Virtual Laboratory Tour

1. Sample preparation

The first thing to happen when samples arrive is to sort and number them so we can keep track of things as the tests proceed. The samples are then dried and crushed.

2. Weighing & extraction

For each test we must extract the elements we are looking for, so in order to relate the result back to what was in the whole sample it is important to start with a very carefully measured amount of soil.

This is actually the part of the process that sets soil testing apart from other types of analysis, since we are mostly looking for the particular chemical 'forms' that plants can take up through their roots - NOT the total amount present in the soil. So, in a sense, our extraction methods need to mimic those of the plant itself - a tricky thing to say the least!

A specific quantity of soil is weighed out for each of the extraction processes. Reagent solutions are added to the soil and the mixture is shaken for prescribed periods. Most extractions use either the side-to-side shaker or the flask shaker, but the Olsen Phosphorus test uses an end-over-end shaker.

On completion of the extraction process, the soil needs to be separated from the solution either in the centrifuge or by filtration.

3. Analysis

Now we come to the really Fun part. It is here that we get to use all our 'High-Tech' stuff! There are a number of analytical instruments in our Lab, ranging from the more straightforward pH/EC meters and high pressure microwave (used for complete digestion of soils, plant tissue and fertiliser when total elements are to be measured).

More elaborate instruments include the UV/visible light Atomic Absorption Spectrophotometer and the mighty ICP-MS. These can measure very small amounts of each element, very precisely and they are automated so we can handle large numbers of samples quickly. However, each instrument is used for measuring specific elements according to which gives the most sensitive reading.

Of course, some things like Exchangeable Hydrogen are still done the old fashioned way with Back Titration.

Another piece of new technology is the LECO Carbon and Nitrogen analyser that gives total Carbon and Total Nitrogen measurements from soil, plant tissue and fertiliser samples.

 

 

 

 

4. Interpretation & reporting

Once all the results are in, they go through our specially developed computer program that acts as a model of the Mikhail System and generates the desirable levels and recommendations needed in printing the final report.

In many respects, this is the most important part of the whole process. This is because soil testing is not just a matter of measuring the levels of various elements in soil. In fact, we are trying to get a "Plant's-eye" view of the soil. That is, how much of each element is present in a form that is "available" for plant uptake (as a nutrient) or present on the exchange sites of clay and organic particles (exchangeable cations). This means that the desirable levels will vary according to the plants being grown and the characteristics of the soil (eg. Cation Exchange capacity, etc.). In turn, the recommendations are based on the differences between the test results and the desirable levels.

5. Biological testing    

If all this is not complicated enough, we now include soil biology in our testing and interpretation processes. Our purpose-built Microbiology lab focuses on culturing the "Active" components of the populations for each of five key indicator groups:

• Fungi
• Yeasts

• Lactic acid bacteria
• Photosynthetic bacteria
• Actinomycetes

The results from these cultures are also interpreted (by our computer program) relative to the other soil conditions, so that recommendations relate to the specific sample - not just a "Rule of Thumb" developed to help sell particular products.