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Certified Crop Advisor Western Region Exam. 388 Questions With 100% Correct Answers 2024.
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Certified Crop Advisor Western RegionExam. 388 Questions With 100% Correct
Answers 2024.
Size of sand and its characteristics
.05mm to 2.0mm, lower CEC, lower water holding capacity
Size of silt
.002mm - .05mm
Size of Clay
less than .002mm
Define bulk density
the ratio of the mass of soil to its bulk volume. expressed in g/cm3
How does bulk density differ with soil texture
sandy soil has higher bulk density because has less overall pore space.
Bulk density ranges of sand
1.2-1.8 g/cm3
Bulk density range for silt and clay
1.0-1.6 g/cm3
How does bulk density affect soils and plant growth
Increased bulk density = more compaction, root growth impaired, aeration and waster infiltration
impaired
How does bulk density affects the interpretation of nitrate levels
oxygen supply and mineralization are slowed. Dry soil sample below 100 degrees F with soil sample .
Increase over time if soil is moist.
Soil structure
Arrangement of soil particles into groupings.
Soil aggregates
the groupings of soil particles
Different types of soil structure
,granular, blocky, prismatic, platy
list benefits of well-developed aggregates
small particles clump together to form more macrospores = better infiltration, aeration, provides habitat
for various microorganism, bulk density
how do soil organisms and soul organic matter affect soil strucutre
aggregation formed by physical and chemical processes.
Soil microorganisms excrete substances that act as cementing agents and bind soil particles together.
Fungi have filaments, called hyphae, which extend into the soil and tie soil particles together.
Roots also excrete sugars into the soil that help bind minerals.
How does soil management affect soil structure
Adding gypsum (Ca2+) = electrostatic attraction binds soil
tillage = breaks up aggregates, increases rates of decomposition reducing soil OM
Cover crops/manures build OM
How does exchangeable sodium affect soil aggregation and waste movement in soils
high NA+ concentration displaces Ca2+ in soil. Sodium cannot bind soil particles because it is a
monovalent ion, which results in deflocualtion and reduced water infiltration. Makes leaching difficult
How does soil salinity affect soil aggregation and water
soluble salts. increase salinity but Na is a small fraction of cation no serious soul structure or drainage
issues
How structure can affect root growth
poor structure, increases compaction, reduces rooting depth/accumulation of nutrients, drain
poorly/waterlogged
How does soil organic matter (SOM) affect soil aggregation
increased OM increases aggregation through physical and chemical processes
SOM affect on water holding capacity and infiltration
increases pore space/network of pores allowing for infiltration and waster holding capacity. Like a
sponge.
a 1% increase in OM, increases water holding capacity by how much
3,400 gallons per acre (3.7% increase)
SOM affect on Cation exchange capacity
increasing OM increases CEC because OM in negatively charged
How OM is related to temperature
,increase in temp, results in rapid decomposition of OM. colder climates generally have higher OM %
Role of OM in pesticide movement
OM binds pesticides and can make them less active
cation exchange capacity
a measure of the soil's ability to hold positively charged ions.
List three ways to maintain OM
reduce tillage, cover crops, avoid soil compaction and keep proper ph
Importance of soil OM in nutrient management
CEC, mineralization C:N ratio, 3% of soil OM overturns each year
Define salt
any ionic compound whose cation comes from a base and it's anion comes from an acid
a user of irrigation water should know the effects that water quality and irrigation practices have on
what (6 elements)?
salt content (salinity) of soil
sodium status (sodicity) of soil
rate of water infiltration
toxic element content of soil
soil nutrient status
plugging of microirrigation systems
define parts per million
1 part of salt to 1 million parts of water
define milliequivalents per liter
a measurement of charge concentration per liter
convert ppm to meq/l
ppm = equivalent weight x meq/l
Define saline soil
a soil containing enough soluble salts to interfere with plant growth, but not containing an excess of
exchangeable sodium
Define salinity
the amount of salt dissolved in water
Define sodium absorption ratio (SAR)
, ratio of sodium to the sum of calcium and magnesium, measured on the basis of cation charges
Define electrical conductivity
measure of the bulk salinity in soil (ECe) or water (ECw)
What is the formula for SAR
SAR= Na/Square root of Ca+Mg/2 (%)
Define total dissolved solids
the measure of bulk salinity, usually only used for water (PPM)
calculate how much salt is applied per acre foot of water?
salts applied in lbs = TDS x 2.72
how many gallons is an acre foot of water
326,000 gallons
Define exchangeable sodium percentage (ESP)
Percentage of cation charges represented by sodium
Formula for ESP
(Na/sum of base cations)x100
Electrical conductivity of a saline soil
greater than 4 ds/m
Exchangeable sodium percentage (ESP) of a saline soil
less than 15 %
pH of a saline soil
less than 8.5
Sodium absorption ratio (SAR) of a saline soil
less than 13
Define a sodic soil
sodium concentration high enough to adversely affect structure, while overall salt concentration is below
saline threshold
Electrical conductivity of a sodic soil
less than 4 EC
pH of a sodic soil
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