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Keith Jordan

Australian Fertilizers Limited. Wagga Wagga

Farmlab was developed by a team of CSIRO scientists led by Dr Dick Bouma to provide a relatively quick and simple method to determine levels of nitrogen and phosphorus in plant tissue.

Farmlab provides farmers with a management tool which when used correctly can assist in formulating fertiliser programmes and making decisions on such things as priorities for pasture top-dressing and the likelihood of nitrogen responses in winter cereal crops.

Farmlab consists of a box containing all the materials and implements necessary to carry out the tests. A simple version of procedures is outlined on the inside of the lid.

An instruction booklet is included which provides more specific details on how to use the kit.

The old axiom “when problems arise and all else fails, read the instructions”, does not apply in the case of Farmlab.

There may be no indication that problems do exist. The end result may simply be that the reading obtained is of little value.

The booklet points out a number of important factors which can significantly affect the accuracy of results.

The instructions on the lid of Farmlab are intended to simplify the steps to be followed when carrying out a test. It is not intended that these instructions be used in isolation without prior reference to the instruction book.

Range Of Crops

At present, crops suitable for testing with Farmlab are subclover, white clover, lucerne, winter cereals and sunflower. A number of other crops are currently being evaluated.


As with any soil or plant analysis, results are only as good as the sample used.

Samples should be representative of the crop being tested. Unusual areas such as stock camps, headlands, timber burns, old fence lines, etc, should be avoided.

Additionally, plants which are under moisture stress should not be sampled.

When testing for nitrogen, samples should be collected before 10.00 a.m., placed in a cool, dark container and the test carried out as soon as possible after collection.

With pastures, only the legume component should be collected. Each sub-sample of clover should be one whole clover leaf.

At least 25 sub-samples should be collected. With winter cereals, the crops should be sampled at the 4 to 5 leaf stage. The youngest fully expanded leaf from at least 25 plants is used.


Clover plants are tested only for phosphorus.

Winter cereals should be tested for both phosphorus and nitrogen. Satisfactory yield increases will not be achieved by applying nitrogen to nitrogen deficient plants, unless phosphorus levels are satisfactory.

To begin the analysis, an extract is prepared from the leaves which have been sampled.

A small amount of acid is added to finely cut leaf material. This is ground into a paste, diluted with water and then filtered.

Prepared chemicals are then combined with the filtered leaf extract according to directions.

When the test is completed a colour develops; blue in the phosphorus test and pink in the nitrogen test.

The intensity of the colour is then matched against appropriate colour chips which are provided in the kit.

The material which has been tested can then be rated in one of four categories depending on the intensity of the colour obtained.

Tests normally take approximately 30 minutes per sample to complete. However, up to six leaf samples can be tested in parallel, thus reducing the test time per sample.

Chemicals provided have a shelf life of 12 months. Replacement kits are available.

Each kit contains sufficient material to carry out 50 nitrogen and 50 phosphorus tests.

Farmlab has been designed to simplify measurements of the various chemicals which are used in the test but it is still necessary for the person carrying out the test to take care and strictly adhere to the instructions.

No special training is necessary to carry out the tests but anyone using Farmlab should appreciate that they are carrying out a chemical analysis.

For this reason short cuts, carelessness and a “near enough is good enough” attitude could produce results which are at best of dubious value and at worst, possibly misleading.

However, if used correctly, Farmlab can provide farmers with valuable information on which to base improved fertiliser management decisions.

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