PDC Soil Health & Regeneration Techniques 4 — Questions and Answers
Question 1: What is 'terra preta' and why is it significant in permaculture soil design?
- A volcanic soil type found in Hawaii known for high mineral content
- Ancient Amazonian dark earth created by indigenous people using charcoal and organic waste, still fertile after 2,500 years (Correct answer)
- A Brazilian biodynamic composting method using clay inoculants
- Deep red laterite soil that must be amended with lime before cultivation
Correct answer: Ancient Amazonian dark earth created by indigenous people using charcoal and organic waste, still fertile after 2,500 years
Terra preta is ancient Amazonian dark earth containing biochar, bones, and organic matter, demonstrating that humans can create permanently fertile soils in nutrient-poor environments.
Question 2: In soil remineralization, what is the purpose of applying crushed basalt rock dust?
- To lower soil pH for acid-loving plants
- To reintroduce a broad spectrum of trace minerals weathered out of agricultural soils (Correct answer)
- To improve drainage in clay-heavy soils
- To add organic matter and increase water-holding capacity
Correct answer: To reintroduce a broad spectrum of trace minerals weathered out of agricultural soils
Crushed basalt slowly weathers to release a broad spectrum of trace minerals and silica, remineralizing soils depleted by agriculture and mimicking natural geological weathering.
Question 3: What problem does 'soil capping' (surface crusting) cause for water infiltration, and what permaculture practice prevents it?
- It increases water infiltration; prevented by compaction
- It seals the surface and causes runoff; prevented by keeping soil covered with mulch (Correct answer)
- It improves water retention; prevented by tillage
- It blocks nutrient uptake; prevented by chemical fertilizers
Correct answer: It seals the surface and causes runoff; prevented by keeping soil covered with mulch
Surface crusting seals pores and causes water to run off rather than infiltrate; permanent mulch cover protects soil structure and maintains infiltration capacity.
Question 4: Which describes the correct layering sequence for a classic 'lasagna' or sheet mulch garden bed from bottom to top?
- Compost → cardboard → straw → wood chips
- Cardboard → compost → straw → wood chips (Correct answer)
- Wood chips → straw → cardboard → compost
- Straw → compost → cardboard → wood chips
Correct answer: Cardboard → compost → straw → wood chips
In sheet mulching, cardboard goes directly on soil/grass to smother weeds, followed by compost for nutrients, straw for moisture retention, and wood chips as a top mulch layer.
Question 5: What is the primary ecological function of 'pioneer species' like fireweed (Chamerion angustifolium) on degraded or bare soils?
- They outcompete all other plants and prevent succession
- They rapidly colonize bare soil, adding organic matter and creating conditions for subsequent species (Correct answer)
- They fix atmospheric nitrogen to enrich impoverished subsoils
- They attract pollinators but provide no direct soil benefits
Correct answer: They rapidly colonize bare soil, adding organic matter and creating conditions for subsequent species
Pioneer species colonize bare or disturbed ground, reduce erosion, add organic matter as they die back, and modify microclimate to enable succession toward more complex communities.
Question 6: In biodynamic preparation BD 500 (horn manure), what is the purpose of burying manure in a cow horn over winter?
- To pasteurize the manure and kill weed seeds
- To allow fermentation and microbial transformation that creates a highly potent soil activator (Correct answer)
- To concentrate nitrogen into a slow-release pellet form
- To create a biochar-like substance through anaerobic decomposition
Correct answer: To allow fermentation and microbial transformation that creates a highly potent soil activator
BD 500 undergoes a winter fermentation process in the horn that Rudolf Steiner claimed transforms the manure into a highly potent substance for stimulating soil microbial life.
Question 7: What does 'percolation rate' measure in a site soil assessment, and why is it important for design?
- The rate of organic matter decomposition per month
- How quickly water drains through the soil, indicating drainage capacity for plant placement and water features (Correct answer)
- The speed at which capillary action draws water upward
- The rate of nitrogen mineralization under aerobic conditions
Correct answer: How quickly water drains through the soil, indicating drainage capacity for plant placement and water features
Percolation rate (measured by the 'perc test') determines how fast water drains, guiding decisions about pond placement, swale design, and which plants tolerate wet or dry conditions.
PDC Soil Health & Regeneration Techniques 4
What is 'terra preta' and why is it significant in permaculture soil design?