As hay prices and demand for forages remain high, incentives have been developed to increase 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. Growing later into the fall, and breaking dormancy earlier in the spring, these lines offer potential to capitalize on more growing degree days, but increase the danger of winter injury or winterkill. During the 2012-2013 winter, nearly 750,000 acres of alfalfa in the state of Minnesota experienced winter injury and winterkill.
Very low success has been observed in replanting alfalfa into dead or injured alfalfa stands, due to low establishment year production and autotoxicity. This research, conducted by the University of Minnesota, investigates alternative production strategies employable as quick and effective responses to winter injury. The primary focus is to assess the viability of summer annual grasses as emergency forages when no-till planted into winterkilled alfalfa. These systems are intended to offer forage producers emergency production strategies that could provide forage for both grazing and haylage. Considering unfavorable planting conditions of a cold, wet spring, seeding as late as June or July may be necessary for warm season grasses to establish properly and meet yield potential.
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 N fertilization and cutting management: Japanese millet, Siberian foxtail millet, teff, brown midrib (BMR) sorghum, annual ryegrass, and perennial ryegrass. Alfalfa was also seeded but was unsuccessful in establishment (likely due to autotoxicity). Grasses were cut (i.e. early vegetative) one month after the June 5th planting date and again first of September. Nitrogen response was assessed through the application of varying rates to the grasses, along with evaluating the subsequent effects on forage yield and quality.
Brown midrib sorghum yielded the highest of all the grasses, producing over 6 tons per acre. Teff, a warm-weather annual grass adapted to moisture regimes ranging from low desert sands to waterlogged clays, produced above 5 tons per acre, whereas perennial ryegrass was among the lowest yielding species at 1.7 tons per acre. Based on NDFd (neutral detergent fiber digestibility), BRM sorghum was among the highest quality grasses, while Siberian millet was among the lowest. Nitrogen fertilization had no effect on total dry matter production (i.e. yield of tons per acre) across all seven species, which indicated that the winterkilled alfalfa supplied enough N to meet the needs of all grasses. Forage protein content and NDFd were both improved with increasing N rates, ranging from 10% and 13% for Japanese millet and BRM sorghum, respectively.