Search
Close this search box.

Fertiliser

Introduction

Fertilisation is a method of improving the nutritional status of the soils, and can be tailored to provide the correct nutritional requirements at the most appropriate time.

Fertilisers are food for plants; they contain plant nutrients (nourishing substances), which all plants need to grow and stay healthy.

Plants take carbon (C) from the air and 12 elements from the soil: Nitrogen (N), phosphorus (P), and potassium (K) are used in relatively large amounts. Sulphur (S), calcium (Ca), and magnesium (Mg) are also often required. Zinc (Zn), iron (Fe), manganese (Mn), Boron (B), copper (Cu) and molybdenum (Mo) are other elements.

The soil provides most of the nutrients needed, and shortages can be overcome by using carefully chosen fertilisers. It would be wasteful to apply a nutrient if your soil already has sufficient.

In general, macro elements such as nitrogen (N), phosphate (P) and potassium (K) are the nutrients most likely added to the soil.

 Applying nitrogen (N) improves overall crop quality. It helps plants develop the green colour they need to take food from the sun, and to take the necessary food from the soil. N increases the number of branches, leaves, seeds and fruits, and accelerates the number of plant cells in the plant. A shortage of nitrogen will result in yellow leaves and poor plant growth.
Phosphorous (P)Adding phosphorous (P) to the soil leads to better root development, helps with grain and seed development. Plants are assisted to ripen early and mature quickly.
Potassium (K)The addition of potassium (K) to the soil improves crop yields and quality, strengthens plants and helps them resist drought and disease. It helps the plant to breathe and plays a major role in the plant’s use of water (stomata) and its build up of starches, sugars, fats and protein.

Although NPK volumes are the highest, it is of utmost importance to emphasise the necessity of all other elements too.

Magnesium (Mg)Magnesium (Mg) helps plants to breathe and phosphorous to get into the plant. Mg is a vital element in photosynthesis. Too much will slow down the plant’s ability to absorb potassium.
Calcium (Ca)Calcium (Ca) forms the ‘building blocks’ in plant cells which ensure firmness, shelf life and quality produce. Calcium (Ca) strengthens plants and reduces/neutralises toxicity in the soil.
Sulphur (S)Sulphur (S) is essential for uptake of Nitrogen (N). S helps in leaf development and increases the quality of grain and fruit. It is responsible for flavour attributes in crops such as onions and garlic.
Zinc (Zn)A key constituent of many enzymes and proteins

 

 

“Straight” and “multi-nutrient” fertilisers

Fertilisers are either “straight” or “multi-nutrient”. Straight fertilisers are products containing one of the main plant nutrients. Some examples are given below:

Plant nutrient Fertiliser
Nitrogen (N)

Urea

Calcium ammonium nitrate (CAN)

Limestone ammonium nitrate (LAN )

Ammoniumsulphate (AS21)

Phosphate (P)

Single superphosphate (SSP)

Triple superphosphate (TSP)

Monoammoniumphosphate (MAP)

Potassium (K)

Muriate of potash (MOP)

Potassium-nitrate (KNO3) and potassium-sulphate (SOP)

P and K are shortened forms: P = P2O5 x 0.44 and K = K2O x 0.83

Multi-nutrient fertilisers contain more than one of the main plant nutrients. There are figures (numbers) printed on a fertiliser bag which will give you the ratios of plant nutrients of that fertiliser. They always follow the same sequence. The first number is the ratio of N, the second is the ratio of P, and the third refers to the ratio of K. Divide the figure given in the ration by 9, and then multiply it by 30. So 3.2.4. (30), for example, means that the fertiliser contains 10% of N, 6.6% of P and 13% of K.

(The above information is taken from the Fertiliser Retailing Guide, put out by the Food and Agriculture Organisation of the United Nations, the Fertiliser Industry Advisory Committee; and Omnia, Yara and Kynoch).
 

The ‘Law of the minimum’ illustrated by barrel staves of varying lengths represent growth-controlling factors. This is also known as Liebig’s law. The barrel story illustrates that success will be limited / handicapped by that element which is deficient. If only one element lacks in availability or is inadequate in supply one will not achieve optimum results. This is why a comprehensive nutrient programme or “balanced diet” is important.

