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NRES 201: Terms
alfisols |
mildly acidic clays,high to medium base saturation
|
andisols |
from volcanic origins with mild weathering |
aridisols |
dry soils,desert shurbs |
entisols |
most recent soils,little profile development |
gelisols |
permafrost,very cold conditions |
histosols |
peat/bog, wet conditions, over 20% OM |
inceptisols |
embryonic with few diagnostic features, mild weathering |
mollisols |
high base saturation, dark colored, soft |
oxisols |
oxic horizon, highly weathered (most weathered of all soils) |
spodosols |
Fe,Al oxides, cool wet, sandy soils |
ultisols |
low base saturation |
mollic epipedon |
-mineral surface horizon noted for dark color (>0.6%organic matter C)
-thickness( > 25cm)
-softness even when dry
-high base saturation bigger then 50%
-moist atlest 3 months out of year when temp is 5C or higher to depth of 50cm
-developed undergrassland |
argillic horizons |
-subsurface accumulation of silicate clays(moved downeard from upper horizens)
-often found as coating
-shiney surface
-termed clay skins or argillans, concentrations of clay translocated from upper horizens |
vertisols |
high in swelling clays, deep cracks form when dry |
O-horizons |
organnic horizons that form above mineral soils or occur in an organic soil profile. They are derived from dead plant and animal residues. |
A-horizons |
The topmost mineral horizons contain enough partially decomposed organic matter. Generally dark |
E-horizons |
zones of max leaching or elluviation of clay , Fe, and Al oxides.It is lighter in color. found below A |
B horizons |
Zones where materials have accumulated by illuviation from the horizons above (O,A, or E) |
C horizons |
unconsolidated material underlying the solum (A and B) |
What are the four basic processes of soil formation? |
Transformation:soil constituents(primary minerals) modified chem or phys
Translocation-lateral/vertal movement of org or inorg material (percolation and capillary most common)
Additions-Inputs of material (fallen leaves)
Losses-materials lost to groundwater and erosion |
How does topography affect the soil formation/weathering |
-steep slopes generally encourage runoff and erosion
-stuff on top most weathered where tend to concentrate |
Four factors that influence the soil formations and how work |
-biota-living organisms including humans
-topography-steep slopes prevent formation of soil from getting ahead of soil destruction
--time-measured by rates of weathering (not yeas )
-temperature-for every 10 degress C loincrease, rate of biochemical reactions more then double. |
Define effective precipitation |
Portion of total precipitation that becomes available for plant growth or for promotion of soil formation.
|
What are principal climatic variable? |
principal climatic variable are effective precipitation and temperature |
Colluvial debris |
debris is made up of poorly sorted rock fragments detached from the heights
above and carried down slope. |
Alluvial stream deposits |
(floodplains, alluvial fans, and deltas): all detrital material
deposited or in transit by streams, including gravel, sand, silt, clay, and all variations and
mixtures of these. |
Lacustrine |
materials deposited in lake water and later exposed either by lowering the water
level or by the elevation of the land. |
wind |
Eolian, outwash,lacustrine,alluvial,marine |
ice |
till,moraine
|
gravity |
colluvial |
water |
lacustrine, alluvial, marine, colluvial |
Describe the characteristics of industrial and municipal by-products |
Municipal garbage-landill,very low nutrients
Food-processing waste-rich in nutrients
sewage efluent and sludge-both micro and macro nutrients
wastes of lumber industry- high c/n ratio |
short term solutions to deal with manure disposal |
•Discourage further manure applications to soils that are already high nutrients
•Promote compositing of manure to reduce the volume
•Eliminate the overfeeding of P supplements to all types of live stock
•Encourage the use of new corn varieties that contain less phytic acid P and more
organic P, resulting in the reduction of P excretion
•Mix Fe and Al compounds (e.g., alum) amendments to reduce the solubility of P |
What trace metals do we need to worry about most? What are the major sources of trace metals? |
Lead, cadmium and mercury are toxic trace metals in sewage effluent and sludge |
Can you name several organic nutrient sources? If so, which one has more N than P? |
Dairy Cow manure, feedlot cattle manure, poultry manure. All of them has more N than P |
what is the story of CAFOs that covered in lecture? |
Now, CAFOs, or concentrated animal feeding operations, are so far away from actual cropland that it is a hassle to transport their manure to the agricultural areas. |
How does the forest recycle nutrients? |
Undisturbed forests lose nutrients primarily by:
1) Leaching and runoff of dissolved ions and organic compounds
2) erosion of nutrient-containing organic litter and mineral particles
3) volatization of certain nutrients, especially during fires |
Maximum Allowable Daily Loading (MDL) |
It is the largest amount of nutrient runoff and leaching (g/ha/day) permitted from an area of land.
