Calcium as a Plant Nutrient
Calcium serves several functions in a plant. It helps plants build strong cell walls. Plant cell walls are important for providing rigidity and protection to plants. Calcium is needed for the cell membrane to be permeable. Fortified membranes prevent toxic compounds from entering plant cell walls. Calcium also affects enzymes involved with certain biological reactions within the plant. The cell wall plays an important role in cell division and cell elongation.
How plants uptake calcium is a critical part of understanding this nutrient. The xylem and phloem are the vascular system of the plant that transport water and nutrients throughout the plant. The xylem is a system of tubes that branch off from the roots and end in the leaves. This system is responsible for transporting water and dissolved minerals from the roots to the leaves. The phloem carries nutrients from the leaves to other parts of the plant.
This is just a brief explanation of the complex vascular system in plants. This process, known as active transport, requires the assistance of a protein called calmodulin. Calcium cations are taken up from young tissue in the roots in a process called active transport that requires the assistance of a protein called calmodulin. The xylem is a vessel that carries calcium to the plant from the roots. Young roots have more permeable membranes than older root tissues, making them key to the plant’s development.
Different plants require different amounts of calcium. This varies by the plant’s species and family. Grasses and other monocot plants require relatively low amounts of calcium. The crops in the brassica family that are grown in gardens require more calcium. Trees need the most calcium. This is because calcium is important in the formation of strong and sturdy trunks.
Spotting a Calcium Deficiency
It is important to know how calcium interacts with each plant when it comes to nutrient deficiencies. Some nutrients present similar deficiency characteristics on different parts of the plant. As an example, a deficiency may only be visible on old leaves and not new ones. These small details are important when diagnosing a deficiency.
An example of calcium deficiency would be blossom end rot in tomatoes. In this case, the bottom of the tomato appears to be rotting. Because calcium isn’t transferred well to the fruit, deficiencies are visible there.
Growing points also can display deficiency characteristics. New leaves may appear stuck together. If there is not enough calcium in the soil, roots may not grow as large as they should. It is easier to diagnose a deficiency by looking at the growing points and fruit than by examining the roots.
Calcium’s Role in the Soil
Calcium is critical for healthy soil structure. It is specifically important for a process called flocculation. In the flocculation process, clay particles are pulled together, separating from other soil particles. This results in the clay particles clumping together, and the soil becoming more dense. This is most easily seen in a basic home soil test, where the soil is mixed with water. The clays are grouped together and this causes the water to be less cloudy compared to soil that has fewer groups of clay.
Reducing sediment in runoff water can help to control erosion. Calcium is more effective than magnesium at holding clay particles together. This is because calcium has a +2 charge. Magnesium and calcium are often found together in many ways but they differ in their ability to function in plants and flocculation.
How Calcium Cycles
Calcium enters the soil in several ways. One way to break down minerals is by degrading minerals such as calcite, limestone, and dolomite. This calcium binds to clay and other minerals and makes them easier to weather. Other soil parent materials release calcium into the soil, which binds to clay and other minerals and makes them easier to weather. Calcium is a base cation critical in cation exchange. Cation exchange capacity is the measure of how many cations a soil can hold.
The process of exchanging cations occurs when calcium ions (or ions with a positive charge) swap places between the soil particle and the solution. There are many positive ions at play besides calcium, all of which vary in their ability to be exchanged. Plants absorb calcium from the soil through the process of cation exchange.
Another way calcium enters the soil is through atmospheric deposition. The atmosphere’s soot and ash deposits add calcium to the soil as they settle. Calcium can leave the soil in two ways. One way calcium is removed from soil is by leaching, as water washes away the calcium not attached to clay particles. Calcium is absorbed by plants through the roots and transported to the leaves.
Why Your Soil is Not Calcium Deficient
Seeing blossom end rot may make you think your soil is devoid of calcium. In most scenarios, this is not the case. Most soils have enough calcium to support the garden. One possible explanation for your blossom end rot is that you have not been watering your plants consistently or deeply enough.
Calcium is taken in by young plant roots through the water. When the plant cells in the roots mature, calcium absorption stops. Watering your plant consistently will allow calcium to enter it easily and make its way to the fruit. You’re unlikely to have a calcium deficiency in your garden because most soils and substrates contain calcium, and generic fertilizers also contain calcium.
If the soil is highly acidic, calcium may not be part of the soil structure. If the acidity of your soil is low enough (around 4.5 or below), aluminum toxicity (as well as iron and manganese toxicity) will occur. The calcium in the soil is not accessible to roots because it is being held onto clay particles.
This scenario is usually easy to pinpoint. If the pH of your soil is too low, it will limit the absorption of other minerals and nutrients, and your plants will not grow as well. A soil test is the best way to find out if your soil is lacking calcium.
Sandy soils that lack clay particles may also cause a deficiency of calcium. The soil in this area is very sandy, making it unlikely that crops would grow well here. Both acidic and sandy soils generally have low nutrient availability. The chances of trying to grow in either condition is slim.
Although it is rare, there can be too much calcium in some soils. The term “calcareous soils” refers to soils that contain high levels of calcium carbonate. These soils will not significantly hinder the healthy growth of plants because they have a pH above 8.0. Although calcium is not the reason for a high pH, it is important to take notice of it. Many people think that calcium is responsible for increasing the pH of soil, when in reality it is the carbonate that is found in lime that is responsible.
How to Add Calcium to Soil
There are a few ways to add calcium to the soil if you know that your soil needs calcium. There are two ways to add calcium to your plants – by buying soil amendments that will add calcium over time, or by buying foliar sprays for a quick boost.
