Unit 3 Flashcards
What number range does the pH scale follow?
0-14
If something has a pH between 0-6, it is…
acidic
if something has a pH between 8-14, it is…
basic
if something has a pH of 7, it is…
neutral
2 ways to determine soil pH:
pHw: water suspension test.. water measures H+ ions attached to soil
pHs: lab field kit
4 ways that pH governs productivity:
- Nutrient Availability
- Strong acidic soils have low CEC occupied by K, Mg, &Ca
- Affects pesticides
- Affects microbial activity
Factors causing pH to change? (9)
- Depletion of bases by erosion
- Amount of rainfall/percolation
- Absorption of bases by plants
- chemical fertilizers
- tillage
- acid rain
- waste & sewage sludge
- irrigation
- plant roots
What is buffer capacity?
The resistance of the soil to changes in pH
what is active acidity?
H ions in solution
What is reserve acidity?
Absorbed H+ & Al+
Reserve acidity depends on…
the higher the CEC, the greater the buffer capacity
Why correct soil pH? (acidic levels)(5)
- Elements can reach toxic levels (deadly)
- Microbial activity and population will be low
- Ca & Mg may be deficient
- Lose more potassium
- low pH can mobilize heavy metals (deadly)
POSSIBLE TEST QUESTION: If on a budget, what should you fix before adding nutrients?
pH
Liming materials
Calcitic Limestone Dolomitic Limestone Burned Lime: Made by heating limestone Hydrated Lime: Burnt lime with water added Marl: freshwater deposit in swamp areas Ground seashells Lime-rich industrial waste wood ash
What is burned lime?
a liming material made by heating limestone
what is hydrated lime?
burnt lime with water added
what is marl?
freshwater deposit in swamp areas
Quantities of lime are determined by?:
Current pH
Desired pH
Buffer capacity
chemical makeup and fineness of liming material used
5 factors influencing liming frequency?
- soil texture
- rate of N fertilization
- rate of crop removal
- amount of lime applied
- pH desired range
When is the best time to lime? (2)
- soil test for lime needed every 3 years
2. 3-6 mos. before planting legumes
What is ENM?
Effective Neutralizing Method
ENM tells us
how many tons per acre of material to apply
ENM on soil test says 850, quarry has calculated ENM to be 475…. how much per acre needs to be applied?
850/475=1.78 tons per acre
Alkaline soils have a pH above…
7
What is a saline-sodic soil?
high levels of both soluble salts and sodium
what is a sodic soil
mostly sodium, called black alkali or slick spots
what is a saline soil?
mainly chlorides and sulfates of Ca, Na, Mg, and K
Causes of alkaline soils (3)
- minimal leaching
- carbon dioxide and carbonates precipitate
- the amount of Na + Ca ions in the soil
About ____ of the soils in the USA are affected by salinity
1/3
Measuring salinity in 2 ways…
Total dissolved solids (TDS)
Electrical conductivity: the more salts in solution, the more current can be passed between them
Problems associated with alkaline soils (4)
- Nutrient deficiencies
- CEC levels tend to be higher
- Calcium Rich Layer (duripan)
- water supply —-> dry soils
2 ways to reclaim a saline soil
irrigate and attempt to leach
gypsum
Soil microorganism groups (5)
- Macrofauna
- Macroflora
- Microfauna
- Microflora
- Mesofauna
What is functional resiliency in a soil?
There are several organisms that carry out similar tasks
more overlapping microbes=more stable and resilient
4 examples of macrofauna:
gophers, ants, mice, beetles
2 broad examples of macroflora:
Mosses and vascular plants
3 examples of mesofauna:
mites, springtails, worms
5 primary producers:
- vascular plants
- mosses
- lichens
- algae
- photosynthesizing bacteria
3 primary consumers
- herbivores
- saprophytes
- detritivores
what is an herbivore
a plant eater
what is a saprophyte
organism that lives on dead material (fungi)
what is a detritivore?
an ANIMAL that feeds on dead material
Secondary consumers:
Predators-carnivores
Microbivore feeders
Tertiary consumers
Feed on secondary consumers: moles, robins, ants, spiders, mites
there are over ___ different genera of bacteria
200
POSSIBLE TEST QUESTION: what is the role of bacteria in the soil?
Breakdown!
5 types of bacteria
- arthrobacters
- streptomycetes
- pseudomonas
- sporulating bacilli
- cyanobacteria
what bacteria is predominant in the soil?
arthrobacters
What bacteria gives soil a smell?
streptomycetes
What bacteria is used in pesticides?
pseudomonas
which bacteria fix Nitrogen?
sporulating bacilli
which bacteria contain chlorophyll?
cyanobacteria
what is the rhizosphere?
millimeter of soil closest to the root surface
The rhizosphere is the most…
biologically active area in the soil
Plants produce the ____ that microbes feed on
organic matter
there are over ______ species of nematodes
15,000
Are nematodes exclusively good or bad?
no. there are good and bad nematodes. can be parasitic or free living
what do nematodes do?
consume bacteria, important for the release of N in the soil
Fungi are important in…
humus formation, nutrient cycling, and stabilizing soil aggregates.
Fungi produce…
penicillin and mycotoxins
6 types of fungi
- acraciomycetes
- myxomycetes
- flagellated fungi
- sugar fungi
- higher fungi
- imperfect fungi
Mycorrhizae are
a fungi that grow in a symbiotic relationship with a plant
advantages of mycorrhizae (2)
extends root zone
puts nutrients in a plant available form
what is bioremediation?
using microorganisms to convert organic contaminants to less harmful products
what 3 points are on the disease triangle?
susceptible host, pathogen and favorable environment.
a disease cannot exist without all 3
functions of o.m. (3)
nutrient and water storage
soil aggregation–resist compaction
prevent erosion
Labile means
easy to decay material: starches, cellulose, hemicellulose
recalcitrant means:
difficult to decay material: lignin
Process of decay (4)
solution
fragmentation
decay
humification
solution is…
nutrients dissolving out of litter into nearby soil water
Fragmentation
shredding up and breaking up
Decay
labile material broken down by microbes
recalcitrant slowly broken down by fungi
Humification
Occurs when N is released from labile decay and re-used to break down C
Humus has…
50% C and 5 % N
Humus has a C:N ration of
10:1
Humus is ____ in color and ____ to decay
dark in color, resistant to decay
factors affecting O.M. (5)
Vegetation, climate, soil texture, drainage, tillage
Prairies generate the most ____ __
soil O.M.
Fine textured soils have more _____ than coarse textured soils
O.M.
Poorly drained soils have _____ ____
more O.M.
Decay is a primarily ____ process
aerobic
Decay is influenced by (4)
- tillage
- amount of water
- amount of life organisms
- structure and texture
2 undesirable effects of O.M.
- N can be tied up
2. some plant residues are toxic to other plants (phytotoxins)
What happens to soil organic matter decomposition when you... add mulch? clear cut? no till into corn stover? Use hairy vetch as a green manure crop?
add mulch?….. slows dow
clear cut?……… speeds up @ first then slows down
no till into corn stover?…… slows down
Use hairy vetch as a green manure crop?…… speeds up
