Both the roots and the leaves of beets provide a nourishing vegetable. Proper fertilization helps the roots reach their full size and flavor, and ensures the plants develop healthy, flavorful greens. Beets have specific nutrient needs for best production. The roots may develop black spot in beds lacking boron. Preventing black spot and other nutrient deficiencies requires careful feeding during the short growing season for the beet crop.
Test the soil pH, following the instructions for the soil test kit you purchase. Beets grow best in soil with a pH between 6.0 and 6.8.
Add agricultural lime to the soil at the rate recommended by the test to bring the soil into the proper pH range. Apply lime at least 30 days before planting. Work the lime into the top 6- to 8-inches of soil.
Sprinkle 3 lbs. of a 5-10-10 or 10-10-10 fertilizer blend and ½ oz. of borax over every 100 square feet of beet bed, one week before you plant. Cultivate the fertilizer into the top 6 inches of soil.
Apply 3 oz. of fertilizer to every 100-foot row, two weeks after the beets germinate. Sprinkle the fertilizer down the row, approximately 6 inches away from the base of the plants.
Fertilize the beets again four weeks after planting if growth is slow or week. Apply 3 oz. of fertilizer per 100-foot row, sprinkling the fertilizer down the row, approximately 6 inches away from the base of the plants.