Soil Flashcards
Fulvic acids
organic acids found in soils derived from organic matter decomposition
- smaller than humic acids, soluble in water, more OH and COO- groups
- strong chelating agents, determine soil acidity
4 functions of soil
plant growth medium
water storage, supply, and purification
modifier of the atmosphere
habitat for organisms (decomposers)
Soil water
mediates organic and inorganic components with microbes
- site of redox, acid-base reactions
Clay
<2um
- site of chemical reactions in soil
Sand
20-200um
Silt
2-20 um
Loam
mixture of silt, sand, and clay
- high nutrients, moisture, and humus
Formation of soil
CLORPT
Climate
Topography (Relief)
Organisms
Parent Material
Time
Colloids
clay particles, mixture that has particles between 1-1000um, evenly distributed
Koalinite
hexagonal sheets, clay mineral
cation exchange capacity
capacity for soil to exchange nutrients with plants
- important for farming
- determined by amount of clay and/or humus present
(meq/100g dry soil)
humic acids
larger, fewer COOHs, soluble in bases (not water) because they become deprotonated
liming
adding CaCO3 to soils to partially neutralize soil acids
Kow
octanol-water partition coefficient
- high Kow = deposit in sediments rather than water and bioaccumulate
- hydrophobic (and/or very large) organic substances
chelation
“binding” of heavy metals onto folic acids
mineralization
cell metabolism wastes are deposited into the soil by microbes
immobilization
microbes complex molecules from the soil and use them for cell metabolism
nitrification
ammonia/nitrite is oxidized into nitrate by nitrifying bacteria (NO3- -> NO4-)
Denitrification
nitrate is converted into nitrogen gas by denitrifying bacteria
Paddy soil
used for rice farming
- anthrosoil: flooded and drained repeatedly
- this cycle produces hydromorphic soil which causes iron toxicity to fish and aquatic life
- flooded: low O2, reduces iron species into toxic molecules
- drained: high O2, iron species precipitate and suffocate fish
Rhizosphere
where microbes and plants work to fix nitrogen in the soil
“root microbiome”
Benthic
bottom of a body of water
Pelagic
relating to open ocean
nitrogen-fixing bacteria
take N2 and make ammonia
ammonification
nitrifying bacteria
nitrification = ammonia -> nitrites (-> nitrates)
byproducts of nitrification/denitrification:
NO and N2O gases
- N2O: insoluble in water and unreactive, very strong CFC/GG
saline soil
high salt content (high ion content)
sodic soil
high NaCl content
calcareous soil
high CaCO3 content, fairly highly oxidized species and high pE
hydromorphic soil
excess water, low Eh, lack O2
