Outline:

  1. Fertilizer Terms
  2. Calculations
  1. Fertilizer Terms

    1. Fertilizer: any substance which is added to the soil ( or sprayed on plants) to supply those elements required in plant nutrution.
    2. Fertilizer Material or Carrier: a material which contains at least one plant nutrient.
    3. Mixed Fertilizer: a fertilizer which contains 2 or more of the primary elements - N, P, K.
    4. Fertilizer Grade: minimum guarantee of plant nutrient content in fertilizers in terms of total N. available P205, and available K20; in that order. ex. 5-10-10

      1. this amount of nutrients in these fertilizers is regulated by law. What they say is in the bag must really be there. This was not always the case years ago.
      2. This grade is the guaranteed minimum content.
      3. If you have a 6-12-18
        Then you have, in 100 lbs, 6 lbs N. 12 lbs P205, and 18 lbs K20.
      4. The nutrients are not present in the oxide forms but this is the method used in reporting them
      5. fertilizer recommendations are made in terms of N, P2O5, and K2O. These are usually called nitrogen, phosphate, and potash.
    5. Fertilizer ratio: the relative amounts of N, P2O5, and K2O in fertilizers.

      Grade Ratio
      5-10-10 1-2-2
      3-9-9 1-3-3
      4-8-12 1-2-3

    6. Filler: a material added to a mixed fertilizer to finish out weight requirements in a ton - commonly use ground lime.'

      Example: ton of 0-8-8

      add 0-20-0 superphosphate 800 lbs
      add 0-0-60 muriate of potash 267 lbs
      filler 933 lbs
      total 2000 lbs or 1 ton

  2. Calculations

    • How much of a given fertilizer is needed to provide a given amount of nutrient?

    • Fertilizer recommendations of 100 lbs of P2O5. How much concentrated superphosphate(0-46-0) is needed?

    • If 120 lbs K2O is needed, how much 0-0-60 must you apply?

    • It has been recommended that 120 lbs of N per acre be sidedresses on corn for achieving maximum yields. You could use ammonium nitrate (which contains 33.5% N) for this purpose. How much material will you need to use?

      What about using sodium nitrate, urea, and anhydrous ammonia?

    • Your soil test report recommended that 100 lbs pr acre of P2O5 be applied? You can buy triple superphosphate (45% P2O5). How many lbs/A will you need to apply?

      How much regular superphosphate (0-20-0) would be required for the same recommendation?

    • How many gals of 30% N solution will you need per A to supply 160 lb N/A on corn? 1 gal 30% N weighs 10.8 lbs

    • 8 lb of 5-12-18 to be applied. How much N, P2O5 and K2O are we really applying?