Teaching Organic Farming and Gardening

Making and Using Compost

Unit 1.7 | 15
Students’ Lecture Outline

j. assessing compost Maturity and stability

1. Parent material should be largely indistinguishable, texture should be crumbly


2. Temperature has cooled down to ambient temperature


3. Signs of macro life (e.g., redworms, sowbugs, springtails), though may not be present in
   large-scale operations


4. Dark brown to blackish-brown color


5. Earthy smell (no ammonium or anaerobic odor)


6. Feels “greasy” or slick when squeezed between fingers


7. Maturity vs. stability: A set of 7 quantitative indicators are used to define the maturity and
   stability of compost

• pH: 6.5 to 8.0

• Sulfides: zero to only trace

• Ammonia = <0.05 ppm

• Ammonium: 0.2 to 3.0 ppm

• Nitrites: <1.0 ppm

• Nitrates: <300 ppm

• CO 2 : <1%

Quantitative indicators adapted from “Quality Guidelines for Compost Chart,” compiled by Jon Nilsson (East Coast

Compost) and Autrusa Compost Consulting criteria (George Leidig, Blue Bell, PA)

K. applying compost

1. Timing

a) Spring, prior to planting

b) Mid season, as “side dress”

c) Fall, with a planting of cover crops

2. Application rates

a) Application rates vary with intensiveness of cropping system and use of cover crops

b) Field scale: ~4–7 tons/acre on an annual basis

c) Garden scale: ~10–20 tons/acre on an annual basis (1–2 lbs/square foot for soil
development, 0.5–1 lb/square foot for maintenance)

3. Placement

a) Field-scale: Top 8–12 inches of soil

i. Side dress: In the root zone of the crop

b) Garden-scale

i. Initial stages of soil development: 12–24 inches in depth (see appendix 3 in Unit 1.2,
Garden and Field Tillage and Cultivation)

ii. Soil fertility maintenance: Top 4–8 inches