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Evaluation of Fertilizer Placement and Timing in Continuous Corn in Three Long-Term Tillage Systems

Study author(s): Daniel Kaiser and Lizabeth Stahl, University of Minnesota Department of Soil, Water, and Climate
Years of study: 2008-2011
Location(s): Southern Minnesota

Important: for the complete report, including all tables and figures, please download using the link(s) to the right.


Economics have shifted to favor a corn on corn rotation versus a corn/soybean rotation for many growers in southern Minnesota. Concern over the high surface residue levels that result from planting corn continuously in a long-term rotation has often led to the use of more aggressive tillage practices, such as the moldboard plow.

Conservation tillage systems, where at least 30% residue cover remains after planting, help minimize soil erosion and runoff potential while potentially leading to reduced fuel use, labor costs, and trips across the field. Although there are many documented benefits of conservation tillage, concern about the effects of higher surface residues in heavy clay soils, particularly in corn on corn, has hindered the adoption of conservation tillage in southern Minnesota.

The University of MN conducted trials across southern Minnesota at four to six locations per year from 2008 to 2011 to evaluate the effect of tillage in a continuous corn system on corn yield and profitability (1). Tillage systems, which included strip-tillage (a conservation tillage system where a strip 6 to 8 inches wide is tilled, typically in the fall, while the area between strips is left undisturbed), a moderately aggressive tillage system such as chisel plow or a disk-rip/in-line rip system, and moldboard plow, were evaluated in long-term replicated trials where corn was planted from year to year. Although yield was not consistently affected by tillage system, the moldboard plow system often resulted in greater yields than the strip-tillage system when differences were found within a given site and year. At the Lamberton site in southwestern Minnesota, corn yields in strip-tillage were consistently lower than in the moldboard plow system. Results have varied for the moderately aggressive system, with this system yielding similarly to the top yielding treatment, the lowest yielding treatment, or to both, depending on the site and year.

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