FAQ

Abbreviations

• Tonne (t)
• Kilogram (kg)
• Grams (g)
• Milligram (mg)
• Parts per million (ppm)
• Hectare (ha)
• Square metre (m2)

Basic numeric conversions

ppm = mg/kg = g/t

1,000,000g = 1000kg = 1t (one million grams = one thousand kilograms = one tonne)

1.0g/m2 = 10kg/ha

10,000m2 = 1ha

1ha = 2.47 acres

One milligram is one millionth of a kilogram, so:

1mg/kg = 1ppm

Hence, there is no difference (see Basic numeric conversions above).

When I try to convert the cations in parts per million (ppm) to milliequivalents (meq) the answer is different to what is on your report. Why is that?

The cations expressed in ppm are Available cations, whereas the ones expressed in me/100g are Exchangeable cations. Available cations relate to nutrients present in the soil that are ‘plant available’. The distinction is made here due to the impact exchangeable cations have on the physical condition of the soil, even though plants will find exchangeable cations are also “available” to them. Hence, available nutrients are the sum of both the soluble and exchangeable cations, which SWEP, to our knowledge, is the only laboratory to provide this distinction.

How do I convert kilograms and tonnes per hectare, to kilograms and tonnes per acre?

Because one hectare = 2.47 acres, divide the amount required (in tonnes or kilograms) by 2.47. This will give you amounts in tonnes or kilograms per acre. For example, Jane has recommendations for 1t/ha lime. She has 2 acres. One tonne divided by 2.47 = 0.4, meaning Jane needs 0.4t/acre (400kg/acre) lime. Likewise, if Jane needed 20kg/ha of phosphorus, she would then divide 20kg by 2.47 to give her a requirement of 8kg/acre phosphorus.

All test protocols and methods used are stated on the report for your record.

We recommend having a Complete Soil Balance Analysis performed initially; this way you will have an overall picture of your soil and will benefit from recommendations for all three soil components.

The Complete Soil Balance Analysis is the result of almost 50 years of research by Ted Mikhail, and will show you the steps to balance each soil component within and between each other.

It is useful to consider the following points before having your soil analysed:

• To achieve the best results, all recommendations are necessary
• Both soil ameliorant and fertiliser applications require sufficient soil moisture following application to be effective, and
• A minimum of 3 to 6 months is required between soil ameliorant and fertiliser applications, depending on your annual rainfall/irrigation practices

Therefore, it is best to collect the soil sample prior to any lime or fertiliser application, or any soil disturbance (so as not to affect the biological results) and when sufficient rain or irrigation can be timed for lime, dolomite and/or gypsum application, and then again for the fertiliser application.

Keep in mind you will also need to leave sufficient time between soil ameliorant and fertiliser application.

We recommend you start with one sample for every distinct change in soil on your property. That is, if you have a brown clay soil in one part of the property and a grey sandy loam in another, you need at least two samples. Changes in the land use will also warrant a separate sample – please refer to Fact Sheet #2 “Collecting samples for soil analysis” for more information.

It’s important to remain within your fertiliser budget, but whatever your budget is, set aside a representative area and follow the recommendations precisely.

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, so it’s important to adjust application rates if lesser quality materials are used. This can be easily calculated using the lime quality calculator, available from the Fact Sheet page of SWEP’s website. This application also allows for comparison between products and product combinations where more than one ameliorant has been recommended (lime and dolomite).

2. Apply the fertiliser and trace elements 6 months later

If possible, you should allow six months (minimum of three months with sufficient rainfall) 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.

In this instance, it would be better to wait until you need a follow up soil analysis (approximately 12 months after the first one, providing all recommendations were followed up). To achieve soil balance, all three soil components must be balanced between each other, not just within themselves. As soil variability (both spatially and temporally) can affect the outcome of results, it is better to have a Complete Analysis performed so as to gain the most reliable results. Additionally, unless some soil from a sample is allocated for biological analysis upon arrival at the laboratory, the entire sample is crushed and dried soon after we receive it. Soil for biological analysis requires a fresh sample; hence, you would need to send another sample for biological analysis, as we cannot use a stored sample.

Ideally, recommendations should be followed up as soon as possible after receiving results. Please also see “When should I get a soil test done? “ and “How do I apply the soil test recommendations?”.

In the case of plant tissue samples, corrective measures (in the form of foliar applications) should be implemented within the first few days after results are received.

