Soils

This week is going to be about the soil. Soil is essential to grow plants, but even more important is soil fertility.  Before going in depth about soils in south Africa and lavender, I will start with the basics.

Soil has different layers and every soil type has around three or four horizons which are described by their different colour, texture and physical features.

O - Organic matter/humus where plant residues in a relative non decomposed form can be found.

A – Surface soil where organics are mixed with mineral matter.

B – Subsoil accumulates minerals and organic compounds.

C – Parent rock consists mainly of large unbroken rocks.

R – Weathered Bedrock layer which cannot be excavated by hand .

Figure 1 Soil Profile (America, 2017)

Fertile soil should be able to supply important chemical nutrients and essential element to a plant and it is important to use proper soil management techniques to prevent soil erosion. Soil erosion means that the topsoil diapers and salinization, soil compaction, nutrient degradation and loss of soil structure (WWF, 217). Next to the loss of topsoil, soil erosion is also causing pollution. Also in South Africa is facing issues related to soil erosion. Water scarcity is common in South Africa and polluted water bodies are a big threat. Due to erosion, many places which have been in used to grow crops are unfertile now. Since the world population is growing we need to conserve and manage our soils very well (ROUX, 2014).

South Africa is a large county with many different soil types. There are a few soil requirements when growing lavender. It needs well drained light, sandy, or sandy loam, or gravelly soils in full sun with a pH between 5,8 and 8,3. It is advisable to prevent moist soils since they will cause poor plant growth or diseases.  Nevertheless, Lavender can cope relatively good with unfertile soils. An excessive application of nitrogen can result in a decreasing oil production. Lavender extracts 0,8 kg of nitrogen, 0,2 kg of phosphorus and 0,8kg of potassium from the soil, for the production of 100 kg of flowers. Phosphorus and potassium are not required in large amounts and vary, dependent on soil type and nutritional status. Nitrogen should applied at a rate of 80 to 100 kg/ha in 3 or 4 dressings throughout the growing season. (Agriculture, 2009)

References

Agriculture, F. a. (2009, November). Lavender production . Retrieved from Agriculture, Forestry and Fisheries: http://www.nda.agric.za/docs/brochures/essoilslavender.pdf

America, S. S. (2017). Soil Horizons. Retrieved from Soil Science Society of America: http://soils4teachers.org/soil-horizons

ROUX, J. L. (2014, November). Soil erosion in South Africa - its nature and distribution. Retrieved from Grain SA: http://www.grainsa.co.za/soil-erosion-in-south-africa---its-nature-and-distribution

WWF. (217). Erosion and Degradation. Retrieved from WWF: https://www.worldwildlife.org/threats/soil-erosion-and-degradation