Certified Crop Advisor Western Region Exam 388
Questions With 100% Correct Answers 2025
what are the two types of plant tissue samples? - ANSWERS-leaf w/ or w/o petiole and
petiole
how many leaves are needed for a composite sample for plant tissue analysis? -
ANSWERS-20-100 of a representative sample
leaf samples are used to measure what? - ANSWERS-total concentration of both macro
and micro nutrients
petiole samples are used to measure what? - ANSWERS-concentration of assimilated
macronutrients
when should petiole samples be collected? - ANSWERS-in morning
store leaf and petiole samples in what? - ANSWERS-paper bags
do N,P,K decline over the growing season in plant tissues?> - ANSWERS-yes
standards are created for tissue sampling (Y or N)? - ANSWERS-yes
how do you handle petiole tissue samples? - ANSWERS-remove from leaf immediately,
oven-dry or refrigerate before sending to lab
what is a critical value or concentration in tissue sampling? - ANSWERS-the level that
results in 90% of maximum yield or growth
what is sufficiency threshold in tissue sampling? - ANSWERS-when a plant will or will
not respond to fertilizer
what leaves do you mostly sample? - ANSWERS-most recently matured (MRM)
when will a response in fertilizer be affective in tissue sampling - ANSWERS-response
@ lower limit of sufficiency range. No response above sufficiency threshold
who regulates the manufacture and use of fertilizers in California - ANSWERS-CDFA
interpret N-P-K on fertilizer label - ANSWERS-by weight basis. Multiply by .83 for K and
by .43 or P.
,Size of sand and its characteristics - ANSWERS-.05mm to 2.0mm, lower CEC, lower
water holding capacity
Size of silt - ANSWERS-.002mm - .05mm
Size of Clay - ANSWERS-less than .002mm
Define bulk density - ANSWERS-the ratio of the mass of soil to its bulk volume.
expressed in g/cm3
How does bulk density differ with soil texture - ANSWERS-sandy soil has higher bulk
density because has less overall pore space.
Bulk density ranges of sand - ANSWERS-1.2-1.8 g/cm3
Bulk density range for silt and clay - ANSWERS-1.0-1.6 g/cm3
How does bulk density affect soils and plant growth - ANSWERS-Increased bulk density
= more compaction, root growth impaired, aeration and waster infiltration impaired
How does bulk density affects the interpretation of nitrate levels - ANSWERS-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 - ANSWERS-Arrangement of soil particles into groupings.
Soil aggregates - ANSWERS-the groupings of soil particles
Different types of soil structure - ANSWERS-granular, blocky, prismatic, platy
list benefits of well-developed aggregates - ANSWERS-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 - ANSWERS-
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 - ANSWERS-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 -
ANSWERS-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 - ANSWERS-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 - ANSWERS-poor structure, increases
compaction, reduces rooting depth/accumulation of nutrients, drain poorly/waterlogged
How does soil organic matter (SOM) affect soil aggregation - ANSWERS-increased OM
increases aggregation through physical and chemical processes
SOM affect on water holding capacity and infiltration - ANSWERS-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 - ANSWERS-
3,400 gallons per acre (3.7% increase)
SOM affect on Cation exchange capacity - ANSWERS-increasing OM increases CEC
because OM in negatively charged
How OM is related to temperature - ANSWERS-increase in temp, results in rapid
decomposition of OM. colder climates generally have higher OM %
Role of OM in pesticide movement - ANSWERS-OM binds pesticides and can make
them less active
cation exchange capacity - ANSWERS-a measure of the soil's ability to hold positively
charged ions.
