Editors Note: Last week we introduced a chapter from the University of Minnesota’s home study beef course written by Greg Cuomo, of University of Minnesota’s College of Food Agricultural and Natural Resource Sciences, and Kirby Hettver, a former UMN Extension Educator who now manages his family farm full time. It described the importance of managing grazing so that plant roots could have the rest they need to grow long and reach resources vital to plants. Their basic take home was that you need to move animals off pastures to rest them. Now they take a look at forages that you might add to your pastures so that you’ll have some place to move your livestock as you let other pastures rest.
Hey – You’re not in Minnesota? Use this information as a starting point to consider what’s happening in your pastures and how these forages might work. Check in with your Extension, NRCS, and Conservation District Staffs for their advice on adjusting to best meet your needs.
Alfalfa can make an excellent complement to cool-season grass based grazing systems. Alfalfa is a high quality legume that grows more during mid-summer than cool-season grasses. Alfalfa already exists on many farms, and can support excellent liveweight gains or milk production. Over 3 years in Minnesota, alfalfa supported 667 lb. of lamb gain/acre/yr (Jordan and Marten, 1988).
Initial spring growth of alfalfa occurs when cool-season pastures are rapidly growing. As such, first cutting alfalfa can be taken for hay. Use alfalfa regrowth for summer grazing. When using alfalfa as pasture, rotational grazing is important. Graze alfalfa similar to the way you would hay it, with about 4 weeks rest between grazings. On dairies where forage intake is critical, moving animals to new forage should be done every milking or at least daily. In beef and sheep systems, less intensive systems can work well.
While animals are grazing alfalfa in summer, the cool-season grass pastures are growing slowly and are stockpiling forage for later use. This stockpiled cool-season grass is then available for grazing in late summer or fall.
Beware of Bloat
Bloat can be a problem while grazing legumes and should not be ignored. Be aware and manage to minimize the risk of bloat. Do not move hungry animals to fresh, lush alfalfa. If animals are hungry, feed them hay before moving them to a new pasture. Also, do not move them first thing in the morning. Wait until after they have had their morning meal (and are not as hungry) before moving them. Do not move animals onto wet alfalfa (from dew or rain). Feed hay in alfalfa pastures, particularly when animals are first turned out on alfalfa. Supply animals with a bloat block or bloat guard. Perhaps the most critical point is to observe animals often, particularly when first putting them on alfalfa and when pastures are rotated. At the West Central Research and Outreach Center (WCROC) near Morris, MN sheep were grazed on pure stands of alfalfa for 122 days in 1997. One lamb was lost to bloat. So be aware, but don’t be afraid.
Warm-season forages produce the majority of growth during July and August in the north-central region. This makes them fit nicely with cool-season grass pastures. There are two types of warm-season pastures: 1) native warm-season grasses, and 2) warm-season annuals.
Native warm-season grasses are perennials. Thus, they can persist for many years with good management. Native warm-season grasses grow rapidly and produce lush, vegetative forage during mid-summer. Keep animals off of the warm-season pastures in the spring while cool-season pastures are actively growing. While grazing warm-season pastures in mid-summer, animals can gain 2 lb./hd/day. While grazing warm-season pastures, cool-season pastures can be rested and forage stockpiled for late summer and fall use.
Native grasses can be challenging to establish and maintain. In addition, as we go north, the midsummer period becomes shorter. Thus, the mid-summer forage slump when native grasses are most needed may not be as long. Good information on the economic benefits of native grasses in the north central region is lacking. However, native grass pastures offer an excellent complement to cool-season grass pastures.
Summer annual grasses such as sudangrass or pearl millet can offer another 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. Under a multiple cut system at the Rosemount Research and Outreach Center in Rosemount, MN, sudangrass produced 5.7 tons/ac. dry matter (dm) of forage that averaged 12.7% crude protein (CP) and 61.0% in vitro digestible dry matter (IVDDM). In the same trial, pearl millet produced 5.8 tons/acre of dm that averaged 19.2% CP and 65.4% IVDDM.
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.
There are other summer annuals that can be used for forage as well. Both soybeans and cowpeas have shown promise as summer annuals for forage in the region. While the tonnage may not be as great (2.5 to 3.5 tons/ac.) as for sudangrass or pearl millet, animal performance can be better with these crops. Over three years, growing lambs gained 0.44 lb./day grazing cowpeas and soybeans as opposed to 0.33 lb./day for lambs grazing sudangrass (Sheaffer et al., 1992). Cowpeas and soybeans may be useful in systems where high intake and high individual animal performance are goals.
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.
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. Table 1 gives nitrogen application recommendations for different grazing management systems and environmental conditions.
Legumes and Animals Can Help With Your N Fertilization
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 are 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. Alfalfa and clovers can make pastures more productive. Planting 10 lb./ac. of alfalfa in bromegrass pastures at the West Central Research and Outreach Center increased forage production 2.3 tons/ac./yr. 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.
Stockpiled cool-season grass
Stockpiling forages is done by removing animals from a pasture at some time during the growing season and letting forage accumulate for later use. Most people consider this an option for fall forage. However, cool-season grasses can be stockpiled for grazing during mid-summer. Pastures designated for mid-summer grazing would be grazed lightly or not be grazed in the spring. Thus, forage would be stockpiled in those pastures for mid-summer grazing. When stockpiled pastures are grazed during midsummer, spring grazed pastures would be rested. Animal performance may be lower in this type of system because pastures would be mature before they were grazed.
Next up: Strategies for Fall Forage and Grazing