Neither Squanto nor the frustrated Pilgrim farmers he tutored at Plimoth could have explained exactly why burying a dead herring at the bottom of a corn hill made the plants spring up and yield. Nor do most vegetable gardeners know the critical element rotting fish contributed to Pilgrim gardening. The high level of nitrogen made available to plants during the process of organic decay plays as an important role in modern gardens as in historic ones--fortunately, with much less odor and more easily regulated results.
Where NItrogen is Found
Nitrogen, along with other critical elements, occurs naturally in soil. Soil testing is important in determining whether the amount of nitrates existing in soil can support the growth of desired plants or crops. County Extension soil testing can be critical to garden and farm success; Iowa State University points out that soil chemistry composition varies widely from one part of the state to another, although Iowa is regarded as having uniformly good farmland statewide.
Sources of Additional Nitrogen
Washington State University's description of how compost is formed describes the bacterial process that makes nutrients available to plants as part of organic decay. Among the sources of nitrogen it emphasizes are animal manures and fruit and vegetable remains. Fish, marine trash and seaweeds are also excellent nitrogen sources. Modern fertilizers employ these and other sources of nitrogen, fortunately in less-odorous forms than their origins. Other good sources include alfalfa, soybeans, clover and other legumes, which fix nitrates in the soil for access by other plants. Planted and tilled into the soil before corn is planted, they function as "green manure."
Obtaining High-Nitrogen Fertilizers
Garden and crop fertilizers display a consistent formula expressing the ratio of essential nutrients to each other. The first number represents available nitrogen (N), the second available phosphorus (P) and the third potash (K). Translate the three numbers in the formula as "parts:" out of 100 parts total in a bag of fertilizer, 10 parts are nitrogen, 10 phosphorus and 10 potash. A 10-10-10 fertilizer is often recommended to home gardeners as a "balanced" or "all-purpose" fertilizer. Corn-growers, however, need nitrogen most of all: a fertilizer that reads 10-5-5 has a higher ratio of nitrogen than a 10-10-10.Unless your extension agent or local experienced growers have a strong opinion, the source of the nitrogen matters less than the amount.
What Nitrogen Does
More than any other growth process, nitrogen governs the formation of abundant, healthy leaves, critical to the photosynthesis plants use to grow. Rapid leaf formation literally "lets the sunshine in," providing the necessary leaf surface to collect both light and water, turning soil contents into food. The link between leaf production and nitrogen explains why gardeners may use one fertilizer on lettuce (high nitrogen for big fluffy heads) and another on tomatoes (nobody ever admired a tomato plant that was nothing but leaves).
In gardening terms, growing corn resembles growing a lawn the way launching a rocketship resembles sprinkling sugar on cereal. Everything about corn is big--the stalk, the leaves, those delicious ears. Everything about corn is fast. Plant after the soil warms, not before. Hope for heat and sun and lots of both. Pour on the water. No time to add a few more seeds if the first ones look peckish. Corn is go--now. Growing corn is a race with summer weather, and you want to win.
Timing is All
Cooperative Extension studies support the rocketship model, concluding that corn does best when its heaviest feeding is at the time of planting. Additional feedings will probably be needed to support growth and mitigate the effects of severe weather stress. Stop feeding when ear formation begins, so plant energy goes into kernels rather than further leaf production.