Soils

Introduction

Healthy soils produce life. It is no surprise that in the creation epic recorded in the book of Genesis, it is from the soil that Adam is created.

It is the soil which determines which crop will be planted, and what livestock is supported. What we do with our soil determines how our ecosystems serve us – and how well we eat.

National identities and characteristics are ascribed in some writings to the soils of their people, and even though the exploration is more metaphorical it grabs something within us which recognises the profound connection between ourselves and the soil.

In addition to this page, the reader will find several others of relevance on our website, including “Precision farming”; “Conservation Agriculture”; “Fertiliser”; “Speciality fertilisers”; “Compost and organic fertilisers” and more.

International business environment

  • Find the Soils Portal on the Food and Agriculture Organization (FAO) website, www.fao.org.
  • International Union of Soil Sciences (IUSS), www.iuss.org
  • International Erosion Control Association, www.ieca.org
  • Read about what the World Overview of Conservation Approaches and Technologies (WOCAT) has to say at www.wocat.net.
  • The Soil Science Society of America, www.soils.org
  • The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) www.ipbes.net

Local business environment

South Africa is a semi-arid country: only 15.8 million hectares (12.4%) of the total land surface area of 122.3 million hectares planted to field crops. In Mpumalanga, Gauteng and KwaZulu-Natal most cultivated fields are on high potential soils. In the other provinces, most cultivated fields are on on marginal potential soils. Over 1.7 million hectares of cultivated fields in the Free State, for example, are on soils that are officially classified as marginal to non-arable. This speaks of the importance of careful land use management, the availability of irrigation, unique soil characteristics, and risks related to terrain and soil management (e.g. erosion). It also underlines a vulnerability with respect to climate.

Source: Bureau for Food and Agricultural Policy (BFAP) Baseline 2024-2033

How to get the most out of your soils (Agricultural Research Council)

Soil sampling and analysis

Soil sampling is the weakest link in the soil testing process – a few grams of soil represent millions of kilograms in the field. Soil’s composition varies horizontally and vertically: the sample should incorporate these variations. It is therefore important that controllable factors, such as the time of sampling, sampling depth, relation to rows and the sampling path through the land, are identical to the previous years.

There are various methods to sample soils. How, where and when the sub-samples should be collected depend on the application of the analytical results. You may be wishing to formulate a fertilisation programme, for example. Here, the method of soil sampling is determined by the crop cultivated. Or you may be investigating plant production problems, or doing a nematode count (here too there are different guidelines depending on where you are doing the sampling e.g. orchards and annual crops require different sampling methods). Or perhaps you are wanting to determine the water-holding properties of your soil.

Several role players have compiled guidelines on soil sampling for their clients. Some examples are:

  • soil sampling to formulate a fertilisation programme for annual crops;
  • soil sampling to formulate a fertilisation programme for perennial corps;
  • site-specific sampling;
  • soil sampling to diagnose plant production problems;
  • soil sampling to establish permanent crops;
  • soil sampling to assess the current fertilisation programme of tree crops;
  • soil sampling to determine the water-holding properties of soils;
  • soil sampling for nematode counts.

Agricultural role players like the Agricultural Research Council (ARC), and your nearest agricultural college, Provincial Department of Agriculture or university will be able to help you with soil sampling.

 

“To be a successful farmer, one must first know the nature of the soil,” wrote Xenophon (400 BC). Photo used courtesy of Helen Gordon, WWF SA
 

Soil teems with life, yet because of bad farming and forestry practices, it is being washed away very many times faster than it is being replenished. On soil’s health depends much of the world’s food and water supplies, the growth of most plant and insect life and therefore the food of life itself.

 

Source: John Vidal, the article “The seven deadly things we’re doing to trash the planet (and human life with it)” on www.theguardian.com.

Soil erosion and Good Agricultural Practice

Soil erosion by wind occurs where a dry, loose soil that is reasonably finely divided on a soil surface that is smooth on which little or no vegetative cover is present.

  • Each year approximately 300 million ton of top soil is washed away.
  • At present 3 million ha topsoil cannot be used for agriculture as a result of erosion and bush encroachment.

