Calcium - 4. Delayed Appreciation

 

The delayed appreciation of the significance of calcium in plant nutrition may be laid at the doorstep of a confused thinking about liming and soil acidity. The absence of lime in many soils of the non-temperate zone has long been known. Lime in different forms such as chalk, marl, gypsum or land plaster, has been a soil treatment for centuries. Lime was used in Rome in times B.C., and the Romans used it in England in the first century A.D. Chalking the land is an old practice in the British Isles. The calcareous deposits like “The White Cliffs of Dover” were appreciated in soil improvement for centuries before they were commemorated in song. Liming the soil is a very ancient art, but a very recent science of agriculture. It was when Liebig, Lawes and Gilbert and other scientists began to focus attention on the soil as source of chemical elements for plant nutrition that nitrogen, soluble phosphate, and potassium became our first fertilizers. It was then that the element calcium and the practice of liming were put into the background. Unfortunately for the wider appreciation of calcium, this element in the form of gypsum was regularly a large part of the acid phosphate that was applied extensively in fertilizer to deliver phosphorus. Strange as it may seem, superphosphate fertilizer carries more calcium than it does phosphorus, and consequently calcium has been used so anonymously or incidentally that its services have not been appreciated. Fertilizers have held our thought. Calcium was an unnoticed concomitant. It has been doing much for which the other parts of the fertilizers were getting credit. Appreciation of the true significance of calcium in plant nutrition was therefore long delayed.

More recently soil acidity has held attention. This again has kept calcium out of the picture. Credit for the service of liming has been going to the carbonates with which calcium is associated in limestone. It was a case of the common fallacy in reasoning, namely the ascribing of causal significance to contemporaneous behaviors. Here is the line of reasoning: “Limestone put on the soil lessens the acidity, and limestone put on the soil grows clover. Therefore the change in acidity must be the cause of the growing clover.” Therefore the change in acidity must be the cause of the growing clover. At the same time, there was disregarded the other possible deduction, namely: “Limestone put on the soil applies the plant nutrient calcium. Therefore the applied calcium must be the cause of the growth of clover.”

The labeling of calcium as fertilizer element of first importance was delayed because scientists, like other boys, enjoyed playing with their toys. The advent of electrical instruments inducement to measure soil acidity everywhere. The pH values were determined on slight provocations and causal significance widely ascribed to them, when as a matter of fact the degree of acidity like temperature is a condition and not a cause of many soil chemical reactions.  Because this blind alley of soil acidity was accepted as a thoroughfare so long and because no simple instrument for measuring calcium ionization was available, it has taken extensive plant studies to demonstrate the hidden calcium hungers in plants responsible in turn for hidden but more extensive hungers in animals. Fortunately, a truce has recently been declared in the fight on soil acidity. What was once considered a malady is now considered a beneficial condition of the soil. Instead of a bane, soil acidity is a blessing in that many plant nutrients applied to such soil are made more serviceable by its presence, and soil acidity is an index of how seriously our attention must go to the declining soil fertility.

Now we face new concepts of the mechanisms of plant nutrition. By means of studies using only the colloidal, or finer, clay fraction of the soil, it was learned that this soil portion is really an acid. It is also highly buffered or takes on hydrogen, calcium, magnesium, and any other cations in relatively large quantities to put them out of solution and out of extensive ionic activities. It demonstrated that because of its insolubility, it can hide away many plant nutrients so that pure water will not remove them, yet salt solutions will exchange with them. This absorption and exchange activity of clay is the basic principle that serves in the plant nutrition. This concept comes as a by-product of the studies of calcium in relation to soil acidity.

Imagine that a soil consists of some calcium-bearing minerals of silt size mixed with acid clays. The calcium-bearing mineral interacts with the hydrogen of the acid clay. The hydrogen goes to the mineral in exchange for the calcium going to the clay. Imagine further that the plant root enters into this clay and mineral mixture. It does so more readily because of the presence of the clay. It excretes carbon dioxide (possibly other compounds) into this moist mixture to give carbonic acid with its ionized hydrogen to carry on between the root acid and the clay particle and the mineral. The hydrogen from the root exchanges with the calcium absorbed on the clay in close contact.

Thus plant nutrition is a trading business between root and mineral with the clay serving as the jobber, or the “go-between”. The clay takes the hydrogen offered by the root, trades it to the silt minerals for the calcium and then passes the calcium to the root. Thus nutrients, like calcium, and other positive ions as well, pass from the minerals to the clay and to the root, while hydrogen or acidity, is passing in the opposite direction to weather out of the soil its nutrients mineral reserve and leave finally the acid clay mixed with unweatherable quartz sand. Acid soils are, then, merely the indication of nutrient depletion.

 

- Excerpt from Albrecht's Foundation Concepts - The Albrecht Papers Vol. 1 - pgs. 149-150

Confusion will prevail until the soil is considered...

Because we turned away from much of the art of agriculture in the absence of a complete science of it, we have a serious confusion. That is all the more serious now and at the moment we discover that we have rapidly mounting numbers of people and are soon running out of ample food for them. We are confused about the natural performances or about the biology in agriculture. We have permitted ourselves to be led astray and are asking the science of agriculture now to bring us back to where we can understand the basic principles rather than merely mimic any practice. We dare not be mere followers of traditions. We must face the problems and solve them. All of that calls for rather clear diagnoses. Let us try and comprehend the fact then that soil fertility properly coupled with plant nutrition is a form of creation, a form of outdoor biology, and not a matter merely of scientific technology. In that combination wisely used there may be some solution for our food problem.

