So, I've read that doing foliar sprays with various acids can increase salt tolerance. I'm guessing that refers to the salt index. I just got the idea that maybe you could use foliar acid sprays in conjunction with more fertilizer in the soil to get the plant to tolerate more fertilizer. I don't know that you would need to do this by any means, but it might be helpful in some contexts.

Humic acid is supposed to increase nutrient uptake.