Tillage Management Considerations for Continuous Corn

Dick Wolkowski, Extension Soil Scientist

It is estimated that ethanol production will consume about 30% of the US corn crop by 2010. This phenomenon is encouraging favorable grain prices and dramatically increasing corn acreage.  A consequence of long-term continuous corn production could be the adoption of more aggressive tillage to manage large amounts of crop residue.  This could potentially lead to decreased soil quality and increased soil loss.  Research has shown that moldboard and chisel systems reduce aggregate stability.  Coupled with the lower surface crop residue resulting from tillage the affected soils are prone to more erosion than no-till or other low disturbance systems.  Soil degradation and increased soil erosion would be a poor trade-off for fuel independence. Therefore, producers must carefully consider tillage options when growing corn on corn.

There are few long-term Wisconsin studies that examine tillage management in continuous corn.  One example is a study that this author has overseen since 1997 that has included fall chisel, fall strip-till, and no-till in continuous corn and corn/soybean rotations, along with several fertilizer placement treatments.  Data for the main effect of tillage in the continuous corn portion are shown in Table 1.  The no-till system did not employ any in-row residue management.  Yield was not measured in 2000.  Of the nine years that these tillage treatments have been in place significant yield differences were observed in three seasons, each time in favor of the chisel system.  Averaged over the nine years grain yield was five and nine percent lower for strip-till and no-till, respectively.  A detailed analysis is required to determine the overall profitability between tillage systems, however more soil loss could be anticipated for the chisel system, especially if stalks were shredded prior to tillage and an aggressive chisel implement were used.

Table 1.  Tillage effect on corn grain yield in continuous corn, Arlington, Wis. 1997 -2006.

Soil loss can be predicted using RUSLE 2, components of which run within the Snap-Plus nutrient management program.  A simulation of the soil loss for six common Wisconsin soils was conducted over a four year continuous corn rotation for an eight percent slope of 150 ft. in length.  Table 2 shows the soil loss estimates for these six soils.  As expected there is variation in soil loss between soils, but in all cases the moldboard system exceeded allowable soil loss.  Using a chisel system substantially reduced soil loss, but depending on the soil the loss may still be relatively high.  No-till generated very little soil loss, but some producers may not be able to produce sustainable crop yields using strict no-till and will likely opt for some form of tillage, which could include strip-tillage or other methods of in-row residue management.

Table 2.  Estimated soil loss for four years of continuous corn using three tillage systems on six Wisconsin soils.

Slope = 8%;  Slope length = 150 ft.

Producers and their consultants need to balance the aggressiveness of the selected tillage system with its effect on soil quality and soil loss.  A return to clean tillage systems will not be sustainable and will likely result in soil loss values exceeding “T”.  While the increase in biofuel crop production is offering opportunities to producers care must be taken to avoid “back-sliding” into practices that in the long term will reduce productivity and impact water quality.