Blossom End Rot of Tomato
Cultural techniques that can be used to reduce the incidence of blossom end rot:
Prevent drought stress on plants by providing at least 1 inch of water per week, and greater amounts for plants in sandy soils or during very hot, dry conditions. Use an organic mulch like wood chips, clean straw, pine straw, peat moss, compost, herbicide-free grass clippings to preserve soil moisture. Avoid excess fertilization, especially with ammoniacal nitrogen sources. Foliar applications of calcium have little effect on this condition, due to the poor absorption and movement of calcium from the leaves to the fruits.