Alternative annual forages
Alfalfa is the most critical and widely produced perennial forage crop in the upper Midwest, contributing immensely to the livestock and dairy production of the region. In recent years though, highly variable and severe winter conditions have increased the risk of winter injury. During the 2012-2013 winter, nearly 1,000,000 acres of alfalfa in Minnesota and Wisconsin experienced winter injury and winterkill. Such environmental threats demand development and improvement of response management strategies to better alleviate loss and maintain production in forage systems. Replanting alfalfa shows very low success due to residual autotoxicity and prevented planting conditions that often coincide with winterkill and persist into the summer months. Warm season annual forages can serve as valuable alternatives to fill this void and account for lost production.
Warm season grass evaluation
Initial trials conducted in Rosemount in 2013 (Experiment 1) evaluated six warm season grasses (Table 1) and provided refinement of species selection for the current study. Field trials are currently underway (2014 -2015) in Rosemount and Waseca, 2), analyzing a range of forage species (Table 1) no-till planted into winterkilled alfalfa residue in late May or early June. Forage yield and quality are assessed in response to intensive cutting management and variable N fertilizer rates. Harvest events occur on 30 day intervals after planting for three cuts, concluding in early September.
Table 1. Warm season forage grass species and seeding rates no–till planted
into winterkilled alfalfa in experiments 1 and 2.
|BMR Sorghum||Sorghum bicolor||35||1,2|
|Sorghum–sudangrass hybrid||Sorghum bicolor x S. bicolor var. sudanense||35||2|
|Annual ryegrass||Lolium multiflorum
|Japanese millet||Echinochola esculenta||35||1,2|
|Italian ryegrass||Lolium multiflorum||30||2|
|Annual ryegrass||Trifolium pretense||8/15|
|Siberian foxtail||Echinochloa frumentacea|
|Perennial ryegrass||Lolium perenne|
Photo 1. Alternative forage crops in vegetative growth stages.
In Rosemount, teff achieved the greatest biomass, averaging 4.45 ± 0.15 ton per acre for total season production. Annual ryegrass, and red clover + annual ryegrass were also among the highest yielding treatments, but suffered greater weed pressure than teff (weed biomass is included in reported yields). Sorghum–sudangrass and Italian ryegrass were among the lowest yielding treatments (Figure 1). At the first cutting event, BMR sorghum was one of the highest producing treatments, but did not regrow under intensive cutting as well as most other warm-season forages. Similarly, in experiment 1, BMR yielded the greatest total biomass of all the grasses, producing over 7 tons per acre when allowed to grow all season and cut once. In experiment 1, nitrogen rate had no effect on forage biomass, indicating adequate residual alfalfa N and efficient utilization, although nitrogen rate did affect yield at all levels in Experiment 2 (Table 2).
Table 2. Yield totals (tons per acre) by species and nitrogen rate, 2014.
|Nitrogen rate (lbs N per acre)|
|Forage yield (tons per acre)|
Field trials at Waseca experienced an extremely challenging growing season. A high percentage of alfalfa and weed regrowth following the initial glyphosate application required a second termination and planting event. A more successful alfalfa kill was achieved, but weed persistence remained an issue. Severe weed pressure, coupled with excessive rainfall in June and two hailstorms during the growing season, resulted in particularly adverse growing conditions. Preliminary observations indicate that teff, sudangrass, and BMR sorghum persisted the best under these conditions. All other treatments were lost to weed pressure. Teff competed exceptionally well, quickly establishing a thick, uniform stand and inhibiting weed encroachment. This weed suppression potential calls for further investigation in future studies, as percent weed cover in teff treatments was often up to 80-90% less than in other treatments.
Depending on production goals, timeframe, and seed cost and availability, best forage options may vary according to specific conditions. A previous study (2002–2003) concluded that corn silage is often the best option in terms of tonnage and nutritive value, even when planted as a late as July. Brown–midrib sorghum is highly competitive in biomass production, especially in one–cut systems, but generally has lower forage quality than corn. The prior research also established that, in multiple–cut (3) systems under favorable conditions, sudangrass and sorghum-sudangrass can produce competitive tonnage with higher crude protein, but lower energy than silage corn. General comparisons of these studies are provided in Table 3. Considering cutting tolerance and regrowth potential, the annual ryegrass options, sudangrass, and particularly teff could be more valuable in grazing (or haying) systems than corn silage, although direct comparisons between all of these grasses and corn have not yet been made.
Table 3. Alternative annual forage management practices and average yields from
multiple studies in Rosemount, MN.
|Row width‡||Total DM|
|2002 – 2003|
|Corn (81 day)||30||SH @ RM||5.9||63.6|
|Corn (95 day)||30||SH @ RM||6.7||62.9|
|Corn (103 day)||30||SH @ RM||7.0||65.4|
|BMR Sorghum||30||SH @ RM||6.0||55.7|
|BMR Sorghum||6||SH @ RM||7.0||–|
|Annual ryegrass||6||3 cuts||4.0||–|
|‡Treatments were planted ∼ June 1–15
Abbreviations: SH, Single harvest
As the current research continues for one more year, comprehensive assessments of biomass production and relative forage quality under varying management practices will provide producers with informed, decision–making tools to implement alternative annual forages when needed.
Copyright © 2015 Regents of the University of Minnesota. All rights reserved.