Soil Health

1
Soil Health
2
Benefits and detriments of microbes in the
rhizosphere
Ecosystem Services
of the Soil Biota

• Decompose organic matter
• Cycle nutrients
• Release nutrients
• N2 fixation and mycorrhizae
• Suppress disease
• Improve soil structure
• Bioremediate contaminants
• Consume greenhouse gases

• Immobilize nutrients
• Cause disease
• Produce greenhouse gases

3
In a gram of soil.there are. Billions of
bacteria Millions of fungi Thousands of nematodes
and protozoa
In a gram of soil.there may be. As many as
10,000 kinds of bacteria 5,000 kinds of
fungi hundreds of kinds of nematodes and protozoa
4
Earthworms
5
What measurements should I make to evaluate the
effects of management on soil function now and in
the future?

• How many should there be?
• How do I know if they are active enough?
• Are there enough of the right kinds?

• Abundance
• Activity/function
• Diversity

6
Disconnection between science and application

• Inability to grasp the importance and activities
  of what we cannot see
• Microbial inoculants and measures - faith-based
  on the part of farmers, with plenty of past
  failures.
• Difficulty in obtaining meaningful data
• Use of physical and chemical measures to
  translate biological responses.
• Scale focus on the molecular, when problems are
  at the landscape level.

7
If it was easy, we would have done it already !
8
Proposed Biological Measures

• Microbial biomass C and N
• Potentially mineralizable N
• Soil respiration
• Biomass C/Total OC ratio
• Respiration/biomass ratio

• CHCl3 fumigation
• Anaerobic incubation
• Field or laboratory measured
• Doran and Parkin, 1994

9
Limitations

• Sample disturbance and handling
• Sampling in relation to antecedent factors
  rainfall, temperature

10

• Hydraulic conductivity
• Porosity (macro/meso)
• Penetration resistance

water

• Porosity (micro)
• Bulk density

saturated
Intact soil cores
Soil respiration NaOH trap for CO2
Soil moisture
Glomalin and other biochemical analyses
Tying soil health indicators to system
performance is still the key.
11
Karlen et al., 2003
12
Doran and Zeiss, 2000
13
Husson, 2003