For soil analyses, the results are relevant for that seasonal cycle; meaning recommendations should be followed soon after receiving results, in the order described above (How do I apply the soil test recommendations?), completed over the next 12 months. This provides a reference point or comparison for the next analysis, usually taken 12 months following the previous. Remember that soil nutrient recommendations are provided based on first fulfilling the soil requirements, then the intended land use for a single growing season. If the land use changes and/or when the season is over the nutrient requirements will differ.

Soil balance can be achieved permanently by following all the recommendations, and then maintaining this balance. With regular (annual) soil tests and by “topping up” the soil with appropriate applications, these maintenance applications will generally be considerably less than the initial inputs needed to build the soil up. The Cation Exchange Capacity along with the land use will determine how quickly a soil will take up or lose cations and nutrients. What this means is, a heavy clay will take longer to balance, but once it is balanced it will need topping up less often than a sandy soil for instance. On the other hand, the sandy soil will very quickly improve in terms of structure and nutrient composition, but it will also lose these more rapidly than will the heavy clay.

Hence, in applying our recommendations, the amounts needed on your soil test report will not be annual requirements. Once applied (in the proper amount, using materials with a quality standard as near as possible to that specified on the report and given time to produce their full effect), you should only require smaller adjustments after each subsequent soil test to replace any productive removals.

Balanced soil management can be expensive initially (especially if you are beginning from a very low base). Whilst there aren’t any shortcuts, it’s a good idea to work out what the total recommendations will cost per hectare by the time they have been applied (purchase price, contractors, water allocations etc.) and then treat the largest area possible within your property budget. If you don’t normally spend any money on fertiliser then consider what you spend on feed and work within this budget instead. Cutting back on recommended quantities or quality will not save you money – you’re better off not spending any money at all than buying insufficient or inappropriate products.

Compare the soil to a “renovators delight” investment property. The house may need a bit of money to be invested to bring it up to scratch. With carefully budgeted spending, skilled tradespeople and quality materials, over time, room by room the house will be restored to its original glory and prove to be a worthwhile investment. Taking shortcuts by trying to do it quickly on the cheap and all at once will only set you up for more costs along the way.

The Cation Exchange Capacity and land use (e.g. crop type) are significant factors which influence recommendations, as the nutrient holding “Capacity” of the soil influences how much is needed to ensure an adequate supply through the duration of the growing season. Therefore, even slight differences between two samples could produce significant differences in recommendations. The percentage of organic matter also has an impact, since this affects the Adjusted CEC. A difference in land use can have a huge impact on input recommendations for soil, but remember we will issue recommendations for up to three (3) land uses per sample at no extra cost. So if you have different land uses between the two samples you are comparing, just let us know and we will send you a pair of reports with the same Land use for better comparison.

CEC is the Cation Exchange Capacity of the soil. Put simply, it is the capacity of the soil to hold cations (i.e. positively charged ions) in an exchangeable form. The most abundant cations and those that have a significant impact on soil structure are Calcium, Magnesium, Sodium, Potassium and Hydrogen. However, during his research Ted Mikhail discovered that a proportion of the exchangeable Hydrogen formed part of the soil organic matter and if we were to attempt to balance all this Hydrogen with Calcium and Magnesium, application rates of Lime, Dolomite and Gypsum would be excessively high and it would result in a degradation of the organic matter. After further research Ted was able to determine what proportion of the exchangeable Hydrogen (relative to the organic matter percentage of the soil) that needed to be left out of the balance relationship. After adjusting the level of exchangeable Hydrogen in this way he added “Adjusted Hydrogen” to the report. Similarly, when this adjusted figure was added to the results for other exchangeable cations (Ca, Mg, Na & K), it gave the “Adjusted CEC”. The importance of this figure is that it allows us to calculate desirable cation percentages for any soil that will make the process of balancing the soil more reliable. In short, it is the reason that SWEP can confidently handle soil samples from anywhere in the world and not just the few places where current field response trials have been done to “calibrate” the results.

Proper cation balance is essential to the development of good soil structure, the proper availability and ‘cycling’ of plant nutrients and the development of a stable and functional biological community in the soil. In short, it is the essential first step in developing an effective and sustainable soil management program.

When balancing soil cations for improved soil structure and physical condition, the percentages of all the cations that occupy the exchanges sites in the soil must be known. Of course, many are present in only tiny amounts and have no impact on soil physics. So in practical terms, only those that are most abundant and that influence soil physics are required. These include Calcium, Magnesium, Sodium, Potassium and Hydrogen. If we ignored the Hydrogen and it comprised (say) 20% of the CEC, then the percentages of the others would be calculated from only 80% of the actual CEC, producing a distorted and misleading result. This effect will also become more exaggerated in soils with high organic matter, since this is naturally high in exchangeable Hydrogen. Put simply, without an accurate measure of exchangeable Hydrogen, you can never be completely sure whether or not you have the balance right.

