Fertilizers Used in South African Agriculture

01

Macronutrients: the core of most fertilizer programmes

Three nutrients form the backbone of most fertilizer blends:

• Nitrogen (N), which drives vegetative growth and is often the nutrient most responsible for visible yield response, but is also the one most easily lost from soil through leaching or volatilisation.
• Phosphorus (P), important for root development and early plant establishment, generally more stable in soil than nitrogen but less available in acidic or highly weathered soils.
• Potassium (K), which supports water regulation within the plant and overall stress tolerance, including drought and disease resistance.

Fertilizer blends are usually described by their N:P:K ratio, and the correct ratio for a given field depends on what the soil already supplies and what the target crop requires at each growth stage.

02

Micronutrients and secondary nutrients

Beyond the three macronutrients, crops also need secondary nutrients such as calcium, magnesium and sulphur, along with micronutrients including zinc, boron, manganese and copper. Many South African soils are naturally deficient in one or more micronutrients, and deficiencies often only become visible once a crop is already showing reduced vigour or characteristic leaf symptoms. Soil and leaf tissue testing are the standard ways to detect a deficiency before it limits yield.

03

Organic and synthetic sources

Fertilizer inputs broadly fall into two groups:

• Synthetic (inorganic) fertilizers, manufactured to deliver a precise, concentrated nutrient content, making them easier to apply at exact rates.
• Organic sources, such as compost, kraal manure and other organic amendments, which release nutrients more slowly and also contribute organic matter that improves soil structure and water-holding capacity over time.

Many farms use a combination of both, relying on organic inputs to build long-term soil health while using synthetic fertilizers to meet precise, short-term crop demand.

04

Soil testing as the starting point

Applying fertilizer without first testing the soil is generally discouraged by agronomists, since it risks both under-application, which limits yield, and over-application, which wastes money and can contribute to nutrient runoff into water sources. A soil test typically reports pH, organic matter content and the levels of major and minor nutrients, forming the basis for a fertilizer recommendation specific to that field and the crop planned for it.

05

Timing and method of application

When and how fertilizer is applied affects how efficiently the crop can use it. Common considerations include:

1. Split applications, where nitrogen in particular is applied in several smaller doses across the growing season rather than all at once, reducing losses and matching supply to the crop's changing demand.
2. Placement, since banding fertilizer near the root zone is often more efficient than broadcasting it across the whole field.
3. Weather conditions, as applying fertilizer shortly before heavy rain can increase the risk of runoff or leaching, particularly for nitrogen.

06

Regulation and registration

Fertilizers sold in South Africa are subject to registration requirements intended to confirm that the nutrient content and claims on the label match what is actually in the product. This registration framework exists to protect buyers from mislabelled or substandard products and to ensure a baseline of consistency across the market.

07

Environmental considerations

Over-application of fertilizer, particularly nitrogen and phosphorus, can contribute to the pollution of rivers and dams through runoff, a concern in agricultural catchment areas. Matching application rates to actual crop need, based on soil testing rather than habit or convenience, is the main way growers manage this risk while still meeting production goals.