Dry land is obviously already a problem, and it seems the problem is only going to increase in North America and elsewhere. I'd never run across this tractor attachment before - or perhaps it hadn't caught my attention until now - but it seems impressive, and essentially simple. "Land Imprinter". Watch this video for the basic intro: https://www.youtube.com/watch?v=-ju4mkQAUMI
Here is a page depicting a small-homestead scale version of the imprinter: http://opensourceecology.org/wiki/Land_Imprinting
The imprinter was developed into some small demonstration models that could be pulled by a small tractor (as shown in the page above), and also into very substantial larger models for treating large-scale fields or projects. Here is a Wikipedia page about the Imprinter - says it was patented a few decades ago, but the design is now in public domain: https://en.wikipedia.org/wiki/Land_imprinter