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Radish

It is best known for its deep tap root, quick emergence and rapid growth. It is primarily used to break up soil compaction, capture residual Nitrogen, suppress weeds, increase water infiltration, and increase soil biology.   The fodder from all types of radishes provides good forage, similar to turnips. It's best to plan a single grazing period, since it does not tolerate traffic well.  Oilseed radish cultivars such as Adagio or Colonel, are similar to the forage radish, but have a stubbier, more branched taproot and tend to be somewhat more winter hardy than the forage radish.

 

Varieties:

Oilseed Radish has been divided in different types, of which 2 are being used as cover crops, they are: Daikon and Forage

 Daikon: Most popular, due to its large taproot.

 Forage:  Lush top growth but a smaller and more branching root.

 

Characteristics:

The Oilseed Radish is an upright cool-season annual that grow 12-18 inches tall. It has rosette leaves with purple, pink, or white flowers and a deep, thick white taproot. Oilseed radish’s large taproot has many lateral roots that help loosen and aerate the soil.

 

Seeding:

Low rates are generally recommended because of the high cost of seeds. In some situations, however, high rates may be more beneficial. These include cases where control of weeds, diseases, and nematodes is the primary focus. Oilseed radish leaves low surface residue in the spring, so it is very appropriate for crops that require a well-prepared seedbed.

Inoculate:  Nitrogen deficiencies have been observed when planting after silage or grain corn on sandy soils or soils that do not have a history of manure application. In such situations, an application of 15 lbs N/acre is sufficient to stimulate rapid initial growth so that the forage radish may be able to capture 100+ lbs of N from deeper in the soil profile. 

Dates:  Forage radish grows best when planted from late July to early September but significant amounts of N can be captured by this cover crop when planted as late as October 1. Forage radish planted in late September may be less susceptible to frost and more likely to overwinter. When planted in late March as a spring cover crop, forage radish did not emerge quickly or grow as well as when planted in fall.

Rates:

  • Drilled: 5-10lbs/acre
  • Broadcast: 6-11lbs/acre – should be followed by a very light disking.
  • Arial: 6-12lbs/acre

Depth: Planted at a depth of ¼” – ¾”

Seeds per pound (PLS):  Average of 34,000

 

Soils:

Types:  Does well on somewhat poorly drained to well drained soils.

Fertility:  Low tolerance of low fertility

pH Level:  Performs best a pH levels of 6.0-7.5

Germination:  Minimum germination at a temperature of 45°F

Nutrients:   Planting oilseed radish in a recently or heavily manured field can be a good strategy since oilseed radish can scavenge residual nitrogen from the soil.

Sunlight:  Low shade tolerance.

 

Growth:

The seedling develops as a rosette and then elongates with the flower stalk.  It grows to a height of 50 to 100 cm. The top growth is rapid and cover is complete.

 Biomass:  Oilseed radish produces about 1.5 tons of dry matter per acre in about 60 days if residual soil nitrate is high. Whether planted in spring, late summer or early fall, oilseed radish grows quickly and produces a large amount of biomass in a relatively short time.

Rotation:  In short-season crops such as snap beans, oilseed radish can be planted before or after the crop. Oilseed radish can also be planted following wheat or cereal rye harvest. It can be seeded after harvest of a short-season crop such as pickling cucumbers, snap beans, wheat, rye, early potatoes or celery. In the fall, it will cover the soil, smother weeds and recycle nitrogen for the next crop. It can also be planted in early spring to provide green manure for cash crops planted in late May or early June.

 To improve weed and pest management, planting oilseed radish on the same field more than

two years in a row is not recommended.Also avoid planting oilseed radish in rotation with cole crops such as cabbage, broccoli and radish because they may be susceptible to similar diseases and insects such as clubroot disease caused by the soil-borne fungus.

Forage and Grazing:  Oilseed radish is highly digestible forage for early and late season grazing.

Termination:  Even though oilseed radish winter kills, it tolerates a few light frosts to 25° F, especially as a seedling.

Management:   The large taproot produced by oilseed radish generally helps to break-up compacted soil layers over time. These taproots break down easily over winter, leaving holes in the ground that aid in water infiltration and rooting of the subsequent crop.  Forage radish does not tolerate very wet soils, so avoid planting it in low spots that collect standing water. Nitrogen deficiency will limit forage radish growth and may limit its ability to compete with weeds or grow through compacted soil.

 

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Excerpted with permission from Managing Cover Crops Profitably, 3rd Edition, published by Sustainable Agriculture Research and Education (SARE) Outreach, USDA – National Institute of Food and Agriculture (NIFA). Citation of SARE materials does not constitute SARE’s or USDA’s endorsement of any product, organization, view or opinion. For more information about SARE and sustainable agriculture, see www.sare.org.