Agriculture Reference
In-Depth Information
Chapter 4
E
COLOGY AND
F
UNCTION OF
C
ULTURABLE
M
ICROBES IN
S
OIL
A
GGREGATION
T.C. Caesar-TonThat, A.J. Caesar,
J.F. Gaskin, U.M. Sainju and W.B. Stevens
United States Department of Agriculture, Agricultural Research Service,
Sidney, MT 59270, USA
A
BSTRACT
Soil structure plays a dominant role in the physical protection of soil organic matter
by controlling microbial access to substrate, microbial turnover processes, and food web
interactions. Good soil structure results in soil productivity, a cornerstone of agricultural
sustainability. While there is a wealth of knowledge about soil aggregation, soil microbial
biomass and microbial diversity of soil, there is little knowledge of the microbial
community ecology of soil aggregates. This review intends to expand upon and examine
the microbial nature of soil aggregation: species causal to aggregation and functional
groups involved. One focal point will be to examine how a quest for identifying and
characterizing key species associated with microaggregates can have implications for
management practices to improve soil aggregation and ultimately soil structure. The
review will attempt to identify some promising avenues for future research in this area of
soil biology that is a central one to soil quality. Our goals are to catalyze rigorous,
innovative research on current approaches and techniques on the microbial ecology of
soil aggregation.
1.
I
NTRODUCTION
Soil structure directly affects carbon sequestration, water holding capacity and aeration,
each in turn affecting microbial activities controlling nutrient turnover and cycling processes.
Conversely, the biotic basis of soil structure is described as due to microbial activity (fungi
and bacterial activity with mycorrhizal fungi given primacy), root growth stimulating
