Chinese radish, a structuring crucifer for intercrops

Technical articles - Soil regeneration, Weeds

Field crops Field crops Cover crops Green manure Nitrogen trapping Soil structuring

The radish Chinese, also called daikon radish, is an annual crucifer with a short cycle, used as a cover crop for its properties of soil structuring, trapping of nitrogen and rapid establishment. Although still little used in France compared to white mustard or phacelia, it presents important agronomic benefits in short or long intercrops, notably in systems aiming to improve soil structure or to recycle mineral elements. It is intercalated between a winter cereal and a spring crop such as corn or sunflower, but can also be used in long intercrops in market gardening or viticultural systems.

A powerful taproot to decompact superficial horizons

The Chinese radish has a developed taproot that can reach 30 to 60 cm depending on the soil and growth conditions . This taproot allows to crack superficial horizons and restore vertical porosity, facilitating water infiltration and root regrowth of the following crop. The variety ‘Structurator’ is particularly selected for this use, with enhanced root development and low sensitivity to bolting. Thus, the Chinese radish acts as a biological subsoiler, creating root and water pathways useful for the next crop.

Rapid emergence and effective coverage

Sown in July-August, at a rate of about 9 kg/ha for a thousand grain weight (TGW) of about 14 g, the Chinese radish emerges quickly, often in 3 to 5 days when the temperature reaches 20 °C . In a few weeks, it develops a significant biomass, generally between 2 and 5 tons of dry matter per hectare, effectively covering the soil. This rapid development makes it an excellent competitor against weeds, particularly useful in short intercrops.

In trials conducted by Interbio Occitanie on market gardening systems, the Chinese radish combined with phacelia showed better soil coverage and higher biomass than other classic crucifers.

Nitrogen recycling and soil functioning

Rapid absorption of residual nitrogen

Like all Brassicaceae, the Chinese radish quickly captures the mineral nitrogen present in the soil. It can absorb up to 30 units of nitrogen per ton of dry matter produced. In the case of a cover of 3 t DM/ha, this represents about 90 units stored, effectively limiting losses by leaching in autumn, especially after a cereal.

Progressive release in spring

After destruction of the cover, the biomass gradually releases mineral elements, depending on climatic conditions and the method of intervention (frost, mowing, rolling). Each ton of dry matter releases on average 30 units of nitrogen, 20 of potassium and 8 of phosphorus. This slow mineralization, spread over several weeks, benefits the following crop. The decomposition of the taproot also stimulates soil biological activity and promotes the formation of root channels useful for vegetative regrowth.

Method of destruction: natural or mechanical

The Chinese radish is sensitive to frost from -4 to -6 °C depending on stage and conditions. In most regions, a winter destruction is sufficient. In case of mild winter or late sowing, a mechanical destruction (rolling, mowing, disc harrow) is recommended to avoid seed bolting. In case of late emergence, the risk of bolting increases in spring, which can hinder management of the following sowing.

It is not recommended to associate Chinese radish with other crucifers in short rotations including rapeseed, to limit the risk of disease development such as clubroot of crucifers. A rotation interval of at least 4 years before returning to a crucifer crop is generally advised to limit parasite pressure.

A complementary cover in association

Chinese radish is often included in mixtures, notably with phacelia, Alexandrian clover or Brazilian oat. These associations allow to diversify functions: rapid coverage, nitrogen fixation, root structuring, soil protection.

In viticultural systems, such as Domaine Gassier located in Gard, the Chinese radish is planted between rows to promote soil aeration and regulate water competition.

Conclusion

The Chinese radish is an effective tool for soil structuring, nitrogen trapping, mineral recycling and weed control. Its moderate cost (~30 to 50 €/ha), ease of establishment and natural destruction make it a cover particularly suited to short to medium intercrop systems.

Its integration in functional mixtures or in market gardening or viticultural systems opens increasing usage prospects in conservation agriculture.