There is a lot of confusion about this, even amongst ‘experts’. The important point to bear in mind is that Aluminium is converted to a plant available form by acidic soil conditions and these conditions are a function of the Hydrogen concentration. That is, Aluminium is a consequence of soil acidity NOT the cause of it.

In balancing the soil we are interested in cations that occupy the bulk of the cation exchange sites and that affect soil structure and physical condition. Aluminium may become more abundant in acidic soils, but once the balance is improved, it disappears again. But even if this were not true, the amount of Aluminium would still not be as large as it seemed. For example, suppose a soil had 130 ppm of Aluminium. If this were all present in exchangeable form it would represent 1 me/100g. On the other hand 130 ppm of exchangeable Hydrogen would be 13 me/100g.

From this it is easy to see that Aluminium cannot be a significant contributor to the cation percentages, especially compared with cations like Hydrogen. In fact, our interest in Aluminium is in its toxic effects on plant roots, and so it is a Plant Nutrition concern – not one relating to Cation Balance (except in so far as its levels will decline sharply once the cation balance is corrected).

These recommendations represent the quantities required to achieve the desired balanced proportions for the exchangeable cations calcium, magnesium, sodium, potassium and hydrogen.

They also represent the sample depth stated on the soil submission form. In other words, the amounts recommended are those needed to correct the soil down to the specified depth. So the recommendations will be correct if the sample depth was also correct.

Sorry, no. This is an important point that we find many people fail to appreciate. We are not in the business of getting you to use more fertiliser. Our aim is to help you understand what is needed to optimise sustainable productivity by achieving soil balance. The first and most important priority for this will be to correct the soil cation balance. This needs to be done about 6 months prior to the application of fertiliser. Most importantly, our nutrient recommendations are prepared on the assumption that the cation corrections have been made. As such, they are not intended to be a ‘stand-alone’ option.

Gypsum is recommended where exchangeable sodium and magnesium are in excess within the soil. A chemical reaction between gypsum and exchangeable soil magnesium and/or sodium (in the presence of water) allows excess salt to be leached through the soil profile and leaves exchangeable calcium in the soil.

However, there must be adequate subsurface drainage present prior to gypsum application. If there isn’t create an appropriate drainage and then apply the gypsum. Otherwise the salt problem will increase in the soil profile. If you are not sure about your current drainage situation, consult a rural irrigation professional.

Also, every 2.5 tonnes of gypsum requires one megalitre of water. Therefore, for those without irrigation, the minimum amount of rainfall required to apply 2.5t/ha gypsum is 100mm/yr. Applications should be timed around the wettest times of the year for your region.

Trace elements are needed for properly balanced plant nutrition. Recommendations are provided according to:

• The amounts present in a plant available form in the soil sample, and
• The land use specified on the submission form.

Our recommendations are only intended to correct any shortage there may be in the soil for various nutrients that are needed during that growing season of the crop or pasture specified. These applications are not a permanent fix and the requirements can be very different for different crops.

If you need further assistance in this area, please contact your agronomist or extension officer.

SWEP recommendations are provided with the intent to achieve and maintain balanced soil and plant nutrition according to the details provided on the submission form (e.g. land use, rainfall/irrigation, type of irrigation, target yield etc.). Hence, if soil nutrient results show a limitation of a particular nutrient known to be essential for the specified land use or yield etc., the recommendations will indicate the amount required to make up the difference, ensuring that nothing in the soil will limit the crop’s potential in terms of growth, yield or quality.

Trace elements in solid forms can be mixed with the fertiliser blend and applied to the soil at the same time (if the soil pH is suitable). Trace elements in liquid forms can be used either as a foliar application to the leaves, or drip fed through fertigation/irrigation systems. If the soil pH is above 8.0 (in water), foliar application of trace elements is the only suitable method of application. See below.

There is one situation in which applying trace elements to the soil would be wasteful – where soil pH is greater than 8.0. In this situation trace elements applied to soil may be ‘locked up’ and be made unavailable to plants. In this situation the requirement remains the same, but the use of foliar sprays will be the only effective means of application. For the same reason trace elements should not be applied with lime, gypsum and/or dolomite. Instead, wait at least three (preferably 6) months after using these products before applying trace elements to the soil.

It should also be noted that the kilos per hectare recommendations is for soil application, and cannot be simply converted to foliar applications. In this instance, the best course is to choose a suitable product and follow the application guidelines on the label. Then, tissue test and repeat the application as required.

