Annual forages are typically grown on arable land to provide productive, nutritious forage when perennial pasture resources are either nonproductive or of poor quality. An increasingly popular use of annual forages is interseeding them into perennial pastures to boost production during the perennials’ dormant periods, add nitrogen, or improve wildlife habitat.
Warm-season grasses have a C4 physiology and convert moisture into dry matter better than most plants. They are useful in dry areas, where they are the only commonly grown crops that reliably grow tall enough to swath and bale.
Sudangrass
Forage sorghum
Sorghums are the most productive summer annual grasses, and considered the most drought tolerant, due to their extensive root system. Sorghums are botanically a perennial, but winter-kill at first frost, with the exception of Johnsongrass, a sorghum that overwinters in the southern half of the United States. Sorghums are very palatable and have a high energy content, but like most other warm-season grasses tend to run low in protein content and tend to be high in fiber, which physically limits intake due to gut fill.
One major advance in the use of sorghums for forage is the discovery of several genes in hybrids that are referred to as brown midrib (BMR) genes. These naturally occurring (non-GMO) genetics prevent the plants from producing lignin, which is the indigestible fiber found in cell walls. Removing lignin from a plant not only makes the cell wall components digestible to rumen microbes, it also makes the cell contents inside those cell walls accessible. The result is a plant that is extremely digestible, despite its high fiber content.
If you want good animal performance, use a brown midrib hybrid. Early-generation BMR hybrids did not yield well, did not stand well, and did not crimp well in a swather, which made them slow to dry down for hay. Newer BMR hybrids exceed conventional hybrids in yield, standability, and ease of haymaking.
Sorghum bicolor (sorghum, sorgo, milo) is a species that contains both grain and forage sorghums, featuring a very tall vigorous plant with a coarse single stalk. Sorghum bicolor is a variable species, with numerous landraces from all over Africa and Asia, such as milo, kaolang, feterita, dhurra, and so on. Grain sorghums are hybrids bred to be shorter to ease harvesting of the seed, with a high grain yield. Forage sorghums tend to be taller, with a higher percentage of leafy material. Many forage sorghums also feature parentage of sorgo, a strain of sorghum historically used for extraction of syrup, because it has a high sugar content in the stem. Sorgos make for a sweet-stalked plant.
Grain sorghum
Sudangrass (Sorghum sudanense) is a fine-stemmed, leafy plant with multiple tillers coming from each plant base, giving it a more “grassy” appearance. Sudangrass is lower yielding than forage sorghums and is not as palatable but regrows well after haying or grazing, and the fine stems cure more rapidly during the haymaking process. There are also parent lines of sudangrass (Piper and Greenleaf) that are low in prussic acid, making grazing a safer process. (More on prussic acid later in this chapter).
In an attempt to combine the high yield and sugar content of sorghum with the fast regrowth and fine stems of sudangrass, plant breeders have created hybrids of the two, referred to as sorghum-sudans. These hybrids are now widely used in the industry and have largely displaced most of the open-pollinated strains of both forage sorghum and sudangrass.
Johnsongrass is a perennial even in temperate areas and was once widely planted for pasture, a purpose for which it is well suited, with one glaring problem. It is very high in prussic acid potential (described later) and often kills pasturing animals. Sorghum and Johnsongrass can be crossed with each other, and the resulting hybrid is called sorghum almum.
Brachytic dwarves are sorghum and sorghum-sudan plants that, compared to typical tall sorghums, are very short but exceptionally leafy. The dwarves feature excellent standability, and the high leaf percentage makes them very nutritious. Brachytic dwarf (BD) sorghum-sudans find their best utility as summer pasture, because the short plants do not outgrow the reach of grazing animals, and because the rapid regrowth under grazing conditions makes for a much higher total leaf yield, higher animal carrying capacity, and better animal performance.
In a study I conducted, a brachytic dwarf BMR sorghum-sudan produced more than 100 pounds more beef per acre in a grazing situation than a market-leading tall BMR sorghum-sudan. Brachytic dwarf forage sorghums are widely used for silage, as they stand very well and yield very well, with an exceptional nutritional value.
Although not yet a common practice, BD forage sorghums work extremely well for stockpiled winter grazing, due to their excellent standability. If desired for winter grazing, BD forage sorghums should be planted later in the season so they do not make grain. Grain production would make acidosis a risk.
Photoperiod-sensitive hybrids do not begin to flower until the length of darkness exceeds 11 hours and 40 minutes in the fall, unlike most sorghums that flower when they experience warm weather for a long enough period. Delayed flowering is highly desirable for a plant used as forage. When a forage plant flowers, several things happen, and all of them are bad. At flowering, growth of both roots and leaves ceases, water use goes up about 30 percent, and the plant begins to increase in fiber content, to hold up the seedhead better.
Photoperiod-sensitive plants will usually have the highest seasonal yield if the plants are left unharvested until just prior to frost, making them ideally suited to single-cut hay yield systems in arid areas, where the low humidity allows the very large windrows to dry out.
Dry-stalk hybrids are designed to speed the haymaking process. Sorghums are notoriously slow to cure out in the swath, often taking 1 to 2 weeks to dry down enough to safely make hay, particularly in the humid eastern United States. Dry-stalk hybrids dry down in roughly half the time of other sorghums.
Male-sterile plants have sterile pollen and are unable to pollinate themselves. The end result is that after flowering, all the sugars that would otherwise get sent to the developing grain kernels have nowhere to go and build up in the stem. Therefore, male sterile hybrids have very sweet, palatable stalks that animals readily consume, particularly if this trait is combined with a BMR gene. Male sterile plants are often used in a single-cut hay system, for swath grazing (described later in this chapter), and for stockpiled winter grazing (also described later in this chapter). Male sterile hybrids should be planted as the only sorghum, because other hybrids (as well as wild sorghums like Johnsongrass or shattercane) can produce fertile pollen and result in grain production.
The wide variety of hybrids available on the market, and the wide array of traits they feature, makes it easy to select a hybrid tailor-made to almost any purpose. Use the table below as a guide for selecting a sorghum or sorghum-sudan hybrid for forage.
Prussic acid, or hydrogen cyanide, is a toxin produced by sorghums under certain conditions. The cyanide forms when a compound found in the leaf epidermis mixes with another compound found in the center of the leaf tissue. This may occur after leaf tissue has frozen and creates a watery, wilted tissue; it also occurs to a lesser degree during chewing. Prussic acid is concentrated in young regrowth of sorghums and increases during plant stress, such as after a frost. Grain sorghum is highest in prussic acid potential, followed by forage sorghum.
Sorghum-sudans have less prussic acid potential, and sudangrass has the least. Most modern sorghum-sudangrass hybrids are quite low in prussic acid potential, due to the use of low–prussic acid varieties Piper or Greenleaf sudan as a parent.
Prussic acid (cyanide) prevents oxygen from being released from red blood cells into body cells, so a symptom of prussic acid poisoning is exceptionally bright red blood. Death can occur very rapidly, within minutes. Prevention of prussic acid poisoning includes the following measures:
Nitrate toxicity is a potential problem of many forage plants but is most frequently associated with summer annual grasses, particularly sorghums.
A naturally occurring plant nutrient, nitrate stimulates plant growth. All plant tissue contains a certain amount of it, and the rumen contains microbes that can metabolize nitrate to a certain degree. If nitrate levels exceed what the microbes can metabolize, however, bacteria in the intestine can convert the nitrate to nitrite, a much more toxic compound that prevents the blood from carrying oxygen. Affected animals show labored breathing and watery eyes, may abort if pregnant, and may die if the nitrate levels are high enough.
