Tina is right, the deeper the tomato plant...the stronger it grows.
If you have access to some freshly caught Fish you might want to try digging your hole a tad deeper , drop a small or halfe a bigger fish into the hole , handfull of lime over the Fish , some soil with a wee bit of slow release fertiliser , soil and then the plant.
Did so this year and most plants strong healthy and loaded with Fruit..