Emergency forages: Warm season grasses
As hay prices and demand for forages remain high, there is incentive to increase the productivity in forage systems, especially alfalfa. In an effort to maximize forage production during the relatively short growing seasons of the upper Midwest, semi-dormant alfalfa varieties have been heavily promoted and widely adopted, which can increase the chance of winter injury and winterkill. During the 2012-2013 winter, significant acres of alfalfa in the state of Minnesota experienced winter injury and winterkill.
Researching alternative forages after alfalfa winterkill
In years where alfalfa is injured by the winter and cool, wet springs persist, options to replant both annual row crops and forages can become more limited. Warm season grasses could provide an alternative emergency forage during such years. Since many of the warm season grasses species require warmer soils for germination, planting as late as July can provide forage during a reduced growing season.
Initial warm-season grass trials
Initial trials of the emergency forage program were conducted near Rosemount, MN in 2013. This research assessed the following six warm-season grasses on yield potential and response to nitrogen (N) fertilization and cutting management: Japanese millet, Siberian foxtail millet, teff, brown midrib (BMR) sorghum, annual ryegrass, and perennial ryegrass. Grasses were cut (i.e. early vegetative) one month after the June 5th planting date and again at the first of September.
Forage yield and quality results
In 2013, brown midrib sorghum yielded the highest of all the grasses, producing over 6 tons ac-1 dry matter. Teff, a warm-weather annual grass adapted to moisture regimes ranging from low desert sands to waterlogged clays, produced above 5 tons ac-1, whereas perennial ryegrass was among the lowest yielding species at 1.7 tons ac-1. Based on NDFd (neutral detergent fiber digestibility), BRM sorghum was among the highest quality grasses, while Siberian millet was among the lowest. To assess N credit from the previous winterkilled alfalfa, nitrogen fertilizer had no effect on the total dry matter production (i.e. yield in tons ac-1) across all seven species, which indicated that the winterkilled alfalfa supplied enough N to meet the needs of all grasses.
Current warm-season grass research
Similar to 2013, harvest intervals in 2014 began 30 days after planting and will continue every 30 days, concluding in early September. According to forage performance in the initial year, this experiment continues to utilize Japanese millet, teff, BMR sorghum, and annual ryegrass, with the introduction of sudangrass, sorghum sudangrass, Italian ryegrass, and a red clover/annual ryegrass bi-culture.
Early forage yield results
Yield data from the first harvest in Rosemount (2014) is available, providing insight into preliminary results (Figure 1). Sudangrass produced the greatest average yield across N rates at 1.41 tons ac-1, closely followed by BMR sorghum (1.40 tons ac-1). Japanese millet returned the lowest average yield potential (0.67 tons ac-1). BMR sorghum, Italian ryegrass, red clover/annual ryegrass mix, and teff showed consistent yield response to increased N. BMR sorghum with 100 lbs N ac-1 produced the greatest treatment yield (1.64 tons ac-1).
Figure 1. Emergency forage yields reported on a dry weight basis from first cutting at Rosemount, July, 2014.
ARYE=Annual ryegrass; BMRS=Brown midrib sorghum; IRG=Italian ryegrass; JMIL=Japanese millet; RC_RG=Red clover & annual ryegrass; SDG=Sudangrass; and SSG=Sorghum sudangrass.
Weed management challenges
Field observations at Waseca indicate that intensive weed management may be critical to stand establishment (Photo 2). Sudangrass and teff appear to have established and maintained the strongest persistence despite heavy weed pressure in all treatments. Teff responded very well to the high seeding rate, with greater germination and stand establishment. It produced relatively tight, dense growth, inhibiting weed encroachment and establishment. Although competitive and well-established, teff did not yield as high, due to its low growth habit and the cutting height used. Sudangrass also displayed strong and competitive establishment potential and closed quickly with enough tall, broad leaves to shade out most competition.
Higher fertilized treatments of BMR sorghum and Japanese millet also appear to be producing relatively well. Sorghum sudangrass, annual ryegrass, Italian ryegrass, and the red clover/ryegrass mixture have generally performed very poorly in this weedy location thus far. This emergency no-till forage research will continue over the next few years with the express goal of developing a set of tools for producers faced with extreme winterkill in alfalfa or prevented planting. As the study progresses, future results will be presented here at the University of Minnesota Extension Forage Website http://www.extension.umn.edu/agriculture/forages/.
Noland, R.L., Wells, M.S., Sheaffer, C.C., Coulter, J.A., and Becker. R. 2017. Yield, Nutritive Value, and Profitability of Direct-Seeded Annual Forages following Spring-Terminated Alfalfa. Agron. J. 109:1–11.