Nitrate is more rapidly released in the rumen from dry hay than from green forage. It is absorbed by plants first into the roots and enters the stem, from which it moves into leaf tissue, where it is converted into protein using the energy from photosynthesis. Anything that reduces photosynthesis increases risk of nitrate toxicity.
It is easier to prevent nitrate accumulation than manage around it after the fact. One of the major reasons plants end up with excess nitrate is that they lack some essential mineral nutrient needed to convert the nitrate into protein. In my experience, this nutrient is most often sulfur. Plants need sulfur in an amount roughly equal to 10 percent of the amount of nitrogen applied to a crop.
Most of the country used to receive sulfur in the form of acid rain as a result of combustion of coal and diesel fuel. Since the Clean Air Act, though, coal power plant exhaust is now “scrubbed” to remove sulfur, and diesel fuel has had the sulfur taken out of it. As a result, sulfur deficiency is now widespread.
Phosphorus is also necessary to convert nitrate into protein, and in higher pH soils zinc and iron are often lacking for this conversion.
Management to prevent nitrate toxicity includes the following measures:
Test in Advance
Graze High
Dilute or Transform
Use Pasture Solutions
If a growing crop is high in nitrate, simply giving it more time to process that nitrate into protein can greatly reduce the nitrate potential. In 2012, I received many calls about cover crop mixtures that contained extremely high levels of nitrate in early October. Ordinarily, these mixtures would have been pastured a month later, but everyone was out of pasture and planning on turning animals out early. I advised people to dip into their stash of hay for a month and keep testing. Sure enough, it seemed every week the nitrate level about dropped in half, and the cover crop yield would about double. Investing a month’s worth of hay in October saved them 2 months’ worth of hay later on down the line.
Pearl millet is second only to sorghums in yield potential. It has the advantage over sorghums of having no prussic acid, which makes pasturing it during the growing season safer and less management intensive. Pearl millet does not regrow as well as sorghum-sudan, and the growing points are located higher on the stem than they are on sorghum-sudan. Pearl millet has a minimum growing temperature of 70°F, so it cannot be planted as early as sorghums, and begins to shut down earlier in the fall. Pearl millet is safe for horses.
Planting: It may be planted when soil temperatures exceed 70°F (21.1°C), at a depth of 3⁄4 inch at a rate of 15 pounds per acre.
Pearl millet
Foxtail millet is a fast-growing plant, but of very rapid maturity, which limits yield potential. It does not regrow well if cut or grazed after heading. It has very fine stems compared to sorghums and pearl millet, which makes haymaking much faster. The hay is palatable, but much less digestible than a brown midrib sorghum-sudan or pearl millet. Hay from foxtail millet should not be fed to horses.
Planting: It may be planted anytime soil temperatures exceed 70°F (21.1°C), at a depth of 1⁄2 inch and at a rate of 15 pounds per acre.
Browntop millet is similar in utility to foxtail millet but has forage that is safe for horses. It can be used for hay or pasture but is primarily used in wildlife food plots for upland game birds, as the seed is relished by birds.
TPlanting: Seeding rate is 15 pounds per acre when soil temperatures exceed 60°F (15.5°C).
Japanese millet is a summer annual that is rather unique among summer annuals: it thrives in very wet soils. It is fast maturing but retains its forage quality fairly well even after maturity. It is a good seed producer, often as soon as 75 days after planting. The seed is valuable for waterfowl and upland game birds and is often seeded in wetland areas for duck food plots.
Planting: A pure-stand seeding rate is 10 pounds an acre drilled at a depth of 1⁄2 inch, and 15 pounds per acre when broadcast. It establishes well when broadcast into mud, making it useful to seed into areas too wet to plant with conventional seeding equipment.
Teff is a shallow-rooted summer annual grass with extremely fine stems, which makes it cure out for hay very rapidly. There are reports of its being swathed and baled in the same day in western climates. The rapid drying rate virtually eliminates mold and limits sun bleaching, so teff hay is usually bright green and has a very pleasant aroma. These features, along with the very fine stems, make teff hay in high demand by horse owners, who will often pay a premium for it over other grass hays.
Teff is not well suited for grazing, at least by cattle, as they tend to pull the shallow-rooted plants out of the ground. The plant is moisture efficient but is dependent on frequent rain for good yields due to the shallow roots. It is difficult to plant with the usual planting equipment, because the seed is so small (1.5 million seeds per pound) that it behaves almost like a liquid and runs right through planting equipment; it also requires a very shallow planting depth (1/16 inch). To aid planting, a clay coating is often applied to the seed to make it somewhat bigger.
Planting: Seed is most successfully planted by broadcasting with harrowing to shallowly incorporate, followed by using a roller to aid seed-soil contact. A pure-stand seeding rate is 6 pounds per acre.
Crabgrass is more familiar as the accursed lawn weed, but it has become useful as a pasture plant for the same reasons it is so difficult in lawns. It grows very rapidly, establishes easily, and is very tolerant of defoliation (either by lawn mower or grazing animal); as an added bonus, it reseeds itself readily, even under heavy defoliation. This is obviously a problem in lawns and can be a problem in annual pastures rotated with grain crops, but crabgrass is an inexpensive way to have a summer annual pasture that does not need annual reseeding, with all the accompanying expense.
Crabgrass
Crabgrass can be broadcast-seeded into a growing crop of wheat or rye, and then be pastured after that crop is harvested or grazed off, as a continuous “one-year, two-crop” rotation. Crabgrass is shade tolerant for a summer annual grass and can be used as an understory plant with taller growing summer annuals. It combines well with annual lespedeza (Korean, Kobe, or Marion varieties) which also readily reseeds, to form a reseeding grass-legume combination for late-summer pasture. Crabgrass can also be overseeded into cool-season perennial pastures to boost late summer productivity and quality.
Planting: A pure-stand rate for crabgrass is about 6 pounds per acre and should be planted around 1⁄4 inch deep. Improved varieties of crabgrass (Red River, Quick-N-Big) are available and are much more productive than wild crabgrass.
Corn is primarily a grain crop, but it is also widely used as a forage crop. Most of this is in the form of silage, but corn also has value as a pasture plant, both in the green stage, and as crop residue after grain harvest. It is palatable and nutritious as pasture but has very poor regrowth after grazing, so should be viewed as a “one time over” grazing crop. There is very little consumption of the stalk in a grazing situation, which some view as wasteful, but there is very little nutritional value in the stalk anyway and methods that force stalk consumption (such as silage) will reduce animal performance.
Corn can be used as both an emergency grazing crop, when grain production is not enough to justify harvest, or as a planned grazing crop. Since corn has a lower growing temperature than other summer annual grasses, it has best use for planting either in early spring or late summer, when the usually more productive sorghums do not perform well.
Brown midrib corn varieties exist and offer far superior animal performance compared to regular grain varieties. The seed corn company Mycogen markets BMR hybrids to the traditional silage market. BMR corn is also marketed as an open-pollinated strain, which makes seed affordable compared to hybrids. These open-pollinated strains are less productive than hybrids but are cheap enough to make corn a useful inclusion in many grazing mixtures where hybrid corn would be unaffordable.
One such example is in late-summer-planted mixtures of brassicas and cereals such as oats and turnips for fall grazing. These fall grazing mixtures are often excessive in moisture content and lacking in adequate fiber, and the inclusion of a frost-killed warm-season grass adds needed fiber and dry matter. Since corn offers better growth in cool temperatures than any other warm-season grass, it far exceeds sorghum or millet for this purpose and can often grow to a height of 6 feet or more, even in a late-summer planting, before it is killed by frost. It is also free of any prussic acid risk, in contrast to sorghums.
Planting: Corn planted for forage is usually planted thicker than for grain production. Corn for silage is usually planted 10 percent thicker than for grain, while an open-pollinated BMR corn for grazing might be planted as thick as 30 pounds per acre (75,000 seeds). Corn performs best when planted deep, from 1.5 to 2 inches. It can be planted when soil temperatures exceed 55°F (12.8°C).
