Sustainable Agriculture: Perennial Plants Produce More; Landscape Diversity Creates Habitat for Pest Enemies

Advances in ecology increasingly reveal that conventional agricultural practices have detrimental effects on the landscape ecology, creating problems for long-term sustainability of crops. In a series of sessions at the Ecological Society of America's Annual Meeting, ecologists will present their ideas on how our agricultural practices can take lessons from natural environments.

The major crops used globally to feed people and livestock - wheat, rice, maize and soy - are based on an annual system, in which crop plants live one year, are harvested, and are replanted the following year. These systems are notorious, however, for stripping organic nutrients from soils over time.

Perennial systems, on the other hand, contain plants that live longer than one year despite being harvested annually. Many agricultural scientists, including Jerry Glover of The Land Institute, say that perennial crops are the key to creating more sustainable agricultural systems.

"Across agricultural history, we've fundamentally relied on annual grain crops," Glover says. "But at the same time we rely on them, they're degrading the ecosystems they're in, which reduces their productivity."

To compare the long-term sustainability of these two cropping systems, Glover and his colleagues conducted a study on the physical, biological and chemical differences between annual wheat fields and perennial grass fields in Kansas. The fields had each been harvested annually for the past 75 years.

In each test, the researchers found perennial fields to be healthier and more sustainable ecosystems. In the perennial fields, the plants' total root mass was more than seven times that of the annuals, and the roots infiltrated about a foot deeper into the ground. The perennial fields also had higher soil microbe biodiversity and higher levels of dissolved carbon and nitrogen in the soil. All these findings, says Glover, suggest that the perennial field soil is healthy enough to maintain high levels of organic nutrients.

In addition to being more ecologically sustainable, Glover's team found that the perennial fields were more energy-efficient in providing productive harvests. Although only the annual fields received yearly fertilizer inputs, the perennial fields yielded 23 percent more nitrogen harvested over the 75 years, despite requiring only 8 percent of the energy inputs in the field - such as fertilizer and harvesting operations - as the annual systems.

Glover says that these results clearly show the need to move away from annual crops and increase our use and domestication of perennial crops.

"So far, little effort has been made to improve perennial crops," he says. "Some of greatest possibilities for transforming agriculture may well come from overlooked systems such as perennial grasses."

Source:
Ecological Society of America (2009). Sustainable Agriculture: Perennial Plants Produce More; Landscape Diversity Creates Habitat For Pest Enemies. ScienceDaily. Retrieved January 5, 2010, from http://www.sciencedaily.com­ /releases/2009/08/090804071358.htm


Posted August 2009