all the rest Flashcards
5 factors affecting soil temperature
- aspect
- latitude / seasons
- vegetative cover
- color / albedo
- humus
only about ____% of solar energy reaches the soil
10
to increase temp. of dry soil by 1°C requires only ____
0.2 cal/g dry soil
(vs. 1 cal/g water)
cooling of soil is mostly through ______
evaporation
it takes ____ cal to evap. 1g of water;
energy comes from either ___ or from ____
540 cal; sun or soil
movement of heat energy in soils is by _______
conduction;
conductivity of water > soil >>>>> air
4 types of mulches
- clear plastic -> greenhouse effect = greatest heating effect
- black plastic -> absorbs heat -> radiates
- wood & other organic mulches: can cool soil, trap moisture
- permeable plastic blocks: meh
temp. effects of changes to soil moisture (3)
- draining in spring alows faster warming
- wet soils stay cooler
- permeable mulch slows evaporation
frost heaving caused by ___ ___ forming in soil and expanding ______
ice lenses; upwards
temperature effects of fire
- greatest temps at surface due to soil water lower down
- loss of O hzn = less insulation (so greater temp variance)
- water repellent layer can form due to gases a few cm deep -> erosion w/ next rain event
micropores are < and macropores > ___mm
.08
humus has _______ charges
pH-dependent
too much clay = ______
bad structure
CEC = ____ & ____ of _____
storage & availability of nutrients
soil water movement controlled by… (3)
- inputs
- soil properties
- energy
energy = _____
ability to do work
high conentration -> low conc. (equilibrium)
high energy -> low energy
potential = _____
- relative ability to do work
- relative to a reference
- ex: pure water @ a specific height
- relative to a reference
Ψs = _______ = __ + __ + ___
soil water potential;
Ψg + Ψm + Ψo;
gravimetric + matric + osmotic
Ψg
gravimetric potential
- higher in soil profile = higher energy
- typically a positive value
Ψm
matric potential
- adhestion to soil particles/surfaces (+ cohesion)
- typically a negative value (b/c it req’s energy to break the bonds; stronger bonds = more negative
- @ saturation, Ψm = 0
Ψo
osmotic potential
- salts can behave like a particle surface
- typically a negative value (costs nrg to break bonds)
- water moves toward concentrated salt areas
in sandy loam, ___ dominates
in clay loam, ___ + ___
Ψg
Ψg + Ψm
-15 bars = -1.5MPa = _____
permanent wilting point = no water available for root uptake
saturation = _____ = __ dominates
all pores filled = Ψg dominates
field capacity = ___ ____ ____ = ~__ hours after saturation
all macropores drained = ~48 hours after saturation
available water content = __ - ___
field capacity - permanent wilting point
what enhances water storage & availability? (4)
- deeper soil
- barrier @ depth to water
- texture
- root access to retained water
inputs (1) & outputs (4) to hydrologic cycle
- precipitation
- leaching
- runoff
- transpiration
- evaporation
infiltration rate equation
Q / (A * T)
quantity / (area * time)
volume / (area * time)
-> depth / time
litterfall is mostly…
- water (75-95%)
- rest is dry matter
- 44% C
- 40% O
- 8% H
- 8% others
component of litterfall and decomposability
- 40-90% quickly decomposing….
- sugars, starches, proteins
- hemicellulose
- cellulose
- 1-10% slowly decomposing
- fat & waxes
- 5-40% slowest decomposing
- lignin
detrital pool = ___
- undecomposed & partially decomposed litter (O hzn)
- buildup is fx of climate, veg., organisms
- aka production vs. breakdown/decomp
- waterlogged + wet + cool = ++detrital pool
- warm + humid = –detrital pool
redox rxns produce (5) and are considered
______ _______
- CO2 + H2O + heat energy
- humus
- new microbes
- non-humic substances
- nutrients
-> incomplete decomposition
3 parts to decomposition
- physical fragmentation (by soil fauna)
- leaching (of soluble components)
- chemical breakdown & synthesis
- by microorgs & enzymes
- -> formation & release of byproducts / nut’s
- -> forms new decay-resistant components
- humus, organic acids
less acidic conditions favor ___
more acidic conditions favor ____
bacteria & earthworms
fungi
factors affecting decomposition (9)
- aeration / water
- temperature
- pH - too high or too low = –decomp
- activity & availability of soil fauna & flora
- texture: clay binds humus, stabilizing it
- litter quality: –lignin = ++decomp
- availability of essential nut’s
- N is most limiting; C:N ratio is key
- C:N ration varies w/ type of litter
- by species
- by tissue (needles take 5 yrs, wood 150)
- toxic components (phytotoxins)
- Humans (tend to inc. decomp rates)
- tillage, fire, slash piles
humus is…
a complex mixture of brownish/blackish amorphous organic substances resulting from microbial decomp. & synthesis
- humin
- humic acids
- organic acids
non-humic compounds are…
identifiable; ex: oxalic acid
benefits of humus (6)
- high surface area (retains nut’s)
- pH-dependant charges
- retains water
- form aggregates (adhesives)
- contributes to soil formation & weathering
- hold nutrients & energy for microbes
muffle furnace uses ___ ____ ____ to measure %OM;
%C equation: ___
loss on ignition = %OM = (weight diff / initial weight) * 100
%C = %OM / 1.78
nutrient = ___
element req’d for an organism’s growth & completion of its life cycle
17/18 macro/micronutrients
CHOPKNS CaFe Mg B Mn CuZn Cl MoCoNi
macro: CHOPKNS CaMg
micro: Fe B Mn CuZn Cl MoCoNi
(Co only needed by legumes)
macros needed in amounts greater than….
