Tomato Blossom End Rot

[Frank]

A response and follow-up to an article appearing in Mother Earth News:
http://www.texasplantandsoillab.com/lab-testing/?p=1078

[Brian Gallimore]

Good stuff Frank! 

Question:
for the layperson (non titrate literate) what would be a typical mixture of Borax, soap, and water for a foliar spray?

[Frank]

Brian - You've asked a bit of a tricky question.  As you know, you can get into trouble with too much of any good thing.  In the case of the micronutrients and trace elements, too much isn't much to get into trouble.  Generally, soils high in Calcium are low in Boron.  But if the soils are also low in Organic Matter, Boron deficiency is endemic.  I presented your question to our Technical Director at TWGGA last week.  With the understanding that we do not like to give blanket recommendations without knowing the particulars about the soil and crop, herewith his response:  

For a foliar spray: two gallons of spray mix per 100 square feet - Adjust the pH of two gallons of water to 6.6 - 6.7 using vinegar (assuming alkaline water - as is generally seen in north Texas) .  This is necessary to break the hardness as Calcium ties up Boron.  Dissolve 2 to 3 tablespoons of Borax in the  water.  Add two tablespoons of humic or fulvic acid and/or molasses as a buffer.  Do not add soap, as Borax is already a surfactant.  Repeat two or three times at two-week intervals.

For a 100 square foot soil application: Correct the pH of two gallons of water as per above.  Dissolve five tablespoons of Borax into the water and apply to the soil ONLY.  Initially, apply only once a season.

Caveats: Plants have varying sensitivities to Boron.  The sensitivity is generally tied to a plant's demand for Calcium - the higher the Calcium demand, the less sensitive to Boron.  Organic Matter holds Boron.  Accordingly, too frequent applications of soil-applied Boron can result in a toxic buildup.  However, if the soil is calcareous, the Boron can be tied-up before much of it reaches the Organic Matter.

Without knowing anything about your soil in particular, we're walking on kind of thin ice with all this.  It is very easy to overdo it and Boron recommendations depend much upon soil chemistry, Organic Matter content and existing levels of Boron.  This is why we urge growers to get their soils tested at least once and preferably twice a year.  Guessing can get one into a lot of trouble.

We have a paper on Boron that goes into much more detail than mentioned here at http://asktheplant.com/?p=779

Hope this helps.