Spread 3 to 4 lbs of a complete, slow release fertilizer over every 100 square feet of garden bed. A 10-10-10 or 8-8-8 fertilizer blend provides sufficient nutrition.
Incorporate the fertilizer into the soil after application. Till it into the top 8 inches of the soil using a spading fork or a spade. Dig into the bed the desired depth and flip the soil and fertilizer over, so it's mixed in with the top soil.
Fertilize the cabbage four to six weeks after the cabbage is transplanted or has sprouted, if you direct seeded it into the bed. Sprinkle 8-8-8 fertilizer at a rate of 3 cups per 100 feet, or apply 1 lb. of ammonium nitrate fertilizer to each 100 feet. Apply the fertilizer 6 inches away from the base of the cabbage plants, as direct fertilizer contact can burn the cabbage.
Irrigate the bed immediately following fertilization. Water dilutes the fertilizer and makes the nutrients liquid, which helps the cabbage roots absorb and use the fertilizer.