Lavender

As a perennial plant with nutritional, horticultural and medicinal uses, lavender fields help build soil, feed pollinators, and reduce the need for yearly tilling. In general, perennial crops are a boon to soil health and reduced greenhouse gasses. One great agricultural advance would be the development of perennial grains such as wheat and rice that wouldn’t need to be sown and plowed every season.

http://www.perennialsolutions.org/perennial-farming-systems-organic-agriculture-edible-permaculture-eric-toensmeier-large-scale-farmland.html