Rio Verde lablab, a recently released forage legume by the Texas Agricultural Experiment Station, could provide some relief to nitrogen fertilizer cost-shock.

Not only does it not require nitrogen fertilizer, Rio Verde lablab is found palatable by both cattle and wildlife, said its developer, Dr. Ray Smith, Experiment Station plant breeder based at Overton.

Natural gas is used to produce nitrogen fertilizer, and its rise in cost raised fertilizer prices. High nitrogen prices hammer row crop producers and livestock producers too. Today's highly productive, improved pasture grasses require large amounts of nitrogen, Smith said. However, Rio Verde, as do other legumes, fixes nitrogen from the atmosphere.

About 80 percent of the Earth's atmosphere is nitrogen gas, but it's not in a form plants can use. Forage legumes have a symbiotic relationship with rhizobium bacteria that live in small nodules on the plant's roots. They take nitrogen gas in the air and convert it into a form of nitrogen that plants can use.

Smith envisions several production niches for Rio Verde, he said. It could be incorporated as a component of wildlife food plots, as livestock grazing, as a hay crop, or as a green manure crop. A green manure crop is one not harvested, but tilled into the soil to improve fertility. "And we developed this new cultivar with Texas seed production in mind," he said. Prior to Rio Verde's release, seed for all other lablab varieties was grown in Australia, Smith said. This was because other varieties were too late in maturing to produce a seed crop in Texas before being killed by the first frost.

"The forage production and nutritive value potential of Rio Verde is about the same as iron and clay cowpeas at about 25 percent," Smith said. "Compared to bermudagrass, it's generally going be higher in protein."

But while cattle don't like cowpeas, they find lablab forage highly palatable, he said. White-tailed deer, which can be picky eaters, will also readily browse lablab, making it a good, low-management crop for supplemental feed in wildlife plots.

Usually, the development of a new forage cultivar by conventional plant breeding techniques requires at least eight to 10 years, Smith said. Though first selections of parent plants were made in the mid-1990s, its development was not considered a high-priority project. Nitrogen prices were low and producers were not interested in summer forage legumes.

As nitrogen prices rose, in 2003, Smith and his Experiment Station colleague, Dr. Monte Rouquette, felt it necessary to speed the process up to meet the emerging market for new forage legumes.

To accelerate the project, they enlisted the help of Experiment Station scientists at Dallas, Stephenville and Beeville. Also, the Texas Foundation Seed Service and three Texas seed companies cooperated to speed up commercial seed production.

It's too late to plant Rio Verde for a summer forage or hay crop this year, but there's still time to try it out in wildlife supplemental food plots, Smith said.

He recommended planting about 25 pounds of seed per acre.

Rio Verde tolerates acidic soils reasonably well, Smith said.

"We've grown here in soils down to about pH 5.5 with good results," he said. "It's not something that will take extreme acidity, but it is better at moderate levels of acidity than some of our other crops."

For summer forage and hay programs, Smith recommended planting from 30 to 50 pounds per acre.

"Use a drill to place seed about 1 to 1.5 inches deep," he said. "An alternative planting method is to broadcast seed on disked seed bed and follow with a light disking to cover. Use care to not cover the seed more than about 1.5 inches deep."

With adequate soil moisture, the legume can be planted from May through July, Smith said. It will start flowering in late August but will remain productive until the first hard frost.

Rio Verde is adapted to sandy loam, clay loam and clay upland soils, including the Texas regions of the Pineywoods, Gulf Prairies and Marshes, Post Oak Savannah, Blackland Prairies, Cross Timbers and Prairies, and South Texas Plains, Smith said.

Current prices for Rio Verde seed are about $4.50 a pound. The seed is available from Turner Seed in Breckenridge. The seed company's phone number is 800-722-8616.

e-mail: rd-burns@tamu.edu