Weed Control in Established Warm Season Perennial Pastures

The importance of weed control in improved as well as native pastures is an essential element in pasture management. A producer can expect to gain one pound of desired forage or grasses for every one pound of weed destroyed. Thus potential yield increase can be as high as 75% in severely weed infested fields.

 Herbicide applications are the most common means of weed control. Herbicide should be applied at spring green up in March through early May depending on weather conditions and locations. The type of herbicide and rate of application used will be determined by the type of weeds, growth stage, soil type, as well as management objectives. If clovers are to be managed in the fall, do not use any chemical with extended residual control. Products such as Grazon P+D, Amber or Ally should be used with caution. Products such as 2,4-D, and Weedmaster have proven their ability to provide adequate broadleaf weed control without excess residual effects

 Depending on the severity of weed infestation, a second application of herbicide after the first hay cutting or graze down may be required.

 Another effective and relatively inexpensive means of weed control is mowing or shredding. This is very beneficial in controlling annual weeds. This method of control is best utilized when weeds begin to flower, but before seed set. Shredding can be utilized not only to control weeds but also to enhance forage quality and forage growth, thus is most beneficial in grazing operations.

 When Mowing or shredding, leave at least six inches of stubble height. Initial shredding should be done according to weed development, plant growth and flowering stage of the plant. In severely infested pastures, early shredding may be beneficial to reduce weed competition. Thus allowing more sunlight and space for desirable grass development.

Fertilizing Established Warm Season Grasses

Fertilizing established perennial warm season grasses will be determined by management practices and intended use of pasture or land. Many grasses have the capability of utilizing different levels of nutrients, and some grasses respond better to higher levels of fertilizer than others do.

 The most commonly used fertilizer components applied to pastures are Nitrogen (N), Phosphate, (P205), Potash (K20), and to a lesser degree lime (Ca). In lower pH soils, applications of lime (Ca) may need to be applied. In high pH soils with excessive sodium or calcium, Gypsum applications may be required. The application of either lime or gypsum should be confirmed by a soil test. Most micro nutrients such as Zinc (Zn), Iron (Fe), Magnesium (Mg), as well as other micro nutrients are typically ignored, however, deficiencies of these nutrients can retard plant growth and limit utilization of major nutrients such as N, P, K, and Sulfur.

Fertilizing for Grazing Purposes

It is recommended, that most Phosphate, Potash, Lime and gypsum should be applied and incorporated (mixed in the soil) to receive full utilization and benefit from these fertilizer components. By incorporating these elements into the soil, these nutrients are placed in the root zone, where maximum utilization can be obtained. Application of these nutrients should be done every 2 -3 years, during stand renovation or soil aeration practices. Soil test on an annual basis to monitor nutrient levels in the soil.

 When moisture is adequate, nitrogen applications, for grazing management should be applied in two applications per season. The first topdress application should be applied at spring green-up between March and May (depending on location and climate). For most grasses, 40-50 units of Nitrogen is adequate for the first application. This will give the desirable grasses a boost of top growth, reduce weed competition as well as increase forage quality. A second application of 40-50 units may be applied after the first initial graze down or in midsummer. Always apply nitrogen fertilizer when expected rains persist to reduce losses due to denitrification and volatilization.

Fertilizing For Hay Production

For hay production, a more intense fertility program is required. Since most of the forage is being removed, very little nutrients are being replaced. One could say, that hay production is a method of mining the soil of its minerals and nutrients, therefore fertility practices are the most important management objective in obtaining high quality and high yielding hay.

Potash (K2O), phosphate(P2O5) and micronutrients should be applied and incorporated to receive full benefit of fertilizer components. These components will need to be replaced more readily or in higher amounts than in grazing pastures and should also be done during stand renovation or aeration practices.

Nitrogen applications should be applied throughout the season. Most improved grasses respond well to 120-180 units of nitrogen per season. For native grasses, 80-120 units of nitrogen per season are adequate. These rates should be split into two to three separate applications, depending on the number of cuttings expected per year. The first topdress application should be applied at spring green up, the subsequent applications after each hay cutting. Soil tests your fields on an annual basis to monitor nutrient needs.

Over-seeding Cool Season Forages in Perennial Grasses

Warm Season perennial grasses may be over-seeded with cool season annuals to obtain year around grazing and total land utilization. This can be accomplished by using a no-till drill or an aerator/ soil scarifier and planter such as the Vaquero.

Warm Season Perennial Grasses (New Planting)

Warm season perennial grasses are normally used for permanent or semi-permanent pastures, or hay production. There are two categories of warm season perennial grass; native or improved (introduced) varieties. Native varieties refer to those plants that originated from a specific area and at some point in time the dominant range or pasture forage. Introduced species are those species which were introduced into an area, from a different origin. Many introduced species have become well acclimated to a specific area and are considered naturalized species. The term perennial refers to a plant that lives for many years. Or it could be said that these grasses with proper management are permanent.

