Reaping More Rewards from Crop Residues
By Ann Perry
June 12, 2009
Wheat and barley producers in
Washington State's Palouse region can refine crop residue management to build
soil organic matter, curb soil erosion, retain soil moisture and maximize crop
yields, thanks to support from the Agricultural Research Service (ARS).
ARS soil scientist
Kennedy and Tami Stubbs of Washington State
University (WSU) worked with other WSU and ARS colleagues to conduct a
two-year study of post-harvest crop residues to identify links between
decomposition processes and fiber and nutrient characteristics of the straw.
Kennedy works at the
Land Management and Water Conservation Research Unit in Pullman, Wash.
The researchers looked at residues from 17 cultivars of winter wheat, 16
cultivars of spring wheat and nine cultivars of spring barley grown at four
locations in southeastern Washington. The team measured the content of
hemicellulose, cellulose and lignin in each type of residue. They also measured
residue levels of carbon and nitrogen and the ratio of the amount of carbon to
The team found that the straw from the different cultivars had notable
differences in fiber composition and C/N ratios. Fiber composition, C/N ratios
and carbon levels also varied significantly by location, probably because of
different soil and growing conditions. Residue samples from Pullman, where
annual precipitation averages 20 inches, had higher lignin and C/N and lower
nitrogen than residues from the driest site, where annual precipitation
averages 11 inches.
These results and other tests on the straw residues indicated that 14
percent of the cultivars had characteristics for slow residue decomposition and
14 percent had characteristics indicating a potential for rapid decomposition.
Crop residues decompose into soil organic matter, which provides nutrients to
crops, limits erosion and helps retain soil moisture. Rapidly decomposing
cultivars are less likely to impede no-till seeding in higher rainfall areas
where more straw is produced.
The identification of differences in these crop characteristics could help
growers select cultivars that produce residues best adapted to reduced-tillage
cultivation. These residues may also benefit subsequent crop establishment,
maximize soil organic matter to improve yield and increase carbon stored in the
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.