The Rural Voice, 1987-03, Page 22BUILDS EVERYTHING
BETTER FOR BARNS
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Contact:
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R.R. 2, GADSHILL, ONT.
519-595-4530
or
IVES CONSTRUCTION
R.R. 2, BLYTH, ONT.
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20 THE RURAL VOICE
REDUCED TILLAGE AND
NUTRIENT LAYERING
There's an article in the November
issue of Country Guide about how
conservation tillage confuses soil -
testing technology, but the story raises
more questions than it answers. The
issue is important and timely, how-
ever, since those of you who didn't
find time to get your soil sampling
done last fall, or didn't have someone
do it for you, have only "one kick at
the cat" left before the crop goes in
this spring.
Stratification of P and K either on
or below the soil surface in conserva-
tion tillage has certainly raised major
questions about the effects on growing
crops and about techniques needed for
the collection of soil samples.
Because of the changing chemical
characteristics of the surface three
inches of soil in conservation tillage,
soil -sampling techniques must undergo
change. But, most importantly, the
interpretation of the laboratory results
and the final recommendation must
undergo the biggest change.
We do know that repeated broadcast
applications of fertilizer P and K result
in higher concentrations of these
nutrients close to the soil surface and
that amounts of P and K adequate for
optimum yields may not be absorbed
by roots when high concentrations of
these nutrients exist in the top two or
three inches and low concentrations are
present deeper in the rooting zone
where root activity is greater.
According to Dr. George Rehm of
the University of Minnesota, one of
the top researchers today in conserva-
tion -tillage fertilization techniques, we
would find nutrient stratification to be
of greater concern in regions where
rainfall is limited and there is a high
probability that the soil surface will
remain dry during the growing season.
Nutrient stratification may not be a
major concern in conservation tillage
systems if we recognize that the
distribution of roots is altered by the
tillage system used.
Studies in Indiana have shown that
there is a higher concentration of roots
near the soil surface in a no -till
system. Thus, if soil moisture is
adequate and there are no restrictions
to root development in the rooting
zone, corn should be able to use P
and K concentrated near the surface.
In situations where nutrients can
be fixed, the potential for fixation is
greater for broadcast and incorporation
systems and less for surface applica-
tion in no -till or sub -surface banding.
With repeated placement of P and K
below the soil surface, the concentra-
tion of these two nutrients should
increase with time, fixation should be
reduced, and efficiency of use should
increase. With adequate moisture and
no restrictions to root growth, im-
proved yield should be the result.
Evidence is accumulating that the
presence of fertilizer in concentrated
bands below the surface is beneficial
to crops. Dr. Stan Barber at Purdue
University has demonstrated that corn
yields are higher when fertilizer is ap-
plied in strips on the soil surface and
plowed under.
As field research continues, fert-
ilizer management systems that will
take the stratification scenarios into
consideration will evolve.
The following are soil -sampling
recommendations for different conser-
vation -tillage techniques from five
U.S. land-grant universities.
University of Wisconsin: Take a
minimum of one composite sample per
5 acres regardless of chisel plow and
off -set disking. Take soil sample to
3/4s of the tillage depth used. When
possible, take samples before fall or
spring tillage; sampling depth can be
determined more accurately and fertilizer
bands applied for the previous crop can
be avoided.
In no -till, take samples to a depth
of 7 inches for fertilizer reconunenda-
tions. Sample between rows to avoid
all fertilizer bands. When N is surface -
applied, take an additional shallow 0 to
2 -inch sample to monitor pH changes.
In ridge -till, sample ridges to a 6 -inch