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Regional,
Monthly All-Breed Horse Magazine
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MSU Assessing Manure as FertilizerSummary:
Producers can assess their fertilizer or manure application rates using an
in-field calibration strip. 10/3/2011
Contact: Clain Jones (406) 994-6076 or clainj@montana.edu For
a ramp calibration strip, an area 10-feet wide by 80- to 120-feet long is marked
in a representative area of the field. The strip is segmented into 10-feet long
sections, or 100 square-feet cells, with each cell receiving a different rate of
fertilizer or manure. Ideally the rate would range from zero (an untreated
check), to a high rate of fertilizer or manure. The rates are increased, or
ramped up, at increments of 10 to 30 pounds nitrogen or phosphorus (or any other
nutrient of interest) per acre. For example, in 100 square-feet cells, each 10
pounds of nitrogen per acre increase requires an additional 0.8 ounce of urea
(46-0-0). Each 10 pounds P2O5 per acre increase requires 0.7 ounce of
monoammonium phosphate (11-52-0). The quantity by which to increase manure is
more difficult to calculate because manures are highly variable in their
nutrient concentrations. Labs can provide nutrient analyses of manure. It is
best if the product is applied by small hand held equipment in these relatively
small cells, using pre-measured bags of fertilizer or manure. The
crop grown in the ramp calibration strip is then visually inspected or evaluated
with a chlorophyll meter mid-season to determine the effectiveness of the
different rates. “Plant
height and leaf color are good indicators of plant health and are useful to help
calculate in-season adjustments of plant-available nutrients, such as nitrogen
or sulfate,” said Clain Jones, Extension soil fertility specialist in the
Department of Land Resources and Environmental Sciences at Montana State
University. A
producer can note at what rate there is reduced growth or color change,
determine the approximate fraction of nitrogen that should have been taken up by
that plant growth stage, and calculate how much nitrogen to add. For example,
wheat takes up approximately half of its required nitrogen by mid-tillering. If
at mid-tillering the strip with 60 pounds of available nitrogen (soil plus
fertilizer) per acre is the lowest nitrogen rate without a noticeable growth
decrease, then the field should have at least 120 pounds available nitrogen per
acre for optimal production. If the whole field had 90 pounds of available
nitrogen pre-plant, then the grower should add at least 30 pounds of nitrogen
per acre at mid-tillering to optimize yield. The MSU Extension publication
titled “Nutrient Uptake Timing by Crops: to assist with fertilizing decisions”
offers guidance on these steps. Yield
and grain protein can be measured at harvest to help with future fertilizer
decisions. “Using
yield and protein results from ramp strips along with crop prices and fertilizer
costs can help determine the best economic rate to apply to the whole field the
next growing season,” Jones said. He
encouraged producers to keep good written and photographic records of the ramp
strips, along with notes on prior crop and growing season conditions, as
valuable information to guide future fertilizer or manure applications. Photos
of an example ramp calibration strip are available in the April 2011 issue of
“Top Crop Manager (West)” at http://www.topcropmanager.com/index.php?option=com_content&task=view&id=
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