What Type of Grass to Plant

Plants selected for seeding depend on management objectives. Many grasses are better suited for grazing and others are more suited for hay production or intense management. Often, mixtures of native and/or introduced species are seeded together, partly as an attempt to simulate natural conditions. Using a mixture is helpful because all areas have variations in soil, moisture and slope, and each species in the mixture is adapted better than other species to certain site characteristics. For instance, variation in rooting habits of species in the mixture allows for more efficient use of moisture and nutrients from the various soil depths. Also, the mixture usually extends the grazing season because each species varies slightly in its period of lush growth and dormancy. Finally, a mixture provides a varied diet that is more desirable to animals.

Under certain conditions, a pure stand of a single species is more desirable. Species low in palatability and needing special management, or species requiring intensive management, should be planted alone. In addition, many introduced species are easier to manage when planted in a pure stand.

Usually, plants best adapted to an area are native ones or adapted strains of introduced or improved species. It is best to select grasses that are growing in the area, so it is important to determine the original source of seeds of native species. When available, use certified named varieties. Generally, seed of native species should originate from local sources or from within 200 miles north or south and 100 miles east or west of the area to be seeded.

 Use seed of known quality. Know the germination and purity of the seed, since seeding rates are based on pure live seed (PLS).

Where to Seed

Planting pasture or rangeland is expensive and the risk of failure is always present, carefully consider areas to be planted. When the management objective is to improve range or pasture condition, evaluate the quantity and distribution of current desirable plants. If desirable plants make up less than 10 to 15 percent of the vegetation, seeding may be necessary. If desirable plants are uniformly distributed and make up more than 10 to 15 percent of the vegetation, use grazing management or weed control practices to improve range condition.

Often however, another management decision dictates the necessity for planting. For example, seeding usually is necessary following a brush control method, such as root plowing that destroys the existing sod. Also, when a better seasonal balance of forage supply is desired, seeding usually is required because the species needed to extend the period of green forage are not present. These plants often are introduced species and are seeded in pure stands.

In addition, seeding is the most effective way to establish desirable vegetation on abandoned cropland, since natural re-vegetation processes may take 50 to 100 years on land barren from farming. On other bare areas, such as newly constructed dams and newly laid pipelines, seeding to establish a plant cover often is necessary to prevent wind and water erosion.

 Seed only those sites having sufficient potential to insure reasonable chances of success. First, survey the area to determine if there is a mixture of range sites or if one predominates; then, decide whether the sites are suitable for planting. If the area is a mixture of sites, expend the most effort on ones with the best chance for success. Select planting sites so the area can be incorporated into the overall ranch management.

Sites with sufficient soil depth for adequate root development and water storage or sites that can be modified mechanically to accomplish a greater effective soil depth usually are suitable. However, avoid barren, rocky sites, which have greater temperature extremes at the soil surface and are more droughty than sites with soil and litter on the surface. Low soil moisture and wide temperature extremes can kill plant seedlings.

Although the amount of precipitation received on an area cannot be controlled, select sites that receive runoff water, thereby increasing the amount of moisture available. However, do not disturb steep, potentially erosive areas.

Seedbed Preparation

Seed bed preparation is the most important practice in establishing warm season perennial grasses. This practice is the single most important and overlooked practice of ranchers and livestock mangers today. More planting failures can be avoided by proper seed bed preparation.

 One phrase to always remember in concerning seedbed preparation is “THE SMOOTHER THE BETTER”.

 An ideal seedbed is firm below seeding depth, free of weeds and has moderate amounts of mulch or plant residue on the soil surface. A major purpose of seedbed preparation is to reduce existing plant competition.

Keep seedbed clean until planting, this may include additional “shallow” (2″) cultivation, to remove germinating weed seedling. Before planting it is recommended that the field be rolled or firmed by rain to ensure a firm seedbed.

When to Plant

Planting warm season perennial grasses should be done when seedlings will have the longest possible period of good growing conditions for establishment. Planting should be timed so that seed can germinate as soon as the favorable growing season begins. Seedling growth may be curtailed by low temperatures, dry weather, or competition from weeds or other vegetation.

 Planting in the late spring and early summer is most successful in the southwest were spring rains and summer rains prevail. The exact date depends on the local precipitation pattern, the species used, the method of planting and the time of weedy growth.

In many areas, where fall rains persist and potential frost date is late,(late November or early December) fall plantings have been beneficial. Fall plantings should be done early enough to allow plant growth 60 -90 days before first frost.

