By: Dr. Ron Heiniger, Extension Specialist, Crop Science, NCSU

Hybrid selection is a critical component of any profitable corn production system. Skillful hybrid selection requires that growers: (a) understand the field environment (b) know how a corn plant grows and develops and (c) collect and properly evaluate information describing the characteristics of hybrids available in their area. The Organic Food Production Act and Regulations (October 2002) state that seed should be organically grown. Unfortunately, many of the organic hybrids that are available are not well suited to growing conditions in North Carolina. However, growers can get a waiver from their organic certification specialist to use untreated corn seed when adapted corn hybrids are not available for their area. Organic corn growers in North Carolina should check with their certification specialist to determine if a given hybrid can be certified before making a selection.

Hybrid Characteristics for Organic Production

For organic growers seeking to identify appropriate corn hybrids, yield is NOT the primary consideration. The key hybrid characteristics for organic corn production are:

• Rapid early growth and vigor
• Standability
• Pest and Disease Resistance
• Stress Tolerance
• Yield

Rapid early growth and vigor

Rapid early growth is essential in minimizing the effects of seedling diseases and insects, increasing root volume, and in reducing weed infestation. Hybrid seed companies list seed vigor ratings. However, there are few that have ratings covering early growth. In general, early growth is closely related to hybrid maturity. Early to medium maturing hybrids (102 to 114 day relative maturity) tend to exhibit better early growth than do late hybrids (> 115 day relative maturity). The best way to select hybrids with rapid early growth for North Carolina is to contact extension agents, seed company representatives, and other growers who have had experience with different corn hybrids.

Standability

Standability is important because it is a measure of how well the crop will stand under difficult environmental conditions. Since pests and diseases can be problems it is important that an organic hybrid has the ability to avoid lodging under stress. Most all hybrid seed suppliers provide ratings for standability or stalk or root strength. Table 2 lists some organic and appropriate commercial hybrids with standability ratings for each.

Pest and Disease Resistance

Resistance to common seedling, leaf, and stalk diseases is an important characteristic for hybrids in organic production systems. There are even some hybrids which tolerate insect pests such as European Corn Borer and Southern Cornstalk Borer. Unfortunately, most hybrids do not have resistance to a wide range of diseases or pests. Growers should select hybrids that combine good early growth characteristics with a good resistance package to diseases that are major problems in their area. Table 2 lists some organic and untreated commercial hybrids with ratings for common diseases.

Stress Tolerance

Stress tolerance indicates the ability of a hybrid to tolerate drought or other environmental stresses and produce acceptable yield. Hybrid seed suppliers often refer to this characteristic as drought tolerance. This characteristic is important since a lack of nitrogen (available nitrogen can be a problem in organic systems particularly when first starting an organic production system) can lead to nutrient and drought stress.

Yield

Growers should look for yield data collected from variety tests conducted using organic practices. Since fertility, weed, disease and pest pressures will differ from tests conducted using conventional growing practices, the only reliable indicator of yield potential in organic systems will come from tests conducted using organic practices. Unfortunately, there is a limited amount of organic yield test information available. Growers should conduct their own hybrid comparisons by selecting 4 to 6 promising hybrids and evaluating them on their farm with their management practices. The best procedure for grower testing of hybrids is the strip test where each hybrid tested is grown adjacent to a common "tester" hybrid. The strip test, with tester hybrids, permits any yield data collected to be adjusted for soil variability. If not using a tester, growers should place the hybrids they are considering beside the hybrid that has performed best for them in the past. Growers conducting their own hybrid evaluations must remember to select uniform test fields with minimal soil variability and restrict comparisons to hybrids of the same maturity.

Important Considerations for Selecting Organic Corn Hybrids

• Hybrids with relative maturities between 110 and 112 days often had greater yield compared with later maturing hybrids. These hybrids had the ability to grow quickly resulting in the ability to capture more light for a longer period of time. Short season hybrids from organic seed companies were not well adapted to the environment in North Carolina .
• While grain yield from organic hybrids was always lower than that from untreated conventional hybrids, adapted organic hybrids performed well across a range of conditions including a severe drought in 2008.
• More information is needed to determine the levels of disease and pest resistance present in organic corn hybrids.