Liquid Cow Manure Fertilizer: N-P-K Dilution Calculations for Student Projects

Key Principle: Dilution Lowers Concentration, Not Total Nutrients

Liquefying = mixing with water. Total N-P-K in the batch stays the same, but concentration per gallon drops proportionally.

Typical Fresh Cow Manure Analysis

~0.3% N, 0.2% P₂O₅, 0.3% K₂O (highly variable—diet, bedding, age).

Example Calculation

• Target: 1 oz N for a young shrub (30 sq ft root zone, 2 lb N/1,000 sq ft).
• 10-10-10 fertilizer: 10 oz supplies 1 oz N.
• Fresh manure (0.3% N): 333 oz (2.6 gal) needed for same N.
• Diluted 1:10 (1 part manure + 9 water): 0.03% N → 26 gallons needed.

Recommendation

Have your specific manure tested by county extension for actual N-P-K. Use results to calculate precise dilution rates. Untested manure teas are unreliable for controlled experiments.