Recommendations
Our recommendations are as individual as your soil is – with its own CEC, Leaching potential, Rainfall (or irrigation), Land use and Target yield.
Recommendations, in general, should be followed in a step by step fashion:
1. Correct the exchangeable cations
The first and most important step in developing a sustainable soil management program is to correct the exchangeable cation balance. This is where the lime, gypsum and dolomite recommendations become the priority. The application rates recommended for these products are based on the best quality products available (Lime containing 40% Ca, Gypsum containing 19% Ca & 15% S, Dolomite containing 11% Mg & 25% Ca) so it’s important to adjust application rates if lesser quality materials are used. This can be easily calculated using our lime quality calculator. This application also allows for comparison between products and product combinations where more than one ameliorant has been recommended.
2. Apply the fertiliser and trace elements 6 months later
If possible, you should allow six months (less with sufficient rainfall / irrigation – cases will vary) following the application of soil ameliorants before applying any fertiliser/trace elements to the soil. This enables the soil to benefit from the neutralising process, and greatly reduces the risk of nutrient lock up following fertiliser and trace element application.
3. Once the soil structural and nutritional components are balanced, apply the biological recommendations.
Biological stimulants should be applied twice a year, using the rates and products recommended in the soil analysis report. This is particularly important, as altering the rates of application/dilution strength can have a significant impact on soil microbial population numbers and types and overuse or incorrect product choice can potentially further upset the balance.
1. Correcting the Exchangeable Cations
Using Lime or Gypsum? With the increasing costs of soil ameliorants many customers ask why they need to use one over the other. Attached is Ted’s article which sheds some light on the different properties of Gypsum (Calcium Sulphate) and Lime (for cation balance corrections). The following is an easy explanation. In brief:
Calcium & Magnesium
The first items listed on the recommendations page are the kilograms of Calcium and Magnesium required per hectare. In most circumstances you will not need to worry about these figures, they are the ones used to calculate the amounts of Lime, Dolomite and Gypsum that may be needed. So long as you have access to good quality materials, you can simply make the recommended applications as given. However, we provide this basic information so that adjusted application rates can be calculated to suit specific materials if necessary.
Gypsum first:
The first step in determining what to apply is to see if the Sodium &/or Magnesium percentages are above their desirable levels. If this is the case we calculate the amount of gypsum that will be required to displace this excess with Calcium. This amount of Calcium is subtracted from the total requirement and the remainder is supplied as Lime.
Dolomite & Lime
If the Magnesium percentage is below the desirable level and exchangeable Hydrogen is high, then the required Magnesium is supplied as Dolomite and the remainder of the Calcium requirement is provided as Lime. In this way, it is possible to have recommendations for all three materials (for example in a soil high in Sodium and Hydrogen, but low in Calcium and Magnesium). The Gypsum is worked out first, then the Dolomite and then the Lime.
Other forms of Magnesium
Some soils can be very high in Calcium and low in Hydrogen, but still have a requirement for Magnesium. In these cases Dolomite is not appropriate, because it contains a significant amount of Calcium (which is not required in such soils). The only other economically feasible materials to use in adding Magnesium to the soil are Magnesium Sulphate and Magnesium Oxide, however, these materials are less efficient at exchanging Magnesium for the ‘excess’ Calcium. For this reason, the amounts recommended are usually much less than the total requirement. In managing such soils, it is better to apply smaller amounts over several years, than to apply the full requirement and get less than a satisfactory result. For these soil, persistence is the most important requirement.
Quality Standards
Since we cannot recommend specific products, our recommendations for Lime Dolomite and Gypsum must be in terms of the generic materials only. However, the quality of these materials will vary from place to place and so our calculations are based on certain quality standards.
Pure Limestone will be 100% Calcium Carbonate (CaCO3), which in turn is 40% Calcium. When choosing a Lime product to use, make sure you do not get these two percentages confused. We often hear people say: “My supplier tells me his Lime is 65% Calcium”. This is impossible, it is more likely that is 65% Calcium Carbonate, which would make it only 26% Calcium! Lets say your recommendation was for one tonne of Lime per hectare. To provide the same amount of Calcium as pure CaCO3 with the material above, you would have to almost double the application rate. Similarly, the Dolomite recommendation is based on a generic material containing 26% Magnesium Carbonate (which would make it 12% Magnesium). The Gypsum recommendation is based on ‘A’ grade Gypsum which is nearly pure Calcium Sulphate (around 20% Calcium).
For a more comprehensive explanation please read this article ‘Is the wrong calcium costing you the earth?’ by Ted Mikhail.
2. Applying Fertiliser and Trace Elements
If the soil pH (H2O) is below 5.7 you should delay application of any trace elements until such time as the recommended applications of Lime &/or Dolomite have successfully increased the pH above this level.
If the soil pH (H2O) is 7.5 or greater , apply any trace elements required as foliar sprays ONLY.
Our recommendations are given in terms of the elemental nutrient requirement (in kg/ha). This needs to be converted into fertiliser, however you should not need to do this yourself. Think of our recommendations as being like a doctors prescription. Any good supplier should be able to convert them into appropriate fertiliser applications, using whatever products they have available. This means that you can use SWEP soil tests to get a good ‘apples for apples’ comparison between different suppliers, products and prices.
Organic V’s Chemical Fertiliser
Our nutrient recommendations also give you the ability to choose whether to use organic or chemical fertiliser, since the process of converting nutrients to fertiliser is the same, only the type of fertiliser is different. If you require large amounts of a particular nutrient, it may not be practical to use an organic type initially – a combination of organic and chemical may give the best results in this case. But over time, as the soil balance and fertiliser improves, many people find that organic fertilisers give the best results.
3. Biological Recommendations
On the Complete soil balance analysis , the recommendations for soil biology are a bit different from the others. Their aim is to accelerate or depress the active bacteria after balancing the cations and nutrients. In situations where there is still alot of soil balancing to be done, inclusion of these recommendations may well pose economic problems. Unless your soil is one that resists the cation balance changes, you can safely leave these recommendations until you have achieved as much as you can with the cations.
Important notes:
- SWEP is 100% independent, so we do not recommend specific products. We also test samples from across Australia and around the World, so even if we wanted to, we could not possibly keep up with all the products available in every area. For this reason, rather than listing fertilisers, we give recommendations in terms of the elemental nutrients as kilograms per hectare. These then need to be converted into appropriate fertiliser applications. Any reputable fertiliser supplier should be able to do this for you.
- Trace element recommendations are also in this form – as kilograms of the elemental nutrient required per hectare, however, there may be more to consider in terms of applying trace elements so you should always read our notes included in our reports (more information below).
- By far the most common causes of confusion, however, relate to the Cation balance recommendations. Importantly, these are for improving soil structure and friability – not plant nutrition – and should be applied separately from fertilisers. The following notes should help make things easier to sort out.