Growing Tillage Radishes
Botanical Name: Raphanus sativus Longipinnatus
Imagine a plant that tills the soil by itself: breaking up compacted ground, helping control pests biologically, and making more moisture and nutrients available for the next year’s cash crops.
The long and robust daikon radish – also known as oilseed radish or forage radish – is that plant. Today it also referred to as tillage radish, and it does even more:
- Protects topsoil from erosion
- Controls weeds
- Adds organic matter to soil
- Reduces dependence on chemical fertilizers
- Helps warm the ground in spring
In northern climates especially, sowing fast-growing tillage radish seeds in fall after cash crops are harvested allows the plants to grow to maturity before heavy frosts shuts down all agricultural activity.
Especially in the coldest climates, winter “kill” will make the radish roots disintegrate. The holes that remain in spring have an effect like tilling: moisture and new crop seeds can find places to settle in.
The oilseed radish can actually break hard packed soil apart organically. These radishes grow a slender taproot that penetrates the soil as deep as six feet. Meanwhile the plump upper part of theradish root can grow several inches in diameter to a depth of nearly two feet. That’s why tillage radishes are sometimes called “bio-drills.”
Growing tillage radishes as a form of “conservation tillage” takes extra time and work in the farming cycle. For one thing, timing must be right to plant the tillage radish seeds; tillage radishes need about 60 days to mature and produce their big, beneficial roots. And in low-frost zones the radishes must be “terminated” several weeks before planting new crops, so that no roots or seeds are present to resume growing.
Researchers are starting to study tillage radishes in detail. So far they are finding that growing radishes for tillage probably doesn’t affect the ability of cash crop seeds to sprout. That’s good news. And breeders are exploring ways to produce the most useful tillage radish seeds. Farmers will find several patented hybrids for tillage radishes.
Some growers are also experimenting with mixing tillage radish with other over-wintering cover crops, notably oats. The results are promising.
Tillage radishes are proving effective at weed suppression in fields. To achieve best results, plants should grow at a rate of five seeds or more per square foot. And seeds should be planted asearly as possible in fall.
An important benefit of growing tillage radishes is that the roots can draw up, or “scavenge,” nitrogen from surrounding soil, preventing it from leaching away and making more nitrogen available for crops to follow.
Two notes of caution: tillage radishes don’t grow well where the soil it too wet, so make sure that there’s enough drainage where you want to plant. And radish roots decomposing in a late-winter field can produce strong rotten egg smells.