Nutrient Management

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Nutrient Management Chapter 16
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Increase, of course. Slower velocity increases
deposition. More organic matter in soil
increases adsorption and the soil environment
is likely richer in microbes, increasing
degradation rate.
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Common sense guidelines on width of buffer strip
needed to be effective.
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These provide better cover of the soil than just
what- ever weeds emerge. Thus, there is less
effect of rain- drop impact on soil detachment
and slower runoff velocity means more time for
infiltration. Since the crop uptakes soluble N
(e.g., NO3-), there is less leaching and if a
legume, there is net input of N into the soil so
less need for subsequent fertilization.
Planted cover crops produce more biomass than
native weeds so add more organic matter.
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Reduce. This is a matter of coverage of the
soil. The more, the better with respect to
runoff and erosion.
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This study indicated that increasing the time
spent in legume both increased corn yields and
diminished the benefit / need for
N fertilization. The treatments were continuous
corn, C-C-C, rotation with soybeans, and a longer
term rotation involving meadow, presumably with
clover or grass-clover mix.
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There are, you know, organic fertilizers that are
chemically synthesized.
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Common problem is that P / N ratio is larger than
the crop needs so long-term use of such
fertilizer materials leads to build-up of P in
the soil and, therefore, increased potential for
P loss to downstream water bodies and their
eutrophication.
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A lot of the stuff but not much acreage for its
beneficial use as a fertilizer.
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So funky barrel to left is P-limited. Fix that
and wind up with funky N-limited barrel.
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Soil testing and plant analysis address the
first two nutrient management questions. To
some extent also the third when you need more
than one nutrient and two can be applied in the
same carrier.
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Lets say there exists a yield curve for crop Y
as a function of the level of nutrient X in the
soil. Typically, it increases from the origin and
levels off with increasing concentration of X in
the soil. Thus, there is an evident
concentration of X associated with near max
yield. Do a soil test and find the
concentration of X in your soil is (optimum
your soil) low, so add the difference. Concept
of calibration.
A lab in NY follows exacting QA / QC and gives
excellent analytical results. It will also give
you, a La. farmer, recommendations based on the
soil nutrient extraction protocol it uses and
calibration curves for soil and
environmental conditions in NY. Perhaps
extraction protocol and calibration curves are
not correct for La. soils and environment. Make
sense?
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Situations for which broadcast is appropriate.
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Plants get what they need. Excess fertilizer
avoided. If fertilizer element is subject to
fixation, concentrated mass of fertilizer in
small volume of soil saturates the fixation
capacity of the soil there so much of the applied
fertilizer remains soluble and available for
plant uptake.
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This is the current situation in La. and many
other states no soil test for N that serves as
the basis for recommendations. Rather, the
recommendation is based on field plot experiments
that indicate the optimum rate on a crop by soil
type basis. The reason for no soil test (like
total N, nitrate, etc.) is the complexity of the
N cycle. Recall?
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