Calcium & Magnesium
One of the fascinating aspects of soil nutrient balancing is the interactions each mineral as within the soil matrix and other nutrients. The Mulder Chart is an excellent illustration of that. It also shows the certain dominance cations like calcium and magnesium have over others.
If you recall in week 39, we discussed pH and how you use pH to adjust cations and anions. The relationships they have with each other need to be taken into consideration as well as the roles they play in soil and plant health.
Calcium and magnesium are two of the major players when balancing soil nutrients. Their ratio is one of the most talked about in the world of soil nutrient balancing. Whether you are of the school backing the ideal 8:1, or some variation of, it can’t be denied the importance of both to not only plant health but soil health as well.
If you recall in week 29, we discussed cation exchange capacity (CEC), and I use two side by side fields to illustrate the power of calcium
It’s calcium’s critical role that brings it front and center in not only soil but plant health as well.
Here are nine critical roles it plays
1. Calcium is a flocculating agent that helps stabilize clay and organic matter leading to aggregate stability.
Calcium and to some degree magnesium, help chemically bind clay and organic matter helping with better drainage and erosion control by making the soil more stable.
2. Proper moisture balance, created by aggregate stability in soil leads to a healthier microbial environment
3. Calcium can neutralize excessive soil conditions, dependent on the source, leading to more robust root growth
4. Reduce weed pressure
5. Reduce leaching of other nutrients
6. Calcium has also been likened to a nutrient filter whereas it regulates the movement and availability of such nutrients’ as sodium, phosphorus, iron, aluminum, and boron
Specifically, in plants
7. Calcium is responsible for proper cell division and cell wall development.
8. It plays a role in nitrate uptake and metabolism
9. It represents a role in enzyme metabolism
Calcium is not mobile on its own in the soil or the plant, leading to the need to be continually supplied. It is transported through the xylem in the plant and dependent on water to complete the process. This is why tomato blossom end rot is not a calcium issue as much as it is an irrigation issue. Without a consistent water supply, calcium cannot move into the plant, hence rendering it calcium deficient.
Magnesium is just as vital to a plants’ health. Several roles it plays are-
1. It is the central element in the chlorophyll molecule
2. Carries phosphorus into the plant
3. It activates and is a component of plant enzymes
4. Aids in plant oil and fat formation
5. Helps control nutrient uptake by the plant
6. Aids in nitrogen fixation
One of the main concerns with magnesium in forage crops is grass tetany. It is a metabolic disease when an animal is deficient in magnesium.
Factors that lead to it are-
1. Low levels of magnesium in the soil
2. Soils higher in potassium
3. Long periods of cool or cloudy weather in spring
4. Poor soil drainage
5. Moving animals from indoor to outdoor feeding
Magnesium can be often overlooked due to the fact it does not always translate to a higher yielding crop, just a more nutrient dense one.
Potential organic sources of calcium and magnesium
Aragonite- Typical analysis is 33-40% calcium
Aragonite is a readily available calcium source. It can be applied in the spring and be available that growing season. It also has a far greater liming effect than once realized, while providing trace minerals and biology to the soil. Raw aragonite brings with is biology from the sea, acting as a built in inocculant.
High Cal Lime- Typical analysis is 38% available calcium
Best used when there are no need for magnesium. Sometimes referred to calcitic limestone
Dolomitic Lime-Typical analysis is ~21% calcium ~11% magnesium
Use when both calcium carbonate and magnesium carbonate are needed
Oyster Shell- Typical analysis can be as high as 96% calcium carbonate
Used as a source of calcium and trace minerals
Wood Ash- Typical analysis is ~32% calcium oxide 3-7% Magnesium
Wood Ash is considered a liming material, supplying about 50% calcium carbonate. Care should be exercised that it is not over-applied due to its rapid reactive nature
Gypsum- Typical analysis is 18-23% calcium 18-29% sulfur
Gypsum is used to correct alkaline and sodic soils. It can improve the structure of heavy clay soil and supply calcium and sulfur when a pH adjustment is not necessary. Can be used to add calcium if magnesium is not needed and soil tests show lower sulfur. Does not remediate sodium issues alone, irrigation is still needed
Bone Char- Typical analysis is ~25% calcium
Has varying amounts of NPK, but is also high in calcium. Bone char has more surface area to bone meal making it more reactive especially at higher temperatures
Crab Meal- Typical analysis is 11-18%
Crab meal is a slow-medium release nitrogen source. It can also be a calcium source depending on how much shell is mixed in. Crab meal also contains an enzyme chitosan, which helps plants build a robust immune system, increases germination rates, and repels parasitic insects and nematodes. Due to the expense, it is often used in fertilizer blends more than a stand-alone.
Epsom Salt (Magnesium Sulfate)- Typical analysis is 10% magnesium 18% sulfur
Epsom salts are a good source of magnesium and sulfur. Can be used as a dry application or foliar. Care should be taken when you spray so not to burn plant tissue
Sol-Po-Mag- Typical analysis is 0-0-22 11% magnesium 22% sulfur
Sul-Po-Mag is a medium to fast release source of sulfur, potassium, and magnesium. It is also known as K-Mag or Langbeinite