ALS 3153 Exam 2
Unusual Soils
*HISTOSOL -organic soils. >20% OM, good for Ag if drained. Lake Okechobee-muck *VERTISOL -expandable clay soils (crack under alternate wet/dry conditions) -Difficult to plow, limited root penetration
soil pore space
-Affects rate of movement of air and water through soil. -Determined by soil texture and aggregate size(structure)
Importance of O Horizon
-Biologically active soil organisms, decomposition -Maintains Fertility -Depleted, altered in ag.
Natural System Examples
-Decidous Forest-big leaf drop in O horizon -Grassland-very deep, rich A horizon (grass roots go deep= high organic matter)
Human health problems with N in water
-EPA standards-10mg/L of nitrate -Toxic to infants and pregnant women
FL Soils
-Entisols -Ultisols -Histosols -Alfisols and Ultisols -coastal land types -spodosols
Phosphorous
-Erosion/ surface runoff -Immobilized quickly in soil -Limiting nutrient (in lakes specifically ) -important in cultural eutrophication -most becomes immobilized in sediments Added P -stimulates plankton circulates rapidly
History of synthetic fertilizer
-Haber Bosch Process -Industrial Revolution- 1909 -Implemented in Ag. -Fixes N2 into NH3 -requires energy.
Best soils for Ag
-Histosol -Mollisol -Alfisol
Dryland challenges
-Limited Rain -Variable Rain -Wind -Slope
biotic decomposition
-Many organisms (bacteria & fungi- only organisms that have the ability to decompose cellulose.) Recycles Nutrients -C & energy -All nutrient elements
Soil horizons in order
-O(literation surface), -A(mineral mixed with humus), - B(mineral soil, organic compounds have been converted into inorganic. - C (unmodified parent material)
Adding organic N to soil
-Organic N materials decompose, release nitrate -Nitrate used by decomposers -decomp and release of nitrate is fast
Black Sea Recovery
-P inputs cut in half -Reduced Synthetic Fertilizer -Closure of Live stock farms. -Closure of industries adding nutrients to water ways
Ways to conserve water
-Raised beds with mulch(delivers water directly to roots and limits evaporation) -Crop and cultivate choice (drought adapted crops like the pigeon pea)
Leaching of N depends on
-Type of N applied(inorganic) -soil type (sandy, porous) -soil depth (close to water table) -Amount of N applied (more N) -Timing of N applied (rain)
Poor soils for Ag
-Vertisol -Oxisol
soil profile
-a vertical section through a soil showing its succession of horizons and the underlying parent material -Horizons: individual layer
types of decomposition
-abiotic process-fire -Biotic process
soils become more acidic due to ...
-aerobic respiration -mineralization -leaching of bases by rain
Remediation of Salinity
-can be costy -option; lower water table. flush with clean water in well drained soils.
sand= silt= clay= OM=
-low WHC, few micropores -medium WHC -High WHC, many micropores (some hold more water than others) -high WHC
Nitrogen
-nitrates (NO3) -Leaching and erosion -more likely in shallow soils -contaminates shallow wells.
Ag. Inputs of water
-precipitation -surface water -ground water
Fire
-releases nutrients quickly -some nutrients lost in volatzation -Ash increase soil PH -more alkaline
Abiotic decomposition
-slash & burn -Swidden -shifting cultivation
4 factors of ET
-soil moisture -plant type -plant stage of development -Weather (humidity, solar radiation, wind)
Importance Of Soil
-support -aertion -water storage -nutrient storage -habitat -mineralization (regarding nutrients )
We have the same amount of water on the Earth now as we did
1 million years ago
Ways to modify cattle feed
1. Improve protein utilization efficiency of cattle (Can feed less N and excrete less N) 2. Develop indicators of N excess or deficiency in cattle. (evaluate milk for a specific type of N)
3 problems that occur with salinity and alkalinity when added NA replaces CA
1. less calcium available to plant 2. NA creates adverse effect on plant 3. PH increases alkalinity (affects availability of P and micronutrients)
Precipitation happens when relative humidity exceeds ____ and water vapor condenses into rain.
100%
Soil pH Level
<7 Acidic Neutral-7 >7 alkaline
Decomposition
A chemical reaction that breaks down compounds into simpler products.
