– Chris Penrose, OSU Extension Agent, Agriculture, Morgan County
Brassicas can increase mid-summer forage availability but have a particular advantage for late fall-winter grazing. Brassicas are easy to establish, fast-growing, high-yielding, high-quality, and can withstand cold temperatures.
These fast-growing crops can reach maximum quality in as little as 60 days and maximum yield in 70 to 90 days. The tops can tolerate temperatures to 15-20 degrees F and the bulbs are 5-10 degrees F hardier. In a 1994 southeastern Ohio trial, Premier Kale, a long season leafy crop, withstood temperatures of -7 degrees F and yielded more than three tons of dry matter per acre (Penrose et al., 1996).
Brassicas can be no-tilled with prior application of a burn-down herbicide. They can also be conventionally tilled with a drill, or broadcasted and cultipacked. Seeding rate should be 1.5 to 2.0 lbs/acre for turnips and swede and 3.5 to 4.0 lbs/acre for rape and kale. A real challenge is to get the seeding rates that low. If broadcasting is an option, consider mixing in fertilizer to keep the seeding rates that low. If fertility levels are adequate, the only additional fertilizer needed is 50 pounds of nitrogen. A stable form of nitrogen such as ammonium nitrate (34-0-0) is recommended to reduce volatilization.
Turnip varieties produce varying amounts of tops and bulbs, and the bulbs are usually available as an acceptable feed for cattle. Some new forage varieties produce a greater proportion of tops to bulbs. For example, in a 1994 study, the garden variety purple top turnip had 39% of the yield in the tops (6,653 lbs/dry matter/acre) 95 days after planting while a Chinese cabbage-turnip hybrid (Tyfon) had 76% in the tops (6,792 lbs/dry matter/acre) during the same time. Some important considerations include the fact that a greater percent of the tops are likely to be consumed than the bulbs, and the tops tend to be higher in quality. In three years of Ohio trials, protein content of tops averaged 17-24% and bulbs 10-15%. Total yields for these crops can range from three to Five tons of dry matter per acre with adequate rainfall.
A farmer in Washington County, Ohio, was selected to demonstrate how brassicas can reduce stored feed costs. On August 3, 1994, 4.3 acres of pasture were seeded to purple top turnips at the rate of two lbs. per acre with a no-till drill. Thirty days after seeding, 68 lbs/acre of ammonium nitrate (34-0-0) were broadcast. All other fertility levels were adequate, and no additional fertilization was required. Samples taken on October 26 (84 days after planting) resulted in a yield of 10,306 pounds of dry matter per acre (50% tops, 50% bulbs). On October 26, 28 beef cows and their calves were placed on the turnips. The animals grazed the turnips for 45 days using strip grazing. Variable planting costs were $50/acre (Ohio State University Farm Rates, 1993). Feed costs were $0.17 per day per cow-calf unit based on 75% utilization. Comparing this to stored feed costs of mixed hay at $80/ton (Ohio State University Extension Enterprise Budgets, 1995) and consumption of 3% dry matter per day, the savings amounted to $1,045 for the period or $23 per day (Barrett and Penrose, 1996).
Available turnip cultivars include Purple Top, Rondo, Wintergreen, Forage Star, Seven Top, Barkant, and All Top. Rape cultivars include Emerald, Crystal River, Rangiora, and Bornopoli; hybrids include Tyfon and Pasja; and Kale includes Premier, Gruner, and Kepti. Most of these varieties are available from major seed dealers in Ohio.
Three years of trials in Ohio have demonstrated the potential of brassicas to extend the grazing season (Penrose et al., 1997b). For what has proven to be the most efficient usage:
- * Seed from mid-July through mid-August.
- * Provide hay or stockpiled forage to improve utilization.
- * Strip graze where the forage is rationed.
Brassicas are fairly flexible in providing nutrition for livestock. However, here are some general guidelines. Any summer grazing should be very light, with only top grazing. Graze small areas through rotational or strip grazing. After maturity, fungal diseases and rot may deteriorate the plants. Brassicas should be planted in the same area for only two years because of disease potential.