A large grass that can grow 5 to 12 feet tall in one summer, corn (Zea mays) needs a lot of nutrition to fuel that growth. Native to Central America, many corn cultivars exist, including kinds of popcorn, sweet corn and ornamental corn. Regarded as a heavy feeder, all corn needs a regular supply of fertilizer throughout the growing season, especially nitrogen and phosphorous. Many fertilizers work well on the annual plant, so choose the products that work best for your gardening conditions and preferences.
Organic fertilizers provide a slow release of a wide range of essential nutrients and also condition the soil so that it holds more moisture, gives better drainage and provides material to hold nutrients within the soil longer. They also provide a more complex habitat for the beneficial microorganisms that inhabit soil. Organic fertilizers for corn include compost, aged manure, fish emulsion, blood meal, bone meal and alfalfa meal. They generally don't burn the roots. Organic fertilizers are best for corn where soils need amending, if you practice organic gardening or if you have a low-cost, readily available source of organic material.
Made by combining different salts and basic minerals or chemicals, inorganic fertilizers usually have fewer nutrients but release them quickly, with the possibility of root damage as a result. They're readily available and have a known chemical formulation, important if soil tests show your corn-growing area has deficiencies of a particular nutrient. Inorganic fertilizers formulated for controlled or slow release are good for corn, which needs steady feeding over about a three-month period.
For amending the soil and adding nutrients before planting corn seed, organic fertilizers such as aged compost work best. Add 2 to 4 inches of compost in the spring and dig it into the top 6 inches of soil. You can also use an inorganic fertilizer such as 16-16-8, which is high in the nitrogen and phosphorus that corn needs, applying 2 pounds of fertilizer per 100 square feet of garden space, mixing it well into the soil. You might like to use both organic and inorganic fertilizers to combine their best characteristics, such as equal parts of compost and 10-10-10 broadcast over the soil at the rate of 4 to 5 pounds per 100 square feet and then digging it in.
Growing Season Fertilizers
Recommendations for fertilizing corn during the growing season differ from place to place. The University of Utah recommends applying 46-0-0 fertilizer to sweet corn twice, using 1/2 pound per 100 square feet when corn plants have eight to 10 leaves, followed by 1/4 pound when silk forms on the ears. Colorado State University Extension calls for fertilizing corn every four to six weeks with nitrogen-rich fertilizers such as ammonium sulfate, which is approximately 20-0-0, or blood meal at about 15-1-1. Apply these products at the rate of about 0.1 pound for every 100 row feet.