@rotor, this won't answer your specific question, but this is what I do. I feel the planting guides are a bit ambitious, so I don't put as many plants in the Earthboxes as they suggest. Last year I staggered 3 okra plants in a triangle fashion, and the roots filled the box. Earthbox says eight to a box!
For tomatoes, I plant one tomato and one basil in the box. I only planted tomatos, okra and lettuces in boxes until this year, as I had my peppers in 5 gallon buckets last year. This year I had only planned to plant four peppers in one box, but I had a plant left over, so I added it because I hated to throw it away. I think four would have been better, but we'll see.
Aside from air flow and diseases, also remember some plants have very extensive root systems that compete for soil space and nutrients, so crowding in the soil itself is also a factor. Sometimes there is no exact right or wrong answer, but judgment and experimentation will determine your results.
Check out Next Level Gardening and Gary Pilarchik (The Rusted Garden) on YouTube for ideas on battling diseases. One of their homemade sprays (peroxide and water) stopped a disease for me just last month that was spreading on my tomatoes. They have lots of info. Best wishes for a great garden this year.
