Fall is lime time! It's the traditional season for making whatever "topdressed" application of calcium to the soil that must be supplied, so the winter rains can soak it in.
Fortunately, our pasture calcium content is holding up well and we can skip applying more for another year. Most of our fertility needs for the pasture are settling down now, with a few exceptions, and we're looking at some relief from restocking our weathered and worn out soil with the missing minerals. Our fertility "bank account" is fairly well stocked and hopefully we'll be mostly drawing off the interest and making more modest deposits in the future. Our financial outlay for grain has gone down to zero.
Breathing life into the soil through remineralization causes no end of interesting surprises on the soil tests. As the calcium and other minerals we have applied become more available, the little soil microbes and earthworms are scrambling to bring the soil into a state of equilibrium. Minerals are microbe and earthworm food. They, in turn, feed the plants. That's why it's so exciting to witness the changes on the soil reports. You don't just add "X" and "Y" and come up with "Z". There are too many biological, chemical and electrical processes being ignited to predict with absolute certainty what the result of mineral applications will be. The only certainty seems to be that when you do it right, the only predictable outcome is good.
For instance, we applied ferrous sulphate - iron - last year. The objective was to get a detrimental "inverted" ratio of manganese-to-iron (more Mn than Fe) corrected. The result was not more iron on the next soil report. There was LESS iron, and LESS manganese, the ratio flipped and both ended up at desirable soil levels. That is probably not entirely from adding more iron, but it was still the outcome of last year's various additions. Molybdenum has taken a decided nosedive, where it was somewhat overabundant before. My guess is the exploding population of clover is slurping it up.
We've replaced the poor sheep genetics and hope to pick up some good Katahdin ewes in the spring. We'll be living off the oversupply of 2009 lambs for a year, and hope to play with the horses more in 2010. The horses, by the way, are shedding the evidence of insulin resistance. Gizmo is losing his regional fat deposits, while Spunky has suddenly lost at least 6" around her gut. It's taken a year and a half, but it seems they are responding well to our pasture fertility program. Disease, begone!
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Calcium is well known as a soil conditioner and pH adjuster. We already know that calcium is needed by animals for strong bones. What we need to explore now is why animals should get their dietary calcium from the plants they eat instead of a mineral box.
LIME AS A pH ADJUSTOR:
How does lime - calcium - raise soil pH (reduce acidity)? We have to go back to the tiniest particles of clay in the soil, so small they require a microscope to see them. These clay particles are called the clay colloid. They take the form of thin layers and have a negative electrical charge. Calcium, magnesium, potassium, sodium and hydrogen and certain trace elements all have a positive+ electrical charge and are called "cations" (cat-eye-ons, not "cayshuns" which is how I first thought the word was pronounced!). Negative attracts positive. The +cations thus cling to the -clay colloid, and also to the negatively charged soil humus. The hydrogen H+ ion has a positive electrical charge. It is a non-nutritive cation, a gas. When the soil is deficient in the other cations, hydrogen H+ will park in all the negative- "exchange sites" on the clay colloid. Thus, the presence of large quantities of H+ in the soil is what makes it acid. Hydrogen is what's left when all the nutrient cations are gone. When calcium Ca++, with its double electrical charge is present, the hydrogen will be knocked off the clay and the pH moves upward.
It stands to reason, if the cation calcium Ca++ can change soil pH, then so can the other cations. And they do! Magnesium Mg++ has something like 1.67 times the pH-changing power of calcium by weight, and potassium K+ and sodium Na+ also have a potent influence.
The Albrecht school of thought regarding "base saturation," suggests ratios of the various cations to one another according to the "Cation Exchange Capacity" of a given soil. CEC is the number on the soil analysis that predicts a given soil's ability to attract and hold on to the cations, thus its potential for maintaining fertility.
So if you are shooting for a pH of 7, or neutral, by means of calcium only, and then you add magnesium and potassium as fertilizer, not realizing their effect on soil pH, you can see why your crops may not be up to your expectations! Too much calcium fills up all the exchange sites on the clay colloid, leaving no room for the other cations.
If you add potassium to your soil every year in anticipation of the yield it will produce, a pH reading alone will never disclose a potential shortfall of calcium.
