Fertiliser plays an important role in any lawn and turf maintenance program. A lawn fertiliser consists of different nutrients, each one plays a vital role in plant nutrition and maintaining good turf health. Nutrients are split into two categories, macro-nutrients and micro-nutrients. The difference is the grass plant requires more macro than micro-nutrients inputs.
There are six macro-nutrients requires for optimum plant health, three of them are primary and the other three are secondary macro-nutrients.
- Nitrogen (N) – Nitrogen is responsible for top growth, it is required by the leaves and stems of the plant. It is arguably the most used element in lawn and turf management. Nitrogen use varies depending on the time of the year. Higher levels of nitrogen are applied through the summer months when the grass is actively growing. It should not be applied in large quantities during the winter months when growth is slow or non-existent. High nitrogen inputs during the autumn and winter months can lead to disease problems, especially fusarium patch.
- Phosphorus (P) – Phosphorus is responsible for root and flower development. It’s also required for the establishment of new turf. It is also an important element in the photosynthesis process and helps the plant withstand stress. High inputs of Phosphorus are not usually required by turf, as it is usually readily available in the soil. Grass that is deficient in Phosphate often takes on a reddish – purple tinge.
- Potassium (K) – The key role of Potassium is to harden off the turf, making it tolerant to stress caused by extreme temperature, wear and turf disease. Many green-keepers / groundsmen apply a high potash feeds, when turf is at high risk to disease pressure. Potash can be leached quickly through the soil, therefore it is wise to apply it occasionally, to maintain adequate levels. A poor root system and soft, yellow growth are symptoms of Potash deficiency.
Secondary macro nutrients
- Calcium (Ca) – Calcium is important for the formation of strong cell walls, that help with disease resistance. It also aids the uptake and movement of other essential nutrients through the plant. Applying too much calcium can increase the soil pH, which can encourage weed grasses, disease and worms. Therefore care must be taken and it should only be applied in small amounts
- Magnesium (Mg) – Magnesium is required for the photosynthesis process, root development and chlorophyll production. It hardens the turf during winter and encourages early season growth. Soft, yellowing growth are symptoms of a deficiency in Magnesium.
- Sulphur (S) – Sulphur is important for overall plant health and the uptake of Nitrogen.
These nutrients are still required by the plant, but to a lesser degree and consist of:
- Boron (B) – Boron is required for the uptake of other nutrients with in the plant. It also helps with shoot and root growth.
- Manganese (Mn) – Manganese is required for the uptake of nitrogen and the production of chlorophyll. Excessive levels of manganese in the soil can be toxic to the turf.
- Iron (Fe) – Iron is the most commonly used of the micro-nutrients in turf care and is often incorporated into fertiliser mixtures. Sulphate of iron is the key ingredient in lawn sand, that is widely used for controlling moss in turf. It’s also important for chlorophyll formation and hardening the turf against disease.
- Zinc (Z) – Zinc is required for sugar consumption, while controlling plant growth.
- Copper (Cu) – Copper is important for the production of chlorophyll, root metabolism and reproductive growth.
- Molybdenum (Mo) – Aids the grass plants ability to efficiently utilize nitrogen.
The majority of lawn fertilisers will only contain the three primary macro nutrients, Nitrogen, Phosphorus and Potassium, as they are, in most cases, the only nutrients that will ever need applying. However, they sometimes contain additional micro-nutrients such as Iron and Magnesium, also referred to as trace elements.
A feed that contains only a single nutrient is called a straight fertiliser, A feed that contains or more than one is called a compound fertilser. If a feed contains all three primary nutrients (Nitrogen (N) ,Phosphorus (P) & Potassium (K) it is often referred to as a complete compound fertiliser.
If you study the fertiliser bag, package or container you will notice 3 numbers. These 3 numbers refer to the amount of nutrients (N,P,K) the bag contains. For example the numbers 24:4:12 means the bag contains 14% Nitrogen, 4% Phosphorus and 12% Potassium. A conventional bag of feed with this analysis would be used during the spring and summer because of the high nitrogen content.
When to apply fertiliser
Although turf can be fed at ant time of the year (subject to weather and ground conditions), the most common period is between March and October.
The initial feed should be applied early spring time when the weather is getting warmer and the lawn is starting to show signs of growth. This feed should contain a high percentage of Nitrogen (spring & summer feed) to help kick start the growth. It may also contain Phospahte and Potash, but Nitrogen is the most important nutrient throughout the growing season.
If moss is a problem coming out of the winter and into spring, then a spring and summer fertiliser containing addition iron should be applied to control the moss. Alternatively a product such as lawn sand can be applied to control the moss.
Lawn sand also contains Nitrogen to help stimulate growth. However the effect of the Nitrogen in lawn sand will be short lived. Therefore a dedicated spring and summer feed should be applied about a month following the application of lawn sand, to maintain consistent grass growth.
In most cases a second application of a spring and summer feed will be required during mid June. This will help maintain consistent growth and good turf health. Avoid applying a high Nitrogen feed after August, as this can cause problems with disease.
Finally an autumn/winter feed containing a high percentage of Phosphorus and Potassium should be applied in the autumn. An autumn/winter fertiliser may also contain a small percentage of Nitrogen, but not the high levels found in a spring / summer feed.
How to apply fertiliser
As lawn fertiliser is available in either a granular/power or liquid/soluble formulation, there are different ways to apply each type.
Granular – The best way of applying a granular feed to the lawn is through a spreader. There are two different types of spreader, a drop spreader and a spin spreader. A spin spreader spins the product onto the lawn, it is quick and efficient and perfect for larger lawns.
A drop spreader is better for tight spaces and smaller lawns where spread accuracy is important. For example: If there was a fish pond next to the lawn, a drop spreader would be the better option, as it only spreads the width of the spreader. A spin spreader throws the fertiliser either side of the spreader and great care has to be taken not to contaminate ponds and non-target plants etc.
Hand held spin spreaders are also available for applying feed to lawns and are great for smaller lawns. Fertilser can also be spread via hand, but this is not recommended unless you have experience with this method. If fertiliser is not applied correctly and evenly, you risk scorching and damaging your lawn.
Liquid – A liquid fertiliser usually comes as a concentrate and it is mixed with water and applied to the lawn through a sprayer or watering can. Liquid feeds generally perform better during the summer, when the soil is warmer. They do not perform well early in the season when soil temperatures are still quite low.
Slow release fertiliser
Many gardeners are now using slow release fertilisers, rather than conventional fertilisers. Slow release feeds last longer, as the nutrients are released over a longer period of time. This means the lawn requires fewer applications. Not only is the longevity increased, the growth is more consistent, eliminating spikes in growth. The main drawback with slow release feeds, is they are more expensive than a conventional feed.