Forage rape is a high-yielding, fast-growing brassica crop used primarily in agriculture to supplement livestock feed and improve soil quality. This versatile plant, sometimes referred to as fodder rape, serves the dual purpose of providing a highly nutritious grazing option and functioning as an effective cover crop. Its rapid growth and substantial biomass make it a valuable resource for farmers aiming to extend their grazing season and enhance land management practices.
Defining the Brassica Family Member
Forage rape is a cultivated variety of Brassica napus, placing it in the same genus as common vegetables like cabbage, broccoli, and turnips. It is closely related to canola, which is an oilseed type of Brassica napus, but forage rape has been specifically bred for maximum leaf and stem production rather than seed yield. The plant is characterized by a large, leafy top and a prominent taproot, which anchors it firmly in the soil.
Cultivars are typically grown as an annual or biennial crop, depending on the variety and climate, with a life cycle focused on vegetative growth. It is primarily a cool-season crop, thriving in temperate environments and exhibiting good frost tolerance. This allows it to remain green and productive well into the late fall and early winter months. Two main types exist: a taller, giant variety preferred for cattle and a shorter, dwarf type often utilized for finishing lambs.
Nutritional Value for Livestock
One of the primary reasons for cultivating forage rape is its exceptional nutritional profile, which provides a high-quality feed source for grazing animals. The crop is highly digestible, with fresh matter digestibility often approaching 100%, meaning livestock can efficiently convert the forage into energy. It is remarkably high in protein (19% to 26% crude protein) and offers a high metabolizable energy content, frequently around 11.5 megajoules per kilogram of dry matter.
This high nutritive value makes it particularly suitable for cattle, including beef and dairy cows, and for sheep, especially for finishing lambs or flushing ewes. The crop is an invaluable resource for bridging the seasonal “forage gap” that occurs when traditional grass pastures become dormant. Its dense, leafy biomass provides a consistent and palatable feed source during periods of scarcity.
Benefits for Soil Health and Structure
Beyond its use as an animal feed, forage rape serves a beneficial function in crop rotation systems as an effective cover crop. The plant develops a robust taproot system that penetrates deep into the soil, which helps to mechanically break up compacted layers and improve overall soil structure. This action enhances water infiltration and aeration, leading to a healthier root zone for subsequent cash crops.
The dense growth of the plant’s canopy effectively suppresses weed growth by shading the soil surface and outcompeting unwanted species. Additionally, forage rape is an efficient nutrient scavenger, particularly for residual nitrogen left in the soil after a main crop harvest. By absorbing this excess nitrogen, the plant prevents it from leaching into groundwater, conserving the nutrient for future crops and reducing environmental contamination.
Practical Guide to Planting and Grazing
Planting Requirements
Forage rape can be planted across a wide window, from early spring for summer grazing to late summer or early fall for winter feeding. The typical growth period is 60 to 90 days until the first grazing. The seed requires a firm, moist seedbed and good soil drainage to establish successfully, with an optimal soil pH range between 5.3 and 7.5. To ensure proper germination, the small seeds must be planted very shallowly, ideally at a depth of no more than one-quarter of an inch.
Grazing Management
Grazing management is crucial for maximizing the crop’s use and ensuring animal safety. Livestock should be introduced to the forage gradually over a period of about two weeks to allow their digestive systems to adapt to the high-energy, low-fiber feed. Rotational or strip grazing is recommended, as this limits consumption to a specific area, reduces waste from trampling, and can allow for potential regrowth if a stubble height of about 10 inches is maintained. A dry fiber source, such as hay or straw, must always be provided alongside the forage rape to balance the animals’ diet and prevent digestive problems like bloat.