If the land is fertile it might make sense to use it (while keeping it fertile) before it turns to desert and the top soil blows away.

I wasn't suggesting we stop farming.

Rather, there's a lot of ways that modern industrial farming isn't as efficient as it could be. A lot of farms farm by brute force: Plant a ton of seeds, spray a ton of fertilizer, blow a ton of water on the fields and hope for the best.

It's how we end up with huge numbers of algal blooms in the waterways - fertilizer runoff is massive in most areas.