4.3 SOIL

Soil quality can vary considerably even over a small geographical area. For this reason, international and regional consensus on the kind of soil standards which require drafting as environmental standards is still taking shape.

The general approach adopted by ISO and other National Standards bodies on development of environmental
standards has been to start with the standardisation of the methods of analysing soil quality. The British Standards Institute has at present grouped environmental standards
into three categories, namely:
(a) Terminology
(b) Sampling
(c) Chemical and biological methods.

Among the published ISO standards on environment are also a small number which employ well understood principles and technology that can be accessed easily by soil laboratories in Kenya. These include the following
standards:

(a) ISO 10381-6 Soil Quality - Sampling:
This has been selected because of its importance as a reference for the other standards proposed.
(b) ISO 11048 Soil Quality - Determination of water soluble and acid- soluble sulphate:
This standard has been prioritised because it is of major role in water pollution resulting from industrial activities in the country.
(c) ISO 11263 Soil Quality - Determination of phosphorus
- Spectrometric determination of phosphorus soluble in hydrogen carbonate:
This standard has been prioritised due to the importance of the parameter in testing for application of fertilizers.
(i) ISO 11268-Part 1, Soil Quality - Effects of pollutants on earthworms.
(ii) ISO 11269 - Parts 1 and 2, Soil Quality - Determination of the effects of pollutants on soil flora.
These two standards above are regarded as very important for the generation of data which will be used in the drafting and revision of soil quality standards in future.
(d) ISO 11276 Soil Quality - Determination of pore water pressure - Tensiometer method. This standard is prioritized because it is a reference
for the other standards proposed.
(e) ISO 11266 Soil Quality - Guidance on laboratory testing for biodegradation of organic chemicals in soil under aerobic conditions. This standard, like ISO 11268 and 11269, is essential for generating of data that will be used for drafting and revision of soil standards in future.

The foregoing ISO standards have also been proposed as references for Kenya standards on those subjects. The methods of analysis are still under discussion and have not yet been standardised at regional and international level. It would therefore be unwise for Kenya to start developing
standards based on the draft methods before sufficient agreement has been achieved.