Middle Age soil
ARDISOL -desert soil -minimal leaching, mineral rich. MOLLISOL -Grassland soil -fertiel, deep A horizon (midwest U.s) ALFISOL -hardwood forest -good soils (northeast U.s)
Permeability
Ability of rock or soil to allow water to flow through it
Salinization
Accumulation of salts in soil that can eventually make the soil unable to support plant growth. Detrimental to soil structure.
effects of desertification
Adverse impact on water cycle -increased runoff and evapotranspiration -decrease soil moisture Adverse effects on water supply -applies to irrigated semi-arid areas -less recharge of ground water -decreased quality of surface water
dryland ag is associated with parts of
Africa, the Western US and the Mediterranean
Given the soil characteristics summarized below, which among these choices would be the best farm for agriculture?
Alfisol, pH 6.5, low sodium, high CEC, high organic matter
Soil Animals
Animals speed up Decomp.: -break litter up. -stimulate microbial growth -predators increase growth rate of fungal and bacteria decomposers
Water logging of plants is a serious issue due to ______
Anoxia: impeded aerobic respiration, build up of toxins from anaerobic respiration. Photosynthetic ability.
Evidence of edema can come in the form of ____ on the underside of leaves where cells have _____
Brown spots or crystallized structures, stretched and collapsed
The field must be prepared beforehand by burying porous pipes under the soil that can _____ (tile drainage) to prevent waterlogging
Collect and drain off any excess water
______ is more prevalent in tropical regions. (Hurricanes)
Cyclonic precipitation: begin over water, Coriolis force causes rotation. Happens near equator. destructive but provides considerable rain.
Young Soil Orders (2)
ENTISOLS -new soils, lack of profile INCEPTISOLS -some beginnings of profile development
___ is when plants take up water faster than it can be transpired; water logging issue
Edema
The plant is ______ above the field surface so that if water pools and stagnates, it will _______.
Elevated on a mound, not drown the roots
___ is water lost from the land surface
Evaporation; requires energy, impacts salt water content, impacts water available to crops.
____ reflects the water lost from both the land and plant surfaces
Evapotranspiration
As pH decreases, alkalinity increases
False
The C horizon is critical to maintaining soil fertility
False
The amount of macropores does not impact drainage
False
The amount of water needed to saturate soil micropores
Field capacity
Water is not considered a ___ resource
Finite
____ is simply channeling water through ditches on the sides of plants in a field
Furrow irrigation
size of particles in order (decreasing )
Gravel-->sand-->silt-->clay
Risky mix of high and low C:N
High C:N residue + Inorganic N fertilizer = N from fertilizer immobilized by bacteria.
Cycle of Salinization
High Na>>Na replaces Ca>>Ca leaches out>>dispersion of clay and breakdown of soil structure>> Less permeability(reduced pore space)>>Less drainage>>Less leaching and removal of salts>> back to high Na.
Cycle of Eutrophication
Increased P --> Nutrient enrichment of lake --> Increased plant growth --> High production(plants, fish,etc)--> Decomposition(low O2)-->Dead organisms --> back to increased P
Household use contributions
Industrial and Urban sources as a non point source. Can be remediated by phosphates being removed/reduced from detergents and soaps.
Sandy soils are characterized by
Large particle size, low organic matter
Macropores promote
Leaching
Why do soils become acidic?
Leaching in high rainfall areas Crop removal of Ca, Mg (increased yield) Nitrification of Ammonium in N fertilizers
wilting point
Moisture level at which plants cannot extract water
PH effect on nutrient availability
Much more important to plants than direct effects of PH on plant growth !!!
how does fertilizer move
Nitrogen from crop leaches into the groundwater. Phosphorus from land occurs runoff into a lake
Fertilizer is a
Non-point source
Green Revolution
Norman Borlaug. a large increase in crop production in developing countries achieved by the use of fertilizers, pesticides, and high-yield crop varieties.
profile under pine forest
O Horizon-shallow A Horizon-(clear, leached) B Horizon-(spodic at top iron rich red)
Old Soil
OXISOL -highly weathered soil -nutrients leached out to great depth. Mineral hard pans (rainforest soils poor for ag.) UTISOL -weathered tropical soils -High Fe, respond to management
Causes of desertification
Overgrazing, Over-cultivation and Deforestation.
Which of the following is one of the worst soil orders for agricultural use?
