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Annual crops can boost forage production

Marvin H. Hall Published on 29 August 2014

While perennial forage species are the backbone of most forage-based livestock systems, annual forages can supplement and complement the perennials to increase production of your operation.

Seasonal production of cool-season foarages

Our traditional cool-season perennial forages do not produce during the winter months in the north and also slow production in the hot and dry months of summer (Figure 1).

During these months, annual crops could continue to produce. Knowing which forage species continue to grow during these periods is the first step to incorporating them into your system. For simplicity, I have grouped them based on the time of year they are productive: fall and spring, summer, and summer or fall.

Fall and spring
Winter cereal crops such as wheat, barley, rye or triticale can provide grazing, silage or grain options. If these crops are used for fall and spring grazing, certain management practices need to be modified from what is normally done for grain production.

Plant three to four weeks earlier than for grain production alone (mid-August to early September). Increase the seeding rate to 3 bu per acre and apply 40 pounds N per acre at planting.

With adequate fall moisture, forage should be available from October through December and then again in late winter. One acre of properly fertilized and managed small grain should support one animal unit (feeding value of a 1,000-pound dry cow) on a limited grazing basis.

Small-grain pasture is lush, high in protein and low in fiber during most of its grazing period. Crude protein levels normally range from 15 percent to 34 percent of dry matter, making this forage an excellent protein supplement for many classes of livestock.

Stocking rate and time of grazing will be somewhat determined by the intended use of the crop. If you are planning to take a silage or grain harvest, grazing should only be moderate.

Heavy grazing can reduce grain yields. Moderate grazing in the fall should not result in significant silage or grain losses provided that moisture and soil fertility are adequate. In fact, fall pasturing can be beneficial where the small grain was seeded early and has made excessive growth.

Average spring forage yield and quality of small grains

Spring grazing may be started when growth resumes. If a grain or silage crop is to be harvested, grazing should be discontinued when the plants start to grow erect just previous to jointing (nodes begin forming on stems). Plants will be injured by grazing at any time after their growing points are above the ground.

The use of temporary electric fencing should provide a practical way to manage these pastures. Small grains can be continuously grazed but rotational or strip grazing can allow for a higher carrying capacity because of reduced wastage and trampling.

Annual ryegrass can be seeded in late summer, depending on latitude and elevation, and be grazed or harvested as hay or silage in November or December and then again in the spring. After spring harvest, the ryegrass can be plowed or killed with herbicide and the area planted to another crop such as corn for silage.

Average annual ryegrass yield

Annual ryegrass establishes rapidly, is high-yielding under favorable environments and possesses high nutrient content. Ryegrass grows best on fertile, well-drained soils but can be grown on soils where it is too wet at certain times of the year for satisfactory growth of other grasses.

Ryegrass will perform less than optimum during a drought or periods of extended low or high temperatures. Ryegrass is a high-quality forage and its high digestibility makes it suitable for all types of ruminants.

Annual ryegrass

There is a challenge with getting corn (silage or grain) harvested and annual ryegrass planted early enough (mid-September in Pennsylvania) to get it established and provide forage during the fall.

Researchers at Penn State have developed an “interseeder” that plants forages in standing corn so the forage is already growing when the corn is harvested. The interseeder can also sidedress N fertilizer and a post-emergent herbicide while seeding the forage crop.

Summer-annual grasses, which maintain relatively high levels of production during hot and dry conditions, can greatly reduce the risk of inadequate forage production during the summer. They can also be used as an emergency forage source when production from corn and hay crops is likely to be less than adequate.

Average yield of summer annual grasses

Grasses in the group “summer annual” differ in growth and production potential, but all grow best at relatively high temperatures (+80ºF) and can grow under conditions of limited moisture.

Sorghum is an upright-growing grass which has been bred for both grain and forage production. The grain sorghum types are relatively short-growing (less than 6 feet) and provide moderate yields when harvested as forage.

Forage sorghum, on the other hand, grows tall (6 to 15 feet) and has the potential for high forage yields. Of the two types, forage sorghum is the preferred type for forage production.

Like corn, sorghum hybrids are classified into maturity classes. Late-maturing sorghum types yield more than earlier-maturing types but may not reach maturity before a killing frost. The forage sorghums are usually harvested only once and used for silage or green-chop production.

Sudangrass usually grows between 3 and 8 feet high and has stems about a quarter-inch in diameter. Solid stands of sudangrass grow shorter than when seeded in rows. Sudangrass develops only fibrous roots and does not have rhizomes. However, many stems may develop from a single seed if space is available. Sudangrass will re-grow following each harvest until cool temperatures or lack of moisture inhibit growth.

Sorghum-sudan hybrids or sudax resemble sudangrass but are taller, have larger stems and leaves, and give higher yields. Hybrids tend to be coarser than sudangrass and vary in seed color and size, yield and growth characteristics depending on their parents. Like sudangrass, sorghum-sudangrass hybrids will re-grow after each harvest unless environmental conditions are restrictive.

Millet has smaller stems and is more leafy than the sorghum, sudangrass or sorghum-sudangrass hybrids. Pearl millet will re-grow after harvest but not as rapidly as either the sudangrass or sorghum-sudangrass hybrids. German or foxtail millet, however, does not regrow after harvest. Millet yields are usually lower than sorghum-sudangrass hybrids.

