Publication Number 460-119, posted January 1997
The purpose of this publication is to define recommended strategies for converting the Sericea-dominant vegetation typically found on older surface mined benches to more favorable forages that can be more effectively utilized by livestock. Techniques for suppressing the growth of Sericea Lespedeza so as to establish quality forage species and for managing the resultant pasture or hayland area were developed from research conducted at the Powell River Project Education Center site between 1980 and 1987.
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Sericea is also able to survive in soil conditions where there are very low levels of soil phosphorus in forms generally considered to be "plant available." The phosphorus requirements of Sericea are very low, compared to those of common forage species. In addition, Sericea is able to utilize soil phosphorus bound in chemical forms that cannot be effectively utilized by other species. These characteristics enable Sericea to thrive on many older surface mine benches, especially where available soil phosphorus levels are low because of the high phosphorus fixation capacities of many minesoils.
Sericea's growth cycle begins in late spring, when it sends up new shoots from the "crown" which occurs where the root mass comes together, just below the soil surface. As this new shoot growth comes up, it draws on the nonstructural carbohydrate energy reserves stored in the fleshy taproot from the previous year's growth (Figure 2). The maximum rate of growth occurs during the June-July period, after which shoot growth begins to decrease. Then, the plant begins to route the majority of the nutrient reserves generated through photosynthesis back into the taproot for winter storage. In late summer (early September) Sericea begins to flower, stemminess increases as does the tannin content in the plant leaves. Tannins are plant compounds similar to those found in unripe fruit which render Sericea unpalatable to livestock and may act to bind plant protein in the animal's gut. This effectively reduces the already low nutritional value of the Sericea forage. As fall turns to winter, the above ground growth turns into woody biomass that is high in tannins and unpalatable to most forms of livestock. In succeeding years, this biomass, which decomposes very slowly, begins to build up on the soil surface, suppressing the growth of competing species. The dead, standing biomass often becomes a thicket that is difficult to penetrate on foot.
Sericea vegetation is moderately palatable to livestock only during a brief portion of the year -- the late spring-early summer period of rapid growth. During that time, cattle prefer the emergent portion of the shoots to many other foods that are available in a typical, unmanaged, reclaimed mine pasture. During the remaining portion of the year, cattle will eat the Sericea as a last resort, when all other food sources have been consumed. Since the nutritional value and palatability of this forage is low, cattle may not achieve optimum weight gains even though given access to large areas of pasture. The resultant low potential live weight gains adversely affect the cattle producers' goal for more efficient livestock production.
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June-July, Year 1: Suppress the stand of Sericea Lespedeza. This can be accomplished by grazing or mowing the stand to the ground, or by applying a suitable herbicide. Producers should obtain and use current approved herbicides and rates of applications for their area. These can be obtained from local extension offices. This should be done during the period of maximum shoot growth, which will cut down on the amount of nutrient reserves that can be sent to the crown for re-growth the following spring. Once all the leaves have been removed, the plant is unable to generate carbohydrate reserves by photosynthesis for storage in the taproot and other fleshly roots.
Fall (late September - early October), Year 1: The first step in fall management will be to mow the Sericea close to the ground or burn the area. The mowing should be followed by a light disking, if possible. Both activities should precede application of fertilizer and seed, as required to establish an annual cover crop.
Fertilization rates should be determined by a soil test. If the test is to be conducted by the Virginia Tech soil testing lab, the box should be plainly marked as containing either a "minesoil" (i.e., blasted overburden; topsoil substitute) or a recycled topsoil, as appropriate, to assure that appropriate soil testing procedures are utilized. Those unfamiliar with soil testing procedures should contact their local extension agent for details on how to sample, where to send the sample, and how to interpret the results. Phosphorus (P) and potassium (K) are the primary fertilizer nutrients to be applied at this time.
A cover crop of a rapidly growing, annual species could be sown to establish organic matter in the soil (Table 1). This crop will take up nutrients that have been applied by fertilization. When these plants are deposited on the soil as litter, nutrients are released and recycled to the roots of other plants growing in the area. The primary purpose for the cover crop -- aside from holding the soil in place -- is to take up as many fertilizer nutrients as possible into the above-ground biomass tissue.
