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3.4 DISCUSSION
Soil sampling and analysis
R. culumnae grows in soils that are richer in nutrients and less saline compared to
the soils in which R. monadelpha and R. sabulosa grows. The concentrations of
nitrogen, phosphorous and potassium was higher in soil sampled from the natural
habitat of R. culumnae in Turkey (KÖK et al., 2007). The soil of the habitat of R.
culumnae had a smaller N:P:K ratio (1.000:6.897:1.069) and a lower salinity. The pH
of the soils from the Namaqualand and Turkey is however similar. R. culumnae also
occurs in a loamy clay soil, which is essentially a combination between the clay soil
(sample 1) and a sandy loam soil (sample 2) in which R. monadelpha and R.
sabulosa occurs, except for the slightly higher sand content that such a combination
would have.
Elements that are in abundance or that are lacking or low in the natural environment
may have an effect on germination and growth in some species (BASKIN & BASKIN,
1998). In soil sample 1 and 2 calcium is abundant. Although the percentage Fe
content was not tested, the red colour of the clay indicates that the soils are rich in
Fe.
3.5 SUMMARY
• The pH and soil texture of soils in which R. sabulosa and R. monadelpha, and
R. culumnae occur is similar.
• Soils in which R. sabulosa and R. monadelpha are found is more saline and
has a much lower percentage nitrogen, phosphorous and potassium than soil
in which R. culumnae is found.
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