To a great extent your farm’s productivity, and therefore its profitability, rests upon your soil(s). With the cost of fertilisers and their application, eating into your profits, soil testing is an essential farming tool.
When assessing your Soil(s) Nutrient Status, it is important to measure the existing soil fertility status before changing anything, so that you have a baseline to measure change. A good record of fertiliser history and quality soil testing is the only way to do this.
Soil sampling should be undertaken at least every two to three years on most intensively farmed paddocks. Some farmers might baulk at the cost of this but in most cases, soil testing returns significantly more to the farmer in improved production, than the cost of the testing.
When you organise to undertake soil tests, you should firstly divide the farm into areas of similar soils, slope and grazing management history. Then set up sampling lines within each area, avoiding gateways, fences, trees, hedges and water troughs as sampling points. Ideally set up at least two sampling lines within each different area.
Collect a soil sample by taking fifteen or more soil cores to a depth of 75mm on each sampling line. You should aim to sample in the same month each year, usually at least six weeks prior to applying fertiliser.
Sampling lines can be permanently identified by painting the fence post tops or by placing pegs under fencelines.
The following Soil Tests are available from most commercial Laboratories and should be used for the following purposes:
- pH - a measure of soil acidity and hence a test for lime requirements.
- Olsen P - a measure of the plant available Phosphorus.
- Quick Test Potassium (K)- a measure of plant-available Potassium.
- Teraphenyol Boron K (TBK) a measure of the potassium supply in some sedimentary soils.
- Quick Test Mg(QTMg) a measure of plant-available Magnesium.
Further recommended soil tests are:
- Sulphate S (SO4 S)- a measure of the immediately plant available Sulphur.
- Organic S (Org-S) - a measure of the long term supply of Sulphur.
- Anion Storage Capacity (ASC)- a measure of the capacity of the soil to store nutrients such as Phosphorus and Sulphur.
- Cation Storage capacity (also called Cation Exchange capacity (CEC) -is a measure of the capacity of a soil to store nutrients such as ca, Mg, K and Na.
One of my biggest frustrations, with most soil testing laboratory services, is the way that they assume that all farmers receiving their results are equally versed in the subtleties of soil science and precious little effort is generally taken to present the results in an easily understood format.
This is an example from ARDC Lanitza, Australia, of Soil testing Results as received back from an un-named laboratory. They are full of relatively meaningless numbers and take ages to digest- time, and patience. So, my challenge, as part of the Topoclimate farm planning process, was how to present soil testing information in a way that farmers could easily grasp the essential messages without having to wade through lots of meaningless numbers, and confusing data.
The presentation method that we settled on after some experimentation and testing is shown in the following diagrams, again using the same ARDC Lanitza data presented by the laboratory (above).
Topoclimate Services now provides a simplified and improved way to understand the chemistry of your soils. The Soil Chemical Analysis Sheets are presented in a manner that allows you to gain an understanding of the fertility of your soils. The Analysis Sheets are provided for both the topsoil and the subsoil.
The topsoil has been tested for a full range of nutrients and these analytical results have been used to derive generic fertiliser recommendations, as plants get most of their nutrients from the topsoil.
For the subsoil, only the pH and the main exchangeable cations (and their ratios) are presented to identify potential problems such as sodic subsoils (high sodium, impermeable soils) or acidic subsoils.
The Analysis Sheets show the amount of each of the soil nutrients that is available to plants, in each of the soils present on the property, (as measured in our soil chemical testing), and also indicate the optimal level for each of those nutrients in an ‘ideal’ soil. These results are presented both as numbers and visually on a bar chart.
Feel free to contact me, Gary Hutchinson, at garyh@topoclimate.com, for assistance in conducting a soil survey, a comprehensive analysis of your soil test results and for soil mapping services and assistance. Further information on Topoclimate is available in the article Topoclimate Concept and how it evolved.
