Lawn Fertilising Tips

WHY fertilise?

Fertiliser is designed to feed your lawn with the nutrients it needs for growth, colour, root strength and overall health. The active ingredients in lawn fertiliser are nitrogen, phosphorus and potassium (N, P and K). Each of these elements has a different, important purpose: nigrogen for plant growth and healthy foliage; phosphorus for growth and vitality of the root system; potassium for strong cells throughout the plant tissue and overall health. When these nutrients are applied properly, your lawn will look great and be more resistant to diseases, pests and weather extremes.

WHAT type of fertiliser should I use?

Fertilisers are available in various formations, with different ratios of the ingredients mentioned above. Since the ingredients are always listed in the N-P-K order, it's easy to tell what each formulation will do for your lawn. If you want lush foliage at the top of the plant, choose a formulation with a high N number, such as 12-4-8. To strengthen the root system, choose a formulation with a high P number, such as 5-10-5. A good all-round fertiliser would be 10-10-10. An easy way to remember which number is which is to think "up, down, all around"!

WHEN should I fertilise?

Late summer and early autumn are the best times of year to fertilise your lawn.

Some people like to fertilise in the spring to get the lawn off to a healthy start. However, caution should be used at the beginning of the growing season because early spring applications of high nitrogen products can cause a growth surge that is bad for the lawn, in spite of the lush-looking results. (During a growth surge, most of the plant's energy goes to the top of the grass, at the cost of the root system.) If you want to fertilise in the spring, use a low-nitrogen product.

Fertilising during the summer gives your lawn the strength to thrive during its main growing season. Not only is growth itself demanding on the plant chemistry but mowing, scarifying, aerating, etc, all apply added stress to your lawn. A healthy, well-fed lawn will do better with these stresses, as well as with extremes in weather and possible pest damage.

In the autumn, fertilising gives your lawn an extra boost to help it through the winter. This application also provides valuable preparation for next spring, helping the grass resume growth and green-up early in the season, without the growth surge discussed above.

HOW do I apply fertiliser?

A good system is to start at the edges of your lawn first. For a square or rectangular lawn, make two passes at opposite ends of the lawn; for an irregular or circular lawn, make two passes around the perimeter. Then move back and forth in straight lines between the edges, making sure to turn the spreader off when turning around. With a drop spreader, overlap the path of the wheel to avoid striping.

After fertilising, water the lawn thoroughly but not too heavily. The idea is to wash the nutrients off of the grass leaves and gently into the soil.

HOW MUCH fertiliser should I use?

Refer to the instruction on your fertiliser bag for application rates, spreader settings and coverage amounts. This varies from product to product, because of the size of granules and the broadcast medium.


You'll need to know the size of your lawn to determine fertiliser, herbicide and pesticide application.

  • For a rectangular or square lawn, simply multiply the length times the width for total square feet.
  • If your lawn is a triangle, multiple the length of tthe base times the hieght, and divide that number by two.
  • If your lawn is circular (or close), measure the distance from the centre of the lawn to the edge. This is the radius. Multiply that number by itself (r²), and then multiply by pi (3.14).
  • If your lawn is irregular, you can either break it up into smaller areas, figure those sizes, then add them up. Or you can estimate using averages. Measure the width of your lawn every 10 feet or so along the length, then calculate the average width. (Add the measurements together and divide the total by the number of measurements you made.) Do this same exercise in the other direction to arrive at an average length. Then multiply your average width by your average length to get a fairly accurate estimate of total square feet.
  • Convert square footage to acreage by dividing your total area by 43,560, the number of square feet in a single acre.


The Green Reaper offers a selection of LAWN FERTILISERS, together with PUSH LAWN SPREADERS and TOWED GARDEN SPREADERS, to help keep your lawn in tip-top condition.


There are two basic types of fertiliser spreaders: drop and broadcast spreaders. The charts below will help you decide which type of spreader is best for your job, and the capacity you need based on the size of your lawn.

Recommended Type of Spreader

  Grass Seed Fertiliser Granular Herbicide Ice Melt
DROP Better Good Best Good
BROADCAST Good Best Good Best

Hand-held spreaders are useful tools also, and are good for overseeding or fertilising small areas, or for applying ice melt to driveways and pavements.

Recommended Spreader Sizes

Approx 1 acre / 40,000 sq ft 20 gallon (dry) / 175lb / 80kg
Approx 1/2 acre / 25,000 sq ft 130lb / 59kg
Approx 1/3 acre / 14,500 sq ft 8 gallon (dry) / 100lb / 45kg
Approx 1/4 acre / 10,800 sq ft 7 gallon (dry) / 75lb / 34kg

(1 acre = 43,560 sq ft)

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