499ST and NT treatments had more SOC and total N stocks, macro-aggregate propor-
tions and MBC than the CT treatment. Mohammadi et al. ( 2010 ) showed that an NT
system increased MBC compared with other tillage systems. Many studies have
indicated that NT practices can increase soil fungal populations while in others, NT
stimulated both bacterial and fungal populations (Helgason et al. 2009 ). Caesar-
TonThat et al. ( 2010 ) observed that an NT spring wheat system in the drylands of
eastern Montana, USA, improved soil aggregation and aggregate stability and
increased basidiomycete fungi and the proportion of soil-aggregating microorgan-
isms. Frey et al. ( 1999 ) measured significantly higher organic matter C and N frac-
tions and mean weight diameter (MWD) of water-stable aggregates in NT relative
to CT in a long-term experiment. Fungal hyphal length and fungal biomass were
significantly higher in NT than CT surface soil. However, bacterial abundance and
biomass were not consistently influenced by tillage treatment. Further, the fungal
biomass was not strongly related to soil texture, pH, aggregation or organic C and
N fractions, but was positively related to soil moisture. The relationship between
soil moisture and the degree of fungal dominance was due to the positive response
of fungal biomass and lack of response of bacterial biomass to increasing soil
moisture.
Soil enzymes are considered potential indicators of soil quality because of their
relationship with soil biology and quick response to changes in agricultural man-
agement practices (Dick et al. 1996 ). Hence, they can be useful for monitoring the
effects of soil management on soil health. Soil enzymes are primarily of microbial
origin and catalyze all biochemical reactions so are an integral part of nutrient
cycling in the soil (Mohammadi et al. 2011 ). Jin et al. ( 2009 ) suggested that the
positive effects of conservation tillage practices on soil enzyme activities mainly
result from the increased water availability. Mohammadi et al. ( 2011 ) indicated
higher activities of acid and alkaline phosphatase and protease in the NT treatment
than the CT treatment. Similarly, Mathew et al. ( 2012 ) reported higher soil carbon
and nitrogen contents, viable microbial biomass and phosphatase activities in the
long-term NT treatment than the CT treatment. The abundance of fungi, bacteria,
arbuscular mycorrhizal fungi and Actinobacteria (as indicated by PLFAs biomark-
ers) was consistently higher in the NT surface soil. SOC was positively correlated
with most of the PLFA biomarkers. However, community qPCR with 16S rRNA
gene sequencing to examine the effects of long-term crop management practices
(NT vs. CT) revealed that NT practices did not significantly alter bacteria or fungi
relative to CT (Ng et al. 2012 ). These differences may be attributed to the different
methods used by the researchers. This highlights the need to evaluate multiple
methods for microbial analysis that complement the potential limitations of other
methods to develop standardized protocols which will ensure uniformity in the
communication of results. Besides, factors such as cropping system, soil type and
timing of sample collection might influence the effects of management practices on
microbial community structure.
These results indicate that soil management practices influence both physico-
chemical and microbiological properties of soil. Shifts in microbial community
structure are expected due to the temporal increase in the microbial niche and water
Application of Microbiology in Dryland Agriculture