Calcium is often an overlooked nutrient in crop production because soil tests report large amounts of this extractable cation. This is the first in a series of three articles exploring calcium in the soil and its need in soybeans.
K. K. Gedroiz, scientist with the Forestry Institute in Leningrad, stated in the 1931 Soil Science Journal, “After the practically complete replacement from the soil of all exchangeable calcium, the plants required for their development the introduction into the soil of calcium fertilization, without which they would not grow at all.” The need for calcium in agricultural has been scientifically proven and soils are known to contain large amounts of calcium, however most of it is not soluble in the soil solution and is not readily available.
Calcium is an abundant mineral in the earth’s crust and is widely distributed in all living organisms. As a cation it plays a unique role in soil and is important to plant growth. Calcium has three functions in the soil that are critical to soil health and crop productivity.
Soil structure is the spatial arrangement or aggregation of soil particles forming pore space. Aggregation mainly depends on the soil composition and texture, but is also influenced by factors such as biological activity, climate and chemical processes.
In soil, calcium (Ca2+ cation) ions flocculate clay and organic matter particles, which improves soil structure and porosity. Good soil porosity insures adequate aeration, which also provides good infiltration and drainage and promotes better root growth.
Flocculation is caused by cations in the soil solution. Calcium and magnesium (in calcareous soils) or iron and aluminum (in acid soils) flocculate soil particles into the formation of stable soil aggregates. In contrast, the monovalent cation sodium disperses these aggregates.
Soil biological activity is critical to soil health and productivity and benefits from calcium. The biology of the soil is aerobic by nature and responds very favorably to the porosity of the soil complex, which is provided by the flocculation of the exchange complex by the calcium cation. Also, soil biology requires calcium in soil to supply the functions.
Biological decomposition and/or organic matter create cementing agents that enhance soil aggregation. Biological agents are involved in the formation of aggregates: plants (roots), animals (earthworms, arthropods, etc.) and microorganisms (bacteria and, especially, fungi) are important.
All agricultural plants require calcium for growth; it is a major secondary nutrient, along with magnesium and sulfur. Research has shown that animals consuming plants with calcium deficiencies will encounter growth problems that result in production losses. Calcium is also an important nutrient for soil organisms.
How are the calcium levels in your soils? Have you noticed any calcium deficiencies in your plants or crops? And how about the health of your soil? Maybe it is showing calcium deficiency signs. Next time you run a soil test, ask the laboratory to run a water extract along with a chemical extract. You will be surprised to learn that there is very little calcium in solution around soil particles and root hairs.
Soybean agronomist Daniel Davidson, Ph.D. posts blogs on agronomy-related topics. Feel free to contact him at firstname.lastname@example.org or ring him at 402-649-5919.