Oxisol
regions that practice some dryland agriculture include the dry side of the Cascades in the ____ in a region referred to as ___
Pacific Northwest U.S., "The Palouse"
___ is more likely to be carried away through runoff
Phosphorus
Algal Turf Scrubber
Prevents farm nutrients from reaching rivers and bays
Water Issues include
Quality Quantity Soil Management
___ are used to prevent water-logging
Raised beds
Water can be ___ to reservoirs in the cycle that we cannot access to that are unusable
Relocated
Desiccation of plants has a negative impact on photosynthesis because the stomates___
Remained closed and cannot exchange gases
Remediation of sodicity
Remediated before salinity!! -expensive -more difficult if soil structure is destroyed
anaerobic respiration
Respiration that does not require oxygen
aerobic respiration
Respiration that requires oxygen
Water losses to the agricultural system include
Runoff and Percolation & Transpiration and Evaporation
Macropores
Space BETWEEN soil aggregates. Macropores drain freely by gravity and allow easy movement of water and air. They provide habitat for soil organisms and plant roots can grow into them. Promotes Leaching!!!
Micropores
Space WITHIN soil aggregates They are responsible for a soil's water-holding capacity. more micropores more WHC
The two most important reservoirs we use for irrigation in agriculture are
Surface water and groundwater
Percolation
The downward movement of water through soil and rock due to gravity. soil texture and structure are important.
soil solution
The liquid phase of soil, consisting of water and dissolved ions that are separate from the soil particles.
Easily available water
The portion of the water that is readily absorbed by plant roots- usually capillary water.
If the roots are sitting in water; _______
They cannot exchange gases
___ is one solution for situations where there is too much water
Tile drainage
___ is water lost from plant surface
Transpiration; passive process, 90% water is transpired. Moves minerals and sugar. Maintains turgor pressure.
Cimate is a major factor os soil PH
True
Hardpans can occur naturally
True
Humus extends into the A horizon.
True
The Ogallala aquifer is located in the
U.S. Great Plains
Soil profile is determined by
Vegetation, climate, weathering, topography and parent material
capillary water
Water that clings in the micropores (small pores, cracks, and spaces) against the pull of gravity, like water held in a sponge. the force is between 0.3 and 31 bars of suction
hydroscopic water
Water that is bound to surface of soil particles by molecular forces. This water can not be evaporated, used by plants or otherwise be removed by natural processes.
_____, water precipitates out of the atmosphere as rain or snow.
When humidity exceeds 100%
Is cultural eutrophication reversible?
Yes! Input being stopped or reduced. Ex, Tampa area and Black Sea
Woodchips
a material with a high C:N ratio
natural eutrophication
a natural process that occurs in an aging lake or pond as that body of water gradually builds up its concentration of plant nutrients. Florida Lakes (Shallow and Productive)
Composting
a process that allows the organic material in solid waste to be decomposed and reintroduced into the soil, often as fertilizer. C:N ratio important for process( determined time frame of availability)
an aquifer is
a water-bearing rock layer
Ecological problems with N in water
accelerates eutrophication
More H than OH
acidic
cultural eutrophication
an increase in fertility in a body of water, the result of anthropogenic inputs of nutrients. (house hold and commercial use of fertilizer, runoff, animal waste)
Nutrients added to lakes stimulate growth of
aquatic vegetation phytoplankton algae
dead zones
areas in water that have no light
more OH- than H+
basic
residual soil has mineral portion formed from...
bedrock below
Rain-fed agriculture ____ found in the semi-arid climate of the Western United States.
can be
the amount of water use ___ the future ability of a reservoir to store water
can change
Nutrients lost to leaching are most likely to ___ to groundwater
carry nitrates
Impair Symbiosis
caustic to bacteria
you can ____ delivered very precisely
control the rate and amount of water
OM is what in color
dark soil=high organic matter light soil(sand)=low organic matter
Moisture on the leaf surface (or even high relative humidity in the air) will ___ water lost from the stomates.
decrease
how does adding mulch impact rates of evapotranspiration?
decrease evapotransipiration
(tailwater return) would ___ the movement of contaminated water off of farms and __ the risk of off-target effects
decrease, decrease
if there is moisture on leaves, that gradient is going to be
decreased
one benefit of tile drainage is
decreased runoff
moisture on leaves ___ transpiration
decreases
this allows you to deliver the appropriate amount of water ____ to the soil surface (drip irrigation)
directly
Furrow irrigation is associated with
ditches
tailwater return
does not increase the off target effects of contaminated water.
