Answer: Blossom-end rot of tomatoes is a physiological disorder caused by a lack of sufficient calcium in the blossom end of the fruit. This disorder results in the decay of tomato fruits on their blossom end. Dry brown or tan areas the size of a dime, that grow to the size of a half dollar, characterize this disorder. This disorder is usually most severe following extremes in soil moisture (either too dry or too wet).
Tomatoes affected by blossom end rot grow slowly and often ripen prematurely. Under certain conditions the outward symptoms may be suppressed almost entirely, while the inner tissue near the blossom end is completely discolored and collapsed. Blossom end rot is most frequently observed on fruit that is 1/2 to 2/3 its mature size.
Maintain a uniform supply of soil moisture by watering plants during drought and mulching to retain soil moisture.
Avoid using excessive amounts of ammonia forms of nitrogen, which reduce calcium uptake. Use nitrate forms of nitrogen instead. Avoid overfertilization during early fruiting.
Light applications of fertilizers high in superphosphate will aid in reducing blossom end rot.
Maintain a soil pH of approximately 6.5. Liming helps supply calcium.
Do not subject plants to sudden and severe hardening before transplanting.
Avoid setting plants in the field too early when the soil is still too cold for rapid growth.
In cultivated fields, cultivate plants to a shallow depth to avoid root injury.
Foliar applications of calcium can be used but they are not always effective.
Regarding your question about fertilizers, the numbers indicate a low nitrogen, high phosphorous, low potassium formulation. This type of fertilizer is to encourage flowering and you can usually find it in the garden section, either for flowering ornamental plants or for vegetables.
Best wishes with your garden!
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