What's the NPK ratio of castings?
Written by
Olivia Mitchell
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.The NPK ratio of worm castings is generally 5-3-2, which corresponds to 5% nitrogen, 3% phosphorus, and 2% potassium. This well-balanced mixture provides the basic macronutrients necessary for plant growth, bloom, and root development. These nutrients are accompanied by calcium, magnesium, and trace minerals, which are often lacking in artificial fertilizers. I test my castings yearly to make sure they are emitted without any change.
Nitrogen (N)
- Stimulates leaf and stem growth through chlorophyll production
- 5% concentration supports vigorous vegetative development
- Slow-release form prevents burning delicate roots
Phosphorus (P)
- 3% content strengthens root systems and flower formation
- Crucial for energy transfer during photosynthesis
- Enhances seedling establishment and transplant recovery
Potassium (K)
- 2% concentration improves drought resistance
- Regulates water uptake and enzyme activation
- Boosts disease resistance in fruits and vegetables
Micronutrients
- Calcium strengthens cell walls preventing blossom end rot
- Magnesium aids chlorophyll synthesis for deeper green foliage
- Trace elements like zinc and copper support enzyme functions
90% bioavailability means plants access nutrients immediately without conversion.In contrast, synthetic fertilizers require microbial breakdown, resulting in a loss of 80% to leaching. My tomatoes show visible growth in a matter of days after applying 4Dog Fertility Figurines. Nutrients bind to organic matter and remain available throughout heavy rains.
Slow-release action provides 2-3 months of feeding. Nutrients in decent feed will flood the plant, causing a burn, and then disappear. Castings, containing compounds that release slowly during use, will keep up with his feeding; therefore, he always has something available. I use it once every 6 weeks during peak growth. This prevents waste while still maintaining good nutritional levels.
To optimize their use, it is essential to understand the species interactions of nutrients. An example would be combining castings with compost for crops that require phosphorus, such as tomatoes. They should be applied during periods of active growth when the soil temperature is above 50 degrees. My soil tests indicate a pH balance after only three seasons, following the discontinuation of synthetic additives.
Read the full article: Unlocking the Benefits of Worm Castings
