Corn residue, tillage, and nitrogen rate effects on soil properties

• We model the soil responses after eight years of treatment at four locations.
• Residue removal lowers SOC stocks under no till to the level of tilled plots.
• No-till had higher BD and PR than tilled plots, even more so with residue removal.
• WAS responded differently to residue removal depending on the N rate added.
• Crop residue harvest results in modest changes in soil under continuous corn.

Harvesting corn (Zea mays L.) residue for use as a biofuel feedstock may alter important chemical and physical properties of soils. Long-term residue removal, linked with tillage and fertilizer practices, could lower soil organic carbon (SOC), as well as increase soil compaction and susceptibility to erosion. A study initiated in 2006 included three levels of residue removal (none, partial, or full removal), two tillage treatments (no-till or chisel plow), and two N application rates (134 and 268 kg N/ha). These experiments were established in continuous corn (CC) at four Illinois sites, with treatments remaining in the same plots each year. In the spring at the beginning of the eighth growing season, we measured total carbon stocks (SOC), water aggregate stability (WAS), soil bulk density (BD), and penetration resistance (PR). Results showed that with all crop residue retained in the field, SOC stocks 13% lower under chisel tillage than in no-tilled plots, but removal of some or all of the residue lowered the SOC levels of no-tilled plots to those of tilled plots. On average for the studied depths, no-till plots had 5% and 39% higher BD and PR, respectively, than tilled plots, and residue removal significantly increased PR under no-till. Regardless of tillage treatment, the highest WAS values were found without residue removal at the lower N rate and with partial removal at the higher N rate. The higher N rate slightly lowered the BD under partial removal of residue for both tillage treatments at both studied depths. Our results indicate that residue harvest generates modest changes in soil properties under continuous corn, likely smaller than the effects of tillage and N fertilizer use in these systems. But as long as residue amount and tillage practices are sufficient to limit losses of soil by erosion to acceptable levels, we believe that corn residue represents a viable feedstock for a sustainable bioenergy industry in the U.S. Midwest.