The author is an associate professor and extension forage specialist based at the University of Wisconsin-River Falls.

A rancher near Siren, Wis., holds some large crabgrass. Notice “rooting” at the nodes of the sod-forming runners.

Summer is a period in the Upper Midwest that is critical for operations that rely on common temperate grasses like orchardgrass, perennial ryegrass, Kentucky bluegrass, or smooth bromegrass. These temperate grasses require cool temperatures and their peak production is in spring and early fall. In the summer, they undergo a significant “summer slump” — some more than others.

This summer drop in grass growth can be mitigated with the use of annual warm-season species that have their highest production in July and August. When this strategy is successful, warm-season annuals can reduce or eliminate the need to feed supplemental hay when cool-season grasses are unproductive.

Forage crabgrass is one such warm-season grass. Originally from tropical Africa, it belongs to the Digitaria grass genus and has long been recognized as an important forage with high quality, quick growth, and exceptional reseeding capacity. Forage crabgrass is a true tropical with no frost tolerance and has been cultivated extensively throughout warm, tropical, and subtropical regions because of high yields in predominantly light-textured soils.

These traits, plus others like high palatability and digestibility, make it attractive as a potential grass for summer use either as an emergency forage or for double cropping. Its extensive root system also makes it a good candidate for use where soil erosion is a concern.

Determination to tackle the summer decline led to cooperative efforts to check the feasibility of summer annuals like forage crabgrass production in northern Wisconsin. The questions were:

Could the grass be grown in northern latitudes given the cool summers and requirement for warm soils?

Would there be enough of a growing window for adequate production?

These concerns materialized into evaluation plantings during the last few years, which have rendered positive results.

Don’t seed too deep

Although there are several commercial varieties available, the one recommended for northern latitudes is the 2006-released Quick-N-Big. This variety met the needed requirements of quick germination, vigorous seedling growth to first grazing or haying, and rapid regrowth. Given the low tolerance to cold temperatures, preliminary evaluations in northwest Wisconsin focused on determining if there was a window of production. In other words, if the grass needed very high soil temperatures, would there be enough days for growth before first frost.

We found it best to plant crabgrass into a clean seedbed. Forage crabgrass seed is small, and seeding should be no deeper than 1/4-inch deep. To achieve this shallow planting, most situations require the use of a roller pass before and after seeding.

Like many forage crabgrass varieties, Quick-N-Big is semi-decumbent, initially growing as a bunch with tillers that curve upward with rooting capacity at the nodes. This grass is ideally suited for sandy soils with a soil pH ranging from 5.5 to 7. It does not generally grow as well in wetlands or tight, clay soils.

Ten-day warm-season crabgrass seedlings planted on June 11, 2015, near Spooner, Wis. Notice the large, wide leaves.

Highly palatable

In the North, plant crabgrass in summer at a rate of 6 pounds per acre once the soil warms to 65°F (usually June 1 to June 15). It germinates and grows vigorously and can be harvested one to two times or grazed several times through September. Crabgrass can also be stockpiled for fall grazing. Total yield ranges from 1,000 to 3,500 pounds per acre, although it can reach 6,000 pounds per acre with ideal growing conditions.

Forage crabgrass is highly palatable, and given the opportunity, this is the first grass that livestock graze in a pasture. If forage crabgrass is grown for hay, its relatively fine stems make it ideal for horses.

Forage crabgrass has high nutritive value with high digestibility and adequate crude protein (CP). Grass samples taken in mid-July, four weeks after planting, had an average of 15 percent CP, compared to 12 percent for a bluestem check. Dry matter digestibility (at 30 hours) averaged 58 percent, similar to a comparative orchardgrass stand, and it was higher than a bluestem check, which averaged 47 percent. As with other grasses, forage quality of crabgrass declines rapidly as plants reach maturity.

In addition to exceptional feeding value, forage crabgrass has proven to be an excellent ground cover. It will help to build soil organic matter and improve water-holding capacity. This speaks to its great potential as a soil conservation grass.

Although crabgrass is considered tropical, we have had great early success in establishing and utilizing the species in northern Wisconsin where the growing seasons are relatively short. Our plans are to continue to refine production methods and make better use of this valuable grazing and hay grass.

This article appeared in the November 2019 issue of Hay & Forage Grower on pages 32 and 33.

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