A number of health and growth problems, such as blossom-end rot, in intensive crop production can be attributed to calcium (Ca) deficiency in the plants being cultivated. This is despite Ca being the fifth most abundant element in the Earth’s crust.
Intensive crop farmers who do not effectively address Ca availability in their crops will lose yield and quality, their production costs will increase, and their enterprise profitability will decrease.
Heather Raymond, plant health expert at Tsama Agricultural Agencies, says that without Ca, life as we know it would be impossible.
“Ca is essential for structure in soils, animals and plants, and for the strong growth of both plants and animals. It belongs to the group of secondary nutrients that are generally needed in lesser amounts than nitrogen (N), phosphorous (P) and potassium (K), but are just as important to the crop,” says Raymond.
She adds that Ca is typically found in soils as CaCO3 (calcium carbonate), CaSO4 (calcium sulphate) and apatite.
The effect of Ca in soils is that it flocculates clays and organic matter, thereby increasing soil porosity, improving air and moisture movement through the soil, enhancing soil biology, and promoting root growth within the soil.
Certain Ca compounds also neutralise excess acidity or alkalinity in soils. This helps improve plant roots’ uptake of other nutrients from the soil.
“It is known that soil pH affects the efficiency of N:P:K in soils. Their efficiency is greatly reduced in acidic soils. In extremely acidic soils of water pH 4,5 or less, about 71% of the soil-applied N:P:K fertiliser becomes unavailable for uptake by plant roots,” says Raymond.
“By increasing soil pH to water pH of 5,5, fertiliser efficiency increases to nearly 80% for N and K, and to 50% for P. At neutral water pH of 7,0, fertiliser efficiency should theoretically reach 100%.”
Low soil calcium levels
There are many causes of low Ca levels in some soils, including if the parent rock contained low Ca levels. Low soil Ca levels may also be the result of over-irrigating soils that have a low cation exchange capacity (CEC), causing Ca to leach out of the soil profile.
In this particular case, it is important for the soil manager to regularly monitor the soil’s Ca levels and to appropriately replace any shortfalls.
Raymond adds that excess nitrates and sulphates in soils can also have a negative impact on the quantity and plant-availability of Ca in these soils.
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