 

What is the effect of water on fertiliser in the soil?

Water dissolves the fertiliser. The nutrients are carried by the soil water to the roots of the plant. If there is not enough water in the soil, the nutrients cannot reach the roots of the plant, nor can they be absorbed by the plant.

Can a farmer apply too much fertiliser?

Excessive fertiliser use can damage crops and reduce yields. It contributes to pollution of soil and ground water. Apart from also being a waste of money, it damages the overall image of agriculture when it comes to looking after the environment.

How do I know how much fertiliser to apply?

This depends on soil and crop. Clay soil, for example, requires a totally different application to sandy soil. If you want to know what fertiliser you need and how much to apply to your soil, take a soil sample from your land or a leaf sample from one of your crop plants and have it tested at an agricultural laboratory or a place where soil can be analysed to show which nutrients are lacking. These places can give a fertiliser recommendation. This money will be well spent because it can save you thousands later.

 

When is the time to apply fertiliser?

If fertiliser is applied at the wrong time, the yields will be lower and the farmer will make less money. The “basal” dressing should generally be applied at planting, and the “top” dressing should usually be completed before the plant flowers.

Best Fertiliser Practice

Fertiliser need

Over fertilising or under fertilising will affect your profit – too much will increase your costs and be bad for the environment; not putting enough fertiliser on will decrease the yield and thus your income. Two factors will assist you:

  • A soil analysis is crucial. Take a soil sample, representative of the field (don’t just take the sample from one place). The interpretation of the analysis must be soil and crop specific. It is recommended that you ask a specialist for help.
  • Determine the target yield.

 

Liming

Liming must by no means be neglected. Too much acid in the soil:

  • decreases the availability of phosphorus
  • inhibits the efficient uptake and use of both water and fertiliser
  • renders applied herbicides insufficient
  • suppresses the effectivity of micro-organisms in the soil
  • mean heavy metals such as Aluminium (AI), toxic to the plant, become present

Under highly acidic conditions it can, from an economic point of view, even be more beneficial to lime instead of increasing the fertiliser application rate.

 

Biological life

The biological life in the soil was neglected in the past. The value of micro-organisms in soil mustn’t be underestimated (and organic matter is food for micro-organisms). The positive influence of a well balanced, healthy micro-organism population on the availability of plant nutrients has been well proven. Experts are available to advise farmers accordingly.

Do not neglect the biological life in the soil. A healthy micro-organism population make more plant nutrients available – a great benefit. Experts are available to advise you.

 

Product choice

Compare the pros and cons of the different products. More concentrated products can reduce costs (there is less to transport), but in general do not contain the same amount of secondary elements.

 

Application

Although band placement of fertiliser is generally the most effective, there is a place and time for broadcast application and foliar sprays. The method of fertiliser application has a definite effect on fertiliser efficiency.

 

Precision farming

This ensures that the whole field is fertilised according to the soil analysis, remote sensing etc. (see “Digital agriculture” page), and expected yield. Money is saved, yields are increased and risk is reduced.

 

Water use

Determine the water content of every field. If there is not enough, then plant less or don’t plant at all. Effective weed control is important since water and plant nutrients are consumed by weeds.

 

Plant sap analysis/plant tissue analysis

Taking regular plant sap samples/plant tissue analysis will help you to address nutrient deficiencies in time. They will also prevent unnecessary fertiliser being applied.

Source: adapted from the article “Best Fertilizer Practices” which appeared in Volume 14 of The FarmAfrica, with additional comments from Yara.

International business environment

The South African industry’s margins are determined largely by world market prices of major raw materials, while domestic prices are primarily driven by import parity cost of commonly traded fertiliser commodities.

The top producers of fertilisers are the US, India, Russia, Canada, Indonesia, and Poland (World Population Review, 2024). The top exporters of fertilisers in 2022 were Russia, Canada, mainland China, US, Morocco, and Saudi Arabia. Fertiliser exports amounted to a total of US$84.6 billion (Workman, 2023).

The main fertiliser consumers in Africa include Egypt, South Africa and Morocco. Total fertiliser consumption in sub-Saharan countries is approximately 1% of the world fertiliser consumption.