If a soil sample has been submitted with “pasture” as a land use option, Copper will always be recommended if Molybdenum is required. This is because Copper and Molybdenum are antagonistic to each other, hence adding one without the other can cause deficiencies or toxicities in livestock. This is extremely important in terms of animal health, so if you choose to apply
Molybdenum without adding Copper then the affected paddocks must not be accessible to stock for at least six weeks (longer if there has been little of no rain).

SWEP does not recommend specific fertiliser products, so your requirements are given in kilograms of each elemental nutrient per hectare. These need to be converted into a fertiliser blend or program. Most fertiliser products will state the nutrient components in percentages. The easiest way to convert SWEP recommendations to nutrient percentages is by the following calculations:

A)Kg/ha of nutrient required ÷ the percentage of nutrient in product x 100.

For example, if I needed 22kg/ha N and the product contains 14%, then (22 ÷ 14) x 100 = 157kg/ha product required.

Similarly, if I had initially planned to apply 80kg/ha of the same product (containing 14% N, requiring 22kg/ha) then I would multiply this amount (in kg/ha) by the percentage of nutrient in the product and divide this by 100.

In this case, you can see that:

B) (80kg/ha x 14%) ÷ 100 = 11.2kg/ha. So 80kg/ha would have only provided half of what I need.

There are plenty of generic products (including organic) that will meet the major nutrient recommendations for Nitrogen (N), Phosphorus (P), Potassium (K) and Sulphur (S). In many cases, sulphur requirements can be met simply by choosing a sulphate form of fertiliser.

Be aware that some suppliers are accustomed to soil tests that recommend the products they supply. They will need to work out which of their products will supply (as nearly as possible) the requirements shown on your soil test, which are expressed in kilograms of each elemental nutrient per hectare.

There may also be other issues that are “niggling” at your supplier, such as lime quantities or certain trace elements. SWEP recommends the use of materials to correct a specific imbalance and we only recommend the actual amount needed to do the job. Just stand firm on this point. If they want your money, they need to do the job you are asking for!

Having said this, custom blending trace elements into a solid fertiliser can be a bit fiddly. In this case, there are two options you can try: Many organic products naturally contain a range of trace elements. They may not meet your exact requirements, but you might be able to use them to reduce the number of trace elements you have to ‘fiddle’ with. The small quantities required for many trace elements often makes them suitable for foliar application using normal spray equipment, or via irrigation. In this case, the application rates should be those specified on the label for the specific product you want to use.

If you are Organic, thinking about being Organic or in Organic conversion, simply choose appropriate certified products or suitable manures or composts (provided you have a reasonably good analysis for them). There are now many manufacturers of organic fertilisers, but if you are not sure where to look, try our list of SWEP Agents as they include some organic fertiliser distributors.

Every plant has its own particular requirement for nutrients, in term of what it requires in order to complete its productive life during the course of a growing season. To obtain these nutrients, it must obtain a continuous supply from the soil throughout the season, so the soil levels must also be sufficient to permit this. Nutrient elements often interact with each other in the soil, further complicating the process, so the first step is to provide the proper balance of exchangeable cations in order to help minimise the effects of these interactions. Having done this, the requirement for any crop or pasture can be determined and adjusted according to the conditions in the soil. The objective here is not to produce a quick “green-up” or a growth response as such, but to ensure that nothing in the soil is likely to be limiting to the crop or pasture achieving it optimum potential.

Like everything on our soil test, the Nutrient graph is intended to be a “decision support” tool, not a decision making tool. It is unlikely you will ever achieve ‘perfect’ balance (perfection is always an unattainable goal), but the less well balanced your nutrients, the more work you will need to do to ensure your crop or pasture can perform to its optimum throughout the season. At some point, you may well decide that your soil simply isn’t suited to a particular Land use. In this case, the nutrient graph (since it will change substantially according to the specified Land use) may be a valuable tool in finding a suitable alternative. SWEP will provide reports for up to three (3) Land uses per sample at no extra cost (further reports will be charged at $10 each). The best thing to do is develop a ‘short-list’ of potential alternatives and then let us know. We can provide reports that can help you narrow things down a bit further.

No. SWEP analyses samples from around the world, so we cannot keep up with trials in every region of every country. More importantly, however, Field trials are based on showing what nutrients (at what application rates) give a measurable growth response under the general soil balance conditions of a particular area. In other words, if you flood the soil to ‘Luxury’ levels with various nutrients, which ones will force the most growth? Clearly, this is not a sustainable approach and the reliability of recommendations it provides will change with changes in the soil – making it necessary to continually repeat the trials in order to “re-calibrate” the interpretation system. SWEP on the other hand, looks at the soil and recommends corrective measures to improve Soil Balance. Once this has been done, the nutrient requirements for a given Land use can be more reliably determined by comparing the needs of the crop or pasture with conditions existing in the soil at the time.

