Organic Grain Production |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Corn Information for North Carolina Corn Growers Vernon G. James Research and Extension Center , Plymouth , NC 27962
Organic Corn Hybrid Selection
Ronnie Heiniger Soil Fertility Specialist and Cropping Systems Specialist North Carolina State University 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 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. Table 1 lists some organic and untreated commercial hybrids with ratings for relative maturity. Table 1. Relative maturity ratings for organic and untreated conventional hybrids suited for planting in North Carolina . At this time no late maturing organic hybrids are available.
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. Table 2. Organic and untreated corn hybrids defined by relative maturity, seed vigor*, early growth rating, standability, disease ratings, and stress tolerance.
* All ratings are based on a scale of 1 to 10. A perfect rating of 10 would represent a plant with complete resistance or tolerance to disease or 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. Figures 1, 2, and 3 show hybrid comparisons for North Carolina . 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.
Fig. 1. Yield from three organic hybrids and a conventional hybrid planted using organic farming practices in Currituck County in 2007. Numbers on chart indicate plant populations tested using one organic hybrid.
Fig. 2. Yield from organic and conventional hybrids planted using organic farming practices in Washington County in 2007.
Fig. 2. Yield from organic hybrids planted using organic farming practices in Halifax County in 2008.
Important Considerations for Selecting Organic Corn Hybrids
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
