Calcium Products - Blossom-End Rot
Calcium Product 98G


Blossom-End Rot

We have received a number of phone calls recently on SuperCal SO4 and SuperCal 98G for tomatoes. SuperCal SO4 is the best product on the market to eleminate blossom-end rot. As always start with a proper soil analysis, then add fertilizers and amendments as need.

Blossom end rot:

Blossom-end rot is a nonparasitic disease of tomato, pepper and watermelon. Losses can vary from a trace to more than 50%.


The first symptom is a slight water-soaked area on or near the blossom end of the fruit. The affected area soon darkens and enlarges in a constantly widening circle until the fruit begins to ripen. The tissues are dark and shrunken and have a dry, leathery appearance. With pepper the rot is tan in color and should not be confused with sunscald, which is white. The affected area may be merely a speck or it may involve half or more of the fruit. Secondary microorganisms may grow on the decayed area.


Blossom end rot is caused by a lack of calcium in the developing fruit. This may be due to a lack of calcium uptake from the soil or to extreme fluctuations in water supply. Incidence of blossom-end rot is also increased where there is a low ratio of calcium to certain other nutrients such as potassium and nitrogen.


Although the most desirable calcium levels for preventing blossom-end rot have not been determined, the application of lime (SuperCal 98G) to fields known to be low in calcium has helped to prevent the disease. Soil should be limed according to recommendations of soil analysis report, usually to pH 6.5-6.8. The use of gypsum (SuperCal SO4), at rates of 500 to 1000 pounds per acre (1 to 2 pounds per 100 square feet) can be be used at all soil pH's.

SuperCal 98G and SuperCal SO4 can be applied 2 weeks in advance of planting due to the fineness of the base material. Other lime and gypsum materials may need to be applied months in advance.




The Blogronomist is maintained by Craig Dick, head blogronomist and VP of Sales and Marketing. Here you will find a wide array of blog articles from Craig and expert guests on topics related to soil and crop health, farming, and so much more. If it’s not here, ask us!

Additional Info

  • Article Reference:: Calcium Products, Inc.
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