Knowing why NPK is important for your lawn will help you to understand how you are helping your lawn when you fertilise.
For the most part, as long as you use a good quality fertilser that is suited to your turf variety (where all the scientific work has been done) your lawn will thrive.
Lawn fertilisers come in many varying types and blends and can be quite confusing as to which is the right option for your. Grass is like any other plant - it takes in nutrients and air through the soil and sunlight through the leaves for photosynthesis where the conversion to sugars and energy takes place. The job of lawn fertilisers is to keep this in balance and help provide the nutrients that your lawn is lacking.
(N) Nitrogen - Nitrogen is largely responsible for the growth of leaves on the plant and is the most talked about nutrient when it comes to lawns and is usually the highest percentage of your NPK ratio. Lawns love Nitrogen, but it is important to strike a balance between strong leaf growth and strong roots capable of supporting it as well. This is where phosphorus comes in.
(P) Phosphorus - Phosphorus is largely responsible for root growth and is actually quite a low percentage of the overall NPK ratio. Phosphorus moves slowly through the soil, and isn't used in great amounts by your lawn.
(K) Potassium - Potassium is a nutrient that helps the overall functions of the plant perform correctly. Potassium is an essential macro-nutrient used in the largest quantities by plants for vigor and growth. Potassium helps grass withstand drought and disease. IT also helps the plant to more effectively use Nitrogen.
By Understanding how these nutrients effect the overall health of your lawn, you will be better equipped to identify deficiencies in your lawn and the tell tale signs of stress, which will help you know when it's a good time to fertilise.
The original blog post can be found on the Lawn Solutions Australia website.