Radish is fast growing crop, often selected for its high yields and effective nematode suppression, it produces masses of green leaf to rot back into the soil as a green manure. With deep taproots that can penetrate hardpans, aerate and break up the soil, they draw up nutrients, which are then available for ensuing crops. Fast growing and hardy, it is often used in emergencies and may be sown as late as September. It is therefore a good “patching” option if there have been any failed areas of crops.
Radish is a ‘dual purpose’ crop; the leaves are edible and have a spicy flavour with a crisp pleasant texture when young. Eaten at micro or baby leaf stage they make a nice addition to salads or can be used as a broccoli or spinach substitute. The seed pods are delicious when used in stir-fry dishes. The roots make acceptable eating when young but later become fibrous.
As a green manure, Radish can be sown at any time once temperatures start to rise in the spring. Sown late in the year, it can be worked into the soil when young or left to overwinter. The plants will gradually die down as the temperatures drop, making it easy to incorporate into the ground in spring. It can grow in full sun or in semi-shade (light woodland) and is suitable for all soil types.
Radish can be interplanted between crops and can be sown with a legume where additional nitrogen is required. Radish contains natural pesticides and glucosinates and can be used as a tool to suppress cyst nematodes prior to planting many crops especially potatoes, tomatoes, carrots, corn and soybeans.
Frequently grown by commercial farmers in Scotland as a catch crop instead of mustard, the benefits of this dual purpose crop also apply to the small-scale farmer. Young leaves can be picked for use as spinach and the cylindrical roots and remaining leaves fed to the cattle.
Radish produces a large quantity of highly nutritious forage per acre. It can be chopped, fed or grazed, producing food in mid winter when you need it most. With similar forage values as turnips, the quality of the leaves is higher than that of the roots. In addition the leaves account for more herbage bulk than the roots prior to leaf senescence (die back) late in the season. The softness of the leaves also makes them palatable to the animals.
For use in the winter timing is important. It should be planted early enough to ensure bulk before winter, but not so early that it will bolt to seed before winter.
Plant parasitic nematodes are an increasing threat to farming. Research shows that fodder radish grown as green manure or trap crop has potential to control crop-threatening nematodes such as Meloidogyne hapla (root-knot nematode) and Trichodorus ssp (Tobacco Rattle Virus).
The use of cover crops grown between the main crops may provide an alternative management strategy. Radish 'Siletina' has been developed to improve soil fertility while being effective at reducing root nematodes.
Sowing Period: Sow from early May to September
Soil: Suitable for all soil types
Growing Period: 3 to 6 months or overwinter.
Coverage: 2.5kg per acre. 100gm covers 18 square metres
Sowing: Sow from early May to September
Prepare the soil by removing weeds, digging over if it hasn't been recently cultivated and raking level. Scatter seeds over the surface of the soil. Make sure the seed is in firm contact with the soil by gently tapping over the surface with the back of a spade. Water in well. Plants will germinate in three to ten days. Bare patches should be covered within two to three weeks.
Plants require irrigation during dry spells in the summer or the root quality will rapidly deteriorate and the plant will go to seed. Sown in spring they will flower 70 to 90 days from germination. (June to August) and the seeds ripen from July to September. Hoe in just before flowering for release of gases that control nematodes. Plants will do the most good if they are left for around eight weeks before digging in. If plants start to flower before this, cut off the tops and dig in.
In general, all green manures should be incorporated whilst they are still relatively soft and green, and before they have chance to set seed. Ideally, they should be incorporated throughout the surface few centimetres of the soil where most rooting of the following crop will occur. This is also the place where decomposing organisms are most active.
It is important to make sure that incorporation is complete so that the plants do not re-root and become weeds in their own right. After incorporating, allow up to four weeks before planting the next crop, particularly if it is to be sown directly into the soil.
Growing medium to long term:
During the growth of a medium to long-term green manure it may be desirable to mulch the crop occasionally by 'topping' it with a mower. The material removed will then decompose and be recycled to the growing green manure crop. It is important that mowing and mulching are carried out whist the crop is relatively short and that it is not cut so low so that regrowth is prevented, or the plants smothered by mulched material.
Radishes are excellent companion plants for many crops especially lettuces, nasturtiums, peas and chervil, tomatoes, carrots and cucumbers. The growing plant repels the vine borers which attack squashes, marrows and courgettes. They also repel beetles from tomatoes and cucumbers. It is also useful for repelling various other insect pests such as carrot root fly.
They grow badly with hyssop and with grape vines.
Brassicas as green manures:
Because they are also susceptible to clubroot and can increase the level of infection, brassica (cabbage family) green manures should not be sown in close sequence with brassica crops. Crop rotations should be carefully planned to avoid this.
- Additional Information
Common Name Raphanus sativus Cover Crop. Other Common Names Japanese Radish, Leafy Daikon, Daikon, Fodder Radish Family Brassicaceae Genus Raphanus Species sativus oleiformis Synonym Raphanus sativus ssp. oleiformis, Raphanus sativus var oleiformis Hardiness Hardy Annual Flowers Radish flowers can be white, pink or purple. Natural Flower Time June to August Fruit Seeds ripen from July to September. Time to Sow Sow from early May to September Germination Three to ten days. Time to Harvest 3 to 6 months or overwinter. Coverage 2.5kg per acre. 100gm covers 18 square metres