Now what are some of these confusions about the basic facts of soil fertility and plant nutrition? First of all, we seem to have lost sight of the fact that the creative business of agriculture has always started in the soil. That great truth was told us about six or more thousand years ago, but we didn’t take that remark very seriously. We are beginning to appreciate it now. We shall face it more seriously when we have the least of creative capacity left in the soil and when we need to know most about it.

In terms of wise fertilizer use, the most shocking confusion prevails when we talk about soluble fertilizers, considering water as the agency for solution, and then we make laws requiring that fertilizers must be water-soluble and thereby so-called “available”. In fact and in nature, these soluble fertilizers are never taken out of the soil because the plant takes them into itself along with water it takes from the soil. The use of the major amount of water by the plant is that of keeping the respiring leaf tissues moist for the exchange of the gases, namely carbon dioxide and oxygen. That escape of water from the leaf is what we call “transpiration”, and it is in that service where most of the absorbed water goes from the soil into the atmosphere. That use of soil water is controlled by the meteorological situation inviting water to evaporate from the leaves of the plants against the forces holding the water in the soil. The plant is an innocent connection between those two opposing forces acting on the water. Does the moisture in your breath move nutrient form your bloodstream into the tissues, or from your stomach into your bloodstream? But yet we take to the concept that the transpiration by the plant has something to do with the movement of nutrient from the clay of the soil into the roots. The transpiration stream of water from the soil, through the plant and into the atmosphere is independent of the nutrient stream from the soil into the roots. That may not be true for nutrients moving within the plant’s conducting tissue. The water uptake by the roots is the result of atmospheric conditions favoring evaporation from the leaves with a set of dynamics which are more than a match against the forces holding the water on the surfaces within the soil.

Nutrient intake by crops is a function of three colloids, or possibly four, in contact. First of all, there are the nutrients on the clay colloid, or on the organic colloid of the soil. The soil colloid is in contact with the root membrane which is another colloid. That root membrane is in contact with the contents of a cell on the inside, namely the protoplasm, or the cytoplasm. Then, in turn, that cell is in contact with another cell. In that you have the combination of the three or four colloids in contact. The movement of the nutrient ions from the clay into the root membrane and into the cells follows the chemical laws controlling their traverse there because of the differences in activities, adsorption capacities, interfering ions and other factors along that line.

That movement of nutrients into the root is independent of the transpiration of water. We have demonstrated transpiration going forward regularly, or water moving from the soil through the plant to the atmosphere when the nutrient ions were moving in the reverse direction, namely, going from the plant back to the soil. We have demonstrated the ions going into the plants regularly when there was no transpiration. You can demonstrate this when you put a bell jar with atmosphere saturated with CO₂ and with water over that plant. In that case, you can stop the transpiration but you don’t stop the ionic nutrient movement into the plant. Some recent work at the California Technological Institute has shown that the desert plants put water back into the soil while they are growing, therefore the water can be going back into the soil while the nutrients are going in the opposite direction. We must get rid of this water-soluble fertilizer bugaboo in considering soil fertility and plant nutrition, because transpiration runs independently of our control and we need to concentrate our efforts on keeping the stream of fertility flowing more regularly into the plants.

Let us not cover either our ignorance or our responsibility toward maintaining the soil fertility by trying to blame the water situation in the soil and the rainfall. The idea that the drought is responsible for the failure of plant nutrition persists. But what is commonly called drought isn’t trouble in terms of water only. It is apt to be due to the fact that the upper layer of the soil, where the fertility is, dries and the roots must go down through a tight clay layer which has almost no fertility. Then, because of the crop failure in the absence of plant nutrition in that soil layer of stored water, we try to blame the drought or the bad weather. Drought may be merely that soil situation in which we have no soil fertility deep enough to feed the plants when they are compelled to have their roots go deeper to get stored water. We have emphasized the water so much that the situation suggests itself as a relic of the old “saloon” days, when men thought they had to stay in a saloon and drink, but forgot to take some groceries home for the family. Plants will scarcely emphasize drink to that much neglect of food. Our confused thinking about drink for plants emphasized the water facts as an alibi for our ignorance of plant nutrition and the soil fertility factor where the emphasis properly belongs. During the drought we don’t use the water to the best of our ability. We neglect to remind ourselves that the plant is about 95% air, water and sunshine, and only about 5% fertility. We are too indifferent to that fact to consider carefully how we can use that 5% as the requirement to produce the other 95% of plant growth, a performance which offers chances as a gamble better than one would scarcely anticipate.

We blame the water. We blame the weather. The water of transpiration from the plants is like the water going over the millwheel, only a part of that coming down the millstream. The amount of grist that one grinds in the mill is determined not so much by the amount of water going over the millwheel, the amount of which is fixed or limited, as by the diligence with which wheat is kept going into the millstones for 24 hours a day at full capacity. We haven’t been keeping the soil fertility well and properly supplied to the crop plant and are therefore in error when for disturbed yields we blame the drought.

- Excerpt from Albrecht's Foundation Concepts - Vol. 1 - pgs.53-55; 1953