 If you want to foliar feed, it's a good idea to look at soil tests and tissue tests first. If your crop starts running low on a nutrient, you can certainly foliar apply most nutrients like nitrogen, sulfur, or the micronutrients. Phosphorus, on the other hand, doesn't go into the plant well through leaf tissue, so we like to see that addressed in the soil. The other big key is to spray earlier rather than later.