Nitrogen is arguably the most discussed nutrient when it comes to lawn but it's use and application is often a little misunderstood. It is primarily responsible for leaf growth, colour and density but also plays a role in stolen, rhizome and root development. While it may be tempting to apply a lot of Nitrogen chasing the rapid growth and response in the turf, excess amounts will cause weak cell walls (increasing vulnerability to disease), poor root development, thatch or potentially leach out of the soil and contaminate groundwater stores. This is why a well balanced nutrient regime, suitable for the climatic conditions and growth rate of the turf is essential.
The NPK values are listed as a percentage on a bag of fertilizer, Nitrogen or N being the first number. 2Spec Elevate for example is 23-1-10 so 23% of the bag is Nitrogen. For every kilogram of product you put down, 230g will be Nitrogen. These can be in varying forms such as Nitrate, Ammonium, Urea or controlled/slow release.
For warm season turf varieties, 2-3kg of elemental Nitrogen distributed over the year is adequate. How much you apply of a given product should coincide with the growth rate of the turf. Spring and Summer, when the growth is strong, will require a higher rate than Autumn when the growth is slowing down as temperatures drop. Winter will require much lower again. Use this 2-3kg of N to guide your fertiliser choices and application rates.
Below is an example of yearly products on 100m2 of Buffalo in Perth and the total amount of N per application/year. Couch we would recommend closer to 3kg and Kikuyu the lower side, around 2kg.
| Month | Product | Rate | % of N | N (grams) |
| Jan | Elevate | 2kg | 23 | 460 |
| Feb | Special Fex | 300ml | 15 | 60 |
| Mar | Elevate | 1.8kg | 23 | 414 |
| Apr | Special Fex | 200ml | 15 | 42 |
| May | Endurance | 2kg | 20 | 400 |
| June | Fusion | 200ml | 12 | 33 |
| July | Fusion | 300ml | 12 | 50 |
| Aug | Fusion | 300ml | 12 | 50 |
| Sept | Accelerate | 1.5kg | 30 | 450 |
| Oct | Special Fex | 300ml | 15 | 60 |
| Nov | Elevate | 2kg | 23 | 460 |
| Dec | Special Fex | 300ml | 15 | 60 |
| Total | 2539g |
It is important to include all Nitrogen sources in the total amount. In the table above, the liquid applications of Fusion and Special Fex contribute 355g (or around 14%) of the total. It is also worthwhile gathering the specific gravity or base density of the liquids you are using from the product's SDS as this will multiply the figures (1L of liquid nutrients won't weigh 1kg, potentially 1.3-1.5 times more). If you can't find the SG, you could simply weigh 1L of liquid.
Do the maths on the products and rates you are using and you may be surprised how much or little Nitrogen you are putting on your lawn compared to it's needs. This can then help you understand why you may be regularly facing certain issues like excess thatch, disease etc.
You can find all the fertilizers listed here as well as many more by clicking here.