|
Define best mangement practices? |
-Butterstrips-one of most cost efective ways to protect water quality
-Cover crops- provide cover or crops, capture soluble nitrogen
-conservation tillage- keep atleast 30% o soil surace covered |
Explain four major goals of nutrient? |
-Cost effective production of high quality plants
-Effcient use and conservation of nutrient resources
-MAintenance or enhancement of soil quality
-protection of environment byeond the soil |
Know the organic carbon distribution in North America. Can you explain why? |
Carbon increases the farther up north we go because the deposition of plant resdues are higher than the rate of decomposition |
How do we gain soil carbon? |
Use no-till or conservation tillage instead of conventional tillage. This maintains a higher carbon level from the old plant material. |
How do we reclaim saline, saline-sodic and sodic soils? Know the methods for each soil including chemical reactions. Can you explain how & why they work? |
Saline: Reclamation of saline soils largely depends on 1) the provision of effective drainage and 2) the availability of good-quality irrigation water
Saline-sodic: -EC > 4 ds/m -ESP> 15 -pH <8.5 -not dispersed
-The high concentration of neutral salts (i.e., sources of Ca 2+ and Mg2+ ) moderates the dispersion effect by Na.
Sodic Soils: -EC < 4 ds/m -ESP > 15 -pH 8.5-10 or higher Na-bicarbonate contribute to the high pH. -dispersed |
In these three soils, explain the stability of colloids and other physical properties |
● Saline soils--since soluble salts help prevent dispersion of soil colloids, plants grown in this soil are not limited by poor infiltration, aggregate stability of aeration.
● Saline-sodic--Excess cations move in close to negatively charged colloidal particles, and reduce particles to repel each other.
● Sodic soils--Poor physical conditions, slow permeability to water, and unstable, cause soil organic matter to disperse. |
Explain what ESP is. Know how to estimate ESP |
Two expressions are used to describe the sodium status in soils:
Exchangeable Sodium Percentage (ESP):
Identifies the degree to which the exchange complex is saturated with sodium
ESP =Exchangeable Sodium (cmolc/kg)/ Cation exchange capacity (cmolc/kg) x 100%
In general, ESP > 15 means that the physical prop. soils are deteriorated and pH is > 8.5 |
How do we measure salinity and sodicity? Can you define two methods? |
total dissolved solid
electrical conductivity |
what are buffering mechanisms of soil |
-resdual acidity- Al oxides associated with clay and organic matter
-Exchangeable acidity-functional groups of OM and clay surfaces
-Active acidity pool-dissolved Al and H in solution |
Bufering mechanisms in soil |
cation exchange reactions
-hydrolysis of Al at very low Ph
-reactions with organic matter at moderate Ph levels
-dissociation of H+ ions from Ph dependent charge sites on certain clays
-precipitation and dissociation of carbonate minerals. |
What are pools of soil acidity |
Active acidity-concentration of H+
exchangable acidity- exchangable H+ and Al near clay mineral surfaces
Residual acidity-non-excahangable forms of H+ and Al 3+ |
Know acidification and alkalinizing processes |
Alkalinizing One- (exchanged carbonic acid at the roots membrane)
If reacts with H2O,
Alkalinizing Two-As long as minerals have enough exchangeable cations to accommodate
incoming H+ ions, pH of soil solution remains stable. |
Expansive clays |
Montmorillonite
smecite
vermiculite |
non expansive clays |
mica(illite)
chlorite
Pyrophyllite |
which soil minerals have IS and/or permanent charge |
1:1 soils do NOT have IS.
2:1 Non-expanding Silicate Clay: Mica (illite), Chlorite.
2:1 Expandable Silicate Clays: Montmorillonite, Smectite,Vermiculite
^All of these soil minerals have both IS and permanent/constant charge. |
what is isomorphous substitutional |
replacement of ions by another of similar size ions in a mineral, without fundamentally changing the structure
|
Explain the relationship between Eh and O2 content. |
Eh increases as O2 increases, and vice versa. They are directly proportional to each other. As soil gets drier, redox potential increases and more oxygen enters the system. Since oxygen is the best electron acceptor, its redox potential is high. |
describe factors influencing the soil aggregation process |
● biotic and abiotic factors
● organic matter acts as a natural glue
● tillage also influences aggregation
● dispersion vs. flocculation (mutual attraction among clay and organic molecules) |
What are the different soil structures? |
○ 1) spheroidal--found on surface, loosely packed
○ 2) plate-like--thin horizons, surface and subsurface
○ 3) block-like--subsurface (B horizon)
○ 4) prism-like--vertically oriented, subsurface with high sodium |
What are five soil properties that are influenced by the surface area (SA) of soil particles? |
1) Water retention: The greater the SA, the greater the retention.
2) Nutrient and other chemical retention: The greater the SA, the greater the retention of nutrients and contaminants.
3) The greater the SA, the greater the rate of release of nutrients from weatherable minerals.
4) The greater the SA, the greater the particle attraction, resulting in aggregation.
5) The SA provides habitats and reactive sites for soil microbes. |
what is hydraulic conductivity and what factors influence it. |
The ease with which a fluid (usually water) can move through pore spaces or fractures
.Alternation of the size and configuration of soil pores
Preferential flow |