Japanese (forage) radish: Versatility redefined

By Petrus van Rooyen, product manager: forage crops, Pannar Seed

Japanese radish (Raphanus sativus) is an excellent forage crop. It is also a good choice in crop rotation systems as it has soil conservation and health benefits. Before utilisation, the large taproot and foliage help protect the soil against erosion. The large taproot of radishes allows these crops to penetrate and break up shallow layers of compacted soils or plough pans. This is where the common nickname of ‘biodrills’ comes from. This action promotes increased infiltration of water into the soil profile and promotes deeper rooting in subsequent crops.

A crop above the rest
Research conducted in Maryland, the United States, found that four times as many corn roots penetrated compacted subsoil after a forage radish cover crop than after leaving it to lie fallow. If planted early enough (preferably six weeks prior to frosts), radish can produce an aggressive growth habit that will spread out and canopy, which outcompetes autumn and winter weeds.

This foliage also helps with the infiltration of any late rainfall into the soil. If unutilised and left to decay in the field, water infiltration and surface drainage improves due to channels left by the large decaying roots. Japanese radish, which is from the Brassicaceae (or Cruciferae) family, is well known and utilised as an autumn or winter crop in the cooler cropping areas in South Africa.

Table 1: The expected dry matter production and stocking rates under different ranges of rainfall (Source: Pannar forage crops production guidelines).

Japanese radish is used widely both in pure stands and mixed pasture systems. Planting times vary across the country, with some cool areas able to plant as early as mid-December. For most areas with relatively reliable rain, the recommended planting window is from January to early March.

Seeding rates are between 2 to 3.5 kg/ha in rows. If planted too early, there is a risk that seedlings could be damaged by hot weather, as well as plants switching into the reproductive phase and flowering early. However, keep in mind that it is normal for a percentage of Japanese radishes to flower earlier and change to seed formation.

Insects can damage seedlings, so be on the lookout for them and apply the necessary chemicals. Conversely, if planted on dryland too late, there is a risk of missing the last rain and having lower soil moisture content, resulting in lower yields.

The production potential of Japanese radish can vary dramatically depending on time of planting, soil potential and rainfall. Under irrigation and high potential soils, 14 ton DM/ha can be achieved. Under dryland conditions, tonnage ranges between 4 to 10 ton DM/ha depending on parameters mentioned (Table 1). The stocking rate on Japanese radish is outstanding for a winter crop, with 6 ton DM/ha able to carry 50 small stock units for 120 days.

Endurance – Exclusive to Pannar
Pannar markets the variety Endurance, which originated from an intensive breeding programme run between the Agricultural Research Council’s Animal Production Institute (ARC-API) in Cedara, KwaZulu-Natal, and PGG Wrightson in New Zealand.

The aim was to produce a highyielding, late-flowering fodder radish variety. Endurance is a later-flowering variety with soft, hairless leaves, and moderate to good resistance to rust infection. Pannar Seed has the exclusive marketing rights to Endurance in Southern Africa.

Japanese radish’s lower water requirements and ability to produce high yields and quality forage compared to other winter crops, has increased its popularity. It is a good choice to fill the forage gap in the winter and early spring.

For more information, contact the author at petrus.vanrooyen@pannar.co.za or 082 822 6438. Alternatively, contact your Pannar Seed representative.

Pannar's Japanese radish, Endurance.