Cornstalks are one of the cheapest forage resources available but are often left unused.
Like their perennial counterparts, annual legumes add protein to the pasture mix.
Cowpeas are standard when it comes to summer annual legumes and have a long history in the southeast United States as a late-summer grazing and green manure crop. They are quite productive, regrow well after grazing, and are nutritious. They are often initially unpalatable, as they have a “weed-like” odor, but once livestock try it they accept it readily.
There are literally thousands of varieties of cowpeas, most of which are grown primarily for human consumption, such as black-eyed and crowder peas. Varieties used as forage include Red Ripper, Chinese Red, and Iron & Clay. Of these varieties, Chinese Red has the shortest maturity and is the least aggressive in growth habit, considered more of a “bush type” variety. Iron & Clay is actually a blend of two varieties that have historically been planted and harvested together and is now considered to be one variety. Iron & Clay is very viney in nature and has a long maturity period, usually flowering too late in most of the United States to produce seed. This long maturity means more vegetative growth for pasture, but seed production is limited to only southern geographies. Red Ripper is intermediate between the Chinese Red and Iron & Clay in both maturity and “viney-ness.” All these varieties are more than a century old.
There is a new variety of cowpea on the market, called simply “Black,” that is more aggressive, with longer maturity than Iron & Clay, and much more productive. In addition, it has smaller seeds, so a pound of seed produces more plants, making Black cowpeas more affordable per acre than other varieties, despite a usual higher cost per pound of seed.
Planting: Cowpeas are usually planted at 40 pounds per acre (Black at 30 pounds) at roughly an inch deep, when soil temperatures exceed 65°F (18.3°C).
Cowpeas
Sunn hemp has traditionally been used as a green manure crop due to its high production of nitrogen, its ability to kill many species of plant-parasitic nematodes, and its ability (unique among annual legumes) to produce large quantities of persistent residue for soil coverage. Its use as a grazing crop has been limited, because the varieties that have historically been available were high in alkaloids that made them unpalatable to cattle, though they are readily consumed by sheep, goats, and deer. The use of sunn hemp as cattle pasture received a huge boost with the increase in availability of the variety Tropic Sun, a USDA release that is low in alkaloids. Tropic Sun is palatable to cattle and retains all the other good characteristics of the plant.
Sunn hemp far exceeds other summer annual legumes in productivity and nitrogen production. It also combines well with viney legumes such as Black cowpea, serving as a trellis for the cowpeas. This combination often performs better than either legume alone. Apparently, the “egg carton”–shaped canopy spreads more leaf area over an acre than a flat canopy and increases the amount of photosynthesis per acre.
Planting: Seed a pure-stand rate of 20 pounds per acre, at roughly an inch deep, when soil temperatures exceed 60°F (15.5°C).
Sunn hemp
Mung beans are similar to soybeans in growth, palatability, nutritional value, and production but have small seeds and are cheaper to plant due to a lower seeding rate. They also are somewhat more drought tolerant than soybeans.
Planting: Seed at a pure-stand rate of 20 pounds per acre, at a depth of about 3⁄4 inch, when soil temps are above 60°F (15.5°C).
Guar is primarily grown for the extraction of the gum that is widely used as a thickening agent in foods such as ice cream and pudding. It is also perhaps the summer annual legume that is the most tolerant of drought, heat, and salty soil, growing where other summer annual legumes fail. The major production area for commercial use is in hot, dry southwest Texas, so it is obviously heat and drought tolerant. Guar is neither highly productive nor highly palatable but has good nutritional value. It becomes palatable after the foliage dries after haymaking or frost.
Soybeans are now considered chiefly an oilseed crop, but they were originally imported from China to serve as a forage crop in the southeastern United States. The variety Laredo is still sold as a hay and pasture variety of soybean, but there have been several newer varieties of soybeans developed for forage purposes. Some of these varieties also contain the GMO trait to make them tolerant to glyphosate (Roundup), which can make control of many weeds easier.
One use of these glyphosate-tolerant varieties is as a smother crop, in which a glyphosate-tolerant forage soybean is planted into a sod intended to be killed out, such as an endophyte-infected fescue sod. The ability to apply glyphosate multiple times throughout the growing season to kill the sod as well as perennial pasture weeds can make this technology quite valuable for the purpose of converting endophyte-fescue pastures into better vegetation. Soybeans are high in protein and very palatable to all livestock species. Animals grazing soybeans select only low-fiber leaves and will respond well if supplemented with grass hay or grasses in the pasture blend to add dietary fiber.
Most modern soybean varieties should be planted at a rate of 60 pounds per acre at a 1-inch depth when soil temps exceed 55°F (13°C), but the small-seeded Laredo variety can be planted at 20 pounds per acre.
Soybeans
Aeschynomene is an annual legume that is often used in soils too wet for other summer annual legumes. It is mostly used in the southeast United States.
Planting: A pure-stand rate is 10 pounds per acre drilled 1⁄2 inch to 3⁄4 inch deep.
|
Yield potential |
Bloat potential |
Grazing method |
Palatability |
|
|---|---|---|---|---|
Annual Lespedeza | L | L | RC | G |
Forage Soybean | H | L | C | G |
Lablab | H | L | RC | G |
Cowpeas | H | L | RC | F |
Aeschy-nomene | M | L | R | G |
Alyce Clover | M | L | R | E |
|
Regrowth |
Best planting time |
Seeding rate, lb/A |
Seeding depth, in |
|
|---|---|---|---|---|
Annual Lespedeza | F | ES | 20–30 | 0.25 |
Forage Soybean | P | S | 60–100 | 1 |
Lablab | G | S | 20–30 | 1 |
Cowpeas | F | S | 30–60 | 1 |
Aeschy-nomene | F | S | 10–15 | 0.5–0.75 |
Alyce Clover | F | S | 15–20 | 0.25 |
|
Ease of establishment |
Thousand seeds/lb |
Inoculant strain |
Reseeding Potential |
|
|---|---|---|---|---|
Annual Lespedeza | E | 200 | cowpea | E |
Forage Soybean | E | 4.5 | soybean | P |
Lablab | E | 1.7 | lablab | P |
Cowpeas | E | 3.6 | cowpea | P |
Aeschy-nomene | F | 180 | cowpea | F |
Alyce Clover | F | 300 | cowpea | P |
|
Tolerance of poor drainage |
Palatability (vegetative) |
Palatability (mature) |
|
|---|---|---|---|
Sudan- Grass | F | G | F |
Sorghum- Sudan | F | G/E | F/G |
Forage Sorghum | F | G/E | F/G |
Pearl Millet | P | G | P |
Foxtail Millet | P | G | P |
Japanese Millet | E | G | F |
Browntop Millet | G | E | G |
Teff Grass | P | E | F |
Crab- Grass | P | E | G |
|
A=annual C=continuous ES=early spring E=excellent F=fair G=good H=high L=low M=medium N=none P=poor R=rotational S=spring |
|||
Annual lespedezas are low-growing, relatively low-yielding annual legumes. They are quite valuable, though, in that they are able to grow on very acid and infertile soils, they readily reseed themselves, they have excellent forage quality, they are tolerant of the pasture herbicide 2,4-D, and almost all of their growth comes in the heat of July and August, when most other forages are declining in productivity. Lespedezas establish easily by broadcasting in midwinter into perennial pastures or growing winter wheat. When seeded into wheat, a stand of lespedeza can be pastured soon after the wheat is harvested, for a high-quality, low-cost late-summer pasture.
Planting: A pure-stand seeding rate is 25 pounds broadcast, 20 pounds if drilled.
