Written by Steve Townsend
Think you have your soil fertility mastered? Well-read on about possibly the most misunderstood soil scientist Dr William
Albrecht, skip this article and you could be missing something

 I don’t think there is anybody in agriculture more misunderstood or misquoted than Dr William Albrecht, who was emeritus professor of soils at the University of Missouri from 1919 – 1959. He began his work in medicine but soon switched to agriculture when he realised that medicine focused on symptoms and not the cause. He reasoned that most health issues were the result of poor nutrition and this could be best addressed by focusing on the soil. He coined the phrase ‘healthy soil, healthy crop, healthy animals’, and we could possibly add to that ‘healthy humans’. Many critics dismiss his work entirely but I believe they are missing the point and that is that crop production is an expression of the soil.

The trouble started, as I see it, when Professor Albrecht allegedly said that the ideal ratio in the soil for calcium and magnesium was 68% and 12% respectively. The wider scientific community took umbrage at this as it threatened the status quo and what they had been preaching on soil fertility. This position still exists today with some scientists saying that Albrecht’s work has been peer reviewed and so doesn’t work or is not relevant. The scientists of this persuasion then set out to prove that this statement was wrong and they found soils could yield just as well without the calcium and magnesium being in these proportions.

This is the crux of the matter. I have read many of Professor Albrecht’s works but not once have I found the alleged statement. He refers to it as the average ratio as you could expect across many different soil types. The ratio he did talk about was that the calcium and magnesium should add up to 80% of the base saturation, then a soil could be considered balanced. Balanced soils he believed gave the most consistent yield and quality, not necessarily the greatest yield at one time. Hopefully that has helped to clear up some confusion and that the Albrecht method of soil testing could have some value to your farm business. Albrecht talked about the soil as a complete entity encompassing chemical, physical and biological attributes.

He recognised that correcting some mineral balances took care of the chemical part of the soil which in turn allowed the physical structure to improve which then provides an environment for the correct biology to flourish. It is a selfsustaining cycle. Of course, like the minerals, the biology has to be there in the first place for it to flourish, it could well be argued that decades of intensive agriculture have depleted our soils to the brink of extinction and the biology may well need re-establishing. Conversely though what this also shows is that there will be little response to ‘bugs in jugs’ if the chemical and physical environment is not there to allow them to flourish.

Exploring Albrecht’s research further, he suggested that there is an ideal ratio between the levels of calcium and magnesium in the soil, which should be related to the soils clay content. While Albrecht did not discover cation exchange he did link cation exchange to the colloidal clay particles within the soil. The clay colloids are negatively charged and have the ability to exchange calcium, magnesium and potassium (amongst many others) for hydrogen with the plant.

Albrecht research initially focused on forage production, and he discovered that calcium was essential in increasing protein content within the forage. He then took this a step further and began trying to relate the calcium content of the soil to the forage and then onto the health of the animal. With this work he found that improved animal health was reflected by the improved forage. This led him on to his hypothesis of the ideal cation ratios in the soil. For the soil he was working on he suggested that the calcium saturation percentage should be 65% and the magnesium should be 15%. But the important point to note here is that the calcium and magnesium percentage should total 80%. Further work by Albrecht and others then suggested that there was a range of ratios depending upon soil clay content. These ratios are where we are today with ideally calcium 60-70% and magnesium 10-20%. Albrecht ignored soil pH reasoning that if the cations are in these ratios the pH will look after itself at around pH6.3

So what does this mean to you?

Many consultants will measure the cation exchange and calculate the calcium and magnesium percentages. A typical result, from a calcareous soil, may look something like this; calcium 84% and magnesium 5% to which you would conclude that all is well. The excess calcium can’t be giving me a problem, after all the calcium is the beneficial element isn’t it and I have low magnesium? But if the calcium level is too high that generally means other cations have suffered as a result. Albrecht discovered that as calcium becomes excessive it ‘masks’ magnesium. In the example above the calcium and magnesium percentages totals 89%, which is beyond Albrecht’s ideal of 80%. If you try to ‘strip’ out the calcium the magnesium level will rise by the corresponding amount. Thus if you lowered the calcium to 70% you would increase the magnesium by 14% to the more accurate figure of 19% which is now a soil with excessive magnesium!

Magnesium in excess is a problematic element in the soil. Excessive magnesium causes clay aggregates to disperse. Clay dispersion reduces soil aggregation in turn reducing pore space (the soil has slumped) and consequently reducing water and air movement. Without air and water movement your soil will no longer have beneficial functioning biology which facilitates nutrient cycling, soil carbon building, and help with soil aggregation to produce the crumb structure and tilth that you need. It has long been known that calcium can ameliorate the effects of heavy soils and their tendency to slump and compact. If your soils slump and compact your crop production will suffer. Your soil will no longer have the pore space to facilitate air and water movement.

But simply adding limestone to correct soil pH using a rough formula based around soil type is imprecise. And what happens if the soil pH is at pH 6.5 or above and there is still a calcium deficiency? I will use the example of a client who had a pH of 7.8, but when the cation exchange was measured revealed a calcium percentage of just 46%. That’s just not possible is it? Well, yes it is, if magnesium and potassium have filled the cation exchange sites they will have a stronger basicity than calcium alone, and result in a high pH.

A simple pH test would suggest that calcium is not necessary, in this situation, and would result in poor crop production (as was the experience in this case), through lack of calcium, poor drainage, low air content and low health soils. Making sure you have the correct calcium content in your soil therefore can’t be achieved by pH alone! Why is this important you might ask? It’s not just about calcium, but blackgrass hates correct calcium & magnesium levels and as mentioned before, producing a healthy soil is difficult without a good balance of these and other elements. If soil health, conservation agriculture or reduced tillage establishment systems are your goal don’t overlook the basics and assume your soil will cope without the right chemical balance. You may be spending money in the wrong areas when a simple soil test will put you on the right track or leave you fighting a chemical imbalance with the cards stacked against you, leading to poor future and present crop performance.