Side-Dressing

If I were the "perfect" "organic" farmer, I would have beautiful black loam out there with huge and healthy plants sticking insect free out of it, but I'm a science grad student, so I have clay soil with bits of wood chips and decaying leaves sticking out, and some plants thriving, with others struggling. My green bean plants have something going on that is causing some yellowing of some lower leaves, with thinning between the veins. I thought it was a fungal infection, but I see no white or black or reddish brown. It could be a micronutrient deficiency like magnesium or manganese or boron (my soil was low in boron on the tests). These minerals are important in tiny amounts for all living things, for the active centers of enzymes. When you eat plants, you get these nutrients by breaking down their enzymes and building your own for your own purposes.

I decided to side-dress the plants (put fertilizer on the ground close to them, trying not to hit the leaves, to be watered in by the next rain) to try to solve the problem with a 5-3-3 fertilizer (not terribly high in NPK) with lots of micronutrients in it. I hope it helps.