Forbs, herbaceous flowering plants, make good grazing additions to mixed pastures. Annual forbs appeal to a wide variety of animals and can extend the grazing season into fall and winter.
Sunflower is a deep-rooted, drought-tolerant forb. Wild annual sunflower is seldom consumed by cattle or horses, although small ruminants will eat it. Domestic sunflower, however, is ordinarily palatable to cattle, and it makes a nice addition to summer forage mixes. It may have its highest and best use in mixtures with sorghums for stockpiled winter grazing, as the high-protein seedheads make a nice complement to the low-protein dormant sorghums (more on stockpiled summer annuals for winter grazing later in this chapter). Sunflowers also have considerable value to many forms of wildlife, including deer, bees, butterflies, and most species of seed-eating birds. Pheasant and quail particularly relish the high-protein, energy-dense seeds.
Planting: A pure-stand seeding rate is 7 pounds per acre, seeded about 3⁄4 inch deep after soil temps rise above 50°F (10°C) in spring.
Okra has been a rather recent entry into the pasture scene but is rapidly gaining acceptance as a palatable, nutritious, and drought-tolerant forage. It seems to outperform even sunflowers in terms of drought tolerance and is usually more palatable.
Planting: Okra is planted at a pure-stand rate of 7 pounds per acre in soil temps above 60°F (15.5°C).
Squash, pumpkins, and melons are other recent discoveries for annual pasture resources. Their foliage is typically not very palatable, but livestock usually relish the fruits after they ripen, making these species particularly valuable as stockpiled forages for fall and winter pasturing. The fruits are nutritious, high in energy, and of moderate protein content. Pumpkin seeds possess deworming properties, a bonus particularly valuable to organic producers, for whom chemical dewormers are not an option. Other varieties of squash may also have this property. The ability of these viney species to “creep” into gaps in the stand and fill in those areas to prevent weed encroachment appeals to many producers, as does the bonus of picking a few fruits for home use while checking the animals!
Planting: The seeding rate and depth vary widely by variety.
Since summer annual grasses are the highest-tonnage forage option, they have often been used to produce winter feed, usually in the form of hay or silage. As costs of mechanical harvest rise, there has been increased interest in using summer annual forages for standing winter forage in the pasture. New advances in plant genetics have improved the utility of summer annuals for winter forage.
It is usually desirable to have a forage that does not produce grain (to avoid acidosis and maintain quality into the winter). My favorite stockpiled summer annuals for winter grazing are a dwarf BMR forage sorghum, planted too late for grain production, along with some oilseed sunflower at 1 or 2 pounds per acre, mixed with a pound of mung beans. The seeds of the sunflower and mung bean act as a protein supplement to the low-protein sorghum forage. The dwarf BMR forage sorghum has a very wide leaf attachment to the stem and stands well into the winter with little leaf loss or falling over.
Swath grazing is the simple practice of swathing sorghums or other summer annuals just prior to frost, so the nutrients are locked into the topgrowth. This allows for drilling a winter annual forage in between the swaths for protein supplement to the high-yielding but low-protein sorghum forage. It is important to strip graze swathed forage, as it otherwise becomes expensive bedding when animals like to lie on it; when they get up they will defecate on it and then refuse to eat it.
Providing nutritious pasture later in the fall and earlier in the spring than perennial forages, cool-season annual grasses extend the high-quality grazing period in both directions.
Many cereals do double duty as grain crops and cool-season forages.
Wheat is obviously grown primarily as a grain crop, but there are many acres of it used as a “dual-purpose” crop, in which the crop is lightly grazed until the jointing stage, and then animals are promptly removed. Grazing in this manner does little harm to grain yields, and the grazing can be considered as a bonus crop. If grazing continues after jointing, however, the grain yields decline rapidly. This practice is mostly utilized in the southern Plains states of Kansas, Oklahoma, and Texas. Farther north, the length of the vegetative period becomes progressively shorter, and the value of wheat pasture diminishes.
Winter wheat can also be planted as a dedicated pasture with no intention of harvesting a grain crop (“graze-out wheat”). Some producers will plant wheat and make the decision to harvest grain or graze out based on the price of wheat grain in the spring. As a winter pasture, wheat is less productive than most other cereals if the intention is pasture alone. If wheat is to be pastured, increase the seeding rate by 50 percent and increase the amount of fertilizer applied. Each 100 pounds of beef produced from wheat pasture requires about 40 pounds of nitrogen and 4 pounds of sulfur.
Wheat varieties differ greatly in pasture value. Varieties developed by the Oklahoma State breeding program ordinarily pasture very well, since pasturing wheat is an important practice in Oklahoma and therefore a focus of the breeding program there. Other varieties are intended to be managed for “pasture only.” The variety Willow Creek was developed to remain in a vegetative state as much as a month longer in the summer than grain varieties, offering a much longer grazing period.
Planting: Wheat for grazing should be planted at 90 to 120 pounds per acre, at a depth of 11⁄2 inches. Planting early increases forage growth but also increases the risk of issues such as barley yellow dwarf virus, wheat streak mosaic virus, and insect damage from Hessian fly, armyworms, and grasshoppers. For optimum grain production, plant around the time of average first frost in fall, and 2 weeks prior to that if pasture is the main goal.
Rye will grow at lower temperatures than other winter annual grasses and is quite valued for staying green later into fall and greening up earlier than any other annual forage. Rye is considered the “toughest” cereal, in that it is probably the winter annual most tolerant of drought and poor soil. The least palatable of the grasses, rye can be nutritious and palatable in the vegetative stage but becomes unpalatable after it heads out.
Rye has considerable value as a cover crop, due to its high amount of winter growth, its ability to control erosion, and because it is allelopathic (contains natural herbicides). Rye mulch provides excellent control of marestail and pigweeds, two of the more troublesome weeds farmers fight today. However, rye is considered to be a serious contaminant of wheat harvested for grain and is difficult to control in wheat with either herbicides or cultural practices, other than a crop rotation in which wheat is not harvested for grain for several consecutive years.
There are varieties of wheat tolerant to the herbicide imazamox (Beyond), referred to as Clearfield varieties, which can selectively control rye in wheat. Growers of Clearfield varieties must sign a nonpropagation agreement and adhere to stewardship guidelines. Clearfield varieties were developed by natural selection and are not considered to be a genetically modified organism (GMO).
Planting: Rye can be planted as early as 8 weeks prior to average first frost in fall, at a pure-stand rate of 50 to 100 pounds per acre and a depth of 1 inch.
Triticale is a man-made plant, a cross between wheat and rye. Triticale was developed more than 100 years ago by traditional hand cross-pollination and is not considered a genetically modified organism. It was developed as an attempt to create a grain with the bread quality of wheat and the winter hardiness of rye, and it was a failure on both accounts. However, it is an excellent forage plant, exhibiting considerable hybrid vigor and higher forage yields than either parent. Although it greens up later in the spring than its rye parent, it finishes stronger, and by the time both head out, triticale will have much more biomass and much more forage palatability and quality than rye. It will also greatly outdo its wheat parent in forage yield and be of similar quality.
There are both winter and spring triticale varieties. Spring triticale finds a similar usage to spring oats and offers higher forage yields than oats. However, it loses palatability upon heading to a far greater degree than oats. There are many beardless (awnless) varieties of triticale, and these varieties offer greater palatability after heading and fewer issues with sore mouths of livestock than do awned varieties.
Planting: Winter triticale should be planted as early as 6 weeks prior to average first frost in fall, at a rate of 80 to 100 pounds per acre. Spring triticale should be planted as soon as possible after spring thaw at a rate of 80 to 100 pounds per acre at 1 inch depth.
