In many high-yielding areas of the Corn Belt, residue buildup has become a challenge.
DuPont businesses Pioneer Hi-Bred and DuPont Industrial Biosciences are collaborating with Iowa State University, performing studies on residue to establish best practices in harvesting, storage and transportation, as well as to assure the agronomic and environmental integrity of cornfields.
"We know the near-term benefits of residue removal," says Andy Heggenstaller, Pioneer agronomy research manager from Iowa. "We're now trying to learn how to take advantage of these benefits with an eye toward achieving similar long-term agronomic advantages."
The primary advantage in reducing surface residue is preventing stand establishment concerns in the following crop. Another advantage is a solution to nitrogen tie-up that can be caused by residues. Some growers increase their nitrogen fertilizer rates to compensate for nitrogen tied up by microbes. Removing a portion of the residue can reduce additional nitrogen applications.
Costs associated with intensive tillage aren't only monetary. Excessive tillage also can damage the soil. Organic matter that supports high crop yields is depleted when oxygen is introduced into the soil through tillage, Heggenstaller says.
Good residue management practices are crucial to overcoming some of the challenges associated with reduced-tillage systems.
The first area of focus for growers should be seed selection. Every year Pioneer conducts extensive emergence trials in a wide range of stressful environments and soil types, including early-planted and reduced-tillage fields. Pioneer assigns each hybrid a stress emergence score based on the genetic potential for a hybrid to establish stand under stress conditions (e.g., cold, wet soils or environments with short periods of severe low temperatures).
Pioneer also assigns high-residue suitability ratings of highly suitable, suitable or poorly suited for hybrid performance in reduced-tillage systems. This rating is calculated based on trait scores for the following: stress emergence, northern corn leaf blight, anthracnose stalk rot, gray leaf spot and Diplodia ear rot.
Because heavy residue can hinder planting efforts, growers also should be sure to set up and operate the planter appropriately. This can help improve stand establishment in high-residue systems. Because planter operation may vary widely with soil type and conditions, it can be helpful to consult with an area agronomist or other no-tillers in the area to determine the best equipment and practices based on needs.
Other planting tips include using row cleaners to clear the planting row of residue, planting slightly deeper to help overcome some of the moisture and temperature variability, and choosing a planting date that allocates extra time for soil under heavy residue to dry before planting.
While these best management practices can help growers today, DuPont Industrial Biosciences is developing solutions for tomorrow that address the residue itself. DuPont plans to build one of the world's first commercial cellulosic ethanol biorefineries in Nevada, Iowa, which will require thousands of tons of stover from Iowa fields.
"Currently, the most plentiful agricultural source of ligno-cellulosic biomass for ethanol production in the U.S. is corn stover," says Steve Mirshak, business director for DuPont's cellulosic ethanol program. "We're currently working with an exclusive group of growers in a pilot program to collect stover in support of the biorefinery. When completed, the plant will be fueled almost exclusively by cornstalks."
Experts are keeping in mind long-term impacts. "University research suggests that at a high yield level (200 bushels per acre or more), growers can remove 40% of stover without negatively impacting soil organic matter," Heggenstaller says. "As we move forward, cellulosic ethanol production may become a common form of residue management."