Test 3 Review Flashcards
soil texture
proportion of sand, silt, and clay in the soil
soil structure
arrangement or grouping of individual soil particles into peds or aggregates
soil particles
sand, silt, clay
factors that influence bulk density (5)
- organic matter
- texture/aggregation
- structure
- compaction
- depth in soil profile
how to increase soil pH
lime
soil water at field capacity
saturated and allowed to drain freely
pedon
smallest unit of soil that contains all the horizons of a specific soil type
catena
a sequence of soils with different horizons caused by differences in their depth to the water table
soil profile
2-D representation of a vertical section of soil from the surface to deepest layers
whole thing from top to bottom
soil horizon
soil layers; roughly parallel layers in the soil with varying compositions and properties
soil color determinants (4)
- mineralogy of parent material
- organic matter
- hydrology
- soil chemistry
tool to determine soil color
Munsell Color Chart
10YR 6/3
10YR = hue
6 = value
3 = chroma
hue
proportions of red to yellow
top right corner
chroma
how bright vs dull
x-axis
value
amount of light reflected
y-axis
amount of soil nutrients
at least 16
amount of soil macronutrients
9
amount of soil micronutrients
8
fertile and infertile soil based on CEC, soil pH, silicate clay type
fertile: higher CEC, neutral pH, and montmorillonite silicate clay
infertile: low CEC, highly acid or highly alkaline pH, Fe and Al oxide silicate clays
in what pH range are N and P available for plants
5.8 - 6.8 (K tends to like more alkaline soils)
molybdenum is usually important for what crop?
soybeans (rhizobium) and legumes
in what pH range is molybdenum usually available for plants?
alkaline soils (pH 7.1+)
lime commonly comes in two forms, CaCO3 and MgCO3, what are their common names?
Ca: calcite
Mg: dolomite
decreasing pH =
sulfur
- potassium sulfate
- anything sulfate (SO4)
classifications of soil organisms
- macrofauna
- microfauna
- flora
- food - herbivores, detritivores, predators
- based on O2 demand - aerobic and anaerobic
- based on energy and C source - autotrophic and heterotrophic
producers
create their own food through photosynthesis (plants)
consumers
eat other organisms for energy (can’t make their own)
detritus
decaying organic matter
decomposers
have the ability to break down organic material releasing useful nutrients
heterotrophs
- heterotrophic from breakdown of OM (carbon)
- most numerous
immobilization
microbes absorb nutrients from the soil, making them unavailable for plant use
mineralization
- the conversion of soil organic matter to plant available nitrogen
- the release of nitrogen from the organic form to the inorganic form
nitrification
nitrifying bacteria convert ammonia (NH3) to nitrate (NO3)
denitrification
wet soil, lack of aeration, and leaching of N because of water
compaction causes the loss of what primary nutrient
nitrogen
nitrogen fixation
converting atmospheric N into usable forms
N2 -> NH4
algae: wetland
bacteria: legumes
role of bacteria
- nitrification
- nitrogen cycle
- improve soil structure
- decomposing OM
- degrading pollutants
role of algae
- producer in aquatic systems
- oxygen production
- carbon sequestration
- water purification
role of earthworms (3)
- soil fertility by producing cast
- reduce erosion and improve aggregate stability
- aeration and drainage
rhizobium
nitrogen producing bacteria found on root nodules on legumes
mycorrhiza
fungi that infect the plant roots of nearly all plants
benefits include plant nutrition (especially P), drought tolerance, disease resistance, and soil structure improvement
types of mycorrhiza and roles
- endomycorrhizae - agriculture
- ectomycorrhizae - forest
various functions of microorganisms in soil
nitrogen cycling
what is soil organic matter
the debris of biological activity in soil
every organic compound that is in soil, which includes roots, animals, and microorganisms
what are the components of soil organic matter
humus and active organic matter
why is SOM important for soil fertility
produces N, P, and S and can hold additional nutrients
very good for P
what nutrients are released during soil organic matter decomposition?
