Fertilization

The three nutrients most frequently limiting growth, and therefore usually required in the greatest proportions, are nitrogen, potassium and phosphorus, respectively. These nutrients are supplied in premixed fertiliser mixtures. Generally, it is recommended that nitrogen application be based on turfgrass growth, while phosphorus, potassium and lime applications be based upon soil tests. Iron and sulphur are two other nutrients that tend to be deficient.

It is always a good practice, before applying fertilisers, to conduct a soil analysis of the area, to ensure that correct amounts of nutrients are applied when fertilising. The function of the common nutrients can be summarised as follows:

Nitrogen (N):

• most critical nutrient in terms of manipulating the overall adaptation, disease susceptibility, recuperative potential and turfgrass quality,
• required by turfs in largest proportion.

Potassium (K):

• valuable for enhancing root growth and hardiness against heat, cold, drought and wear stresses,
• there is evidence that K reduces susceptibility to certain diseases such as dollar spot, brown patch and Fusarium patch.

Phosphorus (P):

adequate levels are particularly critical during seedling establishment as it is associated with increased root growth.

Excessive fertilizer applications can cause as many problems as under fertilization. Excessive N rates stimulate shoot growth, usually to the detriment of the root system. This is followed by death of the root system causing the turf to become prone to wilt and drought stress. Excessive N levels also enhance thatch accumulation and decrease the recuperative potential of the turf, thus decreasing the tolerance to such environmental stresses as heat, cold, drought and excessive moisture.

One should always be aware that the quantity of nutrients required at any time, varies seasonally. For example, temperature and moisture conditions favouring rapid shoot growth will result in increased nutrient requirements. Also, nutritional requirements, particularly N and K, are usually higher on sand, or intensely leached soils in contrast to fine textured soils that are subjected to minimal leaching. Higher nutritional levels will also be required where clippings are removed, such as on greens. Iron deficiencies most commonly occur on soils that have one or more of the following characteristics: waterlogging, above neutral soil reaction, high organic matter content and high phosphorus levels.

Fertiliser should be applied when the soil is moist and any fertiliser falling on the leaves should be washed off to prevent fertiliser burn. Thus it is recommended to broadcast the fertiliser before rails or watering. This practice will also help reduce losses of N through volatilization.