Oat is a grain crop used for both animal and human food but is also an excellent forage crop. Historically, it was spring planted for either grain or forage (usually harvested as hay, since early summer usually offers an abundance of pasture) but is increasingly being planted in late summer as a high-yield, high-quality fall pasture, often in conjunction with brassicas and spring peas. Most oat varieties are considered “spring oats,” but there are varieties of winter oats that survive mild winters, typical of the Deep South.
Oats provide better quality forage than wheat, rye, or triticale and are probably the most palatable cereal. Black oats are a related species to the more common white oats, and they offer more cold tolerance (acting as a winter oat in the south); they are finer-stemmed and deeper-rooted than white oats.
Planting: Oats can be planted in either early spring, soon after spring thaw, or in fall as early as 10 weeks prior to average first frost, at a rate of 90 pounds per acre in pure stand.
Barley offers us more than beer. The grain is widely used as a livestock feedstuff, and the forage is excellent quality. Barley is one of the most salt-tolerant domestic plants and finds considerable use in creating a mulch to improve tolerance of subsequent crops to salt injury. There are both spring and winter varieties of barley. Spring varieties find similar usage to spring oats, and winter varieties are used similarly to winter triticale or rye.
Planting: A pure-stand rate is 75 pounds per acre, with winter barley planted as early as 8 weeks prior to average first fall frost and spring barley planted soon after spring thaw, both at a depth of 1 inch.
Annual ryegrass is unique on this list of winter annual grasses because it is not a cereal grain. Despite the similarity in names, it is not at all related to rye and is most closely related to the fescues, with which it can be hybridized to form the short-lived perennial Festulolium.
Annual ryegrass behaves quite differently from the cereals and thus offers advantages either alone or in combination with a cereal. It has very low growing points and recovers from grazing very well. On the other hand, it has poor tolerance to both heat and drought, and should only be part of a grazing mixture in areas prone to drought. The plant has a very dense root system and penetrates and loosens heavy clay soils; it is used extensively as a cover crop for this reason.
Ryegrass, either annual or perennial, differs from most other cool-season grasses in that it offers a high content of soluble sugars, which tends to readily fatten animals. It therefore is used as a basis for stocker cattle and grass-finishing animals. Dairy animals also perform very well on ryegrass. Ryegrass pasture is too rich for horses and has been associated with founder and colic.
Planting: A pure-stand rate is 25 pounds per acre, planted around 1⁄4 to 1⁄2 inch deep.
Annual ryegrass heads extend above heads of a beardless wheat, an excellent forage combination.
Brassicas are members of the cabbage family and offer exceptional forage quality, high in protein and digestibility. This combination can provide exceptional animal performance but also have some anti-quality factors of which producers should be aware. Brassica forage is very low in fiber, in fact too low for proper rumen function. Animals grazing brassicas should be offered free-choice long-stem grass hay so they can obtain additional fiber if needed. Brassicas also contain glucosides and sulfylmethylcysteine oxides (SMCOs) that can reduce animal performance if brassica intake is too high.
Brassica forage also reduces the availability of certain B vitamins in the animal, and the exceptional high digestibility can lead to a very rapid rumen fermentation that can trigger a form of lung irritation. For these reasons, brassicas are best used in mixtures with other forages such as cool-season annual grasses and legumes.
Best animal performance usually occurs when brassica forage is roughly 30 to 50 percent of the total intake. Supplementing with monensin also seems to greatly reduce problems from grazing brassicas. Brassicas are often bitter and unpalatable during warm weather but become much more palatable upon cooler temperatures. Although brassica grazing has some risks, the high yields and exceptional digestibility make them more than worth including in cool-season forage blends.
Turnips are rather unique among forages, in that much of the total forage yield is actually from the root, which protrudes aboveground. The root is even higher in energy content than the leaves, which are exceptional. However, since the roots are eaten readily, turnips do not regrow after grazing and are best utilized as a stockpiled, end-of-the-season single grazing. The most common variety is the old purple-top variety, which is still a good one. There are now improved varieties and hybrids, most of which offer smaller roots and more leaves and feature a root that is not eaten during grazing; thus these varieties will regrow after grazing.
Planting: Turnips are most often planted in late summer for a late-fall grazing. A pure stand (which is not recommended) is about 5 pounds per acre planted at about a 1⁄2-inch depth.
Occasionally, purple-top turnip roots can become lodged in the esophagus of a grazing animal and prevent the animal from belching rumen gases. This can keep the animal from eating and drinking water and may lead to bloat and kill the animal. Removing turnips lodged in an animal’s esophagus is quite difficult, since the buildup of gases puts considerable pressure on it. A loop of nine-gauge wire is often used to reach behind the root and pull it out, but this is very hard on the esophagus and often causes enough injury to make eating painful for the animal, and it loses condition rapidly. Pushing the root on down with a thick-walled section of rubber hose is often recommended, but this is about as easy as pushing a cork down into a bottle of champagne.
One potential solution is to pierce the rumen with a trocar, the same as with legume bloat, to relieve the pressure on the lodged root, and allow it to be passed on down comparatively easily.
Forage radishes are primarily grown for soil improvement, being one of the absolute best crops for penetrating dense soil layers and alleviating soil compaction. They are a useful forage crop as well, high-yielding and nutritious. Radishes, however, are far less palatable than turnips and are often the last forage eaten in many annual grazing mixtures. This is not necessarily bad, as it allows the radishes time to fully develop their root system and perform their primary function of alleviating soil compaction.
Planting: Radishes perform best when planted in late summer, at about 8 pounds per acre (pure-stand rate) at 1⁄2 inch deep. Again, a mixture is recommended.
Various varieties of “tillage” type radishes, derivatives of daikon radish, are common on the market. They are intended to improve soil and must be planted in late summer or they will bolt (shoot up a flowering stalk) rather than produce roots or foliage. Graza is a heat-tolerant variety that can be planted in spring and is one of the best brassicas for summer forage. There are also radish varieties used for oilseed production and yet others with high glucoside content used for control of plant-parasitic nematodes.
Rapeseed is a leafy brassica that regrows well and has good cold tolerance. It is one of the more palatable brassicas. It can be planted in either spring or fall, because it is fairly resistant to bolting.
Planting: A pure-stand rate for rapeseed is 7 pounds per acre at a depth of 1⁄4 to 1⁄2 inch.
Kale is a long-season brassica, and that long growing season means it is high yielding. It is very cold tolerant, staying green until temperatures drop below 10°F (−12.2°C). It can be planted in either spring or fall and features good winter grazing potential.
Planting: A pure-stand seeding rate is 5 pounds per acre.
Forage collard is a new brassica and offers both heat and cold tolerance. It has very large leaves and excellent forage quality and palatability, and it regrows very well after grazing. It can be planted in either spring or fall.
Planting: A pure-stand rate is 5 pounds per acre at 1⁄4 to 1⁄2 inch deep.
Cool-season annual legumes can add nitrogen to the soil, improve dietary diversity, and provide higher levels of dietary protein, calcium, and magnesium than do other cool-season annuals.
Peas are best known for their edible seeds but are also used as a forage crop. Any variety can be used as forage, but some varieties feature more vegetative growth than others. There are both spring varieties (non–winter hardy) and winter-hardy varieties. The standard winter-hardy variety is Austrian Winter, but now there are varieties even more winter hardy than Austrian, such as Icicle. The standard spring variety is 4010, which is still hard to beat.
Winter-hardy varieties are planted in fall. Spring varieties can be planted either in spring or fall. Fall planting of spring varieties will produce far more fall biomass than will be produced by winter-hardy varieties. Some people will plant a blend of both spring varieties and winter-hardy varieties for a nice balance of fall and spring pasture. Peas come in both white- and purple-flowered varieties. The white-flowered varieties are lower in tannin and are much more palatable to livestock. Peas are good nitrogen fixers.