This is an important point, because SWEP does not simply give Fertiliser Recommendations. We determine nutrient requirements for a specified Land use during the course of its growing season – once the cation balance has been appropriately corrected.

One of the greatest challenges in developing a useful soil biology test is in finding a way to provide a reliable analysis, regardless of the time of year in which the sample is collected and analysed. We found that, to solve this, focussing on the “active” rather than the “total” biological populations could allow for samples to be accurately analysed regardless of the time of year. For comparison, imagine a tree growing in an apple orchard. Whilst growth is not continuous throughout the year, reduced activity does not equate a plant’s death. Likewise, a perennial pasture in summer may look brown and dead. A closer inspection reveals a small green shoot waiting patiently for the rain. In the same manner many soil organisms will vary their activity with the season. Under unfavourable conditions some may die, some may reduce activity and others will completely ‘rest’ until more favourable conditions occur. In the laboratory, when stimulated by the favourable conditions of the culture media, the active organisms will be the first to appear and their numbers will be the same in every season. They will also be least influenced by the time between collection of the sample and arrival at the laboratory. Provided one can understand and interpret the results, this also makes them the most useful organisms to analyse.

The long held assumption that the greater the microbial activity in the soil the better is not necessarily correct. To be at its optimum, a soils’ structure, nutrients and biological components must be balanced – both within and between all the components. SWEP use specific groups to identify the “active” bacteria, and count individual group and total active microbial numbers.

Balancing the numbers and ratios of these biological groups are just as integral to a balanced soil, as the ratios of cations and nutrients are.

While SWEP can analyse samples sent at any time of the year, it must be remembered that soil biology is very sensitive to any disturbance. This situation is similar to that in which soil test results show very high nutrient levels because the sample was taken too soon after fertiliser was applied.

These kinds of results can occur when samples are collected and sent shortly after ploughing out an old vineyard, seedbed preparation for a field crop and renovating pasture. Such results can even occur following application of compost, manure or other bioactive material. Research is continuing in this area so that we can provide some useful guidelines on when and how to sample for biology testing, but for the mean time, try to avoid sampling after any activity that could affect the biological condition of the soil.

There are products available that consist of concentrated cultures of particular organisms and as such, their quality will be determined by cell counts and may well deteriorate with time in storage, however, most ‘bio-active’ materials on the market are not like this. Things like kelp extracts, fish emulsions, humates etc. may well contain bacteria and other microbes, but research has repeatedly shown that these organisms contribute little or nothing to the effectiveness of the product and this is also confirmed by a generally greater storage stability for these products. However, research by SWEP has shown that these products do produce specific changes in the biological profile of soils and the conclusion is that this change is produced by bio-active compounds they contain, rather than any microbial content. This is why we say that our recommendations will stimulate the growth of particular organisms, but it will be a stimulus of organisms already present in the soil. The amounts of materials you recommend for correcting the soil biology balance are very small.

The soil biology recommendations on the Complete Soil Balance Analysis report are based on the results of research into changes in the microbial profile of soil treated with various rates of specific bio-active materials. Interestingly, it was the lowest application rates that often produced the most significant results. While some people have claimed beneficial effects for very heavy and frequent applications of materials like Humates, one type of product that should NOT be used at higher than recommended rates is a Kelp Extract. These materials are generally high in plant hormones and excessive applications can result in significantly reduced growth.

There certainly are many other kinds of organisms in the soil, but our analysis covers five Indicator groups that are important for both direct benefits to plant growth and their interactions with other biological groups in the soil. More importantly, our research has shown that – in well balanced soils (where there is no external source of disturbance such as recent cultivation or use of bio-active materials like manures and composts), the relative proportions of these groups become stabilised in a predictable balance relationship. It is quite likely that other groups could be included in this relationship, but at present this is not necessary. If both the cations and nutrients are well balanced and there is no external disturbance, our recommendations will be sufficient to maintain optimal and sustainable productivity.

Because we focus on the ‘Active’ microbial populations, you can reliably test your soil at any time. Of course, when repeating a soil test it is still wise to do this at the same time of year as the previous one. The only other considerations are to avoid sampling within one or two months of any applications (Lime, Fertiliser, etc.) or any activity that could produce some kind of disturbance to the biological community in the soil (eg. cultivation, application of composts or manures and so on).

The effects of these things are only temporary, but can produce distorted results on a soil test.