The best quality sprouts are produced in the fall with sunny days and light frosts at night. Hot weather results in soft open sprouts which are undesirable. The plants are vigorous, uniform in size and appearance, with dark green leaves and long, narrow petioles, and produce heavy yields of closely spaced, very firm, highly uniform sprouts, averaging about 1 inches in diameter. Any delay in growth will cause disappointing yield and quality of sprouts. A soil high in organic matter so that it will hold a lot of moisture is necessary to keep the plants growing vigorously.
Irrigation is helpful.
If possible, plow under a heavy application of manure and by all means use a good cover crop. Brussels sprouts demand a sweet soil so be sure the pH is about 6.5. Broadcast at least 2000 pounds per acre or 5 pounds for each 100 square feet and work into the soil about one week before the plants are set. This fertilizer should contain some of the minor elements, particularly boron and magnesium. If it does not it would be wise to purchase a small amount of a special minor element mixture and add to the fertilizer according to the directions on the container.