I am currently writing new guidelines for our Soil Therapy™ reports. It occurred to me that these detailed explanations of every facet of a good soil test might be of value to Nutrition Matters readers, so I have decided to share. In this first installment, we shall look at CEC, TEC, pH, paramagnetism and organic matter, as these are the first five categories on a Soil Therapy™ report.
Cation Exchange Capacity (CEC) offers an immediate guideline as to the nutrient and moisture storage capacity of your soil. A light sandy soil might have a CEC as low as 3, while a heavy clay soil might be as high as 60. This is essentially a measure of the clay component of your soil, and it can also indicate the appropriate fertilising strategy. A light, sandy soil, for example, should ideally be spoon-fed via fertigation (if possible) because it is not capable of much nutrient or moisture storage.
The term "cation exchange capacity" refers to the fact that an exchange often takes place when a cation (a positively charged ion, e.g., calcium, magnesium, potassium or sodium) is removed from the clay colloid by the hungry plant. The plant must maintain an internal electrical balance so it releases a cation whenever it takes one on board. There would be no sense in taking in one nutrient and spitting out another, so the plant releases the non-nutrient mineral, hydrogen, whenever it takes in a cation like calcium or potassium. Hydrogen is effectively exchanged on the clay colloid and this lowers soil pH, as hydrogen is the acid element.
This refers to Total Exchange Capacity. It effectively means that the percentage of the non-nutrient mineral, hydrogen, has been factored into the equation. A good soil test must always feature a TEC reading. If not, there is a risk that the relative percentages of the other major cations, that together comprise "base saturation" may be misleading. Base Saturation will be covered in more depth later, but essentially it relates to the percentage of the major cations (bases) that are "saturated" on, or attached to, the clay colloid.
Without the inclusion of hydrogen in the mix, you can be misled into thinking that you have an adequate cation balance when, in actual fact, half of your clay storage might be the acid-forming, non food mineral, hydrogen, that has not been measured. If this were the case, the slice of the pie represented by percentages of calcium, magnesium, potassium and sodium becomes very different when factoring in the 50% dilution effect of all of that hydrogen. In short, your CEC might look fine but you may actually have an empty fuel tank, and it is not apparent if Total Exchange Capacity (TEC) is not included in your soil test.
pH is a measure of the acidity or alkalinity of your soil. Soil pH has a major impact upon nutrient uptake. Most minerals are most available to the plant at a soil pH of 6.4, so this is considered the ideal soil pH. Acidic soils will render some minerals less available and alkaline soils will also compromise nutrient uptake. Please see the diagram below highlighting this phenomenon. An oversupply of hydrogen drives soil acidity, but hydrogen disappears from the equation when the soil pH is above 7 (neutral).
If you have inherited a high pH soil, driven by an excess of magnesium, or sodium, or both, then it is a good strategy to bypass the associated soil lockups via direct route into the leaf. In this case it is always a productive strategy to foliar spray iron, manganese and boron at least twice per season, as they are the minerals most impacted by high pH soils. If your soil pH is 8.0, for example, it can be tremendously effective and profitable to compensate with foliar applications of iron, manganese and boron (in cereal crops, usually at the five leaf stage and again immediately before flowering).
This is a guideline as to the productive potential of your soil. This phenomenon was first described in the soil by the brilliant US scientist, Professor Phil Callahan. Phil identified that the productive fertility of volcanic soils was directly related to their paramagnetic quality. In fact, the higher the reading on a PCSM meter, the lower the problems and the better the outcome.
Here's how it works. Volcanic soils serve as an antennae and receiver to attract and store an atmospheric energy called Extra Long Frequency (ELF) radio waves. This energy was originally derived from lightning bolts, where that explosive energy was converted to a more subtle and stable form in the atmosphere. Volcanic soils do more than attract and store this energy, they can convert it to tiny light particles called biophotons. The release of these measurable light particles into the soil effectively provides light for the plant roots and the army of organisms that surround them. This light energy boosts root growth and nodulation in legumes, and stimulates beneficial microbes.
The good news here is that if you have a non-volcanic soil with low paramagnetism (fertility score), then there is a cost-effective way to build both paramagnetism and productive potential. Basalt crusher dust with a high PCSM reading (over 1600 cg) can be sourced very cheaply throughout Australia. This highly paramagnetic dust can be applied to your soil to lift your levels and increase your fertility. Many quarries will provide paramagnetic scores for their product but NTS also offers a free testing service for crusher dust, to help you determine if local sources are of value. Just send us 100 grams of the dust in an envelope with your email details.
This may be the single most important parameter on your soil test. Organic matter, or humus, is the true essence of soil fertility. If you can work toward building organic matter in your soil, there are a multitude of profound benefits. These range from improved water and nutrient retention and reduced soil loss (through erosion) to greater crop resilience, less need for chemicals and more fun in your farming enterprise.
Organic matter is the "great forgiver". You can weather your way through all sorts of mineral imbalances and deficiencies in your soil, simply because the humus compensates for, and buffers against, most problems. The higher your humus levels, the larger your microbial workforce and the more successful your growing enterprise. Cover crops, microbial inoculums, humates, compost, minimum-till, intelligent grazing strategies and reclaiming earthworm counts are some of the humus building strategies that can make farming more profitable and so much more fun.
Next week we will continue with Part 2 of "Understanding Your Soil Report". Please feel free to email me, or our Agronomy team (firstname.lastname@example.org), if you have any queries or need further explanation. It is immeasurably important to fully understand your soil test. When we comprehend this critically important monitoring tool, we take the guesswork out of nutrition, we are more empowered, and we are less likely to suffer the joy-killing stress that can undermine our farming pleasure.
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