It spreads by rhizomes to produce a thick sod and thrives in cold, damp weather on well-drained, rich soils with a pH of 6 to 7 (Table 1). Although Kentucky bluegrass may be found across the United States, it is most significant agriculturally in the north central and northeastern regions, where the average daily temperature in July does not surpass 75°F. The biggest limiting environmental condition for Kentucky bluegrass productivity is hot summer temperatures.
Table 1 shows the characteristics of Northeast perennial cool-season grasses.
|Grass||Seedling vigor||Tolerance to soil limitations||Winter survival rate||Tolerance frequency||Relative maturityb|
|apH of 6.0
bMaturity relates to the relative period of seed head emergence in the spring, which is affected not only by species but also by variation.
cL = low, M = moderate, H = high
Because it tolerates close and frequent grazing better than other cool-season fodder grasses, Kentucky bluegrass is present in most pastures in the northeastern United States. Because of this, Kentucky bluegrass is an excellent choice for permanently grazed pastures. Furthermore, the deep sod generated by rhizomes of Kentucky bluegrass makes it perfect for erosion management, especially in grass rivers.
The majority of Kentucky bluegrass types have been created for use in lawns. As a result, it is usually regarded as the most significant lawn grass in the United States. In the last 45 years, only three forage-type Kentucky bluegrass cultivars, ‘Park,’ ‘Troy,’ and ‘Ginger,’ have been introduced. Turf-type Kentucky bluegrass types need dethatching to be productive and, in general, require more nitrogen fertilizer and larger irrigation systems than forage-type cultivars.
Kentucky bluegrass seed is used in very few fields in the Northeast. However, Kentucky bluegrass usually grows in these areas from seed or rhizomes in the soil, especially if the site was formerly used as a pasture. When temperatures begin to moderate and showers become more regular, Kentucky bluegrass should be sown at a rate of 10 to 14 pounds per acre in late summer or early autumn. Higher seeding rates result in faster ground cover. Kentucky bluegrass establishes more slowly than many other cool-season grasses. The sluggish establishment is mostly due to slow germination (about 14 days). However, once established, it swiftly spreads because to its vast rhizome production. Because of its nitrogen needs and low summer output, Kentucky bluegrass is suited for sowing with a legume like white clover (4 pounds per acre), red clover (6 pounds per acre), or birdsfoot trefoil (8 pounds per acre). Kentucky bluegrass pastures with legumes have better nutritional contents than pure grass pastures (Table 2). Tall-growing grasses such as orchardgrass, timothy, smooth bromegrass, or tall fescue may also be added in a pasture sowing combination with Kentucky bluegrass when hay or silage harvests will be done each year prior to grazing. Tall-growing grasses often thin out and must be reseeded, but Kentucky bluegrass can last eternally.
Table 2 shows the effect of the percentage of legumes in a combination on pasture quality in Pennsylvania.
|aCP stands for crude protein, ADF stands for acid detergent fiber, and NDF stands for neutral detergent fiber.|
To thicken existing pastures, Kentucky bluegrass may be “frost seeded” (in early spring while the soil is still honeycombed with frost). A good seed-to-soil contact is required for successful seeding. Frost planting may do this by sowing into a field with a thin stand of existing plants or where the pasture was grazed “into the ground” the previous autumn. The best results are usually obtained when frost seeding is accomplished when the soil is still frosty. Delaying sowing until mid-morning, when the soil is slick on the surface, will result in weaker stand establishment.
sowing Kentucky bluegrass alone or in a combination into a traditionally prepared seedbed or no-till sowing may also be a good way to get it started. When seeding, do not plant any deeper than 14 inch. When done in combination with or after band seeding, press wheels or cultipacking increase seed-soil contact and the likelihood of a good stand. The seedbed should be solid in order to achieve the optimum sowing depth. As a result, before sowing, cultipack the seedbed.
Harvest or Grazing Management
Kentucky bluegrass reaches almost 70% of its annual forage output by early June under typical environmental conditions in Pennsylvania. As a result, appropriate management throughout the early growing season is critical in order to optimize output potential. Kentucky bluegrass is good for grazing because it grows to a lesser height than many other cool-season forage grasses.
