Improve pasture quality (and milk) with legumes

Dairy cows fed high-quality forage produce more milk with less supplementation than cows fed lower-quality forage.

High quality pastures do not happen by accident, this is a good time of year to begin planning steps to improve the quality of next season’s pastures.

Legumes are key

Maintaining legume content in pastures is the best way to improve forage quality and animal performance in grass-based operations. Legumes nearly always have lower neutral detergent fiber (NDF) than grasses.

Legumes also are high in crude protein. The lower fiber content of legumes translates into greater animal intake, which is highly correlated with milk production.

High quality legumes in the diet serve to reduce feed costs. Legume content should be at least 30 percent in pastures.

Pure grasses can be equal to or higher in feed value than legume forage, if they are maintained in a young stage of growth. That is difficult to achieve on a consistent basis across the season.

Legumes in pastures help widen the window of time that high quality forage can be maintained.

Three steps

Three important steps to increase and maintain adequate legume content of pastures are to provide adequate soil fertility, interseed improved legume varieties and manage grass competition.

Fertility matters

Most legume species are favored by soil pH above 6.0 (>6.5 for alfalfa) and by adequate phosphorus (25 ppm, 50 lbs/acre) and potassium (>75-100 ppm, >150-200 lbs/acre) levels in the soil.

Use soil tests to determine where liming and fertilization is needed. Nitrogen fertilizer can harm legume content in pastures by over-stimulating the grasses. As little as 50 pounds N per acre is enough to reduce legume content in pastures, so use it sparingly where you want legumes to be present.

Interseeding legumes

No-till drilling and frost seeding can be used to introduce more legume into pastures.

The most reliable method is to use a no-till drill where the grass sod has been suppressed either chemically or by hard grazing.

Frost seeding in February can work very well as a legume seeding method. White and red clovers are the most reliable legumes to establish by frost-seeding.

Frost seeding is most successful where the grass sod is thin and has been grazed really hard in the fall. Mob grazing the area after frost-seeding is a good way to trample in the seed so good seed-to-soil contact is achieved.

Use improved legume varieties. Many improved pasture legume varieties are available on the market.

While these usually cost more than “common,” or variety unstated seed, the benefits from planting improved varieties usually far exceeds the relative small increase in seed cost.

White clover varieties with the intermediate-leaf type have shown greater persistence in grazing trials than the more erect and large leaf ladino varieties.

The improvement in red clover varieties in recent years is especially noteworthy. Along with being more persistent, the newer red clover varieties are higher yielding.

Some alfalfa varieties have also shown improved persistence in University of Kentucky grazing trials.

Grass shading is harmful

Excessive grass competition to legumes is one of the main reasons many pastures lack sufficient legume content. Grasses generally out-compete legumes, especially clovers, for light and many soil nutrients.

Grass competition is especially harmful during establishment period of legume seedlings, but even established legume plants can be weakened by much grass competition.

Shading of white clover by grasses weakens the stolons (horizontal runners), leading to loss of white clover density in the pasture. White clover expends a lot of energy to reach the top of tall grass canopies, so less energy is available for producing and maintaining stolon growth.

Clovers are especially sensitive to shading in the early spring when energy reserves are low after being used for winter survival.

At the same time, grasses are more competitive in the spring due to their rapid growth and reproductive development.

Managed grazing

Grazing must be managed to achieve low grazing heights that open the canopy so sunlight reaches the clovers.

Leaving a tall residual after grazing allows grasses to recover more quickly than legumes, which results in rapid shading of the legumes. To promote more legumes in pastures, graze pastures down to about 2 inches, except in bluegrass dominated swards where the residual height after grazing should be closer to 1 inch.

Such low grazing height residuals can restrict animal intake, so don’t let high producing livestock graze pastures this low.

The practice of first and second grazers would fit well when trying to achieve the low residual heights that promote more legume growth in pastures.

The first grazers would be livestock with higher nutrient requirements that would graze the upper sward. The second grazers would be livestock with lower nutrient intake requirements that graze the sward to the low residual heights.

Rotational grazing provides rest

Rotational grazing management is an important tool for maintaining legumes in pastures because it reduces the opportunity for animals to selectively graze out the legumes. This is especially true for when grasses become more mature.

Rotational grazing provides the rest period legumes need to rebuild energy reserves for strong regrowth after grazing. Rotational grazing also improves the distribution of urine and manure (i.e. recycled nutrients) across the pastured area.

Moving water sources and mineral supplementation can also be used to strategically distribute feces and urine across pastures. These practices will help maintain a more uniform soil fertility status across the pasture and reduce the need for chemical fertilizers.

Summary

Encouraging legume growth and keeping pastures vegetative (lower NDF levels) are the best methods for improving pasture quality and animal performance, while also reducing the need for expensive nitrogen fertilization. The management steps outlined here will help you begin to improve the legume content of your pastures in the coming year.

About the Author

The author is an associate professor in the Department of Horticulture and Crop Science at Ohio State University. More Stories by Mark Sulc

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