Jf. Dormaar et Jm. Carefoot, IMPLICATIONS OF CROP RESIDUE MANAGEMENT AND CONSERVATION TILLAGE ON SOIL ORGANIC-MATTER, Canadian Journal of Plant Science, 76(4), 1996, pp. 627-634
Under natural grassland or native prairie, aboveground residue or surf
ace litter modifies the microenvironment. It promotes water infiltrati
on and, by insulating the soil surface, moderates soil temperatures an
d limits evaporation. Root mass decomposes and transforms within the c
onditions created by surface litter. Together with root exudates, this
below-ground residue or subsurface litter reacts with soil minerals t
o form aggregates, lower bulk density and increase water-holding capac
ity. Bringing such soils under cultivation leads to lower soil organic
matter content, thereby increasing bulk density. The role of surface
litter becomes even more important, as it affects wind and water erosi
on, reduces the impact of raindrops, prevents crusting, protects the s
oil from drying by sublimation, and captures snow. Management of crop
residues depends on the role of the residue. A distinction must be mad
e between above- and below-ground residues: their roles are distinctly
different. Aboveground crop residue protects the soil and creates the
conditions for below-ground residue to decompose and transform. These
decomposition products, in turn, create favourable soil structure for
plant growth. Research is needed on the effect of repeated harvesting
of ''excess'' aboveground residues.