3 June 2009

Ethanol production degrading soil productivity

by Kate Melville

Crop residues are viewed as a low cost and readily available source of material for ethanol production. But these residues are not simply a waste material as they play a pivotal role in sustaining levels of organic matter in soil. Consequently, extensive removal of crop residues for ethanol production - or for other industrial purposes - may impact the long-term productivity of soils.

Agriculture and Agri-Food Canada scientists reached this worrying conclusion after long-term research efforts at the Indian Head Research Farm in Indian Head and the Semiarid Prairie Agricultural Research Centre in Swift Current (both located in Saskatchewan).

The researchers measured the impact of straw removal after 50 years on soil organic carbon (SOC) and soil organic nitrogen (SON) using the Indian Head Long-Term Rotations established in 1958. These rotations included a series of fallow-spring wheat-spring wheat crop sequences where straw was removed through baling on selected plots. In this study, straw removal with baling occurred 2 years out of 3. The study was converted to no-till in 1991.

Another 4-year study was conducted to quantify how much wheat straw is actually removed through baling when different harvesting systems are used. The three harvesting/straw removal systems involved (1) swathing-harvesting-baling, (2) straight harvesting-baling, and (3) harvesting with a stripper header-swathing-baling.

"The results would support the recommendation that some straw could be removed from fields providing that the frequency of removal was less than 66 percent and that no more than 40 percent of the aboveground residues other than grain are removed. From a crop management perspective, proper nitrogen fertility combined with no-till would further reduce the possibility of net losses in SOC and SON," the researchers noted.

The findings from these experiments have been published in Agronomy Journal. Research is ongoing to examine different types of crops for not only their grain and end-use quality but also for their crop residue production and quality.

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Source: American Society of Agronomy