Soil, Forage, & Water Testing Laboratory
ALFA Building
961 S. Donahue Drive
Auburn University, AL 36849-5411

Telephone: (334) 844-3958
Fax (334) 844-4001

Monday through Friday
7:00 am to 12:00 pm
1:00 pm to 5:00 pm

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Soil and Forage Testing Laboratory at Auburn University Alabama Agricultural Experiment Station (AAES)Soil and Forage Testing Laboratory

Chemical Fertilizer Calculator

NOTICE: While the information generated from this site is believed to be accurate, any actions taken based upon the results are the sole responsibility of the user.

This calculator computes ounce, pound or ton of a given fertilizer required per unit area based on one (match) fertilizer at a time. The three numbers prominently displayed on fertilizer labels are N-P-K that stand for percentages of nitrogen (N), phoshate
(P2O5), and potash (K2O).

  1. Enter your fertilizer recommendation for N-P-K as provided from AU Soil Testing lab (usually in lbs/acre).
  2. Select a fertilizer from the dropdown menu.
  3. If your choice is not in the menu, select User Defined and enter your fertilizer grade.
  4. Select Your Application Rate (ton/A, lbs/A, lbs/1000 square feet, etc.) from the dropdown menu.
  5. If you know your exact area, select "lbs/any sqaure feet" and enter your total area by clicking on "Type your square feet".
  6. Select Match by clicking in the radio icon and then click Calculate.
  7. The Output will indicate the amount of fertilizer needed for the selected (Match) and the amount of deficit or surplus for the unmatched two.
  8. You can print a hardcopy by clicking on Print, or click on Reset to start over.
  9. You may choose a single nutrient source fertilizer to complete your deficit.
Caution: Please make sure that you choose the corect Match, Application Rate, fertilizer Grade and Type, and Recommendation. Consider sidedressing your nitrogen through split application.

You may simply fill in the fields, then click on Calculate. The output will be in the Output frame.

N P2O5 K2O Reccommendation
Fertilizer (%): Your Application Rate