یک پاراگراف

By Confesor, R B Hamlett, J M; Shannon, R D; Graves, R E

This observational study was conducted to assess the movement of nitrate and phosphorus into and through the soil profile beneath a compacted gravel compost pad. The accumulation of nitrate and phosphorus in the vegetated filter strip immediately downslope of the pad was also evaluated. Soil samples were taken from the composting site and the immediate surrounding area in two transects each for the Control (outside of compost pad), Old Pad (combined manure stack and compost area), and Extension pad (compost only area). Each transect was divided into three sampling zones: within the pad, in an intermediate area between the pad and the filter strip, and within the filter strip. Compost samples from windrows of different ages and mixes were also taken for laboratory leaching test to determine the potential of the composts as source of nitrogen and phosphorus. The NO^sub 3^-N concentrations in the soil beneath the compost pad of the Old Pad and Extension transects were higher than the soil NO^sub 3^-N concentrations at the same depths and locations in the control transect. These results indicate that the compacted gravel pad did not fully prevent the downward movement and accumulation of NO^sub 3^-N beneath the pad. The NO^sub 3^-N concentrations in the soil surface of the pad, intermediate between the pad and filter strip, and the filter strip areas of the Control and Old Pad transects were not statistically different; suggesting that there was negligible NO^sub 3^-N surface movement and transport from the pad area to the filter strip. The average Mehlich3-P concentration at the soil surface in the pad area was less than in the intermediate and the filter strip areas, indicating that there was surface runoff and downslope transport of phosphorus from the compost site to the filter strip. Statistