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Nutrient Management

Manure Testing

Note: Phosphorus is used in these examples, but the calculations are the same for all nutrients.

Converting manure analyses results from % dry-weight (% dwt) or ppm to “as-is” results (lb/ton or lb/1000 gal)

lb/ton as sampled = (% Solids/100) x (% Analysis dwt/100¹) x 2000 lb/ton

OR

lb/1000 gal = (% Solids/100) x (% Analysis dwt/100¹) x (density² lb/gal x 1000)

¹For results in ppm replace 100 with 1,000,000
²To do this the density of the manure must be known. Liquid manure density can vary from 8-9 lb/gal, but will typically have a density around 8.3 to 8.5 lb/gal. Manure density can be easily estimated with a 5 gallon bucket and a set of scales. See estimating manure density.

Examples

A. Manure Analysis: 10.5% solids, 1.4% P dwt

(10.5% solids/100) x (1.4% P/100) x 2000 = 2.9 lb P/ton

B. Manure Analysis: 10.5% solids, 14,000 ppm P dwt, Manure density 8.3 lb/gal

(10.5% solids/100) x (14,000 ppm P/1,000,000) x (8.3 lb/gal x 1000 gal) = 12.2 lb P/1000 gal

Converting Manure Analysis Results From Elemental to Oxide

Standard Conversion Factors: P x 2.3 = P₂O₅; K x 1.2 = K₂O

Examples

A. Manure Analysis: 2.9 lb P/ton

2.9 lb P/ton x 2.3 = 6.7 lb P₂O₅/ton

B. Manure Analysis: 12.2 lb P/1000 gal

12.2 lb P/1000 gal x 2.3 = 28.1 lb P₂O₅/1000 gal

Converting Manure Analysis Results from Liquid to Solid Or Solid to Liquid

To do this the density of the manure must be known. Liquid manure density usually varies from 8-9 lb/gal. Manure density can be easily estimated with a 5 gallon bucket and a set of scales. Liquid manures typically have a density around 8.3 to 8.5 lb/gal. Estimating Manure Density.

lb/ton = lb/1000 gal ÷ (density lb/gal x 1000) x 2000 lb/ton

OR

lb/1000gal = lb/ton x (density lb/gal x 1000) ÷ 2000

Examples

A. Manure Analysis: 28.1 lb P₂O₅ /1000 gal , Manure density estimated at 8.3 lb/gal

28.1 lb P₂O₅ /1000 gal ÷ (8.3 lb/gal x 1000) x 2000 = 6.7 lb P2O5 /ton

B. Manure Analysis: 6.7 lb P₂O₅ /ton , Manure density estimated at 8.3 lb/gal

6.7 lb P₂O₅ /ton x (8.3 lb/gal x 1000) ÷ 2000 = 28.1 lb P2O5 /1000 gal

Related Manure Testing Web Pages

• Overview of Manure Testing
• Step 1. Manure Sampling
  
  • Solid Manure Sampling Procedures
  • Liquid Manure Sampling Procedures
• Step 2. Manure Test Results
  
• Step 3. Total and Available Nutrients
  
  • Common Manure Test Results Conversions (you are here)
    • Estimating Manure Density
• Step 4. Manure Test Record Keeping

Authors: Doug Beegle, Pennsylvania State University and John Peters, University of Wisconsin