Nutrient Inventory from Manure

The amount of manure produced can be roughly estimated by considering the output by all animals on the farm.  Daily output of manure (feces and urine) is approximately 82 Lbs per 1000 Lbs of live weight.  The following table can be used to quickly calculate total manure output by multiplying the number of animals in each grouping by the respective output per animal, then summing the subtotals for each group.

Table 1.          Manure produced by dairy animals of differing live weight and

over differing time periods.

     Wt of Cow          ½ Day                 Day             Month    6 Months                Year

         250 Lbs          10 Lbs            20 Lbs            615 Lbs          1.8 ton            3.7 ton

        500 Lbs          20 Lbs            41 Lbs          1230 Lbs          3.7 ton            7.5 ton

     1000 Lbs          41 Lbs            82 Lbs             1.25 ton          7.4 ton             15 ton

     1350 Lbs          55 Lbs          111 Lbs               1.7 ton           10 ton             20 ton

Calculations are based on manure production of 82 Lbs per 1000 Lbs of live weight.

Each ton of manure produced by and as it comes from the cow contains approximately 10 Lbs of nitrogen (N), 5 Lbs of phosphorus (P₂O₅) and 8 Lbs of potassium (K₂O).  The actual concentration of these nutrients will be influenced by storage losses and dilution from water (rainfall and milk shed waste) and bedding.

Another method of determining manure production is by calculating the volume of the storage facility for the expected level of fill during a specific filling period.  Stored manure should be sampled and chemically tested to determine its nitrogen, phosphorus and potassium concentrations.  The total volume of stored manure is then multiplied by its nutrient analysis to estimate the total nutrients available.  This process is outlined below in Table 2.

Table 2.  Determining nutrient production based on storage quantity and manure analysis.

Storage Facility            Capacity                     Manure Analysis¹              Total Nutrients

                                  1000 gal or ton                 N        P₂O₅     K₂O           N      P₂O₅     K₂O

______________       __________    ____      ____   ____         ____   ____   ____

______________       __________    ____      ____   ____         ____   ____   ____

______________       __________    ____      ____   ____         ____   ____   ____

______________       __________    ____      ____   ____         ____   ____   ____

¹/Manure analysis will be Lb of each nutrient per 1000 gal or per ton.

Stephen J. Herbert

Dept. Plant and Soil Sciences

University of Massachusetts Amherst

CDL Publ. 00-4