LSU AgCenter's Weekly Message

Managing Erosion in the Landscape – Part 2

My last article addressed some general aspects of soil erosion. This week’s article is about one factor that affects how much erosion occurs and that many people can manage to some extent: the amount of cover on the soil.

Leaves and roots of plants play major roles in reducing erosion. Plant characteristics that help with erosion management include the following: more complete soil coverage by the plant canopy; faster establishment; fine, fibrous roots that extend laterally and help hold onto the surface layer of soil; and deep roots that anchor soil.

The best plant or mixture of plants for minimizing erosion on a site also depends on many of the same factors that play into the “right plant, right place” principle for any location. Plants need to be suited to the amount of sun or shade the site gets, how wet or dry it is, and the overall climate of the location. Some examples of plants that might be used erosion management are mentioned in his article, but many other options exist.

When possible, one option is to preserve the vegetation that’s already there. Unless you’re ready to implement a better plan for reducing erosion, avoid killing the vegetation that you have. Even moss can help reduce erosion.

One of the fastest ways to establish thorough soil coverage quickly is by laying grass sod. On a slope, lay strips of sod across the slope, beginning at the base. As you move up the slope, make sure that the seams between pieces in one row do not line up with seams in the next row but are staggered in a brick-like pattern. Sod staples or stakes can be used to help hold sod in place as roots grow into underlying soil. Be sure to choose a turfgrass suited to the climate and sun level of the site. With enough care, warm-season turfgrass sod can be installed year-round, but better establishment is expected between April and September. If needed, adjust soil pH and nutrient levels prior to sodding, according to soil test results.

If laying sod is outside of your money or time budget, you can seed some types of grasses, or mixtures of grasses with other species. Plant seed at an appropriate time of year for the chosen species or, on the flip side, choose species that can be successfully seeded when you plan to seed. For example, if you are seeding warm-season grasses like bermudagrass or bahiagrass, you can do this between March and July. Later in the year, you could seed ryegrass or cereal rye for temporary cover. Optimal seeding dates for these are between mid-September and mid-October.

Straw or hay helps hold seed in place while it gets established. USDA Natural Resources Conservation Service (NRCS) standards instruct that 70 percent of the ground be covered when hay or straw is used as mulch. Seventy to 90 pounds of hay or straw, or 1.5 to 2 square bales, per 1000 square feet, is expected to provide this amount of coverage. Netting or another way of holding the hay or straw in place may be needed. There are also commercially available erosion control mats made with straw, jute, coconut coir, or other materials.

Besides sodding or seeding grasses, another option to consider is transplanting vetiver grass (Chrysopogon zizanioides). This deep-rooted grass is well known in many parts of the world as an erosion management tool. Vetiver grass grows to approximately 8 feet tall. It’s best suited to full sun

and is cold hardy to approximately USDA Hardiness Zone 8B. While vetiver grass is native to Asia, the commonly sold sterile variety ‘Sunshine’ is named for Sunshine, Louisiana.

Primrose jasmine (Jasminum mesnyi) is another plant that has been suggested for slopes in Louisiana. This yellow-flowered evergreen shrub has a sprawling habit, growing to approximately 8 feet tall and wide. It tends to root where branches touch the ground, adding to its value for erosion management. It is suited to light conditions ranging from full sun to partial shade, though it likely won’t grow well in very wet areas.

If you plant shrubs or trees on a slope, mulch around them to protect soil while plants get established and extend their canopies. On a slope, mulches such as pine straw, wheat straw, or hay are more likely to stay in place than materials like pine bark nuggets and coarse wood chips. Another option is to establish grass or another groundcover and then plant trees or shrubs within mulched circles.

Some soil preparation will be needed when planting on a slope, but there may be a tradeoff between soil preparation for best plant growth in the future and management of erosion in the present. Try to minimize soil disturbance as you spread any needed lime or fertilizer.

Sometimes mulch alone is a reasonable temporary cover. Hay or straw and erosion mat options are mentioned above, following the paragraph about seeding grasses. If you have an inexpensive source of wood chips or other wood products available, these can also be used, but they should be spread to a depth of at least 2 inches.

If you have a significant erosion problem, you might also consider contacting your local USDA NRCS office. Erosion management is one of their specialties.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).