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 chapter, the reader will find other chapters in this book of relevance e.g. “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.
- www.terrafrica.org – regional sustainable land management African network
- The Soil Science Society of America, www.soils.org
- The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) www.ipbes.net
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 members of the South African Soil Survey Organisation (SASSO), the 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.
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
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.daff.gov.za and KwaZulu-Natal Department of Agriculture and Rural Development; Water Wise.
- Land Rehabilitation Society of Southern Africa (LaRSSA) www.larssa.co.za
- South African Council for Natural Scientific Professions (SACNASP) www.sacnasp.org.za
- South African Soil Survey Organisation (SASSO) www.sasso.co.za This non-profit organisation exists for the development of soil surveyors and workers in related fields. It is a forum for soil surveyors to exchange ideas and discuss knowledge about soils. SASSO presents four national workshops distributed over the country each year. Workshops address soil suitability related aspects which advisors are confronted with in the industry e.g. identification of morphological soil properties, classification and mapping of soils and interpretation of the role of soils in different land uses.
- Soil Science Society of South Africa (SSSSA) www.soils.org.za
- Other relevant associations include the South African Society of Crop Production (SASCP) and Southern African Society for Horticultural Sciences. Visit www.sascp.org.za and https://sashs.co.za for more information. Find details of the Combined Congress at www.combinedcongress.org.za.
Department of Agriculture, Forestry and Fisheries Directorate: Land Use and Soil Management (LUSM) Tel: 012 319 7685/6 www.daff.gov.za
Training and research
Also consult the “Agricultural education and training” chapter.
ARC-Agricultural Engineering (ARC-AE)
Tel: 012 842 4000
Research and development of technology related to soil conservation structures, techniques and systems.
ARC-Climate, Soil and Water (ARC-SCW)
Tel: 012 310 2500
iscwinfo [at] arc.agric.za
Pedology and Soil Mineralogy
- Soil surveying, classifying and mapping
- Soil suitability for agricultural production and rehabilitation
- Soil susceptibility to salinity and erosion
Soil and Water Science
- Soil fertility
- Soil-plant-water relationships
- Soil water management
- Standard and specialist analyses
The ARC-SCW develops and maintains comprehensive databases on land type information, soil profile information and soil documentation culminating into soil information systems.
ARC- Plant Protection Research (ARC-PPR)
Tel: 012 808 8000
HabigJ [at] arc.agric.za
The Soil Microbiology Laboratory at ARC-PPR offers services to clients where long-term effects of soil management practices are determined on soil biological properties.
Other ARC Institutes involved with crop production 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. The KZN Department of Agriculture and Rural Development, for example, does training in soil classification, land capability, and in advanced soil fertility. Educational posters in Land Husbandry and management are also available (see heading 8).
AgriSETA accredited trainers (find the list at www.agriseta.co.za).
Companies involved conduct research (find some of these later in this chapter).
Council for Geoscience
Tel: 012 841 1911
Foundations for Farming training offered includes modules on the soil, how to preventing soil erosion etc. Contact Neill Jackson at 082 444 3947. Find details at www.foundationsforfarming.co.za/index.php/training/south-africa
Nelson Mandela University (NMU)
Centre for African Conservation Ecology
Tel: 041 504 2316
Danel van Tonder – 018 299 1092
danel.vantonder [at] nwu.ac.za
Unit for Environmental Sciences and Management
Prof Nico Smit Tel: 018 299 2128
Experts in soil surveys, precision farming, fertiliser recommendations, soil pollution and soil degradation assessments
School of Biological Sciences
Dr Sarina Claasens
Tel: 018 299 2321
sarina.classens [at] nwu.ac.za
NOSA Agricultural Services
Tel: 087 286 9298
Training and/or training materials available
South African Sugarcane Research Institute (SASRI)
Tel: 031 508 7400
SUSFARMS, the Sustainable Sugarcane Farm Management System, deals with soil management on the farm. SASRI also does soil sampling. Contact SASRI for more information.
Southern African Wildlife College
Tel: 015 793 7300
Short courses in community-based natural resource management (including looking after the soil)
Department of Soil Science
Tel: 021 808 4794
University of Fort Hare
Faculty of Science and Agriculture
Tel: 040 602 2232
University of the Free State
Department of Soil, Crop and Climate Sciences
Tel: 051 401 2212
University of KwaZulu-Natal
Department: Soil Science
Tel: 033 260 5421
University of Limpopo
Soil Science, Plant Production and Agricultural Engineering
Tel: 015 268 2599
University of Pretoria
Plant and Soil Sciences
Tel: 012 420 3770
Centre for Microbial Ecology and Genomics
Tel: 012 420 6929
The African Soil Microbiology Project is a world first attempt to survey soil microbiology in sub-Saharan Africa. The University of Pretoria is the South African participant.
