HAYS, Kan. -- The search is on for the best energy source to heat our homes and power our vehicles of the future, and fuels from plants, also called biomass energy sources, are among the options researchers are studying.

Among the many questions still to be answered, however, are what crops will work best, and on what land should they be grown?

What land to use?

"Growing energy crops on prime agricultural land is not a sustainable option because it can compete with food production and increase concerns about land clearing," said Kansas State University soil scientist Humberto Blanco.

"One of the most viable options for growing energy crops can be the use of marginal and abandoned lands. Lands currently enrolled in the USDA's Conservation Reserve Program are potential candidates for growing cellulosic biomass that can be turned into fuel," said Blanco, who is a researcher based at K-State's Western Agricultural Research Center at Hays.

He, along with K-State Research and Extension agronomist Alan Schlegel, have recently synthesized published information on the impacts that converting CRP lands to grain crop production and "energy crops" may have on soil quality, soil carbon sequestration, and water and wind erosion. Schlegel is based in Tribune, Kan.

The CRP was established under the Food Security Act in 1985 to reduce water and wind erosion of soil on marginal or degraded croplands. Landowners voluntarily enroll their land in the CRP for 10 to 15 years and receive annual payments in addition to 50 percent cost-share provided by the program for establishing standard conservation practices on the land enrolled.

Of the states with acreage enrolled in CRP, Texas ranks first, followed by Montana, Kansas, North Dakota, Colorado and others. The largest concentration of CRP lands is in the Great Plains, which comprise about 45 percent of the total land area in CRP. CRP-enrolled land area represents about 8 percent of the farmland in the United States.

"The benefits of CRP for reducing water and wind erosion have been widely recognized," said Blanco, and studies also suggest that CRP has made soils a sink rather than a source of atmospheric carbon -- an added bonus.

But wouldn't growing dedicated bioenergy crops on former CRP land reverse the good that the CRP accomplished in reducing erosion and sequestering carbon? Not necessarily, Blanco said, adding that it can depend on the energy crop grown and other factors.

Which crop?

Corn stover -- the leaves and stalks of the corn plant -- is under consideration as one of the main feedstock sources for producing cellulosic ethanol, Blanco said. But indiscriminate and large-scale removal of crop residues such as corn stover can harm the soil and the environment. In addition, corn is an annual crop that requires planting every year.

For that reason, scientists are also looking for sustainable alternatives that would not involve removing crop residue for biofuel production, he said.

"Unlike crop residue removal, growing perennial grasses and trees has the potential to provide many ecosystem services including water and wind erosion control, soil organic carbon sequestration, and improvement of soil properties which supplying feedstocks for cellulosic ethanol production," he said.

The researcher indicated that growing perennial warm season grasses on retired CRP lands for production of biofuel feedstocks may be an alternative to converting them into grain crop production. Unlike conversion of CRP to grain crops under conventional tillage, growing perennial warm season grasses would maintain the soil and environmental benefits from CRP, Blanco said.

He suggested two options for the management of CRP lands, which could result in a net increase in soil organic carbon sequestration, reduced greenhouse gas emissions, and improved soil and water quality.

"The first option is to intensively manage the existing CRP lands with proper biomass harvest frequency, cutting heights, and additions of manure" Blanco said. "This would preserve the existing grass mixtures in the CRP lands. Because returning CRP lands to crop production can be difficult, due to the large accumulation of plant residues on the soil surface in some CRP lands, enhanced management for biomass production might be a better alternative to cultivation of CRP lands."

"The second option is to plant native warm season grasses or monocultures of perennials into the existing CRP lands," he said. "Recropping CRP lands with grasses such as switchgrass is a possible option. Depending on the region and climate, short-rotation woody crops or fast-growing trees such as hybrid poplars and willow can also be grown on some CRP lands.

Studies have shown that ethanol yields from perennials grown on marginal lands can be greater than yields from corn stover, he added.

"Because of their greater effectiveness for controlling soil erosion than grain crops, perennials may allow application of larger amounts of manure without increasing risks of water pollution," Blanco said. "Growing dedicated energy crops (e.g., switchgrass) on former CRP lands under intensive management can provide biofuel feedstocks and sequester soil organic carbon while improving soil properties and reducing water and wind erosion."

He acknowledged that scientists are a long way from having definitive answers to the myriad questions surrounding biomass energy production, including the type of land on which such production should occur.

While there are many published studies that assess the impacts of cropland conversion to CRP on soil and the environment, Blanco there are few studies assessing the impacts of converting CRP to croplands. The few that have been done indicate that reverting CRP land to crop production can adversely impact the soil and environment, particularly if these lands are intensively plowed. Converting CRP lands following retirement to dedicated energy crops may thus be a potential option, which needs to be looked at more in detail.

SOURCE: K-State.