Introduction
Manure management should be a top priority on any dairy and livestock farm. Mismanagement of manure can have a substantially negative impact on our air, water, and soil. When used appropriately, manure has significant agronomic and economic value. When used correctly, manure improves soil biological activity, tilth, and chemical properties. The purpose of a manure inventory is to estimate the amount of manure produced on a farm and therefore, to calculate the amount of nutrients excrete by livestock and poultry. A manure inventory also will assist a farmer in determining if sufficient land is available for agronomic utilization of manure nutrients.
Currently, manure production or nutrient excretion by various animals are based on body weight of the animal and often does not account for large variations in feeding types and amounts. Also, nutrient content of manure varies widely between farms due to differences in animal species, age, feed ration, bedding characteristics, storage structures, and manure handling.
Calculations
Each ton of manure produced by dairy cows contains approximately 10 lbs. of nitrogen (N), 4 lbs. of phosphorus (P2O5), and 8 lbs. of potassium (K2O) (Table 1). The actual concentration of these nutrients in stored manure will be influenced by storage losses and dilution from water (rainfall and milk wash waste water) as well as bedding.
| Animal Type | Daily Production | Analysis Units | N | P2O5 | K2O |
|---|---|---|---|---|---|
| Dairy cow: lactating (liquid) | 13 gal | lb/1000gal | 28 | 13 | 25 |
| Dairy cow: lactating (solid) | 106 lb | lb/ton | 10 | 4 | 8 |
| Dairy cow: dry | 82 lb | lb/ton | 9 | 3 | 7 |
| Dairy cow: calf and heifer | 87 lb | lb/ton | 7 | 2 | 7 |
| Beef cattle: cow and calf | 60 lb | lb/ton | 11 | 7 | 10 |
| Beef cattle: steer | 75 lb | lb/ton | 14 | 5 | 8 |
| Beef cattle: veal | 5 gal | lb/1000gal | 36 | 27 | 55 |
| Swine: gestation | 4 gal | lb/1000gal | 30 | 35 | 15 |
| Swine: lactation | 10 gal | lb/1000gal | 25 | 20 | 15 |
| Swine: nursery | 14 gal | lb/1000gal | 40 | 40 | 25 |
| Swine: grow-finish | 11 gal | lb/1000gal | 50 | 55 | 25 |
| Swine: farrow to feeder | 7 gal | lb/1000gal | 40 | 35 | 15 |
| Sheep | 40 lb | lb/ton | 23 | 8 | 20 |
| Horse | 45 lb | lb/ton | 12 | 5 | 9 |
| * Adapted from: The agronomic guide 2002. College of Agricultural Sciences, Penn State University. | |||||
Manure production on a farm can be estimated by using the following formula
Manure production = Number of Animals x Average Weight of Animal (lb) ÷ 1000 (animal unit) x Daily Manure Prod. x Manure Collection Period (days) + Estimated Percent of Bedding in Manure.
Example: You have 10 lactating cows, each with an average weight of 1250 lbs. The animals are on pasture for 5.5 months (mid April through early October). You usually add about 5% bedding to the manure.
Total annual collectable manure = 10 (animals) x 1250 (avg. wt.) ÷ 1000 (animal unit) x 106 (daily manure prod. from Table 1) = 1325 (lbs/day). 1325 x 195 (days kept in barn) = 258375 (lbs manure/year).
Total waste production (bedding included) = 258375 x 0.05 = 12919 (lbs bedding added to the manure). 258375 + 12919 = 271294 (lbs/year) or: 271294 ÷ 2000 = 136 (ton/year). Each ton of manure produced by dairy cows contains approximately 10 lbs. of nitrogen (N), 4 lbs. of phosphorus (P2O5), and 8 lbs. of potassium (K2O) (Table 1). The actual concentration of these nutrients in stored manure will be influenced by storage losses and dilution from water (rainfall and milk wash waste water) as well as bedding.
In the above example, nutrient inventory for the farm can be calculated as: 136 x 10 = 1360 lb N, 136 x 5 = 544 lb P2O5, and 136 x 8 = 1088 lb K2O
Manure nutrient inventory for a farm is only practical if used in conjunction with proper on-farm management practices including manure storage and handling, application method, correct timing for crop uptake, and nutrient availability of applied manure.
Note: The purpose of a manure inventory is to estimate the amount of manure produced on a farm and therefore, to calculate the amount of nutrients excrete by livestock and poultry.
This publication has been funded in part by Mass. Dept. of Agricultural Resources in a grant to the Massachusetts Farm Bureau Federation, Inc. and by Mass. Dept. of Environmental Protection, s319 Program.