List three ways to maintain OM - ANSWERS-reduce tillage, cover crops, avoid soil
compaction and keep proper ph
Importance of soil OM in nutrient management - ANSWERS-CEC, mineralization C:N
ratio, 3% of soil OM overturns each year
Define salt - ANSWERS-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)? - ANSWERS-salt content (salinity) of soil
Questions With 100% Correct Answers 2025
what are the two types of plant tissue samples? - ANSWERS-leaf w/ or w/o petiole and
petiole
how many leaves are needed for a composite sample for plant tissue analysis? -
ANSWERS-20-100 of a representative sample
leaf samples are used to measure what? - ANSWERS-total concentration of both macro
and micro nutrients
petiole samples are used to measure what? - ANSWERS-concentration of assimilated
macronutrients
when should petiole samples be collected? - ANSWERS-in morning
store leaf and petiole samples in what? - ANSWERS-paper bags
do N,P,K decline over the growing season in plant tissues?> - ANSWERS-yes
standards are created for tissue sampling (Y or N)? - ANSWERS-yes
how do you handle petiole tissue samples? - ANSWERS-remove from leaf immediately,
oven-dry or refrigerate before sending to lab
what is a critical value or concentration in tissue sampling? - ANSWERS-the level that
results in 90% of maximum yield or growth
what is sufficiency threshold in tissue sampling? - ANSWERS-when a plant will or will
not respond to fertilizer
what leaves do you mostly sample? - ANSWERS-most recently matured (MRM)
when will a response in fertilizer be affective in tissue sampling - ANSWERS-response
@ lower limit of sufficiency range. No response above sufficiency threshold
who regulates the manufacture and use of fertilizers in California - ANSWERS-CDFA
interpret N-P-K on fertilizer label - ANSWERS-by weight basis. Multiply by .83 for K and
by .43 or P.
,Size of sand and its characteristics - ANSWERS-.05mm to 2.0mm, lower CEC, lower
water holding capacity
Size of silt - ANSWERS-.002mm - .05mm
Size of Clay - ANSWERS-less than .002mm
Define bulk density - ANSWERS-the ratio of the mass of soil to its bulk volume.
expressed in g/cm3
How does bulk density differ with soil texture - ANSWERS-sandy soil has higher bulk
density because has less overall pore space.
Bulk density ranges of sand - ANSWERS-1.2-1.8 g/cm3
Bulk density range for silt and clay - ANSWERS-1.0-1.6 g/cm3
How does bulk density affect soils and plant growth - ANSWERS-Increased bulk density
= more compaction, root growth impaired, aeration and waster infiltration impaired
How does bulk density affects the interpretation of nitrate levels - ANSWERS-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 - ANSWERS-Arrangement of soil particles into groupings.
Soil aggregates - ANSWERS-the groupings of soil particles
Different types of soil structure - ANSWERS-granular, blocky, prismatic, platy
list benefits of well-developed aggregates - ANSWERS-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 - ANSWERS-
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 - ANSWERS-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 -
ANSWERS-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 - ANSWERS-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 - ANSWERS-poor structure, increases
compaction, reduces rooting depth/accumulation of nutrients, drain poorly/waterlogged
How does soil organic matter (SOM) affect soil aggregation - ANSWERS-increased OM
increases aggregation through physical and chemical processes
SOM affect on water holding capacity and infiltration - ANSWERS-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 - ANSWERS-
3,400 gallons per acre (3.7% increase)
SOM affect on Cation exchange capacity - ANSWERS-increasing OM increases CEC
because OM in negatively charged
How OM is related to temperature - ANSWERS-increase in temp, results in rapid
decomposition of OM. colder climates generally have higher OM %
Role of OM in pesticide movement - ANSWERS-OM binds pesticides and can make
them less active
cation exchange capacity - ANSWERS-a measure of the soil's ability to hold positively
charged ions.
List three ways to maintain OM - ANSWERS-reduce tillage, cover crops, avoid soil
compaction and keep proper ph
Importance of soil OM in nutrient management - ANSWERS-CEC, mineralization C:N
ratio, 3% of soil OM overturns each year
Define salt - ANSWERS-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)? - ANSWERS-salt content (salinity) of soil
