lanting date also means grazing is delayed until about February for a legume-grass mixture depending on the location. Cutting or grazing the warm-season grass to a 2 to 3 in. height before planting is very important. Emerging cool-season pasture seedlings require sunlight for survival and good growth. This is especially true for small seeded legumes. Carbohydrates stored in the seed provide the energy for seedling emergence and early seedling growth. From this point seedling survival and growth are dependent on the cotyledons, unifoliate leaf, and the first trifoliate leaf receiving sunlight to carry on photosynthesis. A management practice that has worked well is to continue grazing after planting and clover emergence. Hoof damage from grazing cattle has been less detrimental to emerging clover seedlings than competition from the grass sod.
Selecting the Best Legume Species
Selecting the best forage species adapted to your soils is critical for obtaining a good stand and having a profitable pasture system. Soils vary in texture (sand, loam, and clay), slope, internal drainage, nutrient content, pH, water holding capacity, and soil pests such as nematodes. Producers have some influence over the soil nutrient level and pH, but very little control over the other soil characteristics. We cannot change the soil texture, at least not economically. The best soils are generally used for food and grain production. Marginal soils not suited for row crop production because of slope, rocks, low nutrient and water holding capacity or poor drainage are usually planted to forages. Identification and description of soils should be available at the county office of the USDA Natural Resource and Conservation Service.
Temperature and rainfall amount and distribution are the main climate factors influencing plant adaptability. Temperature extremes such as the minimum winter temperature are more likely to determine forage species adaptability than temperature averages. Rainfall distribution during the growing season is more critical than total rainfall. The previous paper discussed where the various legume species are best adapted. Additional information can be obtained from the local County Agricultural Extension Service, Natural Resource Conservation Service, or nearby Agricultural Research and Extension Centers.
Caution should be exercised in planting forage species developed in other countries or areas of the US. Varieties developed locally are usually better adapted and more productive than those from other regions. It is best to plant only a small acreage of a new forage variety the first year to observe how well it performs before making a large investment in seed, land preparation, and labor.
How Many Acres to Plant
Estimating how many acres to establish is dependent on the number and size of animals, management level, and local climate. A general rule of thumb is a good winter pasture can be stocked with approximately 600 pounds of body weight per acre (1.5 – 400 lb calves/acre, 1 – 600 lb calf/acre) in the fall and winter after the pasture has reached a height of 6 to 8 in. A stocking rate of about four pair per acre should be used in estimating number of acres for limit grazing (2 hr/day, 4 hr every other day) for beef cows nursing calves. If grazing full time, about 1.5 acres are needed per cow-calf pair.
Forage production will increase 2 to 3-fold during the spring. Proper stocking for fall and winter will result in excess forage in the spring. A producer needs to use this extra forage wisely. Additional livestock can be added in the spring or the excess growth can be harvested for hay, greenchop, or silage. Excess spring growth must be utilized on overseeded pastures so as not to hinder the recovery of the warm-season perennial grass. This may be a problem if upright species like crimson and arrowleaf are managed for reseeding.
Site Selection
Wet, cloudy weather during the winter months usually results in bogging problems when winter pasture is planted on a well prepared seedbed (disked 4 to 6 in. deep). This is a major problem where soils are level or have poor surface and/or internal drainage. The best drained pasture on the property should always be selected for winter pasture. Overseeding winter pasture on a summer grass sod (bermudagrass, bahiagrass, dallisgrass, etc.) will help provide firm footing for livestock and reduce bogging. However available grazing of overseeded winter pasture is usually 2 to 3 months later than that planted in a well-prepared seedbed.
Planting a combination of prepared seedbed and overseeded pasture is a good option. The prepared seedbed can be grazed first since it will provide earlier grazing. Livestock can be moved to the overseeded pasture during wet periods when bogging is a problem on prepared seedbed pastures. Another consideration in site selection is to avoid areas sprayed with certain herbicides the previous summer. Pasture herbicides Grazon P+D, Ally, and Amber persist in the soil and may kill legume seedlings that emerge for a year following herbicide application.
A soil analysis is a profitable investment, especially for legumes. The soil pH needs to be at least 6.0 for most forage legumes for good establishment, growth, and N2-fixation. If raising the soil pH is necessary, lime needs to be added 3 to 6 months before planting legumes to provide sufficient time for the lime to work. Very fine lime increases soil pH more rapidly than regular lime and is usually a better buy even though it may cost $5/ton more. A soil analysis will also determine if phosphorus, potassium, or other nutrients are limiting and how much should be applied. If any nutrient is deficient, legume growth, and N2-fixation will be reduced.
