Grasses dominate the 7 million acres of pastures and hayfields that serve animal-based agriculture in Kentucky. Renovating these fields to renew grass productivity is one of the most important forage improvement practices.

"More than 30 years of research data and farmer experience have shown that farmers benefit from higher yield, quality and summer production by establishing legumes in grass pastures and hayfields. Another advantage is that the legumes fix nitrogen, thereby lowering fertilizer cost and use," said Garry Lacefield, Extension forage specialist with the University of Kentucky College of Agriculture.

Adding legumes to hay and pasture fields increases the total forage yield per acre. One study showed that using red clover to renovate a fescue pasture produced higher yields than using the equivalent of 180 pounds of nitrogen per acre, according to Lacefield.

Compared to grass alone, a legume-grass mix improves forage quality in such areas as increased palatability, intake, digestibility and nutrient content. Research shows that legumes improve animal growth rates, reproductive efficiency and milk production.

Inoculated legume seed fix nitrogen in the soil, providing a valuable nutrient for grasses and legumes. Various legumes fix different amounts of nitrogen. Alfalfa fixes the most nitrogen, 200 to 300 pounds an acre annually; annual lespedeza, about 75 to 150 pounds. Depending on the cost of nitrogen fertilizer, legumes can put from $18 up to $75 worth of nitrogen in the soil.

Legumes produce more growth during the summer than cool-season grasses. So adding legumes produces forages during the summer -- a slack growth period for cool-season grasses.

"Controlling grass and weed competition is one of the most critical steps to successfully establishing legumes in grass pastures or hayfields," Lacefield said. "Many renovation attempts have failed because competition from existing grass reduced the light, nutrients and water young legume plants needed. Keep grass short by grazing or mowing until new legume plants are 3 to 4 inches tall. Then, cease grazing and mowing for 4 to 6 weeks to allow the legumes to become well established."

When deciding which legume to use, one factor to consider is the ultimate use of the forage. Alfalfa or red clover usually is best for hay. A combination of red clover and ladino clover works well for both hay and pasture. Ladino clover, red clover or annual lespedeza work well in pastures alone.

"Another key to successful renovation is to use legume and grass varieties that perform well in your area," said Jimmy Henning, Extension forage specialist. "The results from our University of Kentucky forage variety trials of alfalfa, red clover, tall fescue and orchardgrass, among others, will help you choose the varieties appropriate for your particular operation. This information is available from your local Extension office."

Lacefield and Henning gave these tips for successfully renovating grass fields:

* Since legumes need a higher soil pH and fertility level than grasses, take soil tests and apply the recommended lime and fertilizer. Do not add nitrogen during the establishment year because this stimulates grass growth that will compete with the seedling legumes.

* Buy certified seed to be sure of what you're planting. Mix a high quality inoculant with the seed before planting. Use a sticking agent to be sure the inoculant adheres to the seed.

* Allow heavy grazing through early winter to remove excess grass cover and make it easier for seed to make good soil contact.

* To improve seed-soil contact, use a disk, field cultivator or field tiller to help break up soil so the legume seed have a better chance to germinate and grow. Another method is to use a no-till renovation seeder. Broadcast legume seed on the soil surface in late winter. The seed become covered as the soil freezes and thaws. This method does not work well with alfalfa.

For more information, consult "Renovating Hay and Pasture Fields" (AGR-26). This publication is available from your local Extension office.