HORT Organic Gardening Final, Hort 3300 Final UPDATED ACTUAL Exam Questions and CORRECT Answers
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Course
HORT Organic Gardening
Institution
HORT Organic Gardening
HORT Organic Gardening Final, Hort 3300
Final UPDATED ACTUAL Exam
Questions and CORRECT Answers
Define and describe the similarities and differences between the 'Law of the Minimum" and
"Law of Return." Include the originators of these theories and explain where they fit into
current garde...
HORT Organic Gardening Final, Hort 3300
Final UPDATED ACTUAL Exam
Questions and CORRECT Answers
Define and describe the similarities and differences between the 'Law of the Minimum" and
"Law of Return." Include the originators of these theories and explain where they fit into
current gardening practices. Is one mutually exclusive of the other - CORRECT ANSWER-
✔✔-The law of minimum is a theory by Justus Von Liebig. The theory states that the soil
must contain all the components it needs to produce good plant growth and if it doesn't have
all the elements then the plant will reach a certain growth and not exceed it
-Law of return is a theory by Sir Albert Howard. This theory focused on more than just the
nutrients in the soil but the soil as a system. The idea is that you grown the plants and keep
what you want and decompose the rest of the plant that is not used that contains good
nutrients back into the soil.
-In current agriculture practices: the reason we add fertilizer and compost today
-The laws are mutually exclusive, because plant residues returned to the soil are a source of
nutrients
-These two theories are the reasons we add fertilizer and compost to our soil today
***what are the similarities and differences?
Law of the minimum states that growth is controlled not by the total amount of resources
available, but by the scarcest resources. Justus Von Liebig- believed plants find nutrients only
in inorganic substances- devalued importance of humus; lacks reference to soil
Law of return (albert howard-founder/pioneer of organic movement): put back in the soil
what you take out the recycling of all organic waste materials back to farmland.
Doesnt disagree with Law of Minimum- believes in composting
Plants produce die and nutrients return to soil
Closed System
The law of the minimum and the law of return are NOT mutually exclusive (modern view:
law of minimum is true but only part of the puzzle; law of return is a gardening practice for
organics)
Describe the overall processes a complex nitrogen source, like feather meal, must go through
in the soil to reach the point at which the plant will take it up. What is the "final" form of N
that is most commonly taken up by the plant? List two soil environmental conditions that
must exist for this to happen. - CORRECT ANSWER- ✔✔-Nitrogen must be converted from
,organic form to inorganic form, and this is done through the microbial activity in two steps:
ammonification and mineralization
--Ammonification is the conversion of organic nitrogen (N) in soil organic matter (like
feather meal) to ammonium (NH4-)
--Nitrification then occurs, which is where the ammonium is rapidly converted by a microbe
to nitrate (NO3-). This is the final form that the plant takes up
***Soil environmental conditions necessary:
-Oxygen must be present for microbes to live
-Temp must be between 77-95 F for mineralization to occur
What is the typical percentage of organic matter (OM) in the soil? List and describe the
components of OM? What component does not continue to break down? What are two (20
garden practices that increase OM? What are two practices that deplete OM? (Explain
how/what these practices actual do to effect OM, not just that they decrease or increase....i.e.
provide a scientific explanation) - CORRECT ANSWER- ✔✔• Typical percentage of OM in
the soil is between 3% and 5% (this is what you aim for)
• Components
i. Dead Plants
ii. Animal and microbial waste products
iii. Humus
1. Humus is the result of dead plants and animal waste broken down into matter that is
amorphous
2. Term coined in the late 1700s
3. Influences bulk density, contributes to moisture and nutrient retention
4. Humus is the component that does not break down further
b. Increase
. Add compost
1. The materials going through decomposition will release OM)
i. Grow cover crops and then till into soil
1. The plant material tilled into the soil will break down into OM)
c. Decrease
. Erosion
1. OM washes away
, i. Excessive tilling
The loose soil that results from tilling has less structure than before; the appearance is
deceptive. Moreover, tillage when the soil is too moist or too dry leads to compaction or
pulverization of soil
What is the "perfect" balance of soil water, air, minerals, OM (in percentages)? List and
describe 2 gardening practices that might negatively affect that balance and 2 gardening
practices that could improve or help maintain that balance. - CORRECT ANSWER- ✔✔-
25% air
-25% water
-45% mineral particles
-5% organic matter
-Negative practice: Compacting the soil (decreases the pore space available for water and air)
and tiling the soil (loss of organic litter on soil surface, increases the soil temp, causes loss of
OM that could be used as food substrate)
Positive practice: adding compost (can increase the organic matter that might be low as 5%)
and cover crop (reduce the oxidation and CO2, slow erosion, and increase water filtration)
Plant Disease. 1a) List the three components (or sides) of the disease triangle. 1b) Describe
three specific environmental manipulations that farmers/gardeners may use to manage or
prevent plant pathogens ecologically (organic practices). 1c) Describe three (3) specific plant
host manipulations that farmers/gardeners may use to manage or prevent plant pathogens
ecologically (organic). - CORRECT ANSWER- ✔✔1a) List the three components (or sides)
of the disease triangle.
1. Host - stressed or injured plant
2. Pathogen - capable of causing disease (many are host specific)
3. Environment - wet foliage or soils, high humidity, poor air circulation
1b) Describe three specific environmental manipulations that farmers/gardeners may use to
manage or prevent plant pathogens ecologically (organic practices).
1. Increasing plant spacing (reduces humidity and decreases infection)
2. Regulating the amount of irrigation and drainage (no excess water buildup)
3. Location selection (climate and soil, landscape, soil biodiversity, etc)
1c) Describe three (3) specific plant host manipulations that farmers/gardeners may use to
manage or prevent plant pathogens ecologically (organic).
1. Purchase and use clean seeds and transplants
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