N, P, S, Ca, and Mg???
common percentage of OM in mineral soils
very low = 1%
average = 2-4%
high = >5%
KY = 1-3%
common percentage of OM in organic soils
greater than 20%
importance of C/N ratio in plant residues as related to N availability for plants
- soil microbes require C to build organic compounds and for energy
- soil microbes need N to produce amino acids, protein enzymes, and DNA
- microorganisms compete for soil N
- helps determine the rate of decay and the availability of N to plants
C/N ratios in soil
8:1 to 15:1 or 20:1
C/N ratios in microorganisms
5:1 to 10:1
C/N ratios in plant residues
24:1ish
C/N ratios in sawdust
400:1 to 600:1
macronutrients
needed in large amounts
macronutrients examples
C, H, O, N, P, K, Ca, Mg, S
micronutrients
needed in small amounts
micronutrient examples
Mn, Cu, Zn, Mb, B, Cl, Fe
non-mineral elements
carbon, hydrogen, oxygen
what forms of N are available for plants
NO3- and NH4+
what forms of P are available for plants
H2PO4- and H2PO4-2
what forms of K are available for plants
K+
functions of N
- promotes growth of leaves and stems
- dark green color; chlorophyll
- amino acids and proteins
N deficiency symptoms
- sick, yellow-green color
- short stems, small leaves, pale colored leaves and flowers
- slow and dwarfed plant growth
functions of P
- stimulates early formation and growth of roots
- ADP -> ATP
- fast and vigorous growth
- stimulates flowering and seed development
- needed for the enzyme action of many plant processes
P deficiency symptoms
- decrease in growth
- slow maturity
- older leaves turn purple in color
functions of K
- form carbohydrates and proteins
- form and transfer of starches, sugars, and oils
- increases disease resistance, vigor, and hardiness
- water regulation
K deficiency symptoms
- mottled, spotted, streaked, or curled leaves
- scorched, burned, dead leaf tips and margins
functions of Ca
- improves plant vigor
- influenced intake and synthesis of other plant nutrients
- important part of cell walls
Ca deficiency symptoms
- small developing leaves
- wrinkled older leaves
- dead stem tips
functions of Mg
- influences the intake of other essential nutrients
- helps make fats
- assists in translocation of phosphorus and fats
Mg deficiency symptoms
- interveinal chlorosis (yellowing of leaves between green veins)
- leaf tips curl or cup upward
- slender, weak stalks
functions of S
- root growth and vigorous vegetative growth
- essential to protein formation
S deficiency symptoms
- young leaves are light green with lighter colored veins
- yellow leaves and stunted growth
why is CEC important for crop production
- influences the quantity of plant nutrients held and made available in the soil
- soils with high CEC hold more nutrients and are better able to buffer rapid changes in the soil solution
why is % base saturation important for crop production
- indicates the balance of essential plant nutrients in the soil relative to acidic cations
- impacts soil pH and nutrient availability
fertilizer grade
represented by three number that correspond to the percentage of weight of N, P2O5, and K2O
ex. 15-5-15
fertilizer ratio
the relative amount of nitrogen, phosphate, and potash in fertilizers
ex. 3-1-3
K -> K2O
%K x 1.2
K2O -> K
%K2O / 1.2
P -> P2O5
%P x 2.29
P2O5 -> P
%P2O5 / 2.29
N fertilizers
- ammonium nitrate
- ammonium sulfate
- anhydrous ammonia
- urea (45%)
P fertilizers
- ammonium phosphate
- diammonium phosphate
- potassium phosphate
- dipotassium phosphate
- phosphoric acid
K fertilizers
potash is used for preparation of potassium sulfate and potassium nitrate
6 different types of fertilizers
- complete
- incomplete
- organic
- inorganic
- soluble
- insoluble
7 different fertilizer application methods
- banding
- sidedressing
- topdressing
- perforating
- broadcasting (oldest way)
- foliar spraying
- fertigation
organic fertilizer
comes from plant or animal matter and contains carbon compounds
inorganic fertilizers
chemical fertilizers
soluble fertilizer
dissolve in water and applied as a liquid solution (fertigation)
insoluble fertilizer
granular and slow release
what causes the wet dirt smell?
actinomycetes
fungi has _______ and ________ that help form and build organic matter
hyphae and mycelium
higher C/N ratio =
nutrients are more immobile
sawdust has the _______ C/N ratio and can harm plants because of _________ _______.
highest; microbial feeding
a lower C/N ratio promotes…
mineralization and plant availability
ammonia is _____ and ___ _______ to plants, instead it…
toxic and not available; goes to the atmosphere and causes N losses
volatilization
NH4 -> NH3 during high temperatures with good aeration
NO3 -> N2O -> N2 in wet soil with poor aeration
denitrification
microbes love what form of N?
N2
NO3 loss: down and horizontal
down = leaching
horizontal = erosion/runoff
functions of Mn
plant metabolism and N transformation
functions of Cu
helps with respiration and use of Fe
functions of Zn
plant metabolism, helps form growth hormones, reprodution
functions of B
water absorption by roots and translocation of sugars
functions of Cl
essential to some plant processes and acts in enzyme systems
functions of Fe
chlorophyll production
