SOIL Flashcards
5 Soil Functions
- Primary Productivity
- Water Regulation/Purification
- Biodiversity Habitat
- Carbon Regulation/Sequestrian
- Nutrient Cycling
Soil Function: Primary Production Function
The capacity of a soil to produce plant biomass for human use,providing food, feed, fiber and fuel within natural or managed ecosystem boundaries
Soil Function: Carbon Sequestration
the capacity of a soil to store carbon in a non-labile form with the aim to reduce the CO2 concentration in the atmosphere
Soil Function: Water regulation/purification
Capacity of a soil to receive, store and conduct water for subsequent use, prevent droughts, flooding, erosion and to remove harmful compounds.
Soil Function: Nutrient Cycling (incl. calc)
The capacity of a soil to receive, provide and carry over nutrients into harvested crops.
Output/input = fertilizer value x recovery x harvest index
Soil Health
Intersection: biology, chemistry + physical.
The capacity of a soil to function within ecosystem and land-use boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health
Soil Function: Habitat for biological activity
capacity of a soil to support the multitude of soil
organisms and processes, interacting in an ecosystem
Causes of High Pathogen Pressure
● Poorly planned crop rotation or diversity
● Poor physical function (e.g. waterlogging)
● Low microbial diversity
Good Soil Tilth Outcomes
●Water storage infiltration
● Aeration
● Root growth
● Soil life
CASH Biological Indicators (Soil Organic Carbon)
- Soil Organic Matter
- Active Carbon/POXC (labile C)
- Soil Respiration
Labile Carbon
Fraction of organic matter readily available as food and energy source to soil microbial community
N Volatilization
nitrogen in an organic form (urea), e.g. animal manures or urea fertilizers is converted to ammonia gas (NH3)
N Deposition
GAS: input of reactive nitrogen from the atmosphere to the biosphere
N Fixation
chemical process that converts atmospheric nitrogen
(N2) into ammonium (NH4), which is taken up by plants or microbes
Biological N Fixation
Rhizobia metabolize atmospheric
nitrogen and convert it into N compounds that the plant can uptake in plant root. In exchange, rhizobia use carbon substrates derived from the plant photosynthesis.
N Cycling Function of Soil Biology (5)
BIMP-D
- Decomposition
- Bioturbation
- Mineralization
- Immobilization
- Plant Root Aquisition
Bioturbation
mixing of plant or animal derived organic material into the mineral matrix of the soil
Immobilization
conversion of inorganic compounds to organic compounds by micro-organisms or plants (prevents uptake of the N by plants)
Mineralization
oxidation of nutrient compounds in organic matter, releasing the nutrients in soluble inorganic forms that are then available to plants
Mineralization sub-processes
AND
Ammonification (organic N to inorganic N)
Nitrification (aerobic)
Dentrification (anaerobic –> heterotrophic denitrifying bacteria & fungi)
Mycorrhizae (P Cycling)
Symbiotic relationship: soil fungi & plant roots.
Plant supplies the fungi with sugars, fungal network improves plant’s capacity to absorb water and nutrients.
3 Pools SOM (?)
- Soil
- SOM
- Biomass SOM (fungi, bacteria, micro/macro fauna)
SOM Additions
Crop residues
Manure
Compost
SOM Losses
Soil Respiration
Erosion
Processes Contributing to Soil C Gains
BAAS: Bioturbation Aggregation Assimilation Stabilization
Processes Contributing to Soil C Losses
Decomposition
Biological Actors of Decomposition
Fragmentation = earthworms, mites, isopods
Microbial Degradation = Bacteria + Fungi
Decomposition Sub-processes
FMM:
Fragmentation
Microbial Degradation
Microbial Grazing
Decomposition Controls
Climate
Soil & Typography
Management
P cycle losses
- Crop uptake
- Runoff and erosion
- Leaching
P & N Cycle Differences
P is tightly bound, adsorption and desorption are very slow processes
N Release Dependent on:
- C:N Ratio (higher= carbon-dominated, requires a lot of decomposition and respiration to get nitrogen)
- soil conditions: temperature, moisture, and oxygen (optimal time=late spring and early autumn)
