Economic Value of Beef Feedlot Manure

Manure from beef feedlots is a source of plant nutrients for annual crops and perennial forages. It is also a source of organic matter that can have a significant, long-lasting effect of improving soil quality, resulting in increased plant growth.

Nutrient Availability

Plants take up nutrients through their roots in the mineral (inorganic) form. The portion of the nutrients in manure that is present in organic matter is not immediately available for plant growth.

When straw used for bedding is mixed with fecal material, approximately 90 per cent of the nitrogen and 50 per cent of the phosphorus remains tied up in organic matter. This leaves little available nitrogen left for the crop in the year of application. The nitrogen that is tied up in organic matter is eventually released to plant- available inorganic forms by microbial decomposition in the soil, but complete release takes several years. It may be necessary to supplement manure nitrogen with commercial fertilizer nitrogen for the first years.

Table 1 lists the percentage of the four macronutrients that are typically available for plant uptake for four growing seasons following field application.

Table 1. Availability of macronutrients in typical feedlot manure for plant uptake following application.

Reference: Dr. Jeff Schoenau November 2015

Nutrient Concentration in Feedlot Manure

The concentration of macronutrients (N, P, K or S) on a dry matter basis in beef feedlot manure can have considerable variation. The variation can occur from one pen to another and from one feedlot to another. Factors influencing the variation are: diet, climatic zone of feedlot location, quantity of straw used for bedding, method and time of manure storage, and method of handling.

In order to measure the nature and value of the manure from a particular operation, you should establish a farm record over a three-year period. Do this by collecting representative samples from separate pens just prior to application, then send the samples to a laboratory for analysis.

Table 2 shows the average content of nutrients in beef feedlot manure at 50 per cent moisture content (MC) that industry is currently using in Saskatchewan. An economic value is calculated based on the nutrients that are available for plant growth for four years after application.

Of the total nitrogen in the manure, an industry average ratio of 10 per cent mineral nitrogen (nitrate or ammonium) and 90 per cent organic nitrogen (proteins, amino acids, urea or plant tissues) is used for the calculation. This ratio will vary based on individual manure samples and tests.

In manure analysis reports, phosphorus is commonly reported as P. However, commercial phosphorus is sold and valued on the basis of phosphate (P2O5). The conversion ratio is 1 lb of P equals 2.3 lbs of P2O5. This is similar to potassium, where 1 lb of K equals 1.2 lbs of K2O. In Table 2, total phosphorus is shown as phosphate.

Table 2. Average nutrients in feedlot manure at 50 per cent MC and economic value of nutrients available for plant growth for four years (November 2015).

It should be noted that potassium accounts for 46 per cent of the total value in the table. Many soils in Saskatchewan have adequate levels of potassium and the majority of soil tests recommend zero to 40 lbs/acre of K20. If the value of the potassium is discounted, the value of the other three macronutrients is $7.30/ton ($13.46 - $6.16). Other considerations for manure values are:

• Economic value of the macronutrients released from the organic matter beyond the first four years;
• Economic value of the micronutrients for four years and beyond;
• Economic value of the added organic matter that improves soil structure, water infiltration rates and soil moisture holding capacity; and
• Cost of manure spreading.

Economic Value of Organic Matter

The economic value of the organic matter in beef feedlot manure is difficult to determine as there is limited long-term research data available. However, it is well known that the organic matter contribution is significant and long lasting.

The value of the micronutrients and organic matter can vary based on soil types and conditions. Fertility trials have compared commercial fertilizers with manure applications. At a manure application rate of 30 tons/acre/ year (50 per cent MC), micronutrients and organic matter are assumed to increase yields in the subsequent crops by 20 per cent.

Using this assumption, the value of nutrients and organic matter in a ton of manure at 50 per cent MC is $16.15/ton ($13.46 x 1.2).  If the potassium is discounted, the value is $9.99/ton ($16.15 - $6.16).

Cost of Manure Application

The costs associated with loading, hauling and spreading manure can vary significantly. One custom operator in southern Saskatchewan identified the cost for loading, hauling one mile and spreading manure is $4.00/ton. A Saskatchewan feedlot indicated that a reasonable estimate is $7.00/ton based on hauling to a maximum of five miles.

Beef Feedlot Manure Production and Moisture Content

For animals averaging 1,075 lbs., Saskatchewan industry currently estimates a manure production rate of 30 lbs/day at 50 per cent MC. This includes fecal material and straw used for bedding. At this rate, one animal will produce a ton of manure in 67 days.

Moisture content of manure is influenced by geography, season, bedding usage and location within the pen. Climates with more rainfall and less evaporation are expected to have wetter manure. Manure removed in spring is expected to be wetter than when removed in fall. Greater amounts of bedding result in drier manure. Manure at the bottom of the pack is much wetter than manure at the surface. In general, moisture content in any given pen at any feedlot could range between 30 and 70 per cent. An average estimate for feedlot manure is 50 per cent moisture content.