Wednesday, 4 May 2011

Perennial wheat?

An article in a recent edition of National Geographic magazine caught my eye.  'The Big Idea: Perennial Grains' describes work being undertaken by the Land Institute and the United States Department of Agriculture (USDA) researchers at Cornell University into developing high-yielding varieties of perennial cereals.

Many of the original species and varieties from which modern crops such as wheat, rice, maize and many other agricultural cereals and vegetables were bred grew as perennial plants.  But, 10,000 years ago, humans made the choice to domesticate annual varieties which die after producing seeds.

Neolithic farmers found that they could rapidly make these varieties better, for instance by replanting the bigger seeds from the more vigorous plants, thus leading to higher and higher yields.  However, perennials didn't benefit from that kind of selective breeding, because they don't need to be replanted.

Researchers today, however, are trying to breed perennial wheat, rice, and other grains.  They are now crossing modern grains with wild perennial relatives to produce plants which have the advantage of perennials – the dense and deep root systems which enable the plants to come back to life each spring as well as allowing exploitation of more of the water and nutrients throughout the entire soil profile – without sacrificing too much of the high yields associated with modern grains.

According to the article, modern, annual cereals can contribute to soil degradation by depleting the topsoil leading to reliance on large quantities of imported, often mineral, fertilisers to maintain high yields. And large fertiliser applications can generate their own environmental problems, such as water pollution.  In addition, leaving the soil bare before and after drilling annual crops can lead to weed invasions.  The main problem highlighted, however, is the erosion of the soil associated with cultivations.  In the US around 1.7 billion tonnes of soil is lost each year, and one estimate suggests that the rate of soil erosion globally at ten to a hundred times the rate of soil formation.

The report argues that perennial cereals would help to address many of these problems, by keeping the ground covered, reducing the need for pesticides, and their deep roots would stabilize the soil and make the grains more suitable for marginal lands.  Their deep roots would also make better us of water and nutrients from deeper in the soil profile.

Yields, however, are still too low to compare with those in the US, but not necessarily with poorer parts of the world, such as Nepal, where yields are lower.  The researchers are optimistic that with the use of cheap DNA sequencing, field-testable perennial maize could be available within ten years.