Cucumbers need a balanced fertilizer for best growth and production. Choose a product that has equal amounts of nitrogen, phosphate and potassium. Fertilizer can be worked into the soil before planting begins, or it can be added after the cucumbers have been planted.
An 8-8-8, 10-10-10 or 12-12-12 fertilizer is good for cucumbers. Spread a layer of fertilizer over the soil at a rate of between 1.5 and 3 pounds per 100 square feet, depending on soil needs and the manufacturer's recommendations. After cucumbers are planted, dig a furrow 1 inch deep about 3 inches away from the row of plants and add fertilizer to the furrow. More fertilizer can be added as growth continues.