Question: I'm have nice healthy looking plants but most of the fruits turning yellow and rotting. I read somewhere this is from being calcium deficient. Do you agree and what would be the best way to add calcium?
Hardiness Zone: 6b
Thanks
Tom from Long Island, NY
Answer: Tom,
It sounds like you're experiencing blossom end rot. I do agree this can be caused by a calcium deficiency in your plants, but probably not in the way you think. The calcium deficiency doesn't usually occur in the soil; rather it's usually caused by the plant's inability to take up calcium from the soil. This is most often the result of sudden fluctuations in water (sudden water uptake following a drought), but it can also be due to high nitrogen or magnesium levels in the soil or happen after a period of rapid growth. Here's why.
Calcium in the soil is dissolved by water and taken up by the plant's roots. In conditions of high moisture stress (like lots of rain or overwatering), water and the dissolved calcium is taken up rapidly by the plant's vascular tissue and moves more quickly than usual from the plant's roots to its leaves. Because a plant loses most of its water through the leaves due to transpiration, after a sudden uptake of water, the majority of calcium taken up with it gets left behind (deposited) in the leaves, before it can be evenly distributed throughout the plant. Because most of the calcium remains deposited in the leaves, it causes a localized deficiency of calcium in the fruit. Eventually the cells in the fruit start to collapse, producing the symptoms of blossom-end rot. Blossom-end rot can also occur in plants experiencing rapid leaf growth due to over-fertilization (especially with nitrogen). This is because the growth of larger leaves increases the amount of surface area available for transpiration to occur, throwing the plant's calcium distribution system off balance.
To prevent blossom-end rot, try to keep the proper soil pH. This will enable your plant's vascular system to take up nutrients properly. (Most vegetables need a pH ranging from 6.0 to 6.8) You should also avoid excessive amounts of nitrogen fertilizer. This can lead to vigorous growth in the short term, but lead to blossom-end rot later.
Try to keep plants on a consistent watering schedule. Apply mulch to help prevent your soil from drying out and keep your plants from experiencing the stress brought on by sudden changes in moisture.
Calcium deficiencies are rarely a soil problem, so before adding any calcium to your soil, you'll want to perform a soil test. If you find out that your soil is deficient in calcium, you can increase its calcium content by adding dolomitic lime or manure.
Ellen
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