Like all living things the grass requires certain amount of feed (nutrients) to remain in a healthy condition.
If the lawn is lacking in any nutrients it’s health will suffer and it becomes susceptible to many types of lawn related problems, pests & diseases. The same can also be said of a lawn that contains too many nutrients, so it is important to get the balance right with the correct lawn feed & fertiliser program.
Nutrients used in lawn fertiliser
There are 3 key nutrients that are used in lawn fertiliser programs. These nutrients are Nitrogen, Phosphorous (Phosphate) and Potassium (Potash).
Nitrogen (N) – This is the most important nutrient in any lawn fertiliser. The role of nitrogen is too produce strong consistent growth. It gives the grass it’s dark green colour during the summer months.
Nitrogen is used in many lawn care products such as lawn sand and weed and feed products. It can also be used a straight (on it’s own) fertiliser but is more commonly used with phosphate (P) and potassium (K) as a complete compound fertiliser.
Nitrogen is used in spring and summer lawn feed and fertiliser programs. It should not be applied in large quantities later than mid August and certainly not during the autumn and winter months. Applying Nitrogen at these times of the year can cause major disease problems during the autumn and winter. You may need to apply nitrogen more than once a year (every 6-8 weeks) as it is easily leached through the soil.
Phosphorous (P) – Phosphorous is important for maintaining a deep healthy root system. This results in earlier growth during the spring, also more nutrients and water can be tapped into during periods of drought and stress due to the increased rooting. Unlike nitrogen it can be applied any time of the year but one application per season is usually enough.
Potassium (K) – Although Potassium is not as important as nitrogen and phosphate it is still required or maintain a healthy lawn. Potassium hardens the turf, helping with disease & drought resistance. It can also be applied at any time of the year, again one application per annum is usually enough.
What to use and when to apply a lawn fertiliser
There are two main types of fertiliser, they are spring & summer and autumn & winter fertilisers. The main difference in these fertilisers apart from the timing of application is the amount of nitrogen contained in each. Spring & summer feeds contain a large percentage of nitrogen while autumn & winter feeds contain very little nitrogen.
Spring & summer fertiliser – A spring/summer feed contains a high percentage of Nitrogen and may also include some additional Phosphate & Potash. This fertiliser can also be part of a weed, feed and moss control formulation.
The spring & summer fertiliser is always the first to be applied, usually from late March on wards when the temperatures have started to rise.
A further application/s may be necessary during the growing season depending on the fertiliser type, climate, soil type etc. However it is important not to apply a spring & summer fertiliser to late in the season (after August). This can lead to disease problems (due to the high nitrogen content) during the autumn.
Autumn & winter fertiliser – Autumn/winter feeds are usually applied once annually, September/October being the optimum time for application.
An autumn/winter fertiliser will contain a high percentage of Phosphate & Potash and small amount of Nitrogen.
An autumn/winter feed may also contain some sulphate of iron (iron sulphate). This will help harden the turf against disease, discourage worms and moss. Iron sulphate also helps cosmetically by turning the lawn a deep green colour without stimulating growth.
Types of lawn fertiliser
There are two types of lawn fertiliser, liquid and granular, both have their advantages and disadvantages.
Liquid fertiliser – These type of fertilisers are have a quick response with a rapid green-up. However the longevity of liquid fertilisers are generally quite short, therefore re-application is necessary quite often.
Liquid fertilisers are generally diluted with water when applied, by means of a hose-end applicator, watering can or a hand held or knapsack sprayer.
Granular fertiliser – Granulars are longer lasting than liquids therefore require fewer applications. They can be slow release (lasts anywhere from 8-12 weeks) or conventional release (lasts about 4-6 weeks).
Granulars can be applied by hand but for the best results a hand or push spreader can be used. It is important that granular fertilisers are watered in after application to prevent scorching the grass or worse.