PDC Soil Health & Regeneration Techniques 2 — Questions and Answers
Question 1: Which soil organism is primarily responsible for forming stable soil aggregates by producing glomalin?
- Earthworms
- Mycorrhizal fungi (Correct answer)
- Nitrogen-fixing bacteria
- Nematodes
Correct answer: Mycorrhizal fungi
Mycorrhizal fungi produce glomalin, a glycoprotein that glues soil particles into stable aggregates improving structure and water retention.
Question 2: In a permaculture sheet mulch system, what is the purpose of the cardboard or newspaper layer placed directly on grass?
- To add carbon nutrients to the soil
- To smother existing vegetation and block light (Correct answer)
- To improve drainage
- To attract earthworms from deeper layers
Correct answer: To smother existing vegetation and block light
The cardboard or newspaper layer smothers existing vegetation by blocking light and oxygen, suppressing weeds while decomposing into organic matter.
Question 3: What does a Brix reading measure in the context of soil and plant health?
- Soil pH level
- Dissolved solids including sugars in plant sap (Correct answer)
- Microbial biomass per gram of soil
- Cation exchange capacity
Correct answer: Dissolved solids including sugars in plant sap
A Brix refractometer measures dissolved solids (primarily sugars and minerals) in plant sap, serving as an indicator of plant nutrient density and soil fertility.
Question 4: Which cover crop is most effective at breaking compaction with its deep taproot?
- Crimson clover
- Winter rye
- Daikon radish (Correct answer)
- Buckwheat
Correct answer: Daikon radish
Daikon radish develops a deep, thick taproot that physically breaks through compacted soil layers, leaving channels for water and air when it decomposes.
Question 5: What is the primary role of the 'fungal to bacterial ratio' (F:B ratio) in soil assessment?
- It measures total nitrogen availability
- It indicates whether soil food web favors perennial or annual plant communities (Correct answer)
- It quantifies heavy metal contamination levels
- It predicts soil water-holding capacity
Correct answer: It indicates whether soil food web favors perennial or annual plant communities
The F:B ratio indicates ecosystem successional stage — high fungal ratios support perennials and forests, while bacterial-dominated soils favor annuals and disturbed land.
Question 6: In humanure composting as described by Joseph Jenkins, what minimum internal temperature must a hot compost pile reach to safely kill pathogens?
- 120°F (49°C)
- 131°F (55°C) (Correct answer)
- 145°F (63°C)
- 160°F (71°C)
Correct answer: 131°F (55°C)
Jenkins' humanure handbook recommends maintaining 131°F (55°C) for several consecutive days to kill pathogens and produce safe compost.
Question 7: Which practice best describes 'keyline plowing' and its primary soil benefit?
- Plowing along contour lines to maximize erosion
- Plowing slightly off-contour to spread water from valleys to ridges (Correct answer)
- Deep vertical tillage to break hardpan
- Minimum tillage using knife-cut slots for seeds
Correct answer: Plowing slightly off-contour to spread water from valleys to ridges
Keyline plowing runs slightly off-contour to redirect water from valleys toward ridges, distributing moisture evenly across the landscape and building topsoil.
PDC Soil Health & Regeneration Techniques 2
Which soil organism is primarily responsible for forming stable soil aggregates by producing glomalin?