Growing Forage Radishes
Botanical Name: Raphanus sativus longipinnatus
There’s a new farm and garden method that’s gaining popularity as a way for a single species of plant – the daikon radish – to plow and condition winter fields without mechanical means. Daikon radish has a host of names: groundhog radish, forage radish, or even groundhog forage radish, as well as oilseed radish.
Forage radishes do more than “plow.” Over the course of the cold winter months they can provide nutritious and easily digestible forage for livestock, and if permitted to flower they can eventually produce seeds that are marketable as a source of biodiesel oil.
The marvelous groundhog or forage radish plays a valuable role as a cover crop to protect fields of cash crops between growing seasons. It can:
- Keep fields from being invaded by weeds after a main crop is harvested
- Capture or “scavenge” available nitrogen in the soil so it isn’t lost to groundwater
- Prevent erosion of bare soil
- Control some pests using natural means
- Break apart heavy or compacted soil
The daikon radish is just right for all these jobs because of its stupendous growth habits. The root structure is perfectly designed to work its way deep into any soil. The longest part of the taproot may extend as far as six feet beneath the surface, while the thick upper root grows a foot or more long and several inches in diameter. Those roots can break apart densely pack soil, letting in air and moisture.
A forage radish cover crop is sown late in the growing season; the seed needs 60 days to grow to maturity, so mustn’t be planted too late in the fall, ideally in late August.
In some cases farmers will plant forage radish seed into the bare soil where a cash crop (say, beans or cucumbers) has already been harvested and the stems plowed under. In other cases farmers may sow forage radish seed right over ripening “standing” crops such as cotton or soybeans, or corn…and let the seeds fall into the soil as the main crop is harvested and disked.
As the forage radishes eventually disintegrate over the winter they leave holes or depressions in the soil where the big roots had been. Those depressions and holes will aerate soil in spring when fields are later plowed for planting. Meanwhile, compounds in the radish can repel some nematodes with biochemical means.
Don’t use forage radish in fields where the main cash crops are broccoli, cabbage, or related plants, as some pathogens can linger and damage those crops.
Look for seed suppliers who sell forage – daikon – radish seed in bulk.