We have to switch from grain agriculture.

It's more like we need to switch how we farm our grains:

The future is Green: Perennial Polyculture Farming

For three decades, the Land Institute has been working to create a sustainable system of agriculture that is patterned after nature itself, that is, in the words of Director Wes Jackson, "more resilient to human folly."

In Jackson's eyes, modern agriculture wages war on nature. Every year erosion eats away 5.5 tons of soil for every acre of farmland in the U.S. Petrochemical based fertilizers and pesticides kill the soils fertility.

The land Institute's Kansas farm is working to reverse this damage by developing cropping systems that mimic the prairie. Rather than planting annual crops, Jackson and the Institute are developing perennial crops that need no plowing or planting. A farm that looked like the prairie would require fewer inputs by farmers, allowing them to keep more of the profit. It would feature a mixture of crops that could be harvested from the early spring to late fall; and perhaps most importantly, it would regenerate the soil into a thriving ecosystem.

The main problem farming with perennials is that they must devote more energy into building a larger root system and have less energy for growing seeds, thus have a lower food yield. Researchers at the Land Institute and several universities are searching for varieties of perennials whose yields can compete with annual crops. The Land Institute has had some success with wheat, sorghum, and sunflowers by cross breeding perennial strains with annual strains. Some lines of wheat have been developed that yield 70% of the best annual varieties. Perennials are hardier than annuals and more resistant to weeds once they are established. In addition they contain stronger resistance to disease. A polycrop field, imitating the prairie, further increases resistance to disease since each type of plant is further separated making the spread of disease more difficult.