Download P and K Calculators for Compaq
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Crop :
Select your crop for recommendations.
Yield Goal:
Select a yield goal that represents your yields of this crop averaged over the last 5
years. Then add 10% to arrive at an estimated yield goal for the next crop year. Yields
should be in Bushels, Tons, or Pounds /acre depending upon choice in "Crop".
Optimum Level:
This represents the Optimum level of available P1 in ppm or lbs/acre in the
soil that is needed before considering adding a build-up amount of P to bring it to this
level. Above this level only maintenance amounts of P are required to maintain the optimum
level. The optimum P1 level for the soil test readings from the Bray P1
and the Mehlich-3P for all crops except wheat and alfalfa is 12 - 20 ppm P1.
The optimum level for wheat and alfalfa is 20 - 25 ppm P1. If the Olson P test
is used the optimum level for all crops except wheat and alfalfa is used the level is 8 -
14 ppm P1.The level for wheat and alfalfa is 15 - 18 ppm P1. The
soil laboratories that provide a Bray P2 test results give those results in
terms of total phosphorus in the soil not as available P to the plant.
Nutrient Removal:
This represents the amount of the nutrient that is removed in each 1 bushel, pound or ton
of yield for a specific crop.
Soil Test Value:
This represents the reading that is shown in your soil test report for the amount of
available P given in ppm or in lbs/acre or in lbs of P2O5 / acre
that is available for the crop to use. The calculator assumes the process used to be Bray
P1. If your lab reports a different number due to using either Bray P2,
Mehlich-3P, or Olson methods, then you should adjust the value to represent Bray P1. You
should consult your lab for specific details but these values can be approximated by the
following: Convert Mehlich-3P to Bray P1 (Mehlich * 0.7174); Convert Olson to
Bray P1 (Olson * 2.0); Convert Bray P2 to Bray P1
(consult reporting lab).
Product Percent Analysis:
This is the amount of P2O5 in a given product that is to be used to
meet the crop’s P nutrient needs. This amount can be adjusted depending on the %
analysis of the product or blend being utilized.
Starter Credit:
This is the amount of credit in pounds/acre that should be allowed in the recommendation
for any P2O5 contained in the starter fertilizer material. This is
based on the Product Analysis % and rate applied at the time of planting.
Product to Apply:
This the amount of fertilizer and product analysis that is recommended to meet the
crop’s P nutrient requirement for the yield goal that has been selected under normal
climatic conditions. This level of nutrients will allow you to capitalize on additional
yield if the climatic conditions are more favorable than normal.
