Kenaf hasn't reached its potential as a fiber crop, but shows promise as a high-quality, high-yielding forage for Southern growers.
This subtropical cousin to cotton grows like bamboo, reaching 20' high in a good year. In some countries, kenaf is an important source of fiber for products like rope and sacks. Here it's seen as a potential source of paper and building materials. But, despite several years of research, those uses are still an economic dream.
Almost by happy accident, scientists have discovered that kenaf makes high-quality forage when harvested or grazed at an early vegetative stage.
"If you manage it right, you can graze or hay kenaf all summer long," says Brian Baldwin, Mississippi State University agronomist who studied kenaf as a forage the past three years.
"We're still learning how to manage it," Baldwin points out. "For example, we were disappointed the first year. We got greedy and tried to cut the crop too close to the ground. It never fully recovered. You need to mow kenaf with an 8" or higher stubble for good regrowth."
Baldwin says kenaf tests 20-29% crude protein when harvested on a 30-day cycle, but protein content drops fast as the plant grows.
"We first evaluated kenaf planted in wide rows," Baldwin adds. "We planted it in 40" rows and mowed it about 60 days after planting, and at 60-day intervals after that. The stuff only made about two tons dry matter per acre, and the quality was nothing to brag about."
In 1996 and again last year, he planted kenaf in various row spacings from 7" to 40", and mowed the crop at 30-, 45- and 60-day intervals.
"It takes kenaf about 40 days after planting to get knee high. Make the first cutting or turn cattle in then," he suggests. "After that, you'll need to cut in cycles of between 30 and 45 days to keep the quality up."
In central Mississippi, kenaf should be planted between April 15 and May 1, says Baldwin. The plant will actively grow through September. Baldwin and Jeff Hollowell, an agronomy graduate student, apply 100 lbs of nitrogen per acre.
Kenaf has a heavy, woody stem and should be crimped if it's to be baled, says Baldwin.
"You need to crush the stalks so they dry down before leaves shatter," he advises. "We've had pretty good success putting kenaf in big round bales; cattle consume virtually all of the material - stalks and all."
In a 1997 grazing trial, Baldwin compared kenaf with fertilized native grasses.
"Cows with calves did very well, and seemed to prefer kenaf to native grasses. We didn't see any scouring or other evidence of off-feed when cattle were moved to kenaf.
"This year, I plan to study green-chopped kenaf, with the crop allowed to grow longer between harvests. We expect to get more tonnage that way, but the quality probably will drop considerably."
Baldwin hasn't tried it, but believes kenaf could be ensiled.
"There could be some problems in making silage, because kenaf's protein content is so high in relation to carbohydrates," he speculates. "It might take longer for kenaf to go through fermentation, especially if it's cut early."