micros needed in amounts less than…
500 ppm = .05%
50 ppm = .005%
chlorosis = ___
insufficient production of chlorophyll, producing yellow or yellow-white discoloration; often due to low N
low N discoloration
yellow @ tips & small
low P discoloration
small & purple (in older plant parts)
low Mg discoloration
small, yellow -> purple gradient
low K
yellow/brown tips
low Ca
wilted new growth b/c Ca used in cell walls
low Fe
yellow tips
Law of the Minimum
level of plant production can be no greater than that allowed by the most limiting essential growth factors
nutrient uptake rules (3)
- uptake req’s energy; plants concentrate elements
- so uptake is fighting conc. gradients
- energy comes from respiration
- __uptake is selective
- plants try to exclude unwanted elements
- uptake is electrically balanced
- export H+ to import cations
- export OH- to import anions
nutrient uptake factors (7)
Plant Metabolism
- O2 supply
- sunlight -> sugars
- temperature (both shoots & roots)
Soil
- water content / O2
- root distribution & access
- nutrient availability
- symbionts
- (competition)
plant affects on soil (5)
- uptakes
- exudates
- microorganisms
- litter
-
rhizosphere
- –pH than surroundings
- very active zone that differs from rest of soil
- ++microbes
- just on fine roots, mostly
soil nutrient sources (6)
- parent materials (weathering)
- atmospheric deposition (dissolved in water particles)
- soil air
- secondary minerals (weathering)
- OM (decomp)
- exchange sites
availability depends on the source
soil solution >
exchange sites >
colloidal fraction (humus/clays) >
coarse fraction (primary minerals)
3 key things to “test” for nutrient availability
- texture - tells you about storage, exch. sites
- humus - color & feel -> storage & availability
- pH - tells you what’s on exch. site & how many
- effects solubility/availability
- optimal range: 6-7
nutrient movement & availability to roots (4)
- mass flow: plant takes up water, nutrients enter roots w/ water
- diffusion: no water mvmt; high conc. -> low conc.
- ions -> rhizosphere -> roots
- plant roots grow to new areas of soil
- symbiants
mobile nutrients
- move readily to roots through soil
- ++conc. in soil solution
- ex: NO3, K, Ca, Mg
- ++competition w/ other plants
immobile nutrients
- tend to be absorbed/precipitate out of sol’n on surface
- complex, –conc. in solution
- not as soluble
- ex: PO4-3, Fe+3
- –competition
symbiants
- mycorrhizae: symbiotic relationship b/t fungi & roots
- very imp. for immobile nut’s
- ecto: ext. to root cells (trees)
- endo: penetrate root cells (grasses, crops)
- nitrogen fixers
- bacteria, actinomycetes
- legume bacteria: rhizobium
- red alder: Frankia actinomycetes
- also by some free-living bacteria
soil amendments
increase nutrient availability
- liming: raise pH; lime (CaCO3); quicklime (CaO)
- fertilizers: N most common, then P
- Ammonium nitrate
- Urea (more common in forests)
- mixed fertilizers (N P K S)
- problems w/ leaching / eutrophication
- composting
- partial rotting of plant waste to make humus
- good compost:
- aerobic decomp
- moisture: 40-70%
- piled to retain heat (50-70°C)
- N: 1.2-1.6%
