When crops are foliar sprayed regularly through the growing season, managing spray solution electrical conductivity (EC) becomes very important.
If crops are only sprayed two or three times in a growing season, it is possible to apply a very concentrated product solution, and only observe positive crop responses. Growers regularly fly on spray solutions that were as much as 50%-70% high EC products with only 30%-50% water at a rate of 3-4 gallons of total solution per acre, with very good results.
When higher value crops are sprayed every 7-14 days through the growing season, managing the solution EC becomes important. When the electrical conductivity of the spray solution becomes higher than 3800 microsiemens (or 3.8 millisiemens), plants seem to not respond as well and absorb nutrients less readily from later applications. I don’t know why this is the case, but a lot of experience indicates this is something we must pay attention to.
It is critical to only use water that is known and tested to be clean, that does not contain bicarbonates above 70 ppm total mineral content.