Buying Seed
Seed quality and rates are an important part of a successful winter pasture program. Quality seed is always a good buy. Buying variety non-stated (VNS) seed has risk associated with it. When seed of a particular species is in short supply, varieties adapted to other areas of the U.S. may be shipped in. Seed that cannot be certified because of contamination by other varieties, species, or weeds is also sold as variety non-stated. Planting a named variety will help ensure that you plant the best adapted variety that will produce the most forage. All planting seed is required by state law to have a seed tag. Information on the seed tag will state the variety, where grown, germination percentage, weed seed content, and date of germination test. Most state seed laws require a germination test within nine months of sale date to prevent the seed retailer from selling last year’s seed without an updated germination test.
A producer should decide early which variety and how much seed will be needed so prices can be compared from different sources. Most retail forage seed dealers will not have more than two or three legume species in stock. However, they are able to obtain seed of most legumes if given sufficient time. When planting a legume species for the first time, it is important to inoculate the legume seed properly with the appropriate bacterial strain. The inoculant should be purchased when the seed is bought. Be sure the name of the legume is stated on the package and that the expiration date has not passed.
Seeding Rates
Seeding rates for the various legume species were listed in the previous paper on legume species. Small grains are usually planted at 100 lb/acre and ryegrass at 25-30 lb/acre when planted in a pure stand. Mixtures containing legumes and small grains or annual ryegrass, should be planted at 2/3 of the recommended seeding rate for a pure stand. For example the seeding rate for a ryegrass (25-30 lb/acre) and crimson clover (16-20 lb/acre) mixture would be from 15 to 20 lb ryegrass and about 12 lb crimson clover seed per acre. Inoculation of legume seed within 24 to 48 hours before planting is recommended for good nodulation to maximize the amount of N2 fixation by the legume. A more detailed discussion on seed inoculation is in the section ‘Legume nitrogen fixiation and transfer’.
Planting Methods and Equipment
Generally, the larger the seed, the deeper a seed can be planted. It is desirable to place seed as deep as possible without reducing emergence. After a rain the soil surface begins drying progressively downward. The deeper the seed, the longer moisture is present to support germination, emergence, and seedling growth. Seed drills, if adjusted properly, place more of the seed at the desired depth than broadcasting the seed on the soil surface and covering by a light disking or dragging. Shallow planted seed will germinate with moisture but may not be able to establish a root system before the soil surface dries out. This is especially true on sandy soils when rainfall of about 0.5 in. or less initiates germination. Seed planted too deep will germinate but the shoot may not reach the soil surface so the seedling dies. Seeding rates should be increased from 25 to 50% when broadcasting seed to obtain the same stand as drilling seed at the proper depth. All forage legumes described earlier except vetch should be planted from ¼-to ½-in. deep, depending on seed size. Vetch should be seeded about ¾-in. deep. Optimum planting depth is ½-in. for annual ryegrass and ¾-to 1-in. for small grains.
The best stands are obtained when planting in a prepared seedbed because all existing plants have been removed and a smooth, firm seedbed allows for accurate seed placement. The poorest stands occur when overseeding a grass sod because it is difficult to place the seed in the soil at the desired depth and the grass sod competes for limited soil moisture, nutrients, and light. Light disking is a compromise between the two that provides some loose soil, reduces competition from existing plants, but does not destroy the existing grass sod.
Planting equipment for legumes and cool-season annual grasses varies from a fertilizer spreader to expensive drills. Because clovers and annual ryegrass are planted at shallow depths, they can be mixed with the initial fertilizer application and broadcast on a prepared seedbed. It is important to drag the pasture after planting to cover the seed. Rolling will enhance seed-to-soil contact and seal in any available soil moisture. Broadcasting small seeded clovers and ryegrass on undisturbed grass sods results in thinner stands and must be delayed until late autumn when temperatures are cooler. These cooler temperatures also slow legume seedling emergence and growth. If seed is mixed with fertilizer, it should be spread within 6 hours to avoid reduced seed germination and seedling vigor and death of the rhizobia bacteria applied to the legume seed. Planting with drills and sod seeders is more expensive and requires more time but better stands are obtained with less seed. This is especially important when planting clovers because a pound of clover seed is 3 to 10 times more expensive than a pound of ryegrass or small grain seed.
| Next: Nitrogen Fixation | Back to Cool Season Legumes |