Teff looks distinctly different from other summer-annual grass forages discussed above. It is a very fine-stemmed grass that only grows 2 to 3 feet tall. A big advantage of teff compared to the other summer-annual grasses is it makes soft hay. Teff is currently grown primarily as forage in the U.S. but there is a growing market for teff grain because it is gluten-free.

After teff emerges, it will be ready to harvest in 45 to 55 days. Cut the teff when it reaches boot stage and before the seed head emerges. It won’t be as tall as other forages, but its quality will decline if you delay mowing while waiting for it to get taller.

It will average 1 to 2 tons of dry weight per acre per cut. Leave 3 to 4 inches of stubble during every cut until the last of the season, and be especially conservative with rotary mowers as they’re notorious for scalping the plant and drastically slowing down re-growth.

Planting and grazing sequesnce for forage brassicas

Summer or fall
Forage brassica crops such as turnip, swede, rape and kale can be spring-seeded for grazing in August and September or they can be summer-seeded to extend the grazing season into November and December (Figure 2).

Brassicas are highly productive and digestible but are utilized almost exclusive by grazing. In addition, crude protein levels are high, varying from 15 to 25 percent in the herbage and 8 to 15 percent in the roots depending on the level of nitrogen fertilization and weather conditions.

Kale varieties differ markedly in rate of establishment, stem development, time required to reach maturity and winter hardiness. The stemless-type kale has a faster rate of establishment than varieties which produce stems. Crop height of the stemless type is approximately 25 inches whereas that of stem kale is 60 inches with primary stems often 2 inches in diameter.

Stemless kale attains maturity in approximately 90 days, allowing two crops per year, whereas varieties that develop stems require 150 to 180 days to attain maximum production.

Rape is a multi-stemmed crop with fibrous roots. The stems vary in length, diameter and in palatability. Forage yields of spring-planted rape increase until plants become physiologically mature. Growth slows or ceases at maturity and yields plateau until leaves senesce and die.

Varieties differ in timing when this occurs. Generally, yields of rape varieties are maximized with two, 90-day growth periods. However, performance of some rape varieties is best with one 180-day growth period, and yields of rape hybrids were greatest with 60 days of growth before the first harvest and a 30-day growth period before the second harvest.

Turnip or turnip hybrids grow very fast, reaching near maximum production levels in 80 to 90 days. Studies in southwestern Pennsylvania showed turnip can accumulate dry matter in October as fast as field corn does in August. Growing “out of season” (October-November) makes turnip a valuable crop for late-fall grazing.

The proportions of tops to roots in turnips varies markedly depending on variety, crop age and planting date. Research by the USDA-ARS showed that turnip crops can vary from 90 percent tops and 10 percent roots to 15 percent tops and 85 percent roots.

Some hybrids have fibrous roots which cannot be readily grazed by livestock. All varieties produce primarily tops during the first 45 days of growth. Sixty to 90 days after seeding, some turnip varieties continue to produce a high proportion of tops while other varieties have nearly equal top and root production.

The significance in the proportion of tops and roots is that the crude protein concentration of roots is approximately one-half of that in turnip tops.

Therefore, greater root production tends to reduce the crude protein yield of the total crop. On the other hand, stockpiled tops appear to be more vulnerable to weather and pest damage than roots. Varieties differ in resistance to diseases, but this often is not evident until the crop is more than 80 days old and the plants are reaching full production.

Swedes, like turnip, produce a large edible root. Yields are higher than those of turnip, but they grow slower and require 150 to 180 days to reach maximum production.

Swedes usually produce a short stem but can have stems 2½ feet long when grown with tall crops which shade the swede. Unfortunately, stem elongation is at the expense of root development. In general, all swede varieties are recommended for late-fall grazing.

Brassica grazing management
Grazing management is important to optimize the true potential of brassica crops. Strip-grazing small areas of brassica at a time provides the most efficient utilization. Grazing a large area increases trampling and waste of the available forage. Rape is more easily managed for multiple grazings than are the other brassica species.

Approximately 6 to 10 inches of stubble should remain after grazing rape to promote rapid re-growth. Re-growth may be grazed in as few as four weeks after the first grazing. Graze rape close to ground level during the final grazing.

When turnips are grazed more than once, only the tops should be grazed until the final grazing, when the whole plant can be consumed. Like rape, regrowth of turnips can be sufficient to graze within four weeks of the first grazing.

Hopefully, this brief overview of non-traditional, annual forage crops has provided you with a cursory knowledge about these forage crops and where they might fit into your forage system.  FG

PHOTO 1: Researchers at Penn State developed an “interseeder” that plants forages in standing corn so forage is already growing when corn is harvested. The interseeder can also sidedress N fertilizer and a post-emergent herbicide while seeding forage. 

PHOTO 2: Annual ryegrass, if planted early enough for establishment, can provide forage during fall after a corn-silage crop is harvested. Photos courtesy of Marvin Hall.

Marvin H. Hall
  • Marvin H. Hall
  • Crop Management Extension Team
  • Penn State University