Nitrogen requirement
The main factors which affect the nitrogen requirements of turf are:
- The geographic location, which affects the length of the growing season;
- Topography, with high, wind swept areas having less of a growing season than moderate coastal areas;
- The type of grass species present, with Perennial Ryegrass requiring more input than Fescues;
- The soil type, which will impact on other nutrient levels and whether a suitable balance is achieved;
- The intensity of use : High wear areas will need more to aid recovery;
- Whether clippings are removed or returned, with the latter requiring less additional input;
- The time of year, which affects the temperature and moisture content of the soil;
- The age of the facility, which may have had time to build up a supply of organic nitrogen.
The total annual nitrogen requirement of turf varies considerably due to the above factors and each situation has to be looked at on its own, however, the following example may act as a basic guide.
Example fertiliser programme
A golf course, situated in Middle England, has greens which are well established, have a sandy loam soil, moderate usage, clippings removed (obviously), adequate supplies of other plant nutrients and with mostly fescue/browntop bent greens but with a significant annual meadow grass content and a thinning sward in quite a few places requiring a heavy overseeding operation in Mid-April.
The suggested fertiliser programme is planned to provide about 16 g/m² as follows:
| Planned application date | Fertiliser content N:P2O5:K2O |
Type / Formulation | Application rate | Amount of nitrogen supplied ( % N x app. rate) |
Accumulated amount of nitrogen |
| Early April | 14:3:7 | Inorganic with controlled release coating / Compound | 50 g/m² | 7 g/m² | 7 g/m² |
| Mid-end May | 8:0:0 | Inorganic and organic / Mixture | 35 g/m² | 2.8 g/m² | 9.8 g/m² |
| End June | 8:0:0 | Organic / Mixture | 35 g/m² | 2.8 g/m² | 12.6 g/m² |
| Mid-end August | 20.5:0:0 | Inorganic - ammonium sulphate / Straight | 15 g/m² | 3.1 g/m² | 15.7 g/m² |
| Total applied | 135 g/m² | 15.7 g/m² |
An ornamental lawn, for example, may only require the equivalent of say 7 g/m² over the season, whilst a football pitch, or creeping bentgrass golf green, based on a sand construction may require 25 g/m².
Comparing the unit costs of fertiliser nutrients
The main comparison is usually carried out for nitrogen as this is the dominant component of turf fertilisers.
Let us look at a few examples:
| Source | % nitrogen | 'General' cost per 25 kg bag | Cost per 1 kg of nitrogen ( £ ÷ (25kg x %N) ) |
| Ammonium sulphate | 20.5 | £ 14.00 | £ 2.73 |
| Hoof and Horn | ~13 | £ 40.00 | £ 12.31 |
| 'Typical' IBDU based fertiliser | 31 | £ 38.00 | £ 4.90 |
| Fine turf fertiliser (8:0:0) | 8 | £ 16.00 | £ 8.00 |
| Controlled release fertiliser (14:3:7) | 14 | £ 23.00 | £ 6.57 |
By using this method, it is quite easy to compare the different fertiliser costs. Whilst different fertiliser sources each provide their own particular benefit, when two similar sources are compared it may be desirable to choose the cheaper unit cost one, if all else is equal.