Planting: A pure-stand seeding rate is 60 pounds per acre for small-seeded forage varieties. Deep planting (up to 3 inches) enhances winter hardiness.
Lentils are used similarly to peas and are also used primarily as seed crop for human consumption. Just as with peas, there are varieties designed specifically for forage. Lentils are palatable to livestock but are less productive of both forage and nitrogen than many other legumes. Indianhead lentils, a variety developed for forage and cover crop, have higher forage yields and smaller seeds, which means the recommended seeding rate is comparatively low and thus less expensive to plant.
Planting: A pure-stand seeding rate is 20 pounds per acre of the small-seeded varieties.
Vetches are perhaps the most productive cool-season legumes. Hairy vetch is the most winter-hardy vetch and is probably the most winter-hardy cool-season annual legume overall. Hairy vetch is palatable to cattle and small ruminants but not to horses. Vetch seed contains toxins, and consumption of it should be avoided if possible.
A small percentage of livestock are also highly allergic to the foliage of vetches, and in these animals vetch consumption can cause pruritic dermatitis, which results in extreme blistering and may even be fatal. This allergy is more common in animals with black hides. Although rare, this condition is devastating, and poorly understood at this time, so it is recommended that producers use extreme caution if grazing vetches.
I no longer recommend the planting of hairy vetch for the purpose of livestock forage, but it is often an existing component of many pastures throughout the southeast United States due to its ability to reseed exceptionally well. It appears the allergen is an alkaloid, and the susceptibility appears to be genetic.
The risk of vetch toxicity can be reduced by blending vetch with other forages, so that the toxic factor is diluted. Forages containing tannins such as peas and arrowleaf clover may be particularly helpful, because tannins help neutralize other toxic alkaloids such as that found in endophyte-infected fescue. Hairy vetch is a good nitrogen fixer and makes an excellent mulch, so it is a preferred cover crop species.
Woolly pod vetch is a similar species to hairy vetch but is somewhat less winter hardy. Common vetch is less winter hardy yet, acting similarly to spring peas in utility.
Planting: A pure-stand rate of vetches is 20 pounds per acre, planted up to an inch deep. Vetch can establish by broadcasting better than most large-seeded legumes.
Crimson clover is one of the more winter-hardy annual clovers, surviving temperatures as low as −15°F (−26°C). It is one of the earliest legumes to green up in the spring. It is very palatable to most livestock but not to horses. It is nonbloating. Crimson clover has beautiful blood-red flowers that are highly attractive to bees, and since it is one of the first flowers to bloom in the spring it is quite valuable to honey producers.
Planting: A pure-stand rate is 15 pounds per acre, seeded as early as 8 weeks prior to average first frost in fall, at a depth of 1⁄4 to 1⁄2 inch. It can be established by broadcasting with favorable rain.
Arrowleaf clover is a highly productive winter annual legume. It greens up later than crimson, blooms about a month later than crimson, and is less winter hardy. Arrowleaf is less palatable than most clovers due to a high tannin content, but this tannin also makes it nonbloating. Arrowleaf is probably the highest-yielding winter annual clover if allowed to grow until mature, which takes about a month longer than other winter annual clovers.
Planting: A pure-stand rate is 10 pounds per acre, planted as early as 8 weeks prior to average first frost in fall.
Balansa clover is perhaps the most winter-hardy annual clover, though it is also perhaps the latest of the winter annual clovers to green up in the spring. It has very small seed and is slow to emerge, but the high number of seeds per pound and low seed cost makes it economical to plant.
Planting: It can be broadcast or drilled at 1⁄4-inch depth as early as 8 weeks prior to average first frost, up until the date of first frost, at a pure-stand rate of 6 pounds per acre.
Berseem clover is an annual clover but a dead ringer for alfalfa. It looks like alfalfa when green, dries as hay at the same rate, and even looks like alfalfa when it is dried and in a bale. This resemblance to alfalfa gives it a unique use. When a stand of alfalfa is thinned out due to freeze damage or standing water damage, berseem clover can be interseeded. It is not susceptible to the autotoxic compounds that prevent alfalfa seedlings from establishing. It is also quite tolerant of wet soil. It can be spring planted in the northern states and fall planted in the south. It is an excellent pasture plant and does not cause bloat. Aside from thickening alfalfa stands, it has potential in annual mixes in areas too wet for other legumes.
TPlanting: A pure-stand rate is 20 pounds per acre, planted in early spring in the north and late summer in the south. The variety Frosty has more cold tolerance than most varieties.
|
Drought tolerance |
Cold hardiness |
Yield potential |
Bloat potential |
Grazing method |
|
|---|---|---|---|---|---|
Subterranean Clover | P | F | F | L | RC |
Arrowleaf Clover | F | G | G | L | RC |
Ball Clover | P | G | F | H | RC |
Berseem Clover | P | P | G | L | RC |
Crimson Clover | F | G | F | L | RC |
Rose Clover | E | G | F | L | RC |
Hairy Vetch | G | G | G | L | RC |
|
Palatability |
Best planting time |
Seeding rate, lb/A |
Seeding depth, in |
|
|---|---|---|---|---|
Subterranean Clover | G | Fall | 15–25 | 0.25–0.5 |
Arrowleaf Clover | G | Fall | 8–10 | 0.25–0.5 |
Ball Clover | E | Fall | 3 | 0.25 |
Berseem Clover | E | Fall | 20–25 | 0.25–0.5 |
Crimson Clover | G | Fall | 15–20 | 0.25–0.5 |
Rose Clover | G | Fall | 10–15 | 0.25 |
Hairy Vetch | F | Fall | 20–50 | 0.75–1.5 |
|
Ease of establishment |
Thousand seeds/lb |
Inoculant strain |
Reseeding potential |
|
|---|---|---|---|---|
Subterranean Clover | E | 54 | subclover | G |
Arrowleaf Clover | F | 400 | clover | E |
Ball Clover | G | 1000 | clover | E |
Berseem Clover | G | 207 | clover | P |
Crimson Clover | G | 150 | clover | P |
Rose Clover | P | 164 | clover | E |
Hairy Vetch | E | 160 | pea/vetch | F |
|
Key: A=annual C=cool E=excellent F=fair G=good H=high L=low LLP=long-lived perennial P=poor grazing method: RC=rotational or continuous |
||||
|
Sand tolerance |
Clay tolerance |
Fall production |
Winter production |
Spring production |
|
|---|---|---|---|---|---|
Wheat | G | G | P | F | G |
Rye | E | G | F | E | G |
Triticale | G | G | F | G | E |
Barley | G | F | G | F | F |
Winter Oats | F | G | G | P | G |
Black Oats | F | G | G | P | F |
Annual Ryegrass | P | E | P | P | G |
Spring Oats (fall- planted) | F | G | E | none | none |
Hubam clover is an annual sweetclover. Like other sweetclovers, it is highly productive, drought tolerant, deep rooted, a very good nitrogen fixer, and tolerant of poor soils. Like other sweetclovers, it has rather poor palatability due to its content of bitter coumarin, which in addition to its coarse stems makes it unsuited to hay production. (See the discussion on coumarin in the “Sweetclover” section of chapter 8.) In the southern states, it is used as a winter annual and it blooms in spring. In northern states, it is used as a summer annual and blooms in late summer and fall. Like other sweetclovers, it is exceptionally attractive to both honey bees and native pollinators and is very productive of honey per acre. If it is spring planted, its late-blooming habit is particularly valuable for honey producers, as fall-blooming flowers are hard to find, and the extra nutrition prior to the onset of winter is particularly valuable to aid winter survival of hives. A pure-stand rate is 20 pounds per acre.
