Tomato - Blossom End Rot
Management options by Alan Walters (SIU):
Try to maintain constant soil moisture from proper irrigation practices or use of some type of mulch (e.g., wheat straw) to cover the soil surface. Timely irrigation scheduling is important to maintain a constant and steady moisture level in soil, but often times this is impossible in Afghanistan. Mulching of the soil is important to maintain constant soil water during times of moisture stress.
When cultivation is necessary (e.g., for weed control), do not cultivate too close to plants or go too deep in the soil profile, so that feeder roots are not injured. If roots are pruned to some extent, this will provide less water and calcium uptake which can increase the incidence of blossom-end rot.
It is best to use nitrate nitrogen (NO3-) as the N source, since the ammonium form (NH4+) may increase blossom-end rot. Excess ammonium ions in the soil compete with calcium ions (Ca2+) for uptake which can reduce calcium ion uptake. The primarily types of fertilizers used in Afghanistan are animal manures, Diammonium phosphate (DAP), and Urea. Under optimal soil moisture (e.g., soil at field capacity) and temperature (about 85oF), the use of DAP provides a quicker process through Nitrification to produce NO3- than either Urea or animal manures.
Tomatoes planted early in cold soils are likely to develop blossom-end rot on the first fruits due to limited calcium uptake, and the severity often diminishes on later setting fruit. Thus, planting tomatoes in warmer soils will often alleviate the problem of blossom-end rot.
It is also important to understand that this disorder does not spread from plant to plant in the field or from fruit to fruit in transit. Since it is of a physiological nature, fungicides and bactericides are useless as control measures.
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