ASAE Conference Proceeding
This is not a peer-reviewed article.
Farmer Estimates of Manure Application Rates
K. M. Mancl and J. D. Slates
Pp. 200-203 in the Animal, Agricultural and Food Processing Wastes, Proceedings of the Ninth International Symposium, 11-14 October 2003 (Raleigh, North Carolina, USA), ed. Robert Burns. ,11 October 2003 . ASAE Pub #701P1203
This study examined the capability of livestock producers and growers to make visual estimates of manure application rates. Manure spreader calibration was demonstrated to 101 farmers at 6 field days. At the beginning of each field demonstration, participants were asked if they had even seen this demonstration before, their occupation and their estimate of manure application based on their experience. Of the 101 participants 13% estimated at or near the actual application rate. Some (22%) estimated high application rates with 2 estimating four times the actual application rate. Most (65%) underestimated the manure application rate with 50% estimating less than one-half the actual application rate. If relying on visual estimates, 50% of the livestock producers and growers surveyed would have applied twice the desired application rate. The tendency to underestimate manure application and therefore over-apply manure reinforces the need to calibrate spreading equipment as a part of a manure management plan.KEYWORDS. Animal waste management, environmental protection, livestock waste, waste disposal
Livestock producers in Ohio and other states are being encouraged to develop manure management plans. Ohio law requires large livestock operation of over 1000 animal units to operate under a manure management plan (Ohio Revised Code section 903, 2002). Smaller livestock operations were encouraged, beginning in 1991, to develop plans (Ohio Revised Code sections 1511 and 1515, 1991).
Manure management plans include testing soil and manure for nutrients and matching the nutrients in manure to the needs of the crop where the manure is applied. Many testing labs and manure management specialist calculate the appropriate manure application rate for each farm and field. For example, several investigators (Levins et al. 1996; Quirke, et al. 2000) have produced computer programs for regulators and planners to determine appropriate application rates for farm operations.
The agronomic benefits of manure applied to soil have long been recognized. The plant nutrients and organic matter in livestock manure improves soil tilth, increases water holding capacity, lessens erosion, improves soil aeration,and is beneficial to soil microorganisms (Loehr, 1968). However, if not applied carefully, nutrients can be lost through volatilization, leaching or runoff.
The first step in determining manure application rates is testing the manure for it’s nutrient value. A survey of 390 Minnesota farmers (Schmidt, et al. 1996) showed that 20% test manure for nutrient value. The survey also found that 37% kept records of manure application.
To apply manure at the desired rate can be problematic. Manure spreading equipment typically used have not been calibrated to apply manure at the desired rate. Schmidt and others (1996) found that only 16% of Minnesota farmers had their application equipment calibrated. Hoban and others (1997) interviewed over 1000 North Carolina livestock producers. They found that 38% tested manure and 36% have calibrated their spreading equipment.
Uniformity of application is also a concern. Wright and Cross (1996) evaluated the uniformity of application from 5 different types of spreading equipment. They found tank spreaders had the higher coefficient of uniformity.
With all the effort to analyze manure and determine appropriate application rates, the next step is to ensure that the manure is applied at that rate. However, with survey results showing fewer than 40% of livestock producers calibrating their equipment the question arises as to the potential for over or under applying manure by estimating the application rate. This study examined the capability of livestock producers and growers to make visual estimates of manure application rates.
Livestock producers, growers and others were invited to six field demonstrations scheduled throughout Ohio. A 30 minute demonstration of manure spreader calibration techniques was presented at each field day. The demonstration followed instructions presented by Woodward (1985).
At each demonstration a commercially available manure spreader was loaded with solid livestock manure. Three sheets of plastic measuring 3 meters by 3 meters were weighed and laid out in an agricultural field. The spreader applied manure in the field, including the areas covered by the plastic sheets. The plastic was carefully gathered and weighed to determine the amount of manure applied to each sheet. Based on the size of the sheet and the average weight of manure, the application rate was determined as:
Kg of manure * 10 = Metric tons of manure per hectare
Size of sheet in m 2
Example: Average weight of manure on the sheets was 5.2 kg
5.2*10 = 52 metric tons of manure per hectare
1 m 2
After manure application in the field demonstration, participants completed a survey (Figure 1). They were asked if they had even seen this demonstration before, their occupation and their estimate of manure application based on their experience.
• Estimate of Application Rate _____ tons/acre
• Have you attended a field demo like this before?
__ No __ Yes
• Which or the following best describes your occupation?
__ Livestock Producer
__ Government Agency
__ Equipment Supplier
__ Other ___________________
Figure 1. Observational survey for manure calibration field demonstrations.
Responses were sorted and only first-time participants in the demonstration were included in the analysis. The responses were also sorted by occupation for livestock producers and growers.
A total of 101 livestock producers and growers responded to the survey at the six field days. Actual application rates varied at the demonstrations ranging from 7 to 36 metric tons per hectare. The manure application estimates are presented in Table 1.
Table 1. Estimates of manure application rate from 101 farmers attending one of six Ohio field demonstrations.
Number of Farms
Application rate (±2 ton/hectare)
1/2 or less actual rate
An estimate was considered if the participant reported the actual application rate plus or minus 2 metric tons per hectare. Of the 101 participants 13% estimated at or near the actual application rate. Some (22%) estimated high application rates with 2 estimating four times the actual application rate.
Most (65%) underestimated the manure application rate. Of the 101 participants 50% estimated less than one-half the actual application rate.
Using visual estimates of manure application, without training, will likely result in over-application of manure. If relying on visual estimates, 50% of the livestock producers and growers surveyed would have applied twice the desired application rate. The tendency to underestimate manure application and therefore over-apply manure reinforces the need to calibrate spreading equipment as a part of a manure management plan.
Manure spreader calibration is quick, simple and inexpensive. Taking steps to calibrate spreading equipment can increase the value of a manure management plan without placing a hardship on livestock producers or growers. Extension offices and Soil and Water Conservation Service offices can work with producers to facilitate calibration by having scales and calibration tables available for farmers. A short demonstration at a local field day can reinforce the need for calibration and demonstrate how quickly and easily it can be done.
Salaries and research support provided by state and federal funds appropriated to The Ohio State University Extension and Ohio Agricultural Research and Development Center.
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4. Ohio Revised Code. 1991. Agricultural Pollution Abatement. Sec. 1511 and 1515.
5. Ohio Revised Code. 2002. Concentrated Animal Feeding Facilities. Sec. 903.
6. Quirke, T., W.L. Magette, T. Curran, and V.A. Dodd. 2000. Computer Software for Pig and Poultry Environmental Management System. Proceedings of the 8 th International Symposium on Animal, Agricultural and Food, Processing Wastes. ASAE St. Joseph, MI.
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8. Woodward, M. 1985. Manure Spreader Calibration Worksheet. Technical Note #4. Cooperative Extension Service. Penn State University.
9. Wright, P. and T. Cross. 1996. Uniformity of Manure Application by Traveling Guns. ASAE paper no. 962038. St. Joseph, MI.