Understanding the NPK Ratio of Fertilizers (With Examples)

✔ https://StudyForce.com
✔ https://Biology-Forums.com
✔ Ask questions here: https://Biology-Forums.com/index.php?...

Follow us:

▶ Facebook:   / studyforceps  
▶ Instagram:   / biologyforums  
▶ Twitter:   / studyforceps  

Note: The NPK ratio is the fertilizer analysis that tells you information about three key nutrients: nitrogen, phosphorus, and potassium. It is usually written in large bold letters on the packaging.

Q1. In package whose NPK ratio is 33-10-5, what percentage of the product contains nitrogen, P2O5, and K2O? If the package weighs 40 lbs, how much of each nutrient does it contain by weight.

Note: If you're asked for the percentage of elemental P and K, the calculation changes.

• Firstly, the molecular weight of P2O5 is 142 grams/mol. The portion of the molecule that is P only is 62 grams/mol. Therefore, P represents 62/142=0.4366 or 0.44 (44%) of the molecule.
• Similarly, K2O has a molecular weight of 94 grams/mol. The portion of the molecule that is potassium is 78 grams/mol. Hence, potassium only represents 78/94=0.8298 or 0.83 (83%) of the molecule.

Q2.

a) For the 50 lb. bag of fertilizer depicted below, state the percent of:

N = ___%
P2O5 = ___%
P = ___%
K2O = ___%
K = ___%
Filler = ___%
Total = ___%
 
b) Calculate the weight of each nutrient in pounds (lb.):
 
N = ___ lb.
P2O5 = ___ lb.
P = ___ lb. 
K2O = ___ lb.
K = ___ lb.
Filler = ___ lb.
Total = ___ lb.