D. J. Undersander1, A. R. Kaminski1, E. A. Oelke2, J.D. Doll1, E.E. Schulte1, and E.S. Oplinger1
1Departments of Agronomy and Soil Science, College of Agricultural and Life Sciences and Cooperative Extension Service, University of Wisconsin-Madison, W1 53706.
The rutabaga (Brassica napobrassica), or swede, is believed to have originated from a hybrid between the turnip (Brassica rapa) and wild cabbage (Brassica oleracea), probably in Bohemia and as recently as the 17th century. Rutabagas are grown for human and animal consumption. Researchers in the United States determined in the early 1900s that the fleshy roots of rutabagas are valuable energy sources for young livestock. However, livestock farmers at that time were turning away from the brassica crops (which also include rape, kale, and turnips) because much hand labor was required for their production and utilization. One study showed that the labor requirement for these crops was three times that needed for corn silage production.
In the late 1970s, however, researchers began to recognize the potential of the root brassicas as forage crops, thereby eliminating the need for manual labor in harvesting and storage. In general, the forage brassicas are high-quality, high yielding forage crops that are well suited to seeding into existing pastures with little or no tillage.
Rutabaga is a cool-weather crop and is grown primarily in the northern parts of the United States and Europe, in Great Britain and in Canada.
Brassicas are high-quality forage if harvested before heading. Livestock readily graze on the stems, leaves and roots of rutabaga plants. Above-ground parts normally have 20 to 25% crude protein and 65 to 80% total digestible nutrients (TDN). The roots have 10 to 14% crude protein and 80 to 85% digestibility.
Rutabaga and other brassicas can provide grazing during the late summer and fall after other forage crops have played out. Rutabaga maintains its nutritional quality and palatability, if not heading, well into freezing temperatures and may be grazed in the Upper Midwest into November.
Rutabaga is a biennial, which can overwinter as a storage root. The 'root' consists of the hypocotyl - the plant part that lies between the true root and the first seedling leaves (cotyledons) - and the base of the leafy stem. A rutabaga root can be distinguished from a turnip by the presence of a swollen "neck" bearing a number of ridges, the leaf-base scars. The storage root may be purple, white or yellow, with yellowish flesh. Rutabaga leaves are bluish, thick like cabbage, and smooth. They emerge from the crown in a broad, low-spreading growth habit that inhibits growth of weeds. Rutabaga flowers are small and have light-yellow petals. They differ from turnip flowers in that they are not raised above the unopened buds on the raceme.
Rutabaga plants are both cold hardy and drought tolerant. They can be grazed 150 to 180 days after planting and can provide forage late in the Fall. Their most vigorous root growth takes place during periods of low temperature. The leaves maintain their feeding quality even after repeated exposure to frost.
Like other brassicas, rutabaga grows best in a moderately deep, fertile and slightly acid soil. Rutabaga will not do well in soils that are heavy, wet or poorly drained.
Rutabaga, like other brassicas, can be seeded into a sod with minimum tillage. The sod should be suppressed or killed, as the young rutabaga seedlings cannot compete with grasses. Once established, the rutabaga plants will smother out most other weeds. To kill sod, apply 2 qt/acre of Roundup at least three days prior to seeding. A reduced rate of herbicide can be used in 3 to 10 gal/acre of water to suppress sod or to prepare a field of wheat stubble for seeding with rutabaga.
Rutabaga can also be planted with a forage crop seeder on a conventional seedbed. Plow the seedbed at least six weeks before sowing. The seedbed should be fine, firm and free of weeds and clods.
The advantages of direct drilling brassicas into sod include fewer crop losses due to insect pests and less soil erosion on sloping sites where pastures are often located. A field of brassicas established in sod gives animals a firm footing in all kinds of weather. It also allows the original sod species to grow again the following spring if it has only been suppressed.
Rutabaga seeds do not germinate well in cold soil. Plant rutabaga when the soil temperature is at least 50°F. This means at com planting time or later. Later plantings may not have sufficient time to produce good forage growth.
Rutabaga seed can be planted in 6 to 8 in. rows at a rate of 1.5 lb/acre with a minimum-till drill. Alternatively, the crop can be seeded with a forage crop seeder on a conventional seedbed or broadcast followed by cultipacking. The seed should not be covered with more than 14 in. of soil.
Test the soil and lime to a pH of 6.0. Fertilizers should be applied at the time of seeding to give the crop a competitive edge on weeds. Apply 100 lb/acre nitrogen to soils containing 2 to 5% organic matter. 120 lb/acre if less than 2% organic matter and 60 to 80 lb/acre if soils contain more than 5% organic matter. Requirements for phosphorus and potassium are similar to those of a small grain. In Wisconsin and Minnesota, when soil tests are in the medium range, about 20 to 30 lb/acre of P2O5 and 120 lb/acre of K2O should be applied. Fertilizer applications should be banded at least 2 in. to the side or below the seed or broadcast. Boron and sulfur may also be needed. If the soil tests "low" in boron, apply 1 lb boron/acre on sandy soils and twice this on other soils. Apply 10 to 15 lb sulfur/acre if a soil sulfur test indicates a need for this element.
Some promising rutabaga varieties for use in the Upper Midwest are Calder and Sensation.
Weeds are generally not a problem once the rutabaga crop is established. However, sod and annual weeds should be controlled chemically before planting. Sod can be suppressed or killed with Roundup, as described under Seedbed Preparation. If annual weeds are present at planting time, eliminate them with a burn-down herbicide such as Gramoxone.
Rutabaga crops may suffer from clubroot, root knot, leaf spot, white rust, scab, anthracnose, mosaic and rhizoctonia rot. In some cases, diseases can lead to crop failure. To prevent problems with diseases, brassicas should not be grown on the same site more than two years in a row.
Insects we generally not a problem on rutabaga crops seeded in sod. However, an insecticide should be applied at the time of planting under conventional tillage.
Rutabaga plants are ready for grazing or green-chop when the forage is about 12 in. tall (150 to 180 days after planting). It is best not to wait too long, because fungal diseases may begin to cut yields after the plants reach maturity. The pasture should be grazed for a short period of time and the livestock removed to allow the plants to regrow. If grazed to a 5 in. stubble, one to four grazing periods may occur, depending on planting date and growing conditions.
The forage quality of rutabaga is so high that it should be considered similar to concentrate feeds, and precautions should be taken to prevent animal health problems. Livestock should not be hungry when put on pasture the first time so that they do not gorge themselves. If the livestock are moving from a feed of low nutritional quality, feed a high-quality diet for two to three weeks prior to grazing rutabaga, or feed rutabaga for 30 min/day for one week prior to heavier grazing. This will allow for the development of a rumen microbial population that is adequate to digest the high levels of protein in forage rutabagas. A lower quality hay should be made available (2 to 3 lb of dry roughage/head/day for sheep and 10 to 15 lb for cattle) to provide fiber in the animals' diet. Livestock should not feed on rutabaga during the breeding season or after the plants have begun to flower.
Rutabaga produces 6 tons or more of dry matter/acre.
Rutabaga is a highly nutritious forage crop that can provide grazing in the late fall after other forage crops are finished for the year.
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