Diagnostic Testing of Plant Nutrients and Deficiencies

Using diagnostic testing of plant nutrients is the only reliable way to control deficiencies and improve plant growth and productivity. However, its important to collect the sample properly and know what to expect from the laboratory tests.

There are limitations to the use of plant nutrient tests from leaves, but they can be very useful if considered in conjunction with a good soil test. This is especially true for trace elements. These are mineral nutrients that are required only in minute amounts. For this reason, a soil test may show an insufficiency, but the plant is unaffected because it can get enough of that nutrient from the deep soil layers, below the sample depth of a soil test. This is often the case with Boron.

Also, in alkaline soils, trace elements can be locked up and leaf testing may be the only reliable way to assess the requirements for plant growth. Truffle and Olive growers rely strongly on this type of diagnostic testing to ensure optimum productivity.

For the major nutrients, it is important to assess the balance, or relative proportions rather than just the individual test levels. For instance, high test levels for phosphorus can be more indicative of a Calcium insufficiency, but Magnesium and Potassium levels can influence this assessment.

Calcium levels are also mostly influenced by root activity, so low levels are a sign of poor root growth.

When using a diagnostic test for plant nutrient requirements, it is crucial to also get a proper assessment of the results that takes all these factors into account.

If you need a leaf or pasture test, simply choose the basic test (this includes: Nitrogen, Phosphorus, Potassium, Sulphur, Copper, Zinc, Manganese, Calcium, Magnesium, Sodium, Iron and Boron), or one with any additional elements you require. Then click the "Add to Cart" button below (you don't need a PayPal account).

There are also some instructions on collecting leaf samples below, but if you would like some help, our sample collection service for diagnostic testing may be of value.

Order Your Diagnostic Testing Here

Choose your exact requirements

Basic Leaf or Pasture tissue test $82.00 Basic + Molybdenum $96.00 Basic + Molybdenum & Cobalt $102.00 Basic + Selenium $97.00 Basic + Selenium & Molybdenum $111.00 Basic + Se, Mo & Co $117.00

Collecting Leaf and Pasture Samples

1. Never take samples of stressed plants. To avoid this problem, always collect your samples before 9am (while everything is still relatively cool).
2. Avoid contamination - wear disposable gloves and use clean containers - anything that gets onto the leaf will influence the result. Mud splatter can be a big problem sometimes.
3. Do not sample after spraying! This is especially important where fungicides are concerned - the high copper, zinc or phosphorus result you get may be due to the spray residue rather than the leaf.
4. If you need to wash the leaves before sending them, make sure you use clean water and pat the leaves dry with a paper towel straight after - even tap water can contain mineral.
5. Collect your sample at the start of the week and send it straight away. That way, it won't be sitting in a pile of mail somewhere over the weekend, or be left to start rotting in the bag while you wait to get to the post-office. Remember this is living tissue and it will quickly start to decompose if you let it. Often, a good idea is to collect the sample on a Sunday or Monday and put in in the vegetable crisper of the refrigerator overnight, then post the next day.

As to how you actually collect the samples, it is really quite simple. Collect 20 to 30 leaves. They need to be the first fully expanded leaf behind an actively growing shoot-tip and there should be an equal number from each of the four compass points. In other words, collect one leaf from the north side of one tree, the east side of the next, the south side of the one after and so on.

If you are just monitoring the nutritional status of an area, then collect the leaves randomly across the whole area. If you want to identify a nutrient deficiency, collect leaves that show the symptoms most. And is you have under performing patches within an area, then take two samples - one from vigorous plants and the other from the under-performing ones.

For pasture samples, simply grab and tear small handfuls at random across the paddock - so you effectively mimic what the animals will be taking and get an reasonable representation of the botanical composition of the pasture. Of course (as with soil samples), you should avoid dung and urine patches, camps, tracks, gates and water troughs.

Order Your Diagnostic Testing Here

Choose your exact requirements

Basic Leaf or Pasture tissue test $82.00 Basic + Molybdenum $96.00 Basic + Molybdenum & Cobalt $102.00 Basic + Selenium $97.00 Basic + Selenium & Molybdenum $111.00 Basic + Se, Mo & Co $117.00