A land user can combat wind erosion:

  • by using rotational cropping
  • by not leaving land fallow
  • by creating alternate strips of natural land with undisturbed cover crops
  • by leaving strips of natural vegetation at right angles to the prevailing wind direction
  • by creating suitable wind breaks, either mechanically or biologically

Intense rainfall on bare soil causes aggregate dispersion, surface sealing, and high runoff and low infiltration of water. The potential of soil erosion is greatest while the surface is bare after ploughing, during seedbed preparation, and at seedling establishment.

 

A land user may apply the following methods to combat water erosion:

  • lay out a land in such a way that the spread of run-off is sufficiently restricted;
  • cultivate land using a crop rotation system;
  • create alternate strips of land with undisturbed cover crops;
  • leave crop residue or plant material on cultivated land to protect the land from being eroded;
  • establish a suitable grazing crop on land permanently withdrawn from cultivation.
Source: www.dalrrd.gov.za

Commercial farmer points of interest

Because soils differ, their suitability to produce crops varies, and this will affect the crop yield. Are you planting the best crop for the soil you have at your disposal?

 

Farmers cannot afford to cultivate any land at a loss. The best soils should be selected for a crop. The low and varying maize price, for example, adds to the pressure and questions whether it is sustainable to grow that crop. Here it would be essential to select only the best maize soils for the cultivation of maize. Different crops would be selected for the balance of the land. Alternative crops would include permanent pastures.

There are variations in permanent soil properties. The South African Soil Classification System accommodates this variation in 73 soil forms and several families in each soil form. Variation in soil fertility and agronomic practices contributes to this variation.

Soil scientists can help farmers matching soil and land use. In order to make progress in optimising land use it is essential to do a soil survey. A land-use plan can then be worked out with the soil information. The aim is sustainable land use.

Precision agriculture with super monitors is a new tool helping farmers to determine exactly what their land is producing on any spot. Precision farming procedures monitor variations in crop yield well. This technology changed the soil survey and land evaluation industry. The other leg of precision agriculture grid sampling identifies variation in soil chemistry and fertility making variable application of lime and fertilisers possible.

  • Have a soil survey done and get hold of the soil map.
  • On the soil map do land use planning for the farm and keep sustainability in mind.
  • Apply the plan.
Based on information sent in by Dr PAL le Roux of the University of the Free State.

For the newcomer

Soil Types:

If you want to plant vegetables, fruit trees, maize or any other crop, you must first find out whether the soil is clay, sandy or loamy because crops do not always grow well in all kinds of soil. If you know what type of soil you have, you will know how to improve it.

Take soil in your hand, moisten it and form it into a ball. Make a fist, squeeze, then open your hand. The wet soil will have formed a sausage.

  • clay soil will form a firm sausage
  • loam soil will form a poor sausage that will break up if you roll it back and forth in the palm of your hand.
  • sandy soil will form a broken sausage (if it manages to form one at all!)

You can also tell the difference by looking carefully at your soil.

  • clay soil forms very hard dry clods
  • loam soil also forms dry clods
  • sandy soil has soft clods, or no clods at all.

Loam soil is the best as it retains just enough water and allows the right amount to drain away.

A soil that has too much clay or too much sand can be improved by adding lots of compost or manure.

  • Water does not penetrate easily into clay and plant roots do not grow easily.
  • Water penetrates quickly into sandy soil, roots grow easily but the soil becomes dry quickly.
  • Loam soil contains both sand and clay. Roots grow easily. The soil holds water and nutrients.

 

Acid soil and lime:

Most agricultural crops give better yields on soils that are not too acid or too sweet (alkaline). Many South African soils – especially those in the eastern parts of the country – are acid. On the whole, acid soils are poor and unproductive. A lime product must therefore first neutralise the acidity. Most crops benefit from lime application to increase the pH. The amount of lime applied depends on the pH, texture and base saturation of the soil. The more acid the soil, the more lime it requires. Clayey soil and soil with a high organic matter content must also be limed.

Source: Info Pak from www.dalrrd.gov.za and KwaZulu-Natal Department of Agriculture and Rural Development; Water Wise.

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.