Be sure to check the nutrient content of your granular calcium fertilizer before applying it to your garden, as many of these products also contain other necessary nutrients. If you want to know if your soil is lacking other nutrients, you should test it.
Do not forget that having too much of a good thing often results in a negative outcome.
Although you may believe that providing your plant with excess nitrogen will be beneficial, it is not the case. If you add too much nitrogen to your plants, it will either damage them or cause them to grow lots of leaves but not many fruits.
No one wants that!
There are many ways to add calcium to your garden soil. Some of the best methods include using limestone, bone meal, and gypsum.
- Use a Calcium Fertilizer
If you find that your plants are not getting enough calcium early in the season, a calcium fertilizer is a good option. It takes time for them to work into the soil and provide your plants with nutrients, but they also last the longest.
Before applying fertilizer, use a soil test to determine which nutrients your soil needs. Make sure the fertilizer will not increase a nutrient that is already present in abundance.
- Add Lime in the Fall
The best way to add calcium to your soil is to apply lime to it in the fall. You can buy calcium carbonate from most garden and farm stores. It is made from crushed limestone and is a powder.
Lime can alter the pH of soil, making it more alkaline. This can be a problem if not done properly.
I would recommend getting your soil tested to find out what your pH range is before using lime. Lime is a great source of calcium for your plants, so if your soil needs more calcium, lime is a great way to add it. However, if your soil is already close to being neutral, you won’t want to use lime.
If your soil is acidic and needs calcium, lime is a good choice for you.
If your soil lacks magnesium and calcium, try applying dolomite lime to the soil. Adding coffee grounds to your garden will not only provide it with essential nutrients, but it will also help to raise the pH level of the soil.
You’ll find plenty of garden lime choices. I’m a fan of Jobe’s Organics; their garden lime comes in a user-friendly bag at a reasonable price. It will increase the soil pH range.
Another option is to use Down to Earth Organic Garden Lime. This product comes in 5lb boxes and has been approved by the OMRI for use in organic agriculture.
- Use Eggshells
If you have a flock of chickens, you likely have an organic source of calcium in eggshells.
You can add eggshells to your compost to increase the calcium levels. This is safe to do and will improve your composting pile. You could also try putting eggshells in the hole where you plant your tomato seedlings to help prevent blossom end rot.
I prevented blossom end rot from happening to my tomatoes this year by taking action, and it’s been two years since any of my tomatoes have had the condition.
- Foliar Applications
If your plants lack calcium, you can try using foliar applications, which will cause the leaves to absorb the calcium. Foliar sprays are a great way to give your plants the nutrients they need because they are applied directly to the leaves. Calcium acetate, calcium nitrate, and calcium chloride are all great options for foliar sprays.
Foliar sprays help prevent blossom end rot by delivering calcium to the top of the plant where the blossoms develop. Foliar sprays are used by gardeners for another reason: they will not change the pH range of the soil like granular fertilizers will.
Apply a solution of 1/2 to 1 ounce of calcium chloride or calcium nitrate in one gallon of water to your plant.
My preferred option is Rot-Stop by Bonide. It comes in a concentrate and a ready-to-use spray. It only takes a little bit of time for this product to help your plants get a calcium boost. Another option for preventing blossom end rot is the Southern AG Stop Blossom End Rot concentrate. The container holds a large amount of the product, enough to last for an extended period of time.
- Apply Gypsum – Calcium Sulfate
If you don’t want to Change your soil’s pH range, adding gypsum is an excellent option. Gypsum is a mineral that contains calcium. It can be used to improve the soil by loosening it up and breaking it up.
Gypsum comes with many benefits for a garden.
It prevents the soil from crusting, water erosion, and helps young plants grow easier. Gypsum also helps to remove salt from the soil that could potentially inhibit plant growth. If you live in a coastal area with high salt content, you need something exactly like this.
Garden gypsum can be easily found and bought at most garden stores.
- Use Ground Oyster Shells – Calcium Carbonate
If you have chickens as I do, chances are you already have oyster shells, known as calcium carbonate, around your homestead. Adding oyster shells to your chicken’s diet is a great way to help them lay eggs with stronger shells.
Oyster shells can be used in your garden, but because they contain calcium, they will make the soil more alkaline.
Although oyster shells take a long time to break down, they don’t raise the pH of the environment as quickly as lime does. You will not be as benefited as you would have been if you had helped.
- Wood Ash – Calcium Carbonate
You can raise the calcium levels in your soil by adding wood ash from your fireplace or fire pit. Hardwood ashes contain twice as much calcium as ashes from softwoods.
Wood ash can also help to improve the fertility of your garden. It includes potassium, boron, and phosphorus, all of which are essential nutrients for plants.
Using this source of calcium has pros and cons. The item in question is free, and it also provides calcium to your soil naturally. You shouldn’t use it if your soil is at a neutral pH or slightly alkaline, because it will make the soil more alkaline.
You will need to use twice as much wood ashes as you would lime in order to achieve the same goal. Ensure the wood ash doesn’t come into contact with your plants; make a barrier around your plants because wood ash is corrosive and will damage them.
- Bone Meal
Organic gardeners love bone meal, myself included. This product is made from the bones of animals which is a fantastic source of calcium. This fertilizer contains nitrogen and phosphorus, so it is considered more balanced.
It should only be used on acidic soil.
Bone meal can help add calcium to the soil for up to four months. If you add the fertilizer at the beginning of the growing season, it will be enough for the whole season.
Bone meal is a great fertilizer for all types of plants, not just vegetables. Use it on flowering plants, bulbs, and root crops.
You can find bone meal at many garden stores and farm supply stores. It’s something all gardeners should have on hand. I usually use Down to Earth Organic Bone Meal; I only need one container for two gardening seasons.