Ideal pH: 6.0-6.8. Radishes are moderate to heavy feeders. Best in rich, loamy soil amended with composted manure. add 1 cup of complete organic fertilizer for every 3m (10') of row for background fertility. Lime beds the previous fall. The real secret to growing this little vegetable is speed. Sow a short row frequently, thin them quickly, keep them watered, eat them quickly, and sow some more.