Anywhere I can find, the no-till fields have better water retention.

http://southwestfarmpress.com/mag/farming_moisture_retention_advantage/

http://www.sunflowernsa.com/magazine/details.asp?ID=212&Cat=2

I guess that a good example would be water runoff in rivers near uncultivated and cultivated areas. Near farm fields the water is coloured from soil and overflows river banks. Near an uncultivated area the runoff is less (but runs for a longer period) and the water is clear.

Dan O.