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.
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:
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 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.
A land user can combat wind erosion:
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:
Source: www.dalrrd.gov.za
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.
Based on information sent in by Dr PAL le Roux of the University of the Free State.
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.
You can also tell the difference by looking carefully at your soil.
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.
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.
Further reference:
Companies involved:
Government:
Training and research:
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:
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:
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.
Find the soil moisture option at www.weatherphotos.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.
