Ultimately, farmers are not in the business of raising crops; they are in the business of growing soil. Top soil is the beginning and end of farming. Soil is also an immensely complex system, varying from place to place, even over short distances, and containing a stunningly intricate system of life. Chemical, structural, and biological processes must all be fostered if a farmer wishes to improve his soil.
On our farm, the soil is a fairly heavy clay, which tends to be dense and sticky when wet and hard when dry. It has low organic matter and a slightly alkaline pH.
In a soil, the base cations, (Calcium, Magnesium, Potassium, and Sodium) should be in a certain ratio; Calcium should take up the vast preponderance of the available “storage” (cations are stored on humus and clay particles) followed by magnesium, potassium, and sodium in that order. While Calcium can be as high as 70%, magnesium should be around 15%, and potassium should be a mere 2-5%. (Sodium should be always lower then potassium, and is not essential.) If these ratios are off, plant growth, soil life, and even soil texture will suffer.
It should be pointed out that this is just one of many different theories on soil health. Some farmers target other ratios, though always with Calcium taking the largest share. And many farmers don’t look at ratios at all; instead, they add a sufficient amount of each nutrient for the upcoming growing season. After much research, I’ve decided to follow the Albrechtian ratios as given above, since they were developed with a focus on the health of the whole system.
It is also important to realize that plants don’t “eat” as we do. There are a number of nutrients they need from the soil; Nitrogen, Phosphorus, Calcium, Magnesium, Potassium, Sulfur, Zinc, Copper, Iron, Manganese, and Boron are the most important. However, taken all together they make up a very small percent of a plant; most of the plant’s bulk is make of carbon, hydrogen, and oxygen drawn from the air and water.
In any case, if the chemistry of a soil is corrected, the soil will come to life biologically.
On our farm, the potassium is much too high. This is a complicated problem. For one thing, just like salt in soup, you can’t easily get a nutrient out of the soil. For another thing, most organic matter is high in potassium relative to the other nutrients it contains, so importing lots of organic matter will further imbalance this soil. The other cations are in fairly good shape. We are slowly resolving the problem by adding some gypsum every year. Gypsum a compound of sulfur and calcium. The calcium will replace the potassium, which will then combine with the sulfur to create potassium sulfate. Potassium sulfate is water soluble, so it will move deeper into the soil, away from the root zone. (The sulfur is also a necessary nutrient in the soil.)
Nitrogen is also necessary in fairly large amounts every year; but since it is fundamentally tied to the organic matter content of the soil, I will discuss it in the next post.
The soil started out with slight deficiencies in boron, copper, and zinc. These nutrients are tricky because they are needed in fairly small amounts, and an overdose can damage the soil. For instance, in the topsoil of a whole acre, there needs to be four pounds of boron; no more and no less. This translates into a tiny sprinkling of borax on each bed. These nutrients can not be added without careful soil testing.
In my next post, I will discuss our strategy for the organic matter and microbial life in the soil.