Probably not, at first. Dirt doesn't taste anything like a ham sandwich. But all food comes from dirt, either directly or indirectly.
Corn grows in the ground and milk comes from a cow, which eats hay that also grows in the ground.
By tracing lunch ingredients back to dirt students can see their place in the farm food web. As after-lunch movement picks up, gather students around the felt board. Ask them what they ate for lunch. Challenge disbelievers to think of something they ate for lunch that didn't come from dirt. We eat plants and animals that depend on dirt for survival.