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Alternative annual forages: Warm-season grasses

Alfalfa is the most critical and widely produced perennial forage crop in the upper Midwest, immensely contributing to the region’s livestock and dairy production. However, highly variable and severe winter conditions increase the risk of winter injury.

For example, during the 2012-2013 winter, nearly 1 million acres of alfalfa in Minnesota and Wisconsin experienced winter injury and winterkill. 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.

Fortunately, warm-season annual forages can serve as valuable alternatives to fill this void and account for lost production.

Research on warm-season grasses

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Strategies for warm-season grasses

The best forage options may vary according to specific conditions, including production goals, time frame and seed cost and availability.

Corn silage

A previous study from 2002 to 2003 concluded that corn silage is often the best option in terms of tonnage and nutritive value, even when planted as late as July. BMR sorghum is highly competitive in biomass production, especially in one-cut systems, but generally has lower forage quality than corn.

Sudangrass and sorghum-sudangrass

Prior research also established that, in multiple-cut systems (e.g., three-cut systems) under favorable conditions, sudangrass and sorghum-sudangrass can produce competitive tonnage with higher crude protein, but lower energy than silage corn. Table 3 provides general comparisons of these studies.

Grazing and haying

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. However, direct comparisons between all these grasses and corn haven’t yet been made.

Table 3 shows values from multiple studies in Rosemount. Treatments were planted around June 1 to 15.

Crop Row width Total dry matter (DM): Harvest time Total DM: Tons per acre Total digestible nutrients (TDN)
2002-2003 -- -- -- --
Corn (81 day) 30 inches Single harvest at R3 5.9 tons per acre 63.6%
Corn (95 day) 30 inches Single harvest at R3 6.7 tons per acre 62.9%
Corn (103 day) 30 inches Single harvest at R3 7.0 tons per acre 65.4%
BMR sorghum 30 inches Single harvest at R4 6.0 tons per acre 55.7%
Sudangrass 6 inches 3 cuts 5.7 tons per acre 49.5%
Sorghum-sudan 6 inches 3 cuts 5.8 tons per acre 48.4%
2013 -- -- -- --
BMR sorghum 6 inches Single harvest at R4 7.0 tons per acre --
2014 -- -- -- --
Teff 6 inches 3 cuts 4.5 tons per acre --
Annual ryegrass 6 inches 3 cuts 4.0 tons per acre --
Sudangrass 6 inches 3 cuts 4.0 tons per acre --

Reagan Noland, graduate student, College of Food, Agricultural and Natural Resource Sciences (CFANS); Craig Sheaffer, agronomist, CFANS and Scott Wells, Extension agronomist

Reviewed in 2018

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