What Is Fertilizer?

Q: What is fertilizer?

A: Every bag of fertilizer has a set of numbers called N – P – K; Nitrogen – Phosphorus – Potassium (Potash).  The numbers represents the percent of that macro-nutrient in that particular bag.  These nutrients are essential to plant health.  Some bags of fertilizer may also contain micro-nutrients and/or pesticides.   The type of fertilizer, weather, and the actual property all play a role in timing of an application in order to keep grass attractive and resilient.

Too much fertilizer or too little, both can be detrimental for a lawn.  You want to decide on the right fertilizer, at the right time of year in order to be efficient and most beneficial.  Temperatures effect which nutrients to use (N – P – K) and how slow the fertilizer releases.  The way fertilizer is coated effects the release of nutrients, dictating how long fertilizer can stay in the soil.  Depending on the time of the year, you may want a slower/faster release fertilizer.  Fertilizer can stay in the soil anywhere from 4-6 weeks, but rain/water will cause nutrients to leach faster.  This is one reason why over-watering can be bad.  The minimum, by law, is a 20% slow release fertilizer.

Other laws in New Jersey are limitations on phosphorus, only being allowed to apply it with seed or if you have a soil test and results show a deficiency.  Only 1 pound of nitrogen can be applied at once per 1,000 square feet.  New Jersey law even states that fertilizer can only be applied between March 1st and November 30th.  These laws were put in place to prevent algae from forming in waterways, which was hurting our ecosystem.

How do these macro-nutrients help my lawn? Lawn Care Treatment Services Colonia


Nitrogen promotes plant growth. Nitrogen is part of every protein in the plant, which is part of every process, from growing new leaves to defending against pests. Nitrogen is also part of the chlorophyll molecule that is involved in creating food through photosynthesis, giving plants their green color. Older grass tends to have less mobility of resources within the plant.  This could lead to more yellowing at the end of the season, before dormancy, when grass reaches a certain age.


Phosphorus promotes new growth and root growth,.  Root development leads to winter hardiness and improves the defense against other environmental stresses, including disease.  Phosphorus is required for establishing roots, seed development, cell division, and the synthesis process used by plants.  Phosphorus is not very mobile in soils, so it doesn’t have to be applied regularly.


Potassium is what keeps our grass strong.  This nutrient is involved in cellular metabolism, environmental stress resistance, disease resilience, internal water management, and wear tolerance.  It reduces transpiration, so grass needs less water.  Potassium also stimulates plant enzymes used in protein, sugar, and starch synthesis.  Being deficient in potassium could lead to permanent injury from drought, winter, traffic and/or disease.

Why we test your soil?  Please visit Rutgers Soil Testing Laboratory.