Fertilizer FAQs

What does N-P-K mean?  What are the numbers on a bag of fertilizer? EX: 21-6-5

  • N – Nitrogen promotes rapid growth, dark green leaf color, improves quality and quantity of foliage, increases protein content of food crops
  • P – Phosphorus stimulates rooting, vigorous growth and fruit/flower formation, hastens maturity
  • K- Potassium improves disease resistance and protein production, allows plants to trans-locate sugars, starches and oils

Should I use liquid or dry fertilizers?

  • Liquids – fast acting, applied in a hose end attachment, such as Miracle Grow
  • Dry products – applied with spreaders for even distribution; watering necessary ASAP to wash off foliage and walkways; beware stain cement.
  • Combination of both liquid and granular products for best results

What are examples of natural and synthetic fertilizers?

  • Natural products – grass clippings (bananas), manure, worm castings, etc.
  • Synthetic products – pelletized granular fertilizers, Gro Power, 20-0-0, etc.

How do I use mulch?

  • Recommend top dressing beds and lawns, ½” – 1″ layer
  • Suppresses weeds, improve soil texture and hold moisture.
  • Quarterly fertilizing program, double check directions
  • Bi-annual mulch application

How does soil type affect my choice in fertilizer?

  • Clay soil – heavy, water retentive, fertilizers move slowly
  • Sandy soil/volcanic cinder – grainy, water passes through quickly, so do fertilizers (Use time release only!)

More Tips

  • For best results, get on a schedule.
  • Magnesium is lacking in most Hawaii’s soils and is necessary to promote green leaves especially in Palms.


Nothing Seems to Work!?!?  If you’re following the directions and not getting the result you want, it’s time for a soil test. You can contact our office to schedule a consultation or the College of Tropical Agriculture at University of Hawaii – Manoa.