Spodosols
dominant soil order in many parts of FL
leaching occurs as water moves ___ through soil regions that cannot hold more water
downward
The most efficient water delivery is through ___ because it is delivered right to the soil surface with less loss from evaporation
drip irrigation
the most efficient method of water delivery in irrigation systems is
drip irrigation
which of the following is not a type of precipitation we discussed in class?
dryland
The region on the _____ is where much of the wheat is grown
east side of the Cascade Mountains in Washington
it allows for the soil to collect moisture
fallow rotations - a trade off is intensive tillage *mechanically controls weed *erosion *water loss
water is a nonpolar molecule
false
water is easily extracted from all reservoirs
false
if you compared soil nutrient content and soil water content, there is ___
greater range for optimal growth in soil water content
Subsidence can be an issue in agricultural areas using
groundwater
Alkalinity
having a pH greater than 7
Fe forms insoluble compounds at ...
high PH
low porosity =
high permeability (sandy)
Water vapor moves from areas of ___ to ___ concentration
high to low. Ex. increased water on leaves means reduced transpiration & ET.
If the relative humidity at the leaf surface is ____, the air saturated with water and transpiration will be ___ because less water is able to evaporate into the air.
high, low
hard pan (b horizon)
impermeable layer high in iron Agriculture -from frequent plowing Natural -from leaching of surface minerals -mineral deposits
how will an increase in temp impact the rate of biotic decomposition
increase
Overuse of synthetic fertilizer can...
increase soil salinity
Wind will ___ evapo-transpiration because it _____ at the surface of the leaf that contains vaporized moisture.
increase, removes or decreases the boundary layer
Desertification leads to
increased runoff
Wind ____ it will ___ evapotranspiration
increases, increase
___ is a practice that is often used in conventional agriculture and can be associated with negative outcomes like increasing soil erosion and compaction
intensive tillage
gravitational water
is water held at low pressures that will drain freely down through and out of the soil in response to gravity. This water is unavailable to plants. occupies all marcopore spaces.
Aral Sea
lake that has lost 90% of water volume from irrigation projects; runoff with chemicals inside it flows into this lake and has made it polluted. Ecological Disaster.
arid climate
leaching limited by low rainfall. high salinity
Any reduction in water in the atmosphere creates a gradient for water to move from the
leaf to the atomsphere
An increase in pH makes phosphates and some micronutrients
less available
theses dryland agriculture regions receive __
less than 20 inches of precipitation annually
Soil in Gainesville is characterized by ____ organic matter
low
P forms insoluble compounds at ...
low PH
high porosity
low permeability (clay) *not always true
anaerobic decomposition releases....
methane
high C:N ratio
microbes use up all nitrogen in organic matter when consuming carbon, then the microbes use up the nitrogen in the soil. N becomes unavailable ex: wood, sawdust, uncomposted bark, high carbon, low nitrogen. Nitrogen tied up for awhile and Nitrogen robbing
saturation point
micropores and macropores filledddd with water (dripping and flooding)
soil components
minerals, organic and inorganic matter, chemical and physical weathering
Grasslands are typically
mollisol
lower PH
more acidic
soils receiving high precipitation
more acidic
soils receiving little precipitation
more alkaline
higher pH
more basic
Synthetic fertilizer (inorganic fertilizer)
most problematic. Inorganic and Soluble.
plow layer
no real O layer because O & A mixed
nutrient pollution
non-target effect. Concern of Nitrogen and Phosphorous in the environment. concern in aquatic systems. Sources; CAFOS, fertilizer, Industrial
The majority of organic fertilizers are __ immediately available for use by plants
not
you will __ find dryland agriculture is tropical environment like Malaysia
not
organic fertilizer
not immediately soluble. immobilized until mineralized. Not as prone to leaching.
water is __ to infiltration
not lost
Ph and plant growth
not much of a direct effect except at extreme PH values.
Nitrogen is ___ in the soil so it is easily leached
not quickly immobilized
What is the most common way that soil pH affects plant growth in agriculture?
nutrient availability impacted by soil pH
___ is stored in usable reservoirs
only 25%
Importance of C/N ratio
organic N becomes mineralized into Inorganic N or vise versa. As C:N ratio decreases decomposition proceeds faster. More organisms ca join in.
