High Residue Suitability Rating for Pioneer brand Corn Hybrids

• High residue cropping systems including no-till and strip-till are increasing because of a desire to reduce input costs, manage more acres, conserve soil and in dry areas, moisture, and comply with government conservation programs.
• High residue fields typically have cooler, wetter soils at planting and higher disease inoculum levels. This can delay corn emergence and growth, then flowering and drydown, and ultimately reduce yield, especially in cooler northern growing areas, and on poorly drained soils.
• Pioneer researchers have assigned a High Residue Suitability rating for all Pioneer brand corn hybrids. The goal of this rating is to give customers guidance on selecting hybrids suitable to high residue tillage systems.
• The High Residue Suitability rating is based on field observations and a weighted calculation of five published trait scores customized by CRM group, geography/climate factors, and market regions.
• Based on these criteria, Pioneer hybrids are rated as Highly Suitable (HS), Suitable (S), or Poorly Suited (X) for high residue environments. Pioneer rates its hybrids for High Residue Suitability to help customers position products under reduced tillage.
• These hybrid ratings will be available from your Pioneer sales representative after mid-December. The rating tables will also be available on the GrowingPoint website in January, and in product positioning profile sheets and product catalogs in 2006.

Pioneer rates its hybrids for High Residue Suitability to help customers position products under reduced tillage.

Farmers have steadily increased acres managed under high residue cropping systems including no-till, strip till and other conservation tillage practices (Figure 1). This change has been driven largely by soil conservation, tilth and organic matter benefits, lower production costs, reduced labor, and in more arid areas, improved soil moisture. For these reasons, as well as possible incentives from conservation-based government programs in the future, the trend toward increased acres under high residue farming practices is expected to continue.

Figure 1. Crop acres under no-till in the US, 1994 to 2004.

At the same time, technological advances have reduced the stand establishment and weed control risks often associated with high residue systems. Planting equipment is better designed to handle crop residue, and herbicide resistant crops allow post-emergence application of effective, broad-spectrum herbicides such as glyphosate for control of perennial as well as annual weeds.

In spite of gains in technology, knowledge and grower experience that have reduced risks with high residue farming, challenges remain, especially in cold soils with high crop residues. Several practices can help reduce these challenges, including uniform distribution of residue, reasonable planting dates, and hybrid selection. To assist growers in selecting hybrids under high residue systems, Pioneer researchers have developed a High Residue Suitability rating for all hybrids in the Pioneer lineup.

A corn crop produces more than twice the residue of a soybean crop. This has advantages in reducing soil erosion, but also results in cooler and wetter soils at planting, and higher disease inoculum levels. This is especially true for poorly drained soils. Seedling emergence and plant development can be delayed in high residue environments because of the lower spring soil temperatures and higher moisture compared to conventional tillage.

Seedling emergence delays can lead to delays in vegetative growth, tasseling and silking, and grain dry-down. These delays can cause yield losses in shorter season growing areas, or where hybrids are planted with a relative maturity that is long for the region where they are planted. Not surprisingly, many failures in high residue farming have resulted from early planting on high residue fields. Often, this has occurred when planting corn on previous corn ground with high levels of corn residue.

Earlier Planting - As planting dates move ever earlier, the potential for cold soil at planting and cold, wet weather after planting increases. When this occurs, it is not unusual for corn to remain in cold, saturated soil for two to three weeks or longer before emerging. This issue is not limited to northern states. Because of early planting, most areas of the US and Canada can now experience early season seedbeds that are inhospitable for corn germination, emergence and early growth.. In this environment, corn faces abiotic challenges related primarily to cold effects on plant tissues, and biotic challenges related primarily to corn diseases.

Cold Stress Injury - The optimal temperature for corn emergence is in the range of 80 to 90ºF. Emergence slows at lower temperatures and is effectively halted around 50 to 55ºF or below. Since soil temperatures in the early season are almost never optimal, emerging seeds will experience some stress almost everywhere in North America. The degree of stress, and potential damage from stress, is determined to a large extent by soil and water temperatures during imbibition and seedling emergence. Any cold damage at emergence is generally irreversible.

For successful emergence to occur, all parts of the corn shoot (roots, mesocotyl, coleoptile and leaf within) must work in a coordinated way to push the coleoptile above the soil surface and allow the first leaf to unfurl. Damage to any one of these structures will likely result in loss of the seedling and its yield potential. Imbibitional chilling injury when dry seeds imbibe cold water 50ºF or below may result in seed death or abnormalities such as corkscrewed seedlings or fused coleoptiles. Damage to the emerging root will likely reduce vigor and increase the potential for disease and insect injury. Pioneer rates its hybrids for stress emergence, the genetic potential of hybrids to emerge under stressful environmental conditions including cold, wet soils or short periods of severe low temperatures.

Diseases - Corn disease pathogens survive in corn residue and build up over time. Leaf diseases such as gray leaf spot, northern leaf blight, anthracnose, and eyespot are all known to increase in long-term, high-residue farming systems. Stalk rot and ear rot fungi such as Fusarium, Gibberella, Diplodia and Aspergillus also survive in crop residue and increase in high-residue systems. Pioneer rates its hybrids for these and other important corn diseases.

Pioneer researchers have assigned a High Residue Suitability rating for all Pioneer brand corn hybrids. The goal of this rating is to give customers guidance on selecting hybrids suitable to high residue tillage systems. The rating is based on a formula using five key defensive traits adjusted for each major market region. Key defensive traits such as disease resistance and stress emergence are critical for high residue fields, whereas genetic yield potential is much less influenced by tillage and residue.

The High Residue Suitability rating is based on field observations and a weighted calculation of these five published trait scores:

• Stress emergence
• Northern leaf blight
• Anthracnose stalk rot
• Gray leaf spot
• Diplodia ear mold

In assigning the ratings, researchers used a formula in which the relative importance of the above trait list varied by CRM group and geography, and was therefore adjusted for each market region. Based on these criteria, Pioneer hybrids are rated as Highly Suitable (HS), Suitable (S), or Poorly Suited (X).

These hybrid ratings will be available from your Pioneer sales representative after mid-December. The rating tables will also be available on the GrowingPoint website in January, and in product positioning profile sheets and product catalogs in 2006. Customers are encouraged to talk to their Pioneer sales professional for help in choosing the best hybrid for their tillage program and residue level.