The global chaos in fertiliser markets will encourage countries to diversify where they source fertiliser from, and encourage others to invest in producing key fertiliser compounds (Bureau for Food & Agricultural Policy [BFAP], 2022).

Further reference:

  • www.fertasastats.co.za provides trade statistics.
  • The various presentations under “Events” at www.fertasa.co.za are also a source of useful information.
  • Find the discussion of the global fertiliser market in the BFAP Agricultural Outlooks. See www.bfap.co.za.
  • The Africa Fertilizer Financing Mechanism is a special fund housed at the African Development Bank. See www.afdb.org/en/affm.
  • Read about the African Fertilizer and Agribusiness Partnership (AFAP) at www.afap-partnership.org. Its East and Southern Africa Fertilizer Trade Platform (ESAF) is designed “to facilitate and co-ordinate enhanced private sector investment and participation in the procurement and distribution of fertilizer in the region”.
  • The latest Africa Agriculture Status Report includes an overview of the continent’s fertiliser sector. Find it at https://agra.org/publications/africa-agriculture-status-report-aasr/.

View the following websites:

South Africa: imports and exports

  • South Africa Imports of Fertilizers was US$823.41 Million during 2023 (COMTRADE, 2024).
  • In 2023 South Africa imported 2 174 911 tons, and exported 736 411 tons (Fertasa, 2024).
  • The absence of urea production facilities and sources of potash in South Africa is one reason for high levels of imports (urea and potassium chloride make up the bulk of imported product) (BFAP, 2020).
  • Nearly two-thirds of South Africa’s fertiliser exports are to Zambia and Zimbabwe. Other destinations include Botswana, Mozambique, Australia, Brazil, Malawi, Namibia, Swaziland, Angola, Democratic Republic of the Congo and Kenya.

Local business environment

The industry supplies around 2 million tons of fertiliser products to the local market annually at a value of around R10 billion. In South Africa the maize industry consumes between 40% and 50% of all fertilisers and the market, therefore, is much influenced by what happens to this industry.

Negatives for the fertiliser industry include a land reform policy where it takes some time for new farmers to be fully established as commercial farmers, and if farmers were discouraged from planting maize and went instead for crops which use less fertiliser than maize. The emergence of a biofuel industry would be a positive for the industry as the crop demand would impact favourably on the need for fertiliser.

Further reference:

  • www.fertasastats.co.za provides trade statistics.
  • The various presentations under “Events” at www.fertasa.co.za are also a source of useful information.
  • Find the monthly Chemical and fertilizer report on the Grain SA website, www.grainsa.co.za.
  • The BFAP Agricultural Outlooks look at the effect of steep input costs on farmer profitability. Find the document at www.bfap.co.za.

National strategy and government contact

The “Legislation & regulations” option at www.fertasa.co.za is of great help here. It sets out the fertiliser regulations, registration documentation and contacts at the Department of Agriculture, Land Reform and Rural Development (DALRRD). The reader can also find information by looking for the “Agriculture Inputs Control” option at www.dalrrd.gov.za.

The Bureau for Food and Agricultural Policy (BFAP) has previously warned of the reliance by South Africa on imported agricultural inputs (machinery, chemical fertilisers, ingredients for animal feed and plant protection chemicals) (BFAP, 2020). The country becomes vulnerable on account of supply availability and cost. Previous baselines and government’s Agricultural Policy Action Plan (APAP) have also raised this issue.

The Fertilisers, Farm Feeds, Agricultural Remedies And Stock Remedies Act, 1947 (Act No. 36 of 1947) provides for:

  • the appointment of a Registrar of Fertilisers, Farm Feeds, Agricultural Remedies and Stock Remedies;
  • the registration of fertilisers, farm feeds, agricultural remedies, stock remedies, sterilising plants and pest control operators;
  • to regulate or prohibit the importation, sale, acquisition, disposal or use of fertilisers, farm feeds, agricultural remedies and stock remedies;
  • the designation of technical advisers and analysts.

