9 research outputs found
Influence of irrigated agriculture on soil microbial diversity
Organic carbon (C), bacterial biomass and structural community diversity were measured in Southern Idaho soils with long term cropping histories. The soils tested were native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation – chisel – tilled crops (ICT) and irrigated pasture systems (IP). Organic C concentration in soils decreased in the order NSB 0–5 cm > IP 0–30 cm = ICT 0–15 cm > IMP 0–30 cm > NSB 5–15 cm = NSB 15–30 cm. Active bacterial, fungal and microbial biomass correlated with soil C as measured by the Walkely Black method in positive curvilinear relationships (r2 = 0.93, 0.80 and 0.76, respectively). Amplicon length heterogeneity (LH-PCR) DNA profiling was used to access the eubacterial diversity in all soils and at all depths. The Shannon–Weaver diversity index was used to measure the differences using the combined data from three hypervariable domains of the eubacterial 16S rRNA genes. Diversity was greatest in NSB 15–30 cm soil and lowest in the IMP soil. With the exception of IMP with the lowest diversity index, the samples highest in C (NSB 0–5 cm, IP 0–30 cm, ICT 0–15 cm) reflected lower diversity indices. However, these indices were not significantly different from each other. ICT and IP increase soil C and to some extent increase diversity relative to IMP. Since soil bacteria respond quickly to environmental changes, monitoring microbial communities may be one way to assess the impact of agricultural practices such as irrigation and tillage regime
Deficiencies in the soil quality concept and its application
Soil quality is a concept that has deeply divided the soil science community. It has
been institutionalized and advocated without full consideration of concept weaknesses and
contradictions. Our paper highlights its disfunctional definition, flawed approach to
quantification, and failure to integrate simultaneous functions, which often require contradictory
soil properties and/or management. While the concept arose from a call to protect the
environment and sustain the soil resource, soil quality indexing as implemented may actually
impair some soil functions, environmental quality, or other societal priorities. We offer the
alternative view that emphasis on known principles of soil management is a better expenditure of
limited resources for soil stewardship than developing and deploying subjective indices which fail
to integrate across the necessary spectrum of management outcomes. If the soil quality concept
is retained, we suggest precisely specifying soil use, not function or capacity, as the criteria for
attribute evaluation. Emphasis should be directed toward using available technical information to
motivate and educate farmers on management practices that optimize the combined goals of high
crop production, low environmental degradation, and a sustained resource
Influence of irrigated agriculture on soil microbial diversity
Organic carbon (C), bacterial biomass and structural community diversity were measured in Southern Idaho soils with long term cropping histories. The soils tested were native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation – chisel – tilled crops (ICT) and irrigated pasture systems (IP). Organic C concentration in soils decreased in the order NSB 0–5 cm > IP 0–30 cm = ICT 0–15 cm > IMP 0–30 cm > NSB 5–15 cm = NSB 15–30 cm. Active bacterial, fungal and microbial biomass correlated with soil C as measured by the Walkely Black method in positive curvilinear relationships (r2 = 0.93, 0.80 and 0.76, respectively). Amplicon length heterogeneity (LH-PCR) DNA profiling was used to access the eubacterial diversity in all soils and at all depths. The Shannon–Weaver diversity index was used to measure the differences using the combined data from three hypervariable domains of the eubacterial 16S rRNA genes. Diversity was greatest in NSB 15–30 cm soil and lowest in the IMP soil. With the exception of IMP with the lowest diversity index, the samples highest in C (NSB 0–5 cm, IP 0–30 cm, ICT 0–15 cm) reflected lower diversity indices. However, these indices were not significantly different from each other. ICT and IP increase soil C and to some extent increase diversity relative to IMP. Since soil bacteria respond quickly to environmental changes, monitoring microbial communities may be one way to assess the impact of agricultural practices such as irrigation and tillage regime
Deficiencies in the soil quality concept and its application
Soil quality is a concept that has deeply divided the soil science community. It has
been institutionalized and advocated without full consideration of concept weaknesses and
contradictions. Our paper highlights its disfunctional definition, flawed approach to
quantification, and failure to integrate simultaneous functions, which often require contradictory
soil properties and/or management. While the concept arose from a call to protect the
environment and sustain the soil resource, soil quality indexing as implemented may actually
impair some soil functions, environmental quality, or other societal priorities. We offer the
alternative view that emphasis on known principles of soil management is a better expenditure of
limited resources for soil stewardship than developing and deploying subjective indices which fail
to integrate across the necessary spectrum of management outcomes. If the soil quality concept
is retained, we suggest precisely specifying soil use, not function or capacity, as the criteria for
attribute evaluation. Emphasis should be directed toward using available technical information to
motivate and educate farmers on management practices that optimize the combined goals of high
crop production, low environmental degradation, and a sustained resource