From http://www.sciencemag.org/cgi/data/328/5986/1638/DC1/1
"It has pretty much become a given that grain crops, such as wheat and barley, need to be started from scratch every spring...There are such things as perennial grains, however - plants that, like the grass in your lawn, simply pick up in the spring where they left off in the fall.
'Increased Food and Ecosystem Security via Perennial Grains' points out that perennials have longer growing seasons and longer, denser roots than annuals. Those longer roots, which can reach down 10 to 12 feet, allow the crops to reach and hold more water and nutrients, reduce erosion, and condition the soil.
Annual crops, by contrast, are said to lose five times as much water as perennials, and 35 times as much nitrate - a plant nutrient that regularly leaches out of fields and pollutes waterways. Needless to say, annual crops also involve the rearing, transportation, purchase and sowing of seeds every year, which leaves definite carbon, chemical and financial footprints."
Those of you with a subscription or academic database access will find the paper in the latest issue of Science, the journal of the AAAS (American Association for the Advancement of Science). You can find a summary here and supporting online materials here, both outside the paywall.
Such thinking is not completely new. Anne Simon Moffat wrote on the topic in 1996. "It is possible to boost dramatically the seed yields of at least some perennials, including cousins to corn and wheat. These studies may eventually lead to new, more environmentally friendly crops." (Moffatt, A. (1996) Science, 29 November 1996, Vol. 274. no. 5292, pp. 1469 - 1470 DOI: 10.1126/science.274.5292.1469)
So, will "Big Agriculture" aggressively pursue the development of crops that will reduce the need for annual seeding, fertilizer, pesticides, and herbicides? Time will tell.