Agriculture Reference
In-Depth Information
Calcium
Calcium is one of the most important minerals for both plants and microbes, probably
the
most important. Yet we know there's really no such thing as one mineral being the most
important, because they're all important. Interestingly, it
is
the most needed element by
weight and volume for plants, and without sufficient calcium, nothing works. While nitro-
gen and potassium get a lot of attention, more and more focus is being put on calcium, par-
ticularly in organic horticulture.
Calcium helps plant cells communicate with each other by physically moving between
cell membranes. Not only is it integral in the basic structure of plants, with a deficiency of-
ten showing up as thick, woody stems, it's largely responsible for the availability of nutri-
ents in plants and has a strong influence on microbial activity. In the topic
Mainline Farm-
ing For Century 21
, Dan Skow says “calcium is essential for its energy creation potential in
the soil to release the other elements that cause a plant to grow.”
With enough calcium, roots and fine root hairs proliferate, stimulating soil microbes and
building humus. This means that without enough calcium in the soil plants can't access or
utilize nutrients very well. Likewise, foliar fertilizers and microbial inoculants will have
little effect if there's a major calcium deficiency. You can waste a lot of time and money on
fertilization if you don't have sufficient calcium.
We're looking for 60-75% calcium on a base saturation test, and a 10:1 calcium to mag-
nesium ratio with a minimum of 2,000 pounds per acre of available calcium on a Reams
test. This goes down to 60% and 7:1 for grasses/grains and very sandy soil. If your calcium
is less than 60% on a base saturation test or 2,000 pounds per acre on a Reams test, there's
a good chance your soil will be compacted and riddled with grassy weeds, your soil food
web will be unhealthy, your plants will be sick, and your fruit will be weak and easily
bruised. This can happen even if you have enough total calcium, but your calcium to mag-
nesium ratio is less than 7:1 on a Reams test. In fact, the list of things that fall into place
when the calcium to magnesium ratio is in line is really too long to put down here.
Microbes need this ratio to be in line in order to create a soil that is free of compaction.
The microbes need to be there in order for the calcium to be available, too. You can pile on
bags and bags of calcium and you won't get anywhere if you don't have the humus and mi-
crobes to make use of it.
A calcium shortage needs to be improved before other nutrient ratios will be fixed. For
example, adding sulfur in the form of gypsum or ammonium sulfate can bind with excess
magnesium and leach it, but you need sufficient calcium for this to happen efficiently. Cal-
cium is associated with nitrogen fixation and amino acid formation, so low calcium means
the nitrogen cycle in the soil will also be less efficient and nitrogen will more easily leach.