In the spring, Kentucky bluegrass fields are often undergrazed, resulting in a buildup of mature, low-quality fodder. High stocking densities should be used early in the growing season when Kentucky bluegrass is most productive, or extra growth should be harvested as hay or silage. As grass growth decreases later in the grazing season, reduce stocking density. Grazing of Kentucky bluegrass should begin on south-facing slopes in mountainous locations because they warm earliest and begin growing early in the spring. Maintaining a stubble height of 2 to 4 inches in spring encourages tiller (new shoot) production, which aids in the maintenance of a thick sod. Excessive defoliation often results in weak rooted, open sod, and weed invasion. These impacts are more detrimental to Kentucky bluegrass during a dry summer, when it has fewer chances of recovering. Proper pasture rotation and relaxation boost Kentucky bluegrass output significantly.
In maintained pastures, Kentucky bluegrass has a high percentage of its leaves at the soil surface and below the grazing height. This makes it more resistant to overgrazing than most other cool-season grasses. As a result of abusive management, tall-growing grasses diminish, but Kentucky bluegrass volunteers and thickens, providing high-quality fodder and soil erosion protection. Heavy stocking numbers and continual overgrazing (common in sheep and horse pastures), particularly in June when grass growth has halted, can damage Kentucky bluegrass and encourage weed invasion.
As the development of Kentucky bluegrass slows in the summer, cattle productivity on these pastures decreases, especially during a dry growing season. Furthermore, Kentucky bluegrass has fewer grazing days per year and lower animal gains per acre than other cool-season, tall-growing grasses. Exceptions to this tendency may be seen at higher altitudes and latitudes when temperatures and rainfall are not as severe.
Depending on climatic circumstances and grazing management, the botanical composition of Kentucky bluegrass pastures fluctuates over and within growing seasons. The quantity of Kentucky bluegrass in a pasture will diminish under circumstances of high temperatures, insufficient rain fall, or poor soil fertility, enabling undesired weed species to enter. Grazing management has a significant impact on the ratio of Kentucky bluegrass to white clover in a pasture. As the quantity of clover in the pasture decreases, the grass may be grazed more closely, causing the clover to compete less with the grass. If there is too much white clover in the pasture, letting it to grow to a height of 8 to 12 inches can encourage the Kentucky bluegrass to compete better with the white clover. Furthermore, nitrogen fertilizer promotes the Kentucky bluegrass component of the pasture and may be utilized to change the clover to grass ratio.
Soil testing should be used to evaluate the lime and fertilizer requirements of Kentucky bluegrass. The soil pH should be between 6 and 7 for optimal results. If a considerable number of nutrients are required by the soil test, they should be supplied prior to planting and integrated into the seedbed. If the Kentucky bluegrass has already established, surface application of the appropriate fertilizers is equally advantageous.
Nitrogen application to Kentucky bluegrass is not suggested if the pasture contains more than 30% legumes. Applying 25 pounds of nitrogen fertilizer per acre to Kentucky bluegrass in early spring before green-up will accelerate growth and enable grazing to begin sooner. Additional nitrogen treatments should be provided to pure Kentucky bluegrass stands in late spring and early autumn, when the grass is developing fast. Remember that nitrogen treatment will boost the competitiveness of the grass at the cost of clover and weeds in the stand. By adding lime and fertilizers according to soil test recommendations, Kentucky bluegrass-white clover pastures may be maintained permanently and their fodder quality increased. In a recent research, when soil pH was corrected to 6.5 and 60 pounds per acre of P2O5 and 30 pounds per acre of K2O were treated to a Kentucky bluegrass pasture, total digestible nutrient output, carrying capacity, and beef production rose by 50% compared to unfertilized pastures. An extra treatment of 120 pounds of nitrogen per acre enhanced meat yield by 39%.
Many of the same diseases affect Kentucky bluegrass as they do other cool-season forage grasses. These diseases have a low impact on plant persistence, but they may diminish production and quality.
Grubs are the most damaging to Kentucky bluegrass meadows. Adults of the Japanese beetle, May beetle, green June beetle, northern masked chafer, and European chafer lay eggs in overgrazed bluegrass pastures, and the larvae feed on bluegrass roots and rhizomes. During dry years, damage is the most severe and rehabilitation is the slowest. In Kentucky bluegrass fields, controlling insects is most readily accomplished via excellent grazing and fertilization methods that maintain a strong and robust grass stand.
Marvin H. Hall, associate professor of agronomy, wrote this.