Managing perennial cool-season forage grasses in Minnesota

The yield range reflects variations due to climate and nitrogen (N) fertilization rates.

To maximize establishment and productivity in the seeding year, give special consideration to these management practices.

Soil fertility

Take soil tests and follow recommendations for applying and incorporating essential minerals before seeding. Information on soil sampling strategies, soil testing and fertilizer recommendations are found in Fertilizing hay and pasture grasses and Fertilizing grass-legume mixtures in Minnesota.

• Nitrogen fertilizers can promote grass growth.
• Test your soil pH. Most crop plants prefer a pH of about 6-7, but grasses have a wider tolerance for a range in pH.
• You can raise soil pH by adding lime (calcium carbonate).

Seeding depth

• The optimum seeding depth for these grasses is ¼ to ½ inch.
• Broadcast seeding using cultipacker seeders or grassland drills with seeding depth control provides consistently shallow seeding depths.
• When drilled with small-grain companion crops, it’s critical to seed the small-grain and small-seeded grasses through separate seed boxes with separate delivery tubes. This allows for deeper placement of the small grain and shallower placement of the forage grass.

Seed-to-soil contact

Cultipacker seeders, rollers, or press wheels that promote contact of the small legume seed with soil and soil moisture enhance both germination and establishment.

Reduce competition with seedlings

• Control existing vegetation with a combination of herbicide and tillage. Some perennial weeds like Canada thistle and common milkweed may require multiple herbicide applications.
• Begin control efforts of perennial weeds at least 4 weeks before the target seeding date. Respraying may be required for troublesome weeds.
• Minimize competition with annual broadleaf and grass weeds by seeding in late summer (Aug. 15-Sept. 1) when weeds are less abundant.
• For spring seedings, postemergence herbicides can control some weeds but their use may be restricted depending on the weeds present.
• Mowing at a 4-inch height can also be an effective weed control method during the seeding year.
• If small grain companion crops are used for spring seeding, harvest the grain and straw promptly at maturity to reduce shattering, lodging, and smothering by straw windrows.
  • Minimizing grain shattering is important because volunteer small grains will compete with legume seedlings.

Harvesting during the seeding year

Spring seedings can be grazed or harvested at about 60 days following seeding. However, seedlings do not have adequate root systems and sods have not formed so harvest when soils are dry to minimize damage.

Summer seedings in August and early September will typically not have adequate fall growth before killing frosts to warrant harvesting.

At the first harvest of all cool season grasses in the spring, forage yield increases with increased maturity from vegetative to seed production stages, while forage quality declines. Declines in forage quality with maturity are due to increases in the proportion of stems in the forage.

Harvesting or grazing at or just before stem elongation is a compromise to balance forage yield and quality. For haymaking, grasses are typically harvested between the boot and flowering stage of maturity.

At subsequent regrowth in the season, perennial grass growth habits differ depending on species:

• Reed canarygrass, smooth bromegrass, and timothy go through stem elongation resulting in similar quality reductions at the first harvest.
• Orchardgrass, tall fescue, meadow fescue, and perennial ryegrass produce only leafy vegetative forage, so quality changes less over time.

All regrowth depends on stored carbohydrate reserves. As leaf area increases, photosynthesis recharges root energy reserves, and root and crown mass and tillering increase.

At flowering stages, stored energy reserves have been recharged, and the plant can experience more rapid regrowth following harvest or grazing.

• Leaving a 4-inch stubble and rotationally grazing benefits grass persistence.
• Because carbohydrate reserves need to be recharged, most grasses, except Kentucky bluegrass, require a rest period between grazing or harvests to persist.
• Only Kentucky bluegrass persists well under continuous grazing.
• Maintaining a 4-inch stubble height helps preserve leaves near the soil surface and protects storage reserves in stem bases of tall grasses.

Multiple harvests over a full growing season maximize forage yield and nutrient removal. For example, in southern Minnesota, three harvests before early September will typically result in the highest forage yields. In contrast, two harvests will maximize nutrient removal in northern Minnesota.

*Fertilizer treatment application of 275 lb N/acre. Source: Marten et al. 1979. Agron. J. 71:650-658.

All harvesting strategies aim to remove as much of the standing forage from the field as possible. Field losses during grazing range from 1 to 5% due to defecation, trampling and selective grazing.

Harvested hay must lose much more water than baleage before it can be safely stored. Here are the moisture levels required for safe storage:

• Hay in small square bales: below 20% moisture
• Large square and round bales: 15% moisture
• Baleage and low-moisture silage: 50-65% moisture (to ensure proper fermentation)

When drying time in the field is shorter, losses in forage weight and quality are also reduced. Fresh grass and legume forage crops are about 80% water, so they need to lose water before they can be harvested and stored.

Harvesting steps like mowing, raking, and baling round bales cause an average loss of 14% dry matter. Quality losses can be higher because leaves, which are rich in nutrients, tend to break off easily.

Rain is especially harmful to partially dried forage. It washes away sugars and minerals, with the damage worsening as rain gets heavier. If rain soaks forage windrows (piled forage), it may need to be turned multiple times with rakes or inverters to finish drying. However, raking causes more leaf loss, further reducing the nutrients and total yield. To avoid this, time harvesting to minimize exposure to rain.

Driving equipment over fields during raking, harvesting, or collecting forage can damage the plants and lower future yields. This is especially true for grasses and legumes that have started to grow back. To limit damage, complete harvesting and pickup within 5 to 7 days of mowing.

To prevent more losses, store hay, baleage, and silage properly. Leaving hay uncovered outside can cause significant loss of nutrients and dry matter due to water washing through it, reducing its value as animal feed and market value.

For more information, see Preserving the value of dry stored hay.

*Calculations based on a dry matter yield of 4 tons per acre. Source: Rotz and Muck, 1994. In Forage Quality. ASA, CSSA, SSSA, Madison, Wi.