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Nutrient
Management
By Sam Custer
OSU Extension Darke County
November 7, 2012
Harvest is finally beginning to wrap up for this unusual year for Darke
County farmers and nutrient application is taking place now.
Application and retention of manure nutrients is critical to reduce
environmental impacts and increase economic returns.
Greg LaBarge, OSU Extension, shares in this week’s C.O.R.N. newsletter
that phosphorous and potassium exist naturally in the soil as a part of
rock, clay and other minerals that make up soils. Levels of phosphorous
in the soil can be between 100 to 3000 pounds of total P per acre.
Potassium exists in higher quantities of 10,000 to 50,000 pounds of
total K per acre. These levels are substantial but plant available P
and K are the important measure in crop production. Due to the
buffering of the soil solution quantities of nutrient from these
sources along with the associated fixation and release with fertilizer
addition or crop removal does not affect soil test level on a 1:1 basis.
The buildup formulas for P and K fertilization found in the Tri-State
Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa give
us some indication of the amount of fertilizer needed to change soil
test levels 1 ppm for both P and K.
This concept plays a role in what we need to do when we have a year
like 2012 where drought substantially reduces yield, or where we have
high soil test levels due to past practices, and want to know how long
until we would draw down to maintenance limits.
The buildup equations in the Tri-states indicate that it takes 20
lbs./A of P2O5 to change soil test P levels one ppm. For potassium the
equations indicates 6 to 10 lbs./A of K2O are required to change soil
test 1 ppm depending upon the soil CEC.
Just to use phosphorous as an example a 150 bushel/acre corn crop will
remove 55 pounds of P2O5/acre in the harvested grain. Thus the 150
bushel corn crop would move soil test level approximately 3 ppm.
A new Factsheet, Interpreting a Soil Test Report AGF-514-12, can be
found at
http://ohioline.osu.edu/agf-fact/pdf/Interpreting_a_Soil_Test_Report_AGF-514-12.pdf
. This will help you understand the various factors found on a soil
test report and how they relate to soil fertility needs for a crop.
Greg McGlinch, Darke County Soil and Water Conservation, recently
shared practices that agricultural producers can do to retain valuable
manure nutrients in the soil and reduce environmental impacts.
Implement cover crops like wheat and cereal rye after soybeans and
corn. Both cover crops are winter hardy, tie up nutrients, and reduce
erosion. Planting a bushel of either grass crop will be
sufficient for cover crop use.
Reduced tillage with increased residue coverage can protect soil from
erosion and nutrient loss.
Application to frozen or snow covered ground is not recommended.
If manure application is needed in these conditions follow a few of the
tips:
Do not apply on more than 20 contiguous acres and include at least a
200 foot break between the 20 contiguous acres. Apply to fields with at
least 90% surface residue cover (cover crops, hay/pasture, corn
residue, or wheat residue). Reduce application rates. Increase
application setbacks to a minimum of 200 feet from all grassed
waterways, surface drainage ditches, streams, inlets, or any water body.
McGlinch’s final request is “soil test, soil test, soil test!
Soil tests will guide a producer to apply the correct nutrient amounts,
especially phosphorus, to meet crop removal needs.”
If you have any additional questions on stockpiling and applying manure
please contact the Darke Soil and Water Conservation District at
937-548-1715, ext 3 for additional information.
For more detailed information, visit the Darke County OSU Extension web
site at http://darke.osu.edu, the OSU Extension Darke County Facebook
page or contact Sam Custer at 937.548.5215.
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