Several years ago farm magazine articles were discussing alfalfa becoming part of a crop rotation in corn and soybean fields across the Midwest based on USDA-ARS research involving harvesting alfalfa leaves separately from stems.
Under such management, a forage leaf harvest would provide a high quality feed without the need for hay equipment to condition low quality stems. The lower quality stems could be harvested at a later time and used for heifer or dry-cow feed.
At the time, the prospect of using simple field strippers to remove alfalfa leaves for their high protein content promised row-crop farmers another cash crop by supplying nearby dairies with feed, while at the same time fortifying their fields with additional organic matter through alfalfa’s fibrous root system. The benefits of growing the “Queen of Forages” could be realized without a long term acreage commitment to a hay meadow.
“By separating the leaves and stems, a cattle feeder can mix appropriate amounts of each for a variety of feeding scenarios,” explained Doug Karlen, research soil scientist at the USDA-ARS National Laboratory for Agriculture and the Environment in Ames, Iowa. “We looked at alfalfa-in-rotation cropping plans in western Iowa for about 9 years during the 1990s, and once the operators were accustomed to handling the forage we saw substantial reductions in nitrogen requirements for corn.
“Also, if there was excessive nitrogen in the soil profile, we found the alfalfa was a good scavenger for that nutrient,” he added.
In 2014, comparisons of leaf-stripped alfalfa forage and typical early-bud-stage harvested alfalfa showed no significant feeding differences in dairy herd milk production.
Today, while alfalfa-in-rotation management hasn’t become common place, Ron Hatfield, research leader at the U.S. Dairy Forage Research Center in Madison, Wis., says engineers have continued to hone the efficiency of field strippers for alfalfa leaf harvest, to the point growers can expect to harvest a highly enriched 80% leaf fraction.
“The big challenge, however, is how to store such a harvest. Typically we’re dealing with a crop containing 76-78% moisture,” he says. “So far, we have had success ensiling the leaf-stripped alfalfa up to 140 days in 2016 research trials, but overall, such a crop is difficult to handle because of its high moisture content. It doesn’t flow well.”
Hatfield says another obstacle to widespread adoption of the technology revolves around a farmer’s return on investment for embracing the process of separating alfalfa leaves at harvest.
“Without a high-value market for the high protein leaf harvest, it’s difficult to get farmers interested in making changes,” he explains. “That’s why there is ongoing cooperative ARS research at the University of Minnesota to develop products to use the leaves.”
Currently, such projects are examining extracting leaf proteins for aquaculture of tilapia (grass carp) production. “We’ve also loaned one of our prototype strippers to UC-Davis researchers who are working on a leaf-stripping experiment in California dealing with sequestering leaf proteins for possible human nutrition products,” Hatfield explains.
Agronomically, Hatfield says Wisconsin 2017 research currently centers on cutting alfalfa and allowing it to wilt for a period in the field to reduce moisture content for improved ensiling qualities, work that certainly would help spur interest in the process in the Upper Midwest.
Overall, separating alfalfa harvest into two product streams uncouples the process from forage quality demands of today’s harvest schedules and weather-induced problems of managing high quality alfalfa, he says.
Other benefits include possible expansion of alfalfa’s use in soil-building and erosion control efforts in row-crop rotations, as well as environmental clean up of fields high in nitrogen levels.