Table 1. Recommended fall cover crop species and seeding rates.
| Common Name | Scientific Name | Seeding rate (lb/a) |
| Crimson Clover | Trifolium incarnatum | 20-25 |
| Winter Oats | Avena sativa | 60-80 |
| Rye | Secale cereale | 90-100 |
| Annual Ryegrass | Lolium multiflorum | 20-30 |
The cover crop should include both grass and legume components. Grasses to be considered are annual rye grass, cereal rye or winter oats, wheat or barley. The purpose of the legume species (such as red or crimson clover, or hairy vetch) is to fix atmospheric nitrogen for recycling to next year's vegetation and to provide a more balanced forage for grazing animals.
The fall seeding can be accomplished by broadcasting seed into the Sericea stubble.
Spring (April or May), Year 2: The cover crop should be removed by a close grazing or a mechanical cutting. Remnants of the Sericea stand will generally shoot up at this time. The cover crop can be harvested for hay or straw, or mowed and allowed to remain as mulch.
June - July, Year 2: Suppress the Sericea stand again, as during the previous year.
Fall, Year 2: Fertilize, and establish desired pasture species. Suitable species are listed in Table 2. P and K fertilizer should be applied at rates consistent with the results of a soil test. It is vital to establish one or more legume species if the pasture is to be a self-sustaining source of nutritious forage. Hence, the soil test should also check the levels of micronutrients necessary for the planned legume species. Lime should also be applied if the soil test shows a need to raise soil pH. Once again, seed can be broadcast into the Sericea stubble.
Table 2. Recommended fertility levels and soil pH's for various pasture species
Species | Legume | Soil pH | P Fertility Requirement* (lbs./A) | K Fertility Requirement* (lbs./A) | Seeding Rate (lbs./A) |
| Alfalfa | yes | 6.5-7.0 | 110-140 | 110-140 | 10-15 |
| White Clover | yes | 6.0-6.5 | 90-120 | 60-90 | 1-2 |
| Red Clover | yes | 6.0-6.5 | 90-120 | 60-90 | 4-6 |
| Annual Lespedeza | yes | 5.8-6.2 | 60-90 | 30-60 | 15-20 |
| Tall Fescue | no | 5.6-6.2 | 90-120 | 90-120 | 20-30 |
| Rye Grass | no | 5.8-6.2 | 30-50 | 30-50 | 10-15 |
| Switchgrass | no | 5.8-6.2 | 75-100 | 75-100 | 4-6 |
| Sweet Clover | yes | 6.5-7.0 | 40-70 | 50-80 | 15 |
| Birdsfoot Trefoil | yes | 6.0-6.5 | 40-70 | 50-80 | 4-5 |
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Typically, both P and K fertilizer will be necessary to bring the minesoil up to a high fertility level. Liming will also be desirable in some situations, as soil pH should be at least 5.7. The potential productivity of the soil will be a key determinant of the economic benefit of fertilizer and lime expenditures. In general, it will only make good economic sense to invest in fertilization and/or liming on soils where productivity is not limited by physical factors, such as heavy compaction and/or shallowness to bedrock. As a general rule if the Sericea and associated vegetation are not thriving on a particular area, it will not make economic sense to invest in fertilization and liming.
Fertilization and liming are vital components of the conversion process for a number of reasons. First, low fertility (especially low P) favors Sericea over other legume species, since Sericea is well adapted to low P conditions. Secondly, most agronomic legume species do best at moderate pH, high soil fertility conditions. If these conditions are not established, then the agronomic legumes will not thrive. A healthy legume species is vital to any forage crop production system.
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However, both Sericea and tall fescue suffer from the problem that their digestibility is reduced in late summer, so from an animal management standpoint, this lower cost option may not be as desirable as converting the existing vegetation to a more typical agronomic forage crop mix.
Where tall fescue is present in small quantities, the fescue component can be increased at the expense of the Sericea by keeping the pasture closely grazed or mowed during the May-June-July portion of the year. The area should be fertilized with as much P as the owner can afford, up to the recommended level from the soil test. If possible, an alternative legume should be established, with the objective of supplementing the forage protein content during times when Sericea and fescue are both low in nutritional value. Recommended legumes for these situations are ladino clover, red clover, and annual lespedeza.
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