 
Woolpert Africa – https://woolpert.com/woolpert-africa Soil mapping and soil erosion risk assessment
Johnson’s Soil Augers – https://johnsonsoilauger.co.za Effective soil sampling, soil classification, soil moisture determination etc
Rural Integrated Engineering – www.rieng.co.za
NviroTek Labs – www.nviroteklabs.co.za Independent analysis of soil

Regenerative Agriculture Association of South Africa – www.regenagsa.org.za

JMA Consulting – www.jmaconsult.co.za
University of the Free State Department of Soil, Crop and Climate Sciences – www.ufs.ac.za/natagri
University of Limpopo (UL) Soil Science, Plant Production and Agricultural Engineering – www.ul.ac.za
North-West University (NWU) Geology and Soil Sciences – https://natural-sciences.nwu.ac.za/geology-and-soil-science
Soil Science Society of South Africa (SSSSA) – https://soils.org.za
Council for Geoscience – www.geoscience.org.za
Land Rehabilitation Society of Southern Africa (LaRSSA) – www.larssa.co.za
Combined Congress – https://combinedcongress.org.za “The Combined Congress is an annual congress of three scientific societies, including Soil Science Society of South Africa (SSSSA), Southern African Society for Horticultural Sciences (SASHS) and the South African Society of Crop Production (SASCP)”.

Further reference:

Companies involved:

Government:

  • Department of Agriculture, Land Reform and Rural Development (DALRRD) Directorate: Land Use and Soil Management (LUSM)  www.dalrrd.gov.za

Training and research:

  • ARC Campuses not listed above are involved with soils e.g. the Small Grains and Grain Crops will be able to help with soil samples and issues of the soil.
  • The agricultural colleges, working closely with the Provincial Departments of Agriculture, offer training courses.
  • Companies involved conduct research (find some of these later on this page)
  • Also find role players on the “Agricultural education and training” page.

Websites and publications

Read about the South African Journal of Plant & Soil at www.soils.org.za/SAJPS.html and www.nisc.co.za.

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 Soils of South Africa covers the properties, classification, genesis and use of various soils e.g. organic, humic, vertic, melanic, silicic, calcic etc. The book was authored by Prof Martin Fey (with contributions by three others). Find it on https://books.google.co.za.

Download the Sustainability Initiative of South Africa (SIZA) “Guidance on South African Legislation” document, available on its website, www.siza.co.za. Soil development is one of the chapters.

Van Huyssteen C.W. 2020. Relating the South African soil taxonomy to the World Reference Base for soil resources. DOI:10.18820/9781928424666

Stika J. 2016. A Soil Owner’s Manual: How to Restore and Maintain Soil Health. CreateSpace Independent Publishing Platform.

Le Roux P.A.L. 2013. Field Book For the classification of South African soils.

Kejafa Knowledge Works has a number of books on soil in stock. Visit www.kejafa.com.

Soil classification: A Taxonomic system for South Africa (also available in Afrikaans) is available at ARC-SCW. Visit www.arc.agric.za or call 012 310 2500.

Call 012 842 4000 / 17 or email iaeinfo [at] arc.agric.za for the following publications available from ARC-Agricultural Engineering:

  • Barricades and small structures for the prevention of soil erosion (also available in Afrikaans)
  • Combating erosion with silt fences (also available in Afrikaans)

Provincial Departments of Agriculture produce brochures, posters   and other material. On the KwaZulu-Natal Department of Agriculture website, www.kzndard.gov.za, find documents like  “Acid Soils and Liming”.

Find the soil management guidelines on the Conservation at Work website, https://conservationatwork.co.za/guidelines.

The following Info Paks (booklets) are available from the Resource Centre at the Department of Agriculture, Land Reform and Rural Development (DALRRD), www.dalrrd.gov.za:

  • Soil Erosion
  • Soil: Acid soil and lime (most crops benefit from increased lime application)
  • Soil: Application of lime (the amount of lime added to the soil depends on various factors)
  • Soil: Kraal manure as fertiliser (a viable alternative for chemical)
  • Soil potential
  • Soil: Suurgrond en kalk
  • Mulching (a blanket on the soil)

The Soil Health Prism provides a holistic analysis of your soil’s health and translates this into a simple visual representation that makes data interpretation and solution recommendation simple and accurate. Find details on www.fertilizer.co.za.

Provincial agencies like Cape Nature have guides on soil management. Find their details on the page on biodiversity.

Watch videos like “The Magic of Soil” and “Living Soil Film” on YouTube.

Some articles

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