- Dr. Joel Gruver, Western Illinois University
- Dr. Ray R. Weil, University of Maryland
- Charles White, Penn State University
- Dr. Yvonne Lawley, University of Manitoba
Over the past decade, radishes have been redefined; once known almost exclusively as a pungent vegetable, radishes have recently gained recognition for their cover cropping potential. After reading this article, you’ll be able to make an informed decision about whether cover crop radishes are worth a try on your farm.
Radishes have made rapid inroads as a cover crop for several reasons. First, the radish phenotype is well suited to perform many valuable cover crop functions—provide soil cover, scavenge nutrients, suppress weeds, and alleviate compaction—while creating few of the residue management challenges associated with many other cover crops. Second, recent research including many on-farm trials has documented beneficial effects of radish cover crops on soil properties and subsequent crops. Third, the seed industry has ramped up production of radish seed, brought new branded products to market, and promoted radish as a cover crop. Fourth—but perhaps most important in terms of the exponential growth in interest by farmers—radish cover crops have become a hot topic of discussion in rural coffee shops and on-line agricultural forums. Between 10/1/2011 and 12/1/2011, there were 51 threads about radishes in the Crop Talk forum of New Ag Talk, with over 500 responses and more than 240,000 views.
Most of the radish varieties currently marketed for cover cropping (e.g., GroundHog radish™, Nitro radish, Sodbuster, and Bio-till radish) are large rooted selections of daikon-type oilseed or forage radishes, but are not the product of formal breeding programs. All are morphologically similar to the large white daikon radishes traditionally used in Asian cooking. Hybrid daikon-type culinary radish seed is prohibitively expensive (more than $100/lb for bulk seed) for use in cover cropping, but open pollinated culinary daikon varieties may have some potential with bulk seed available for about $5/lb. Standard oilseed radish cultivars (e.g., Adagio, Colonel, and Defender) tend to have a stubbier, more branched taproot, greater winter hardiness, and lower seed cost than larger-rooted daikon types (Ngouajio and Mutch, 2004).