Hydrogen will pretty much be gone from the soil when the pH reaches 7. That's just fine if you are using root-feeding commercial fertilizers, especially since many of them tend to "acidify" the soil anyway. But for the exchange of soil nutrients via microbial activity as happens in healthy soil, some hydrogen is required for the "exchange" of soil nutrients between roots and soil. So a pH of around 6.5 is more desirable for most crops, and as you can see, should be achieved by balancing the cations, not just dumping on lime. The plant roots take in a little calcium, give off a little hydrogen, and the cycle begins again. Whatever is removed with the crop and taken off the farm has to be put back.
Soil pH affects the availability of all the other soil minerals. Each mineral becomes more "available" to plant roots at different levels of pH. The majority of them seem to be relatively available for plant uptake at around pH 6.5. For all its virtues, too much calcium in the soil has its own health-depressing effects, notably by tying up a number of the other soil minerals and making them unavailable.
To get calcium in the soil, we usually apply some form of lime. Different kinds of lime do different things to the soil. Calcium carbonate, also called sweet lime or ag lime, is finely ground high calcium limestone. It will help the soil structure become looser, allowing better air, water and root penetration. It may not be the best choice for fast draining, loose sandy soil. Dolomite lime contains magnesium, which tends to tighten soil, and therefore may be a better choice for those sandy soils. Tight soils may already contain too much Mg, so dolomite may not be the best bet there. Gypsum is a mixture of calcium and sulphur. It does not change soil pH, but the two minerals together will be just the ticket where soils need both minerals. Gypsum is also used to correct a soil imbalance of too much magnesium, potassium or sodium, replacing them with calcium.
So much for soil. My aim is to convince the reader that having our livestock obtain their minerals from nutrient dense forage produced on mineral-balanced soil is preferable to feeding minerals in supplement form. Obtaining proof of this has been MUCH harder than I expected! There is plenty written about soil fertility for healthy plants. There is an equal amount of material that talks about mineral nutrition for the body. The abyss that has been hard to bridge is finding everyday language about how minerals are used by plants to biosynthesize a vast array of other nutrients that are required for both plant and animal health, and that animals cannot make for themselves! These nutrients are called "phytonutrients, from the Greek word "phyto," meaning plant.
The plants that our animals eat are not just convenient little bags of minerals, compartmented off from the vitamins, enzymes, proteins and myriad phytonutrients that we expect the forage to deliver to the animal. In fact, the minerals are very much "second hand" bonus nutrients that come along with the plant after they've been used by soil microbes and plants to fabricate all of these other life-giving substances! Feeding calcium carbonate in the mineral box can most definitely relieve a specific calcium deficiency in the animal, but there can also be deficiencies of other nutrients in the forage as a result of low calcium levels in the field soils. That is why mineral supplementation can never take the place of forage-derived calcium.
At the very genesis of nutrient cycling in the soil, "microbes eat at the table first." In other words, the soil life take what they need of soil minerals before delivering them to plant roots in a form that the plants can use. Earthworms are dependent upon an adequate supply of calcium for their existence, so in the first order, adequate soil calcium, along with the other soil minerals, underpins the foundations of living soil.
Never take the soil microbes for granted. There are more tons of soil life under the surface than could ever be stocked in cattle above. Feed them well.
Calcium regulates the "protein pump" responsible for uptake and movement of nutrients into the roots and through the plant cells. At the root level, calcium stimulates the protein channels that take up other soil nutrients, so adequate calcium must be available to the roots in order for the plant to take in the other minerals it requires for its metabolism.
Anything that short circuits plant metabolism will result in degraded nutrition for the animal
The first consideration when liming the pastures instead of liming the animals is that a deficiency of any one of the soil minerals becomes a limiting factor in the plant's ability to biosynthesize complete nutrition for the grazing animal. When lime is applied only as a pH-adjusting factor, we ignore the role that calcium plays in the production of many other phytonutrients.
It was recognized as early as the mid 1920s that with a decrease in soil calcium comes a decrease in plant protein. (Orr, Minerals in Pastures, 1929) That of itself should be enough to swing the pendulum toward liming pastures that show a need for calcium through a soil analysis. The word "protein" embraces many substances, including amino acids and enzymes. Amino acids and enzymes come from the "starter compounds" of plant sugars and starches. These sugars and starches are the products of photosynthesis, before the plant begins metabolizing them into a huge array of nutrients in the presence of adequate soil minerals. It is no accident that our low protein, high water-soluble-carbohydrate hay that was slowly killing my horses (like it does all EMS/I-R horses) has corrected to a very desirable ratio of protein to carbs for such horses, with no manipulation of the plant population (i.e. no planting of supposedly "low sugar" grasses), only replacing soil minerals.