Medics are low-growing annual legumes that are closely related to alfalfa. Of Mediterranean origin, they often grow in areas of mild winters. They offer good forage quality but are not highly productive except for a brief period in spring. There are many species, including black medic (the most winter hardy), button medic, bur medic, snail medic, barrel medic, and many others.
Beets — sugar beets, fodder beets, and mangels — are very palatable livestock forages. All three are the same species but bred for different purposes. Sugar beets are of course grown primarily for sugar extraction but also can be a high-energy forage. By-products of sugar beet processing, such as beet pulp, beet tops, and beet molasses, are often used for livestock feed, and fields of sugar beets unharvested for whatever reason can be pastured. Mangels have been bred for higher yields but have a lower sugar content than sugar beets. Fodder beets are a cross between sugar beet and mangels and are intermediate between the two.
Beets are slow to establish and compete poorly with weeds and other forages in mixtures. Beets also tend to contain high levels of oxalates, and intake of beets or beet by-products should be limited to half the diet or less to reduce the risk of oxalate crystals forming in the urinary tract. Feeding supplemental calcium reduces the risk of oxalate-related issues.
Phacelia is a small forb native of the southwest United States. Its primary use is for bee pasture, as it produces a huge volume of nectar and pollen, and high yields of excellent-quality honey. The root system is also very good at loosening the top layer of soil. Although the forage yield is low, livestock find it palatable, even at advanced stages of maturity. If bloom is desired, it must be spring planted, although for forage purposes it can also be fall planted. It winter-kills when temperatures drop below 20°F (−6.7°C).
Planting: A pure-stand rate is 7 pounds per acre, planted in early spring at 1⁄4- to 1⁄2-inch depth.
In much of the southeast United States, cool-season annuals are interseeded into warm-season perennials such as bermudagrass to extend the grazing season. Winter oats and cereal rye are often drilled; annual ryegrass and winter clovers such as crimson are usually broadcast into subtropical grasses such as bermudagrass and bahiagrass. The addition of a cool-season annual to a warm-season pasture offers many benefits. Not only is the grazing season extended, but the high protein of the cool-season annual growing intermixed with the dormant warm-season grass in the winter encourages both consumption and digestion of the low-protein dormant grass. The additional biomass, manure generated, and presence of actively growing roots and root exudates over a longer period of time helps improve soil as well. If the interseeded annual is a legume, it can also provide nitrogen for the perennial sod.
Cool-season annuals can be planted after the harvest of summer crops, interseeded into growing summer crops, or aerially seeded into growing summer crops to provide winter grazing. Planting after harvest allows good seed placement with a grain drill and full sunlight but occurs later in the season and allows only limited fall growth. Aerial seeding into standing crops enables earlier planting but offers poor seed-to-soil contact, and the cover crop emerges in the shade of the summer crop.
A scenario in which an aerial-seeded winter grazing crop is quite successful is the broadcasting of forage seed into fields producing hybrid seed corn. When hybrid seed corn is being produced, the “female” plants (the plants from which ears are harvested) are detasseled, which removes part of the canopy, and the “male plants” (or pollen donors) are completely removed after pollination occurs. During the destruction of the male plants, it is common to broadcast seed of turnips or other cool-season annual plants, followed by irrigation to help ensure germination. The removal of all that plant material allows much more sunlight to reach the ground and aid establishment of the cover crop. After the corn harvest, the combination of the dropped ears, corn residue, and green cover crop provide high-quality pasture.
The success of this system, compared with the often disappointing results from aerial seeding into corn harvested for grain, has led many to explore techniques to improve the success of cover crops established prior to corn harvest. One method gaining traction is to use a modified corn detasseler set up to simultaneously broadcast seed and cut off the corn plant tops above the ear, conducted at “black layer” (the point at which corn grain is fully developed, after which no more yield is accumulated). This has many advantages. It opens the plant canopy, drops the corn tops on top of the seed for a mulch, and speeds drying down of the ears to promote an earlier harvest, which also opens the canopy even more.
Another approach to improve success of corn interseeding is to establish the cover crop very early during the life cycle of the corn, around V3 to V5 stage (when corn is three to five leaf). This allows the corn to get a head start on the cover crop to prevent undue competition yet is early enough that the cover crop gets enough sunlight to allow it to get a good root system established prior to the corn’s forming a solid canopy. Research has shown that cover crops established after corn hits the V3 stage do not reduce corn yield. This approach has been successful under abundant moisture conditions during midsummer, as occurs with center-pivot irrigation.
Cool-season annuals can be planted as a dedicated winter pasture. If pasture is the primary goal and grain harvest is not a goal, then best results come from planting a mixture of plants to take advantage of varying growth patterns. For example, a blend of brassicas, spring cereals, winter cereals, and annual ryegrass will vastly outyield any one of the components alone. Brassicas and spring cereals will produce several times the fall growth of the other components, but they winter-kill in most latitudes and offer no spring grazing.
Winter cereals, such as triticale and rye, offer the earliest green forage in spring but recover poorly from spring grazing and “play out” early. Annual ryegrass greens up quite a bit later than winter cereals but recovers from grazing well and can provide excellent quality grazing into early summer. One of my favorite winter annual pasture mixtures, planted in late August, is 10 pounds per acre BMR corn, 60 pounds of cereal rye, 10 pounds of annual ryegrass, 2 pounds of forage collards, and 30 pounds of oats. This mixture will produce several times the forage of simple wheat pasture, which is still the most commonly planted winter annual pasture.
Grass tetany, caused by very low levels of magnesium in the blood, is a potentially fatal condition often seen on winter cereal pastures as well as cool-season perennial grasses, particularly in early spring. Traditionally, the recommended prevention has been to include magnesium oxide in with the mineral fed to livestock. Recent research as well as practical experience has indicated there may be more successful approaches. For example:
Increase phosphorus availability in the soil to increase magnesium levels in forage plants, since there seems to be a link between low phosphorous and poor magnesium uptake.
Substitute a more palatable form of magnesium than the bitter magnesium oxide traditionally used in mineral supplements. New research indicates that tetany is triggered as much by low sodium levels as it is by low magnesium, and including the bitter oxide in a salt-and-mineral mix reduces the sodium intake of the animal. There is a very palatable form of naturally occurring mica mineral that is high in magnesium, a form of lamproite mined near Buffalo, Kansas, and marketed as Micro-Lite. Results from this product so far are very encouraging. Including legumes, which are higher in magnesium than grasses, in the grazing mixture also can greatly reduce tetany issues.
The large acreage of grain crops across the country creates an abundance of crop residue that can be utilized by livestock after harvest. Because crop residue is a by-product of the grain crop, it is often available to pasture for low cost, particularly in areas with low livestock concentrations. Corn, sorghum, and soybean residue can be utilized as pasture. The residue of small grain crops such as wheat, barley, oats, and rye are not well utilized as pasture, although there are still some means to make them valuable as a portion of a livestock ration. Here are some considerations for pasturing crop residue:
Nutrients Offered by Crop Residue |
||
|---|---|---|
|
Residue type |
% protein |
% digestibility |
|
Corn grain |
10 |
91 |
|
Corn leaves |
7 |
50 |
|
Corn husks |
3 |
68 |
|
Cornstalks |
4 |
40 |
|
Corncobs |
3 |
33 |
|
Grain sorghum leaf |
8 |
56 |
|
Grain sorghum stalk |
4 |
50 |
|
Soybean fallen leaves |
12 |
53 |
|
Soybean pods |
6 |
40 |
|
Soybean stalks |
4 |
33 |
|
Soybean seeds |
40 |
90 |
|
Needs, nonlactating beef cow |
8 |
50 |
|
Needs, lactating beef cow |
10 |
60 |
Most crop residues are quite low in protein and nearly devoid of vitamins and minerals. Cornstalks, sorghum stalks, and soybean residue are all too low in protein and energy to be used as the sole diet for lactating or growing livestock but can be used effectively for nonlactating beef cows. The low cost of residue pasture, however, can often make it economical for other classes of livestock, even if supplemented. Typically, about half the protein needs of the animal must be supplemented if the animal is either growing or lactating, and nearly all the mineral needs of the animal will need to be supplemented.
