Page 10—Corn Talk, Lancaster Farming, Saturday, October 12, 1996
TILLAGE AND
CROP ROTATION
EFFECTS ON
CORN YIELDS
Dr. Gregory W. Roth
Associate Professor
Agronomy, Penn State
A recent study published in
the Journal of Production Agri
culture by M. G. Lund, P. R.
Carter and E. S. Oplinger eva
luated the effects of two tillage
systems, no-till and moldboard
plowing and crop rotations
(continuous cropping, com/
soybean, wheat/soybean/com,
and soybean/wheat/com) on
the growth and yield of com
wheat and soybeans.
The study showed that conti
nuous cropping reduced yields
of com by 10 percent and soy
bean by 15 percent compared to
when the crops were in rotation.
Generally, yield reductions
due to continuous cropping
were greatest under no-till. The
effects of rotation and tillage
were less consistent on wheat
as the effect varied from none
m one year to a 36 percent
reduction in another. With
wheat, the tillage influence on
the rotation effect was less con
sistent in some years the
tilled plots were most affected
and in another year when Sep
toria and leaf rust diseases were
severe, no-till treatments were
more affected by continuous
cropping.
Com yields were similar in
each of the three rotation sequ
ences except for no-till com
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after wheat, where yields were
reduced by 6 percent. The
authors suggest that the same
allelopathic factors that reduce
yields of com following rye
may cause the yield reductions
following wheat, since the early
season com was about 8 inches
shorter than the no-till com fol
lowing soybeans. In this study,
the straw from the wheat was
not baled or removed and this
may have increased the poten
tial for allelopathic effects.
This study did not show any
difference in soybean yields for
a one or two year rotation.
Some previous research has
shown a benefit from increas
ing the time between soybeans
in the rotation to more than just
one year, but the authors sug
gest it may need to be more than
two years as they had in this
study to be significant.
In summary, the study did
not show any consistent
improvement in com and soy
bean yields by going to a three
year rotation including wheat.
In Pennsylvania, the the
advantages of wheat in a rota
tion may be greater than in this
study for several reasons: 1) In
southeast Pennsylvania, wheat
yields arc not reduced by late
planting following com and
soybeans as much as they arc in
Wisconsin: 2) In some areas,
soybeans can be double
cropped with the wheat, adding
to the profitability of the wheat;
and 3) control of perennial
weeds in no-till programs can
be successful following wheat
harvest.
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