The main provisions of Act No 36 of 1947 are: control over the registration of fertilisers, farm feeds, agricultural remedies, stock remedies, sterilising plants and pest control operators; to regulate or prohibit the importation, sale, acquisition or disposal of these inputs. This Act applies where a person imports, sells, acquires or disposes the mentioned articles. It is therefore advisable to be aware of these requirements. The Act is currently being revised and a Fertiliser Bill is out. Keep your eyes on the “Legislation & Regulations” option at www.fertasa.co.za.

Role players

Note: Click to expand the headings below.  To get a free listing on our website like the ones below, visit here for more information or place your order here. Disclaimer: The role player listings are not vetted by this website. Fertasa members (2022) are indicated by a tick – “√”.

 
Geysers – http://rossmin.co.za Category: Agricultural lime
NutriBio – see VS Agri
Westfert Tel: 053 444 1936 Category: Mineral fertiliser and/or mineral fertiliser ingredients
Afri Lime – https://afrilime.co.za Category: Agricultural lime

Fertilizer Society of Southern Africa (Fertasa) – www.fertasa.co.za Fertasa, a non-profit company, represents the interests of the fertiliser and aglime industries in South Africa.

ExperiCo√ – www.experico.co.za “Optimising plant health”

Agricultural Inputs Forum (AIF) – www.afma.co.za Agricultural Inputs Forum (AIF) members are AFMA, CropLife SA, FERTASA, Petfood Industry Association of South Africa (PIFSA), the SA Animal Health Association (SAAHA) and the SA Pest Control Association (SAPCA). Find the Proposed Regulatory Strategy and other documents on the AFMA website.

Further reference:

Training and research

  • The Agricultural Research Council campuses periodically do fertiliser-related research.
  • Fertiliser Advisors, Certification and Training Scheme (FACTS), a fertiliser advisors’ training course, administered by the Fertasa, is aimed at improving the skills of fertiliser advisors. Candidates are drawn from private sector, government, agri-business and co-operatives in South Africa and from neighbouring countries. For more information on the course contact Fertasa.
  • Fertiliser companies conduct in-house training and research within their own Research and Development departments.
  • Find universities, agricultural colleges and other role player details on the “Agricultural education and training” page.

Companies

Biofertilisers

Organic fertiliser producers

Websites and publications

Visit the websites listed earlier on this page.

Neil Miles, renowned soil scientist, runs the Agrispex Soil Productivity Expertise website, http://agrispex.co.za. Find the many articles to do with soil and fertilisers here.

The following publications are available from Fertasa:

  • Fertilizer Handbook (also available in Afrikaans). This is a hard cover handbook that has primarily been written for the use of persons who are involved in some way or another in a fertiliser advisory capacity. It is not intended to be a complete technical handbook, but rather a concise presentation covering a wide range of topics. For this reason, interested farmers and students will also find it to be a useful guide. It is prescribed as part of the agricultural curriculum at some universities and universities of technology in South Africa.
  • Deficiency Symptoms in Maize. A4-size colour pamphlet depicting the deficiency symptoms in maize.
  • Plantfood & Fertilizers. Illustrated publications for the emerging farmer. A4-size, in ring-binder format.
  • Soil Acidity and Agricultural Lime (also available in Afrikaans as Grondsuurheid & Landboukalk). This brochure contains the two chapter “Soil acidity” and “Agricultural lime” which appear in the Fertilizer Handbook. This brochure is intended as a general guide for agronomists and farmers alike who have a common purpose in sound liming.
  • Soil Fertility. Illustrated publications for the emerging farmer. A4-size, in ring-binder format.
  • Fertasa Journal – a publication containing the proceedings of the Fertasa annual congress
  • The Proceedings of previous Symposiums

Visit www.kejafa.com for the following publications from Kejafa:

  • Bemesting Fertilizer
  • Sea Energy Agriculture
  • Fertility from the ocean deep
  • Fertilizer Handbook

The ARC‘s excellent Maize Information Guide (MIG) includes notes on fertilisation. Download it from www.arc.agric.za.

Take a look at the annual South African fertiliser market analysis report on the  DALRRD website, www.dalrrd.gov.za. On the same website, find the Info Paks  that deal with soil. These include “Soil: acid soil and lime” and “Soil: application of lime”.

Read the AgriSETA Assessment Guide Primary Agriculture “Soil fertility and plant nutrition”.

Some articles:

Table of Contents

Buy the Book