BELLEVILLE, Ill. — A Southern Illinois University study
shows that tillage methods may not affect corn and soybean yields in fields
treated with a full fertility regimen.
A long-term fertility plot at the university’s Belleville
Research Center compared corn and soybean yields using different tillage methods
and fertilizer mixes. The preliminary result is that there is no yield
difference among tillage methods.
The study spans 40 years with continuous corn, including 20
years of a corn-soybean rotation. Begun at the College of Agriculture Science’s
Belleville Research Center by the late no-till pioneer George Kapusta, it now is
tended by Rachel Cook, who teaches soil fertility at the college.
The study encompasses four tillage practices: conventional
till, chisel plow, no-till and alternate — two years no-till, one year
conventional. Plots were divided into three fertilization applications: nitrogen
only; nitrogen, phosphorus and potassium; and a check, with no fertilizer
“If you’re putting on your full fertility management,
tillage really doesn’t change that much,” Cook said.
That’s good news to farmers who are concerned they may be
losing yield with no-till. While yields with every tillage scheme were nearly
identical, the bottom line could dictate the tillage method.
“So if not a difference in yield, what else?” Cook said.
“Fuel costs. No-till is better on fuel costs. Yield isn’t the final story. The
final story is how much money you’re making at the end of the day per acre.
There are different costs for different management systems.”
There was no advantage to applying starter fertilizer. But
that may be because of the rates put on the plots in the study.
“There are a lot of questions in terms of how effective is
starter fertilizer. Out here they found that starter fertilizer really didn’t do
much,” Cook said. “If you look at the rates we’re putting on here, it was pretty
high rates. We probably weren’t getting much response from starter fertilizer
because we were putting on so much anyway.”
While tillage methods didn’t affect yields, rotation made a
big difference. In the 20-year corn-soybean rotation trial with full fertility –
1992 to 2012 — corn yielded an average of nearly 190 bushels per acre, while
continuous corn yielded an average of only about 135 bushels per acre.
“There was a big yield increase when they switched from
continuous corn to a corn-soybean rotation,” Cook said. “Hybrids are changing
every year, so take that into account. But we did have more corn yield when we
switched to the corn-soybean rotation.”
The NPK treatment yielded much better than the plots with
nitrogen only, and, not surprisingly, much more than the check plots, which
brought in only about an 85-bushel rate. No-till corn fared worse in the check
plots, on which fertilizer had not been applied.
While the long-term study has provided some answers, there
still are a number of concerns that are yet to be addressed.
“If you have a bad year, does no-till have more organic
matter, so it holds more water – therefore, might do better in a dry year? Those
are some of the questions people are interesting in answering,” Cook said.
“We’ll continue to look at that. There are so many things we can look at with