An approximate nutrient analysis is given in the table below, compared to the nutrient needs of a lactating cow and a dry beef cow.
Supplements are a common way to overcome the nutritional deficiencies of crop residues. In most instances, the most critical need is for protein. A dry beef cow will be marginally protein deficient on most crop residues, while a lactating or growing animal will need about half of its protein needs supplemented with an external feed source.
A convenient supplement, although expensive, is a “lick tub” of condensed liquid that animals can access only slowly, through licking. The better-quality tubs will feature all-natural protein, while cheaper ones will contain urea as a source of non-protein nitrogen. When priced per pound of protein, these tubs are usually much more expensive than distillers’ grains, oilseed meal, or legume hay. They are quite convenient, however, and usually combine a salt and mineral package with the protein.
You can handfeed oilseed meals or distillers’ grains to limit consumption, or you can blend them with salt to make a homemade, limited-intake supplement. Legume hays are hard to limit feed if fed in large bales, but it has been found that animal performance improves if protein supplement is fed as a double ration every other day, or even as a triple ration every third day.
Feed enough of these materials to make up the protein deficiency of the crop residue; in the case of a lactating beef cow on corn residue, that is roughly 1 pound of supplemental protein, high in calcium. It is almost always necessary to supplement a complete mineral package to animals on crop residue pasture, but oilseed meals and distillers’ grains are high in phosphorus, and legume hay is high in calcium.
Use adjacent fields of high-protein forages, such as alfalfa stubble or winter cereals, in combination with residue fields to form a more complete diet. It is not effective, however, to simply allow animals free choice between the two, as they will completely consume the high-protein vegetative forage before utilizing much of the residue. You’ll have to strip-graze the combination, allowing one day’s worth of each at a time, or find some other way to limit access to the high-protein forage, such as time-limit grazing (discussed in detail in the chapter on horses).
For additional protein and forage, seed cover crops right into the grain crop prior to harvest. This works best with irrigated corn or soybeans. Timing seems to be optimal when the bottom leaves of the corn plant are drying up, or when soybean leaves are beginning to yellow prior to harvest. Some graziers are experimenting with planting companion crops with corn at the corn’s three- to five-leaf stage, so the companion crop will have access to sunlight during establishment. Studies have shown that companion crops seeded after the three-leaf stage of corn do not cause yield reductions. See more information on this practice.
Grain sorghum residue has a much higher value for pasture than corn residue. Unlike corn leaves, which are usually shredded and dropped on the soil surface during harvest, sorghum leaves remain erect and intact after harvest, and they are not in soil contact, reducing rotting. The sorghum leaves will stick up through most snowfalls instead of getting buried like corn residue can. Sorghum leaves are also coated with a waxy layer that reduces weathering losses during winter, so the plant retains its value longer into the winter than corn. Grain sorghum leaves are also typically higher in protein than corn husks and leaves, high enough that a protein supplement is not needed for nonlactating animals.
Soybean harvest leaves very little residue per acre, but the dropped leaves, pods, and spilled beans are readily eaten by animals. The stems have virtually no value to animals. This plant’s residue is definitely worth fencing and utilizing, particularly if adjacent to corn residue. Since soybean leaves and unharvested beans are a good protein source, they provide a good nutritional complement to corn residue.
Wheat straw and other cereal grain residues are not usually eaten by animals in a pasture situation. Straw is very low in protein , minerals, and digestibility, and it requires the supplementation of basically all the protein and minerals required by the animal. To get animal utilization by livestock usually requires baling the straw and either mixing with high-protein feeds (such as legume hay, distillers’ grains, or oilseed meals) or treating the straw with anhydrous ammonia, a common agricultural fertilizer.
High-protein cover crops can be no-till planted into cereal grain stubble and allowed to grow up and intermingle with the straw. The straw is unavoidably eaten along with the cover crop and is blended with the usual high-protein cover crop forage for better utilization.
Other crop residues like cornstalks can also be baled and ammoniated. It is important to realize that baling cornstalks creates much higher tonnage of feed than grazing per acre, but the nutritional value of this feed is much lower than animals can select while grazing, since so much of the material by weight is the largely indigestible stalk. Ammoniation can dramatically improve the value of this material.
Grain left in the field can pose a risk of acidosis, as discussed in chapter 10, on how animals digest and utilize forage. It is often assumed that this is a risk only when large amounts of grain are left behind, but since animals will aggressively select grain over other plant parts, if they are allowed enough area, even small amounts of grain per acre can trigger acidosis, because they have access to the entire area. I would actually argue that nearly every ruminant animal placed on grain crop residue without some strip-grazing strategy will develop some level of acidosis. Even if not fatal, subclinical acidosis can dramatically reduce animal performance, and we have just taken this suboptimal performance for granted.
How much grain is too much? Acidosis begins when the grain intake exceeds one-half of 1 percent of body weight daily. Therefore, a 1,000-pound cow should receive no more than 5 pounds of grain per day.
The solution to preventing acidosis is, of course, strip grazing. Begin at the water source, provide only one day’s worth of grazing at a time, and gradually move the fence away from water. Since there is no regrowth to protect on crop residues, there is no need for a back fence. Strip grazing with modern portable fencing is easy and takes very little time.
Strip grazing cornstalks has been compared to set stocking the entire area at numerous agriculture universities in the Corn Belt, and the results are eerily identical: strip grazing allows you to roughly double the amount of days livestock can spend on cornstalks. I know of few other activities in which you can gain so much from so little investment in time.
In the event there is a very high amount of unharvested grain, the maximum allotment may actually be smaller in area than the minimum allotment. In this case, it may be necessary either to use the maximum allotment area and supply supplemental roughage to meet dry matter needs or to trend closer to the calculated minimum area and take measures to prevent acidosis.
Many landowners refuse to let animals on their cropland for residue grazing because they fear livestock will cause compaction and reduce future crop yields. While this may seem a reasonable fear, research at numerous universities across the Corn Belt have shown there is virtually no yield loss in crops after livestock graze crop residue.
The University of Nebraska has probably done the most exhaustive studies, and their research often shows a very slight improvement in yield with residue grazing, and slight increases in soil organic matter and soil microbiology. This has been true with clay soil and sandy soils, no-till and conventional tillage, fall grazing and spring grazing, continuous corn and corn-soybean. They all say the same thing: residue grazing does not reduce future crop yields unless the grazing is so severe that all the surface residue is removed.
Remember, under proper grazing, only about one-sixth of the residue should be removed. It always amazes me how so many landowners are concerned about the weight of a 1,400-pound cow on the soil but are completely unconcerned about the presence of a 70,000-pound combine or grain cart.
That said, it is still probably prudent to reduce episodes of pugging, or churning of soil by animals, during wet weather. It is advisable to locate water tanks and hay feeding areas on grassed areas if possible. It is also smart to have a fenced-off location with some hay bales, set on a grid pattern, that can be rationed out with portable fencing so animals can be removed from the larger area easily in the event of heavy rain. This setup is also handy in case snow or ice covers the residue and makes grazing difficult.
It is also important to realize the real cause and real cure of compaction. Compaction is blamed on traffic, and that is a contributing factor, but the real cause is lack of soil structure. Soils with good structure are quite resistant to compaction caused by traffic. Soil structure is created by soil microbes. Therefore, compaction is cured by practices that improve soil microbial populations: these include no-till, growing cover crops, leaving adequate surface residue, and, yes, livestock grazing for addition of manure.