Demonstrating Manure Spreader Calibration at Field Days

Introduction

Livestock producers are being encouraged to develop manure management plans. Ohio law requires livestock operation of over 1,000 animal units to adopt a manure management plan (Ohio Revised Code 903). Smaller operations were encouraged, beginning in 1991, to develop plans (Ohio Revised Code 1511 & 1515).

Manure management plans include testing soil and manure and match nutrients to crop needs. Many testing labs and manure management specialist calculate the appropriate application rate for each farm and field. Several investigators (Levins, Schmitt, & Richardson, 1996; Quirke, Magette, Curran, & Dodd, 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 manure improves soil tilth, increases water holding capacity, lessens erosion, improves soil aeration, and benefits 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 manure nutrient testing. A survey of 390 Minnesota farmers (Schmidt, Jacobson, & Schnitt, 1996) showed that 20% tested manure and 37% kept records of manure application.

To apply manure at the desired rate can be problematic. Spreading equipment is typically not calibrated to apply at the desired rate. Schmidt, Jacobson, and Schnitt (1996) found that 16% of Minnesota farmers calibrated application equipment. Hoban, Clifford, Futreal, and McMillian (1997) interviewed over 1,000 North Carolina livestock producers. They found 38% tested manure and 36% have calibrated their spreading equipment.

Uniformity of application is also a concern. Wright & Cross (1996) evaluated the application uniformity of five types of spreading equipment: drag hose, center pivot irrigation, V-spreader, traveling gun irrigation, and tank spreader. They found tank spreaders had the highest coefficient of uniformity.

The next step is to ensure that manure is applied at a rate to match the nutrient needs of a crop. However, with surveys showing fewer than 40% of farmers calibrating equipment, what is the potential for over or under applying manure? In the study described here, field days were used to demonstrate how to calibrate a manure spreader. The demonstration also illustrated the limited capability of farmers to estimate manure application rates just based on their experience and the importance of calibration.

Methods and Materials

Livestock producers, growers and others were invited to six Ohio field demonstrations including a 30-minute spreader calibration demonstration. The demonstration followed instructions presented by Woodward (1985).

A commercially available manure spreader was loaded with solid livestock manure. Three, 10-by-10-foot plastic sheets were weighed and laid out in a field. The spreader applied manure, 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 converted from pounds of manure per square feet to tons of manure per acre using the following conversion factor:

Lbs. of manure * 21.8 = Tons of manure per acre

Sheet size in ft²

Table 1 shows the conversion to tons per acre for different sized plastic sheets. As a part of the demonstration, following spreading, participants completed a survey (Figure 1). They were asked if they had seen this demonstration before, their occupation and manure application estimate. Responses were sorted for first-time participants who were livestock producers or growers.

Figure 1.
Observational Survey for Manure Calibration Field Demonstrations

 

Results and Discussion

A total of 101 livestock producers and growers responded to the survey during the demonstrations. Actual application rates varied at the demonstrations from 4 to 18 tons/acre. The application estimates are presented in Table 2.

Of the 101 respondents, 13% estimated at or near the actual application rate (± 1 ton). Some (22%) estimated high rates with 2 estimating four times the actual application rate. Most (65%) underestimated the rate with 50% estimating less than one-half the actual application rate.

Summary and Conclusions

The survey, conducted as a part of the field demonstration, illustrated that experience and visual estimates of manure application, without training, will likely result in over-application of manure. Without calibration, 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.

The 30-minute field demonstration showed that spreader calibration is quick, simple, and inexpensive. Calibrating 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 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.

Acknowledgements

Support provided by OSU Extension and Ohio Agricultural Research and Development Center.

References

Hoban, T. J., Clifford, W. B., Futreal, M., & McMillian, M. (1997). North Carolina producer' s adoption of waste management practices. Journal of Soil and Water Conservation, 52(5), 332-339.

Levins, R. A., Schmitt, M. A., & Richardson, D. W. (1996). Extension programming for teaching manure management to farmers. Review of Agricultural Economics, 18(1996), 275-280.

Loehr, R. C. (1968). Pollution implications of animal wastes--A Forward oriented review. US Department of the Interior. Kerr Water Research Center, Ada, OK.

Ohio Revised Code. (1991). Agricultural Pollution Abatement. Sec. 1511 and 1515.

Ohio Revised Code. (2002). Concentrated Animal Feeding Facilities. Sec. 903.

Quirke, T., Magette, W. L., Curran, T., & Dodd, V. A. (2000). Computer software for pig and poultry environmental management system. Proceedings of the 8th international symposium on animal, agricultural and food, processing wastes. ASAE St. Joseph, MI.

Schmidt, D. R., Jacobson, L. D., & Schnitt, M. A. (1996). A manure management survey of Minnesota swine producers: summary of responses. Applied Engineering in Agriculture, 12(5), 591-594.

Woodward, M. (1985). Manure spreader calibration worksheet. Technical Note #4. Cooperative Extension Service. Penn State University.

Wright, P., & Cross, T. (1996). Uniformity of manure application by traveling guns. ASAE paper no. 962038. St. Joseph, MI.