Phosphorus belongs to a subgroup of nutrients referred to as the "primary macronutrients." Along with nitrogen and potassium, it's one of three essential nutrients for the growth of plants. Corn specifically uses large amounts of phosphorus during growth. Although naturally found in soil, farmers and gardeners often correct phosphorus deficiencies in soil by adding phosphorus fertilizers in water-soluble, citrate-soluble or other forms.
Utilization of Phosphorus
Corn uses phosphorus as a vital part of the photosynthesis process. Phosphorus aids in the transformation of solar energy into chemical energy, according to the North Carolina Department of Agriculture. Proper phosphorus levels in farmland or gardening soil help corn to mature efficiently and withstand stress through well-formed root growth and high blooming levels. According to the Virginia Cooperative Extension, the corn plant requires phosphorus in order to start the growth of stems, leaves and ears.
Balancing the Factors
Soil contains phosphorus in both organic and inorganic forms. Humus and other organic material provides organic phosphorus through the mineralization process. When inorganic phosphorus is present, it is often in a negatively charged state. This results in a reaction with iron, aluminum and calcium. The process results in the phosphorus being "tied up" and not as readily absorbed by corn plants.
The pH levels in the soil indicate how readily inorganic phosphorus will tie to other minerals. When the phosphorus in the soil is unavailable, corn plants cannot use it to grow properly. The challenge for farmers and growers is in finding the proper balance within the soil to enable the free usage of phosphorus.
Phosphorus Placement and Timing
According to Purdue University Forage Information, the majority of soil test reports do not indicate how phosphorus should be applied. Purdue recommends the application of both phosphorus and potassium at the same time for the production of corn. Starter fertilizers are important for optimum plant growth in corn. By the time a corn plant reaches 25 percent of its total dry weight, it has already absorbed 75 percent of its total phosphorus requirements, according to the Government of Alberta.
Purdue recommends for the tri-state area of Michigan, Indiana and Ohio specific application rates based on the results of soil testing. For soil that tests at 10 pounds per acre of phosphorus, 85 pounds of phosphate should be applied for a potential yield of 100 bushels per acres. For a yield of 180 bushels per acre, the phosphorus application rate should be increased to 116 pounds per acre. For test results indicating 80 pounds or more of available phosphorus, no phosphorus application is necessary.
Phosphorus Application Process
Apply starter fertilizer consisting of N1P2O5 in a band 2 inches to the side and 2 inches below the seeds, also known as banding. Banding protects the the seed and seedling from injury due to high levels of salt. Purdue recommends that the total amount of salts remain below 100 pounds per acre for corn production with the banding technique but less than 5 pounds per acre for direct contact. Direct contact usually occurs when the farmer uses a seed drill to plant corn.