Planting Methods

The two most common methods of seeding perennial warm season grasses are drill planting (row) and broadcast applications.

 Drilling is a superior method because the seed is placed in the soil at a controlled planting depth, thus improving the probability of stand establishment. When using this planting method, the seedbed must be clean, free of rocks, stumps and other litter. This method is not suitable for rocky rough terrain, as associated with many range seeding.

Broadcast applications refer to spreading the seed over the soil surface. Broadcast applications can be accomplished through scattering the seed by hand, rotary spreader, with air stream or exhaust or seeder boxes of the fertilizer-spreader type. Broadcast seeding seldom is effective without some soil disturbance before the seeding operation. Small, slick seed lend themselves to broadcast seeding much better than fluffy seed.

Seeding Rate

Seeding rates depend upon the species, method of seeding and potential site productivity. Seeding rates of many grass species are based on pounds of pure live seed (PLS) per acre. PLS is the percentage of the bulk seed material that is live seed. This is determined by multiplying percentage germination by percentage purity of the lot of seed. When hard seed are involved, PLS = (percent germination + percent hard seed ) x percent purity.

Planting Depth

Optimum seeding depth is dependent on seed size. Since smaller seeds have a smaller quantity of stored energy, do not seed them as deeply as larger seed. As a rule, grass seed should be planted 1/4 inches deep . When using a mixture of small and large seed, always plant at the depth of the small seeded variety in the mixture. Planting small seeded grass seed too deep is the single most reason for crop failure.

Management After Planting

Protect a newly seeded area from grazing until plants are established. Some species establish sooner than others, but in general, plants should be well rooted before grazing to prevent pulling up the seedlings. Length of deferment from grazing varies. In exceptionally good growing conditions, deferment through one growing season may be sufficient. During periods of harsh growing conditions, however, 2 or 3 years of deferment may be necessary. Grazing during dormant periods may help improve the stand by scattering and trampling seed into the soil. After plants are established, practice good grazing management to maintain the seeded stand.

During the first year little growth may be observed with perennial forages. Some perennial grasses may show only a few small brown leaves their first dry season and be almost invisible until they resume growth the next year. Because of this, plantings should not be plowed or replanted until they have had ample time – at least 2-3 years to demonstrate success.

Newly seeded perennial grasses need to be protected from grazing until the seedlings are large enough to withstand pulling and trampling by livestock. This may require 1- 3 years. depending on weather, and other growing conditions. As a rule of thumb it is best to keep livestock off newly seeded pastures until seed heads appear. Weather it be after the first growing season or after several years.

Weed Control in Newly Planted Perennial Warm Season Grass

Weeds compete for moisture, light as well as space and nutrients. In newly planted warm season perennial grasses, weed control is required, to ensure adequate growth and stand establishment.

Early weed control begins during the fall before the initial spring planting, during seedbed preparation. Early seedbed preparation consists of deep disking and or chisel plowing, in mid November or December. Remove, all existing forage or ground cover is recommended. At this time apply and incorporate all phosphate, potash, micro- nutrients and lime as required by a soil test. Do not apply any nitrogen. Level seed bed to desired smoothness.

 Allow fall and winter rains to firm seedbed and build up subsoil moisture. As weed seed began to germinate, cultivate field very shallow, to remove newly sprouted weeds. This may be done several times before planting.

 After planting, weed control in perennial warm season grasses is best managed by shredding. Herbicide applications can injure or weakened grass seedling, so it is not recommended to spray any herbicide until stands are established, or after the first growing season

Fertilizing Newly Planted Perennial Grasses

When fertilizing a newly established perennial warm season grass. A soil test is recommended. Many people attempt to guess on what the crop needs, however they are normally unaware of what is actually needed.

During early season land preparation, (November- December) apply and incorporate all required potash, phosphate, lime and micro nutrients (Zn, FE, Cu etc.) as recommended by soil test. Incorporating these elements by deep disking will ensure that adequate nutrients are in the root zone area (6-8 inches below soil surface) and reduce losses due to leaching and washing. Fertilizing during this period will also allow time for fertilizer to go into soil solution and be readily available when required for adequate plant growth during the spring the following year.

Since initial growth of perennial grass seedlings are slow, and the main emphasis in early season growth, is root development no nitrogen fertilizer should be applied until the newly planted grass seedling are 6″ in height. At this point, a top dress application of nitrogen may be applied to stimulate top growth and yield.

Applying nitrogen fertilizer, before or at planting will create excessive weed competition, and will not be adequately utilized by desired grass seedlings. The application of excessive nitrogen at early stage of growth (seedling to 5-6 leaf stage) will only increase cost of establishment, not only in fertilizer cost but weed control cost as well.