University of Venda
Department of Soil Science
Tel: 015 962 8431
- AfriWeather Tel: 021 851 5134 http://afriweather.co.za/index.htm For the supply, installation, maintenance and calibration of instrumentation for monitoring weather elements and soil moisture conditions.
- AgriScan Tel: 083 327 0138/076 951 1728 www.agriscan.co.za Use satellite readings to check soil conditions
- AquaCheck Tel: 021 970 5140 www.aquacheck.co.za Soil moisture management software
- DFM Technologies Tel: 021 904 1154 https://dfmtechnologies.co.za Soil moisture sensors planted permanently in the ground. These take hourly moisture and temperature readings at six depths.
- Ecosoil Tel: 021 848 9434 www.ecosoil.co.za Jako Pieterse consults farmers on creating healthy soils.
- Faktor2 Grondkundiges Tel: 083 740 0297 www.faktor2.co.za consultants
- JMA Consulting Tel: 013 665 1788 www.jmaconsult.co.za
- NviroTek Labs Tel: 012 252 7588 / 082 889 0139 www.nviroteklabs.co.za Independent analysis of soil
- Soiltech Tel: 072 408 8211 www.soiltech.co.za
- Spilo Tel: 021 862 6100 www.spilo.co.za Agri weave netting improves soil condition, prevents erosion, assists in root development by retaining soil moisture
- Terrasoil Science Tel: 012 993 0969 www.terrasoil.co.za
- Terratek Tel: 018 581 1016 http://suid-wes.co.za
Websites and publications
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.
From the South African Soil Surveyors Organisation comes Field Book For the classification of South African soils. Order it at www.sasso.co.za.
Kejafa Knowledge Works has a number of books on soil in stock. Visit www.kejafa.com.
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)
Land type data and acquired knowledge are being used to solve a variety of problems such as land use planning. Detailed soil and climate surveys are integrated into a comprehensive Agricultural Geo-referenced Information System (AGIS), www.agis.agric.za, [website not working, 27 June 2018] which allows for a variety of applications, including assessment of agricultural potential and land suitability. Also at the AGIS website are the easy-to-understand Infotoons. Visit www.agis.agric.za/efarmer [website not working, 27 June 2018]. The following four subjects are covered:
- Making the most of rainwater;
- Mulch: A blanket on the soil;
- Compost: Nature’s fertiliser;
- How to get your soil tested.
Provincial Departments of Agriculture produce brochures, posters and other material. On the KwaZulu-Natal Department of Agriculture website, www.kzndard.gov.za, find the the “Soil Analysis” option as well as documents like “Acid Soils and Liming”.
The following Info Paks (booklets) are available from the Resource Centre at the Department of Agriculture, Forestry and Fisheries (DAFF). They can be downloaded from www.daff.gov.za (take the “Resource Centre” option):
- 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)
www.daff.gov.za/docs/erosion/erosion.htm – notes on soil erosion and preventing it.
Find the soil moisture option at www.weatherphotos.co.za.
Videos to do with soil (with specific reference to the deciduous fruit sector) can be watched at www.saorchard.co.za.
Provincial agencies like Cape Nature have guides on soil management. Find their details in the chapter on biodiversity.
- Joseph, F. & van der Westhuizen, M. 2019, January 13. “How old tyres can stop soil erosion in its tracks”. Farmer’s Weekly. Available at www.farmersweekly.co.za/crops/field-crops/old-tyres-can-stop-soil-erosion-tracks/
- Read the blog “Overberg media trip: stabilising soil structures (part 5)” at https://agribook.co.za/blog/overberg-media-trip-stabilising-soil-structures-part-5/
- Uys, G. 2018, June 21. “Pursuing soil health precisely”. Farmer’s Weekly. Available at www.farmersweekly.co.za/crops/field-crops/pursuing-soil-health-precisely/
- Watts, J. 2018, March 26. “Land degradation threatens human wellbeing, major report warns”. The Guardian. Available at www.theguardian.com/environment/2018/mar/26/land-degradation-is-undermining-human-wellbeing-un-report-warns
- General, R. 2017, September 18. “Chinese Scientists Develop Revolutionary Paste that Transforms Desert Into Fertile Farmland”. Nextshark. Available at https://nextshark.com/chinese-scientists-develop-revolutionary-paste-transforms-desert-fertile-farmland/
- Le Roux, J. & Smith, H. 2014. “Soil erosion in South Africa – its nature and distribution”. Available at www.grainsa.co.za/soil-erosion-in-south-africa—its-nature-and-distribution
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