This is my third year as a gardener. I'm all about trial and testing even though the risk is increased for mistakes and disasters. The results in this test are 50/50. In one 50 Gallon fabric pot, I added enough soil to fill 3/4 of the pot. In the other pot, I filled it to about 1/3.
For the pot with more soil, I planted beets and onions because the roots would need enough room to grow. As time went on, there was enough space between crops to add one lettuce. I purposely mixed a root + a green vegetable to see how they would grow sharing the same pot. It worked! The pot on the left grew great big, healthy beets, onions, and lettuce.
For the pot with 1/3 soil, I reserved that one for radishes since the seed packet stated it only need 4" of soil. That's the pot on the right. Though it was lush green, there were no radishes. For some reason in zone 10, I've been unsuccessful with radishes each time since I started planting. I've planted in the fall, winter, in the greenhouse, outside and each time attracts a tone of aphids. The crop did not go to waste. My mom made super green smoothies for about two months and I made some pesto out of it.
Lesson learned? Fill 3/4 of the pot and combine vegetable groups with enough space in between and consider the height of each crop when planting next to each other.