Sequence of events of decomposition
organic matter-->Detritus --> humus--> inorganic compounds
One of the most critical water quantity involves
over drafting of our groundwater supplies
Subsidence negatively impacts
percolation
subsidence negatively impacts...
percolation
the most critical nutrients transported by runoff and leadings to eutrophication is ....
phosphates to lakes
transpiration is evaporation from the
plant surface
CAFOs (concentrated animal feeding operations)
point source for N & P additions
___ is any agricultural situation in which more than one crop is grown at the same time
polyculture
Dryland agriculture relies on only __
precipitation (reservoir = atmosphere)
The region rely completely on ___ through the winter to maintain soil moisture
precipitation and the snow pack
orographic precipitation
precipitation that develops when warm, moist air cools and condenses as it rises against mountains. (prominent in the cascades, Sierra Nevada)
convective precipitation
precipitation that is induced when warm, moist air is heated at the ground surface, rises, cools, and condenses to form water droplets, raindrops, and eventually rainfall (FL summer storms)
C:N ratio
proportion of carbon to nitrogen present in organic matter. Slower decomposition if C;N is too high
the stratification of oxygen in oceanic dead zones can be attributed to
pycnocline
Phosphorus is ___ in the soil so it is NOT easily leached
quickly immobilized
Sodicity
refers to the concentration of sodium
this is because when water goes from liquid to a solid state, it ___ (exothermic reaction) (sprinklers)
releases heat
tile drainage
removes excess water
Deforestation contributes to desertification in semi-arid environments by
removing windbreaks
Microbes
required to mineralize those nutrients so that plants can utilize them
two kinds of entisols
rock & sand
_____ refers to water that moves over the surface of the land
runoff
which of the following does NOT represent a form of water used for irrigation in agriculture?
runoff
___ are going to be issues that impact surface water reservoirs
runoff, erosion and evaporation
Furrow irrigation can be associated with ___ (regarding issues)
salinity issues
percolation contributes to...
salts in groundwater reservoirs
Gainesville soil qualities
sandy and low OM
____ can also be contained in outgoing water and result in off-target effects
sediments and toxins
natural eutrophication occurs in ...
shallow, productive lakes
when remediating soils you must treat ____ before you treat ____
sodicity before salinity
In sodic soils
sodium replaces calcium
Rates of transpiration depend on the water potential gradient from the
soil to the atomsphere
Water holding capacity depends on..
soil type and amount of micropores
Ionic forms of nutrients are..
soluble in water
one of the concerns with utilizing overhead sprinklers is the
spread of water-borne diseases
____ may be utilized for frost protection
sprinklers
Reduced photosynthesis ; Desiccation
stomates must remain closed. CO2 taken up.
groundwater reservoirs are negatively impacted by ___
subsidence
soil characteristics
texture, structure, color, PH, CEC
matric effect
the amount of force needed for a plant to remove water from the soil. Low soil water= more energy to get water. Desiccation
Salinity
the amount of salt in water. Measured by electrical conductivity.
field capacity
the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. Micropores are full of water.
Field Capacity
the amount of water needed to saturate soil micropores
groundwater footprint
the area required to sustain groundwater use and groundwater-dependent ecosystem services
cation exchange capacity
the capacity of a soil for ion exchange of cations between the soil and the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect groundwater from cation contamination. Affected by PH. Good thing! Available to plant long term.
hydrological cycle (water cycle)
the movement of water through the environment from the atmosphere to Earth and back
Transpiration
the process of water movement through the plant with evaporation through stems, leaves, etc.
Groundwater use for irrigation is an issue because
the rate of use is higher than the natural rate of aquifer recharge
relative humidity
the ratio of the amount of water in the air at a give temperature to the maximum amount it could hold at that temperature.
Porosity
the volume of open spaces in rock or soil
where is cyclonic precipitation most prevalent?
tropical region
Nitrates can be toxic to human health.
true
Decomposition Rates...
vary widely -climate and temp (faster decomposition in warm climates) -tillage increases decomposition. composition of the material (C:N ratio)
water of hydration
water that is chemically combined with a substance to form a hydrate and can be expelled (as by heating) without essentially altering the composition of the substance
infiltration
water that is soaks into the ground, into the rhizosphere or root zone where plants can utilize it
Inorganic nutrients are the forms that are ___ so they can move off-farm and have negative off-targets impact
water-soluble
the excess water often contains ___ or other compounds that can contaminate groundwater supplies
water-soluble nutrients
Aggregates:
what soil structure is really referred to. groups of soil particles that hold together. Important for aeration and water holding capacity.
compensation point
when all carbon dioxide that plants produce in respiration is used up in photosynthesis, the rates of the two processes are equal and their is no net release of either oxygen or carbon dioxide.
dew point
when condensation occurs. -surface- fog & mist -atmosphere- clouds -rain-as temp drops.
permanent wilting point
when the water potential of the soil is so low that water cannot be extracted by the roots. Not enough moisture.
tailwater return
would suggest that water that is moved through agricultural fields is collects and contained
