Not far from your farm is a company that buys specialty corn, and you have made good profits from the premiums paid over the past several years. You have signed a contract for growing more next year, and have ordered seed for the type of corn desired by the plant. It is time to settle in for a long winter’s nap, but suddenly you are awakened by a nightmare that the fertility monster is about to eat your premium.

Quickly you hop out of bed, turn on your computer and begin to scour resources about the fertility needs of specialty corn. A few minutes later your spouse flips on the light in your office and asks what you are looking at on the Internet at 2 a.m. Your story about searching for the fertility needs of specialty corn may be far enough out of the box to be believable! But just so you’ll get a good night’s sleep, let’s say your concern is justified, so let’s talk about the solutions.

Even though commodity prices have nearly doubled in the past two years, the demand for specialty corn still exists. Ethanol plants may pay premium prices for hybrids that have highly extractable starch (HES). Also food companies need hard endosperm corn (HEC) for dry grind into corn meal and corn flour and regularly offer premiums for contract delivery. The irony is that HES is high starch and low protein and HEC is low starch and high protein. High amounts of nitrogen fertilizer will increase protein levels and decrease starch levels, and you may be trying to increase corn yield with high amounts of anhydrous ammonia, but deteriorating the quality of the corn you are trying to deliver.

Another agronomic issue is plant population. High population decreases protein and increases the starch yield. There may be other agronomic issues that you can control to help achieve your high protein or high starch goal, whatever it might be. Issues such as the previous crop could have an impact, particularly if it was soybeans that may have added to the nitrogen content of the soil. The bottom line should be to manage your specialty corn crop in a way that it helps your bottom line, and not hurt it.

Agronomists at the University of Illinois conducted a wide range of research on nitrogen rates and plant populations to determine impact on the trait content of various kinds of corn. The experiments were conducted at several test plots, with various nitrogen rates, planting dates, and plant populations. Soil tests were taken and grain samples were analyzed for protein, starch, oil and extractable starch. The hybrids tested were common hybrids, known for their desirable traits for extractable starch, hard endosperm, and being nutridense (ND).

Yield. Your priority is yield, since a 10 cent premium will not make up for a 10 per cent reduction in yield. And there was a large difference in yield, determined largely by location of the test plot and its environmental conditions. On average the HEC and the Yellow Corn control were the highest yielding at 224 bu./A, followed by the HES hybrid at 212 bu., and the ND at 192 bu.

Nitrogen response. Nitrogen increased yield at all sides, but there were variations in magnitude and maximum yield achieved. The largest response (107 bu./A) was in continuous corn in one plot, but rotated corn (following soybeans) provided the largest nitrogen response across all plots.

Rotation. The continuous corn yielded 194 bu./A, compared to the corn after soybeans at 208 bu./A. “Interestingly, the same maximum yield was achieved by both rotations, but continuous corn required 222 lb N/A to reach it compared to only 146 lb N/A for rotated corn.”

Population. The effect of plant population was of much smaller magnitude than that of fertilizer. The largest response was only 13 bu./A, and there was no difference in yield response to population when compared to continuous or rotated corn.

Grain composition. The highest protein concentration was obtained with the HEC hybrid (8.4%), and the HES hybrid had the lowest protein concentration (7.3%). The HES hybrid had the highest starch and extractable starch concentrations (73.8% and 68.3%) and the ND hybrid the lowest (72% and 63.1%). However, the ND hybrid produced grain with the highest oil concentration (5.5%) and the HES hybrid the lowest oil concentration (3.9%).

Protein. Protein increased with the increase in nitrogen applications, on average 1.3%. Grain protein concentration of unfertilized continuous corn (6.2%) was lower than in rotated corn, but both reached 8.2% protein with high rates of nitrogen. Protein levels were reduced with higher plant populations, and declined the most between 28,000 and 36,000.

Extractable starch. Extractable starch decreased with greater levels of nitrogen, as much as 1.7%. That occurred between the unfertilized corn and the highest rate of N, but there was still a 1% drop in starch content when the nitrogen rate was increased from 100 lbs/A to 200 lbs/A. By increasing the plant population, the amount of extractable starch increased as much as 0.9% when plant populations were increased from 28,000 to 40,000.

Corn oil. Both increased plant population and nitrogen reduced the amount of oil concentration, particularly in the ND hybrid, but the magnitude was smaller than for protein or starch.

Bottom line:
1) Grain protein concentration is maximized with management practices that increase N availability.
2) Soybean as a previous crop should be preferred over corn, the plant population should be maintained as low as possible without affecting grain yield, and N fertilizer should be applied at a slightly higher rate than the optimal N rate for grain yield.
3) Conversely, extractable starch can be maximized by management practices that limit N availability.
4) In order to maximize grain extractable starch concentration, continuous corn is preferable over rotated corn, plant population should be increased and over fertilization of N should be avoided.

Summary:
Farmers who are utilizing production contracts to gain premiums for specialty corn, specifically for high protein or high starch, have the opportunity to make agronomic decisions that will maximize the starch and protein content of the grain. However, those decisions may be counter to typical decisions or maximizing yield, such as nitrogen application and plant population.