The moldboard plow is making a comeback…in corn-on-corn rotations with $3 corn.

Yields increase significantly by using a moldboard plow in the fall and cultivating again in the spring on second-year corn compared to using other common tillage systems, says Jeff Vetsch, an assistant scientist with the University of Minnesota Southern Research and Outreach Center, Waseca, MN.

“Our study shows that the early growth of corn is important when planting corn after corn,” says Vetsch. “A higher percentage of residue cover on the surface strongly correlates to negative growth. So, the faster you can build that plant factory and get the plants growing, the better it sets the stage for good yields later in the season.”

Yet, full-width tillage will provide no apparent benefit when rotating to corn after soybeans. “Only when it comes to second-year corn is there is a significant yield advantage to the moldboard plow — at least at our research center,” says Vetsch.

The Waseca study is based on just one location over two years, points out Vetsch. Therefore, the results may prove inapplicable for other locations with different growing conditions. However, North Central Iowa mimics the growing situation at Waseca, he adds.

The higher costs associated with full-width tillage also tend to hamper its profitability in second-year corn unless prices stay above about $3/bu., he adds. “With the higher corn prices we're seeing this year, there's an opportunity to go with more tillage in corn after corn to garner higher profits,” says Vetsch. “However, don't forget about the other tillage systems, which can also be very competitive, especially in a corn-soybean rotation.”

Even with potential $3-plus corn prices, a moldboard plow would be ill-suited for use on lands with a propensity for erosion, cautions Vetsch. “In the short term, the moldboard plow gives an economic advantage this year on corn-after-corn acres on land that is not prone to erosion,” he says. “In the long-term, the moldboard plow only shows an advantage if corn prices stay high. There is no significant advantage from it if corn prices return to previous levels, even on corn after corn.”

As of early December, the posted county price for corn was $3.27/bu., which would provide a $501/acre (partial gross) return when using full-width tillage in second-year corn, says Vetsch. The other tillage systems in second-year corn provided a range in profit from $469/acre for a spring disk system to $476/acre for a strip-till system.

For corn following soybeans, conservation systems are equivalent if not superior in their profit potential to full-width tillage systems, points out Vetsch. “There are potential production savings with other systems that can be attained by combining trips across the field and/or using fewer inputs, but in this analysis we kept everything the same except tillage,” says Vetsch. “The economic returns were only based on the variable costs of tillage, not on any fixed costs.”

Plus, conservation practices can sometimes qualify for conservation program incentive payments, he adds. “If that's the case,” says Vetsch, “you could greatly increase the economic impact of a conservation tillage system, compared to using full-width tillage.”