Alternative Forage Management Strategies for Summer Forage
(Lesson 6. Managing for a Year-Long Forage Supply continued)
Summer annual grasses such as sudangrass or pearl millet can offer an option for mid-summer pastures. They also produce lush, vegetative growth during mid-summer, and are therefore a good complement to cool-season pastures. However, summer annuals can be expensive, as a result of annual seeding. Good management including rotational grazing and/or staggered planting dates are needed to make summer annuals economically viable. The sudangrasses (and all sorghum species) can cause prussic acid poisoning if grazed after a killing frost. Pearl millet will not cause prussic acid poisoning. As a general rule, pearl millet produces better on lighter soils and sudangrass better on heavier soils.
Summer N Fertilization
Soil fertility on pastures is often overlooked as a management tool to increase summer forage production. To determine fertility needs, a lab should test soils, which can make fertility recommendations for your soil and climate. Contact your UMaine Extension county office or local NRCS office for information on soil testing and manure testing.
Nitrogen fertilizer will increase plant growth. In many instances N is applied to pastures in spring. If the pastures are harvested for hay, this is a way to increase hay production and may be a viable option. However, under grazing systems, forage is often in abundant supply in spring, so additional growth at this time may not be efficiently used by grazing animals. This can result in poor return from money invested in fertilizer. It may make more sense in a grazing operation to apply fertilizer in June. This way the additional forage production will occur in mid-summer, when additional forage is needed. The carrying capacity of the cool-season grasses is greater in mid-summer when N is applied later in the growing season.
How much fertilization can be profitably applied to pastures can be difficult to determine. Growing more grass does not make fertilization profitable. Remember, for every dollar spent on fertility (or any input), more than one dollar must be made in return. Therefore, fertilizing to grow more forage in the spring and letting that forage get too mature and lower in quality is not profitable. Nitrogen should only be applied to grass if additional forage is needed. Because most pastures are under-used in spring and over-used in summer, one application of 50-80 lb. N/ac. in mid-June to mid-July may be the most profitable in many pasture systems.
One thing to consider with N fertilization is that N can be applied to pastures in several forms. Supplying N to pastures by growing legumes or with animal manure can be an excellent option. Legumes can provide 80 -100 lb. N/acre to grasses in a pasture. In addition, over 80% of the legume N grazed by livestock is returned to the pasture through manure and urine.
Forage Legumes in Grass Pastures
Legumes benefit grass pastures by providing N to the grasses, by improving the distribution of forage growth through the grazing season, by increasing animal intake, and by improving animal performance. Clovers can make pastures more productive. To effectively use and maintain legumes in pasture systems, good pasture management is critical. Special attention to soil fertility and grazing management is needed to maintain legumes in pastures.
Forage legumes offer a number of advantages for pastures. However, there are several challenges for using legumes in pastures. Legumes can have poor persistence (particularly under continuous grazing) and low tolerance to poorly drained soils and low soil fertility. In addition, many legumes can cause bloat. As such, grass/legume mixed pastures are easier to manage than legume monocultures, and therefore may be desirable for pastures. Common legumes grown with grasses for grazing in Maine are alfalfa, red clover, ladino or white clover, and alsike clover.