Manure from hog operations is a source of plant nutrients for annual crops and perennial forages. This document calculates the economic value of liquid hog manure. The value can be incorporated into the business plan for a hog operation, and can be used for crop fertility decisions.
The calculations below are based on a finishing barn with earthen manure storage. It needs to be recognized there is a significant range of nutrient levels in hog manure. Producers are encouraged to sample and test their own hog manure for nutrient levels. In this document, industry accepted average values are used in the calculations.
Nutrient Availability
After application, a portion of the nutrients in hog manure are tied up in the soil and are not available for plant growth. Of the nutrients that are available, not all are readily available during the first growing season. Table 1 lists the percentages of the four macronutrients that are available for plant uptake during the first three growing seasons. The majority of these are available during the first growing season. The percentages from the three year total are used for the valuations.
Table 1. Per cent of plant macronutrients available in hog manure over time
| Year 1 % | Year 2 % | Year 3 % | 3 Year Total % | |
| Nitrogen - Mineral | 100 | 0 | 0 | 100 |
| Nitrogen - Organic | 25 | 12 | 6 | 43 |
| Phosphorus | 50 | 12 | 6 | 68 |
| Potassium | 90 | 0 | 0 | 90 |
| Sulphur | 50 | 0 | 0 | 50 |
Nutrient Production and Value
A finishing barn normally has three cycles/finishing space/year. During each cycle, the average liquid manure production is nine litres/space/day. At this rate, a finishing space will produce 3,285 litres/year (724 gallons).
Table 2 lists the nutrient levels produced from a finishing space in a year, and the economic value of the nutrients based on the percentages available for plant uptake. Of the total nitrogen produced, an industry average of 75 per cent mineral nitrogen (nitrate, ammonium, ammonia) and 25 per cent organic nitrogen (proteins, amino acids, urea, plant tissues) is used for the calculation. This ratio can vary based on individual manure samples and tests. In manure test reports, the phosphorus is commonly reported as P. However, commercial phosphorus is sold and valued on the basis of P2O5. The conversion ratio is one lb. of P equals 2.3 lb. of P2O5. Similarly with potassium, one lb. of K equals 1.2 lb. of K2O.
Table 2. Nutrients produced finishing space/year
| Nutrients | Total/finishing space/year (lb.) | Per cent available | Available/ finishing space/ year (lb.) |
| Nitrogen - Mineral | 16.8 | 100 | 16.8 |
| Nitrogen - Organic | 5.6 | 43 | 2.4 |
| Phosphorus (P2O5) | 7.2 | 68 | 4.9 |
| Potassium (K2O) | 10.1 | 90 | 9.1 |
| Sulphur | 1.5 | 50 | 0.7 |
The value of the micronutrients and organic matter can be variable based on soil types and conditions.
The cost of liquid manure application is about 1.25 cents/gallon. If a finishing space produces 724 gallons in a year, the cost of application will be $9.05. After application costs, the net value of liquid hog manure is about $20/finishing space/year.
Economic Value per Acre
The typical rate of liquid hog manure application, for both optimum crop response and minimal environmental impact, is 6,000 gallons/acre. It requires 8.29 finishing spaces to produce 6,000 gallons of manure.