Amongst the proteins, there are fairly insoluble "fibrous" proteins, and water-soluble "globular" proteins, such as enzymes. For horse owners faced with soaking hay to remove excess carbs and potassium, then supplementing minerals, it seems readily apparent that the loss of the globular proteins to the soak water is not desirable.
There are ten "essential" amino acids for the grazing animal. That means they must all come from the diet, because the animal cannot biosynthesize them for itself. One of the references I keep coming back to is the elevation of tryptophan in calcium-rich forage. Tryptophan was a disappearing amino acid in forage plants as far back as the mid 20th century.
From a grower's point of view, adequate calcium makes the plants stronger and more able to resist pest and disease attacks. The plant uses calcium to construct strong cell walls, and in the glue that holds cells together. Strong cells are less liable to attack by opportunistic pathogens and bugs. Some weeds, such as field bindweed, are able to etch enough calcium out of parent rock to thrive, and it positively loves potassium, as most weeds do. Such a weed will frequently pull up stakes and move out when the soil chemistry is corrected to favor the more demanding and highly desirable forage plants. We have almost eliminated grass-killing mats of oxeye daisy and Queen Anne's lace, simply by putting back the missing minerals.
Calcium is necessary for cell division and permeability of cell membranes and water movement in cells. It activates enzymes. It regulates the absorption of nutrients across plasma cell membranes. It is necessary for the uptake of nitrogen in plants, and nitrogen is the "mother" of protein.
For those of us managing horses with "Equine Metabolic Syndrome" or Insulin Resistance, some nutritionists are recommending dietary calcium-to-magnesium ratios of 2:1, in amounts at least 150% higher than National Research Council (NRC) recommendations. Why isn't the daily recommendation for healthy animals 150% higher to begin with? Why does a sick horse get more than a well horse? If the well horse got 150% of the NRC requirement, would it not get sick in the first place? Who knows? My guess is the NRC researchers have never actually seen a true model of health, either in a pasture or a horse, or considered the impact of adequate mineral nutrition coming from the forage instead of the mineral box.
The current NRC requirement for calcium in the idle horse is 0.25% of the dietary dry matter and of magnesium, 0.10%. The calcium content of our 2009 grass hay is 0.43% and of magnesium, 0.19%. This is a "natural" unimproved sward growing on remineralized soil. We are pushing close to 200% of the NRC-established requirement for maintenance horses. It is just a little troubling that meeting the NRC "ideals" would require only half the minerals delivered by a mineral-rich meadow.
Soil needs calcium to maintain a structure where water, air and nutrients can penetrate. Microbes need calcium for their own metabolic processes. Plants need calcium in order to take up nitrogen and other minerals, for their metabolic processes, structural integrity and reproduction, and animals need the phytonutrients that are catalyzed into existence by plants in the presence of adequate calcium.
None of this comes from the mineral box. It all needs to take place at the beginning of life, from the soil up.
Recommended Reading:
Plant Nutrition and Nutritional Disorders
http://ag.arizona.edu/CEAC/basics/notes/chapter7.pdf
Calcium Nutrition in Plants by Greg Patterson, CCA
http://www.calciumproducts.com/Calcium_Nutrition_in_plants.pdf
20 Mineral Elements for Plant Growth by Craig Dick
http://blog.calciumproducts.com/posts/20-mineral-elements-for-plant-growth.cfm
Plant Nutrients and Vitamins
http://plantcellbiology.masters.grkraj.org/html/Plant_Cellular_Physiology3-Mineral_Nutrients_And_Plant_Vitamins.htm
Equine Metabolic Syndrome, by Wellington Veterinary Clinic, Wellington, OH
http://wvc.relmax.net/forms/metabolic_syndrome.doc
How gypsum Works: http://www.hmhgypsum.com/why.htm
The Ideal Soil by Michael Astera, www.soilmineral.com
Hands On Agronomy by Neal Kinsey, www.kinseyag.com
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