Fact Sheet No. 25: Manure Loading into Streams from Direct Fecal Deposits

Introduction

Livestock grazing on rangelands can contribute to nonpoint source pollution in streams. Although sediment is generally considered the largest water quality problem from livestock grazing, nutrients and pathogens may also be of concern. The major nutrients coming from cattle are:

• nitrogen (N),
• phosphorus (P),
• and potassium (K).

The relatively benign Fecal Coliform (FC), and Fecal Streptococci (FS) bacteria are used to indicate the presence of possible pathogens.

To be considered a pollutant, nutrients and pathogens must reach a stream. Nutrients and pathogens can reach the water either by direct deposit or by overland transport during a runoff event. In most semi-arid environments runoff events are infrequent. Therefore, direct deposit of manure and urine into streams seems to be the most likely mode of nutrient or pathogen loading by livestock. The potential for this mode of contamination depends on:

• time,
• density,
• and access.

The amount of time that livestock spend in or near streams can be variable as shown by studies at the San Joaquin Experimental Range (SJER) in the foothills of the Sierra Nevada Mountains in California and in Eastern Oregon (Table 1). The difference in drinking time in Table 1 may be that cattle drank from a trough at the SJER, and from streams in Eastern Oregon.

In 1989, Oregon researchers observed the daily fecal deposits and amount of time spent in the creek by different classes of cattle and during different seasons in a high desert stream in Central Oregon (Table 2). They found that time spent in the creek and direct fecal deposits varied by season. This perennial stream is one to three feet wide and ½ to three feet deep. It is characterized by 100 to 300 yard wide riparian zones and bottom-land stringer meadows with slopes generally less than five percent dominated by Kentucky bluegrass with some alfalfa and clover. During the winter months some meadows were used for supplemental feeding areas. These meadows and riparian areas were part of a larger pasture that included uplands with 10 to 40 percent slopes consisting of juniper woodlands, sagebrush, and bunch grass. These uplands were dry and relatively unpalatable by early to mid summer.

The fecal loading rate of grazing cattle depends on the amount of time the cattle are grazing in a pasture with a stream. Using the values in Table 2 with estimates of defecation rates, nutrient content, and bacteria concentration in manure (Table 3), we estimated the potential nutrient and bacterial loading directly into the stream (Table 4).²

The estimates in Table 4 indicate that the amount of manure loading into a stream for any given day, season, or year from one cow is quite small. However, there may still be a concern about pollution. As much as 95% of deposited manure will settle to the bottom of the stream within the first 50 meters (Biskie et al. 1988). The bacteria in the sediment may remain alive for several weeks (Sherer et al. 1992). Less is known about what happens to the nutrients that enter the stream in the manure.

Therefore, daily inputs from directly deposited feces may accumulate on the stream bottom. Any disturbance, such as peak flows, can resuspend sediment, creating high concentrations of bacteria, and possibly nutrients for a short period of time. The higher the density of livestock, the higher the concentration of pollution.

Any practice that reduces the amount of time cattle spend in a stream, and hence reduces the manure loading, will decrease the potential for adverse affects of water pollution from grazing livestock. It has been shown that providing a water trough as an alternative drinking source may reduce the instream fecal deposition during the winter by as much as 90 percent (Moore et al. 1993, see Fact Sheet #20). In addition, Clawson (1993) found that summer stream use dropped from 4.7 min/cow/day to 0.9 min/cow/day and bottom land use dropped from 8.3 to 3.9 min/cow/day when a water trough was provided as an alternative water source. This indicates that substantial reductions of creek use by cattle canbe achieved without fencing out the creek.

Clawson, J.E. 1993. The use of off-stream water developments and various water gap configurations to modify the watering behavior of grazing cattle. M.S. Thesis. Oregon State University, Corvallis, OR. 80 pp.

Biskie, H.A., B. M. Sherer, J.A. Moore, J.R. Miner, and J.C. Buckhouse. 1988. Fate of Organisms From Manure Point Loading Into Rangeland Stream. ASAE Paper No. 88-2081. St. Joseph, MI 49805.

McInnis, M.L. 1985. Ecological relationships among feral horses, cattle, and pronghorn in Southwestern Oregon. Ph.D. Dissertation, Oregon State University, Corvallis, OR. 166 pp.

Moore, J.A., J.C. Buckhouse, and J.R. Miner. 1993. Impact of waterer location on the bacterial quality of rangeland streams. Completion Report for Cooperative State Research Service Report 90-38300-5311. Oregon State University. Corvallis, OR. 80 pp.

Moore, J.A., J. Smith, S. Baker, and J.R. Miner. 1988. Evaluating coliform concentrations in runoff from various animal waste management systems. Agricultural Experiment Station, Oregon State Univ., Corvallis, Oregon. 80 pp.

Moore, J.A., and T.L. Willrich. 1982. Calculating the fertilizer value from manure from livestock operations. Oregon State University Extension Service EC 1094.

Larsen, R.E. 1989. Water quality impacts of free ranging cattle in semi-arid environments. M.S. Thesis. Oregon State University, Corvallis, OR. 75 pp.

Sherer, B.M., J.R. Miner, J.A. Moore, and J.C. Buckhouse. 1992. Indicator bacterial survival in stream sediments. Journal of Environmental Quality 21(4):591-595.

Sneva, F.A. 1970. Behavior of yearling cattle on Eastern Oregon range. Journal of Range Management 23(3):155-157.

Wagon, K.A. 1963. Behavior of beef cows on a California range. California Ag. Exp. Stn. Bull. 799. 58 pp.

Johnstone-Wallace, D.B., and K. Kennedy. 1944. Grazing management practices and their relationship to the behavior and grazing habits of cattle. Journal of Agricultural Science 34:190-197.