Plant Nutrition and Fertilisation

Essential Plant Nutrients

Of the more than 100 chemical elements known, only 16 have been shown to be essential to plant growth. Three of these, Carbon, Hydrogen and Oxygen are primarily taken from the air and water. The other 13 are normally absorbed from soil by plant roots. These 13 are divided into 3 groups: Primary, Secondary and Micro Nutrients.

Primary Nutrients                                         Secondary Nutrients

  • Nitrogen (N)                                                                 Magnesium (Mg)
  • Phosphorus (P)                                                           Calcium (Ca)
  • Potassium (K)                                                              Sulphur (S)

 Micro Nutrients

  • Iron (Fe)
  • Zinc (Zn)
  • Manganese (Mn)
  • Copper (Cu)
  • Boron (B)
  • Molybdenum (Mo)
  • Chlorine (CL)

Nitrogen (N)

  • Nitrogen is an essential component of protein which is essential for root and shoot growth
  • Required by grass plants in the largest amounts
  • Responsible for turf colour
  • Improves resistance to heat, cold, disease and drought tolerance

N Deficiency’s

    • causes grass plants to yellow and become stunted
    • diseases (such as dollar spot and red thread) are more prevalent in N deficient turf
    • weed infested thin weak turf


Phosphorous (P)

Phosphorus is a constituent of nucleoproteins which are necessary for cell division and the development of meristematic (new) tissue. Hence, phosphorous is an important nutrient for the establishment of new turf.

P Deficiencies

  • Reduces grass plants ability to spread and retain moisture
  • Grass plants can become narrower, turn purple and curl

Potassium (K)

Potassium is essential for over all plant health. It contributes to an increase in drought and disease tolerance and improves winter hardiness.

K Deficiency

  • shallow root system
  • soft drooping leaves with poor development of supportive tissue
  • turf is susceptible to stress

Magnesium: there is an atom of magnesium in each molecule of chlorophyll. Chlorophyll gives the plant its green pigment. It is also the site of photosynthesis.

Sulfur: an important constituent of many amino acids. If sulfur is deficient, S containing amino acid production is slowed and plant growth is reduced.

Calcium: constituent of cell walls; required for meristem growth; neutralizing factor for potentially toxic substances within cells; influences uptake of other nutrients i.e. potassium

Micro Nutrients

Cu, Fe, Zn, Mn, CL, B and Mo are components of the plant’s enzyme system, catalyze biological reactions and are required for the conversion of sugar to starches.

Iron – important for chlorophyll production

Manganese– part of chlorophyll

Boron, Copper, Zinc, chlorine and Molybdenum required in very low quantities.

What is a fertiliser?

  •  plant food which provides food that is either taken up through the soil or via the leaf to sustain growth and health of any plant.

If you don’t fertilise and you continuously cut or harvest the turf, eventually the plant will require food and get weaker and suffer resulting in poor plant count and poor performance. Fertiliser is normally manufactured with an NPK analysis which means:

  •  N: = Nitrogen
  •  P: = Phosphorus
  •  K: = Potassium

Balanced Nutrient Input

Too Much Nutrient

  • Affect nutrient uptake
  • Excess top growth
  • Slow greens
  • Poor Root system
  • Potential disease

Too little Nutrient

  • Susceptible to wear
  • Poor surface condition
  • Poor color response
  • Potential disease

What is Granular Fertiliser?

There are two different types of Granular Fertilisers:

Compound: each granular contains N P K plus other ingredients; it is made by mixing all ingredients together in a liquid soup then drying all the moisture out creating a granule of different sizes, it is then sieved to create either a fine or coarse grade. Main advantage is: each granule contains all the ingredients, therefore when the product is spread a good placement is created, the main disadvantage is that large quantities have to be manufactured at one time and therefore you cannot be flexible with ingredients or small quantities.

Blended: the word ‘blend’ means a number of different ingredients of same particle size, mixed together in the right proportions to provide an N P K granular fertiliser. Blended fertilisers are becoming more popular because of their flexibility i.e. .you can change key ingredients at any time to suit the application, such as more slow release etc. because of the technology of producing accurate particle size blended fertilisers will spread the same as compound fertilisers.

Types of Nitrogen

It’s not enough just to know the amount of nutrients. You’ll also need to know what kind of nitrogen is in the fertiliser. Fast release nitrogen is available to the plant immediately. Weed Man slow release nitrogen is coated, so that the nitrogen is only available to the plant when soil bacteria have broken down the coating. This process is gradual, so the slow release nitrogen provides nutrients to the plants over a period of about 8 weeks.

Controlles Release

There are two advantages to slow-release nitrogen:

1. The nitrogen is made available to the plant as the plant needs it, over an 8-week period. With a fast release fertiliser, it’s either feast or famine for the plant.

2. Since the fertiliser is used gradually, very little is wasted.

Benefits of using a fertiliser programme

  • To achieve maximum continuity which will increase and maintain plant count all year round.
  • By increasing the hardiness and stress tolerance of the turf you will be able to carry out more aeration /scarification to keep thatch to a minimum, which reduce disease and cut down costs.
  • If your root zone has a deficiency, this can be included into the programme and rectified.
  • To feed all year round, which will increase winter hardiness and spring start up.
  • Increase continuity and better plant count will allow you to reduce the height of cut, which will increase the performance of your fine turf.
  • Allow you to budget an overall cost per green/area per year

The Weed Man Fertiliser Program

A Weed Man fertiliser program will feed your lawn 3-6 (depends on location) times a year at approximately 6-10 week intervals. Weed Man uses only the highest quality products, which have been specially developed for home lawns. As you can see, Weed Man fertiliser contains a small percentage of fast release fertiliser that is immediately available to your lawn. Larger quantities of slow release nitrogen will become available to the lawn as it needs the nitrogen. Weed Man fertiliser also contains phosphorus, potassium and soil conditioners. Combined with proper mowing, watering, aerating and weed control (and in the absence of disease and insect problems), Weed Man’s fertiliser program will give you a healthy lawn all season long.

Factors Affecting Fertiliser Input

  • Time of the year
  • Weather conditions
  • Annual Soil Test results
  • Turf requirement
  • Nitrogen source

Fertilisers and the weather

Before feeding: check the weather forecast. If possible, pick at time where showery weather is likely. Avoid feeding during prolonged dry weather. If treatments must be done at such times, water thoroughly shortly before application and then treat as soon as the foliage is dry.

When feeding: the grass should be dry and the soil moist at the time of treatment. Never feed the lawn when it is raining.

After feeding: if rain does not fall for 2 days after application, water the treated lawn thoroughly to carry the fertilizer down into the soil.

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