There aren’t too many things that deliver 100% of the time. But one agronomic attribute that comes mighty close is that corn following soybeans will out-yield corn after corn, according to Dan Walters, soil scientist at the University of Nebraska-Lincoln.
The yield boost from rotation is substantial — especially in a drought.
In upper Midwest rotation trials, first-year corn outyielded continuous corn by 15%, and corn rotated annually enjoyed a 13% boost. Another study — a four-decade series of crop rotations at the University of Wisconsin’s Lancaster Agricultural Research Station — recorded a 10% drop in yield in second-year corn and an additional 5% to 7% reduction in third-year corn; then it leveled off, according to UW agronomist Joe Lauer.
You can’t buy yield back with high rates of nitrogen. The long-term trials showed a yield gain in continuous corn of just 0.9 bushel per acre per year after 200 pounds of applied nitrogen. In the extended rotations, applying 100 to 200 pounds of N increased corn yields
as much as 80% more — 1.4 to 1.6 bushels per acre per year.
Rotating crops impacts a wide array of factors, including:
- disease pressure
- populations of insects, including corn rootworm
- weed management, as rotating crops may open up opportunities to rotate herbicide modes of action as well to control resistant weeds
- residue buildup, which can interfere with consistent, uniform emergence
- soil compaction, which can be aggravated by tillage and heavy equipment in corn or alleviated by deep-rooted crops like alfalfa or wheat
- nitrogen tie-up, as microbes monopolize soil N supplies to fuel the breakdown of crop residue
- balance in the soil microbial community
“What’s good for the soil will ultimately be good for the pocketbook,” notes Lauer.