I'm in zone 10 and my onion plants have been in the ground since early December and are probably a month or two away from maturity. They are planted in two 20 foot long rows with a fertilizer trench in between. Because I'm a backyard gardener and have limited space in the direct sun, I'd really like to use this area to put my tomatoes. I was thinking I could just plant them in the trench between the onions and simply keep the fertilizer away from the plant stems. Good idea? Bad idea? Pros/cons?