N. Bissonnette et al., Interactive effects of management practices on water-stable aggregation and organic matter of a Humic Gleysol, CAN J SOIL, 81(5), 2001, pp. 545-551
In many soils, the content and quality of organic matter (OM) control water
-stable aggregation, which in turn preserves soil surface integrity. The ef
fects of management practices on soil OM and aggregation remain to be deter
mined for certain soils and climatic conditions. We assessed the effects of
eight management systems involving two crop sequences: [barley (Hordeum vu
lgare L.) monoculture (M) and barley in rotation (R) with a forage mix of r
ed clover (Trifolium pratense L.) and timothy (Phleum pratense L. 'Champ')]
, two fall tillage [moldboard plowing (MP) and chisel plowing (CP)] and two
nutrient sources [liquid dairy manure (LDM) and mineral fertilizers (MIN)]
on soil aggregation and OM fractions of a silty clay Humic Gleysol. Soil s
amples from the 0-7.5 cm layer were taken periodically during 7 yr, and the
total C and N, microbial biomass C (MBC) and carbohydrate (AHC) contents,
alkaline phosphatase activity (APA), and water-stable aggregation were dete
rmined. By the 7th yr, initial total C and N contents of the surface soil h
ad increased by 35 and 45%, respectively, in R-CP-LDM. They were slightly i
ncreased in R-CP-MIN and R-MP-LDM, whereas they decreased by an average of
19% in R-MP-MIN and all monoculture plots. Increases in C contents were att
ributed to higher annual C inputs from forage residues and LDM, less freque
nt tillage in the rotation, and shallower tillage with CP. The MBC, APA, AH
C and aggregation generally responded faster and to a greater degree to con
servation management practices than total C and N. Overall, conservation ti
llage and manure applications resulted in greater improvement in surface so
il conditions when used in a rotation system rather than in a monoculture.
The rapid rate of changes in soil properties suggests that the surface qual
ity of this cold silty clay soil can be improved relatively quickly with se
lected management combinations.