohio State University soil specialist.
"To get maximum grass forage production, the status of the soil’s fertility should be known and adjusted if necessary," says Watson.
The best strategy for achieving optimum soil fertility is to test the soil several months prior to seeding the grass crop. Watson recommends the following guidelines:
Maintain pH in the 6-6.5 range. If it drops below 6, nutrients such as phosphorus, calcium and magnesium will become less available to plants.
If the soil is too acidic, apply limestone. Under most situations, lime will begin to increase soil pH within three months. But it’s usually best to apply lime six months before seeding.
Apply enough nitrogen to ensure high yields. Add 20-40 lbs/acre at seeding plus 30-50 lbs/acre in late summer or early fall. Then make annual nitrogen applications after the grass is established.
Establish optimal phosphorus and potassium levels before planting. High-yielding grasses need plenty of both nutrients, especially potassium, and it’s more difficult to increase soil levels after the crop is established.
Build soil levels by broadcasting fertilizer and working it into the soil. If more than 300 lbs/acre of actual potassium are applied, use two applications, incorporating after each application. If manure is used, wait 10-14 days after application before seeding. The manure should be worked uniformly into the soil to a depth of at least 4-6".
Maintain sufficient levels of magnesium. If magnesium levels are low in relation to potassium levels, plants tend to take up more potassium. That can contribute to grass tetany in livestock.
Watch for sulfur deficiencies. They’re rare, but may happen in sandy soils with very low organic matter content. The sulfur status is considered low when sulfur concentration in the leaf tissue is 0.20% or less.
Apply micronutrients cautiously. Plants need very small amounts and overapplications can be toxic to them.