PDC Soil Health & Regeneration Techniques 3 — Questions and Answers
Question 1: What is 'biochar' and how does it primarily benefit soil in a permaculture system?
- A liquid seaweed extract that feeds soil bacteria
- Charred organic matter that provides long-term carbon sequestration and microbial habitat (Correct answer)
- A composted manure blend with activated minerals
- A biological fungicide derived from wood ash
Correct answer: Charred organic matter that provides long-term carbon sequestration and microbial habitat
Biochar is charred organic material with a porous structure that persists in soil for centuries, improving microbial habitat, water retention, and nutrient holding capacity.
Question 2: Actinomycetes (actinobacteria) in healthy soil are responsible for producing which recognizable characteristic?
- The sour smell after heavy rain
- The earthy petrichor smell of healthy soil (Correct answer)
- The ammonia odor in over-fertilized fields
- The sulfur smell in waterlogged soils
Correct answer: The earthy petrichor smell of healthy soil
Actinobacteria produce geosmin, the compound responsible for the characteristic earthy 'petrichor' smell associated with healthy, biologically active soil.
Question 3: Which nitrogen-fixing tree is widely used in permaculture agroforestry to rapidly build soil fertility through chop-and-drop mulching?
- Black walnut (Juglans nigra)
- Leucaena (Leucaena leucocephala) (Correct answer)
- Eastern red cedar (Juniperus virginiana)
- Osage orange (Maclura pomifera)
Correct answer: Leucaena (Leucaena leucocephala)
Leucaena is a fast-growing nitrogen-fixing tree widely used in tropical permaculture systems for chop-and-drop mulching, providing high-nitrogen biomass to build soil.
Question 4: What does 'cation exchange capacity' (CEC) measure in a soil test?
- The rate at which water drains through soil
- The soil's ability to hold positively charged nutrient ions (Correct answer)
- The proportion of sand, silt, and clay particles
- The total organic matter percentage
Correct answer: The soil's ability to hold positively charged nutrient ions
CEC measures the soil's capacity to hold and exchange positively charged nutrient cations (Ca²⁺, Mg²⁺, K⁺, Na⁺), indicating fertility and nutrient availability.
Question 5: In Elaine Ingham's soil food web model, what role do protozoa play in nutrient cycling?
- They fix atmospheric nitrogen directly into the soil
- They graze on bacteria and release nitrogen in plant-available form (Correct answer)
- They decompose lignin and complex carbon compounds
- They transport phosphorus from parent material to plant roots
Correct answer: They graze on bacteria and release nitrogen in plant-available form
Protozoa graze on bacteria and excrete excess nitrogen as ammonium (NH4+), releasing it in a plant-available form in the rhizosphere near plant roots.
Question 6: What is the main purpose of inoculating compost or soil with 'effective microorganisms' (EM)?
- To sterilize the soil and prevent pathogen competition
- To introduce beneficial microbial consortia that accelerate decomposition and suppress pathogens (Correct answer)
- To adjust soil pH to neutral
- To increase soil density for better root anchorage
Correct answer: To introduce beneficial microbial consortia that accelerate decomposition and suppress pathogens
EM introduces a consortium of beneficial microorganisms (lactic acid bacteria, yeasts, photosynthetic bacteria) that improve fermentation, decomposition, and disease suppression.
Question 7: Which nutrient ratio is most important for healthy fungal growth in compost, and what is its ideal value?
- Nitrogen to phosphorus (N:P) ratio of 10:1
- Carbon to nitrogen (C:N) ratio of 25-30:1 (Correct answer)
- Calcium to magnesium (Ca:Mg) ratio of 7:1
- Potassium to sulfur (K:S) ratio of 15:1
Correct answer: Carbon to nitrogen (C:N) ratio of 25-30:1
A C:N ratio of 25-30:1 provides the right balance for microbial decomposition — enough carbon energy for fungi and enough nitrogen for protein synthesis.
PDC Soil Health & Regeneration Techniques 3
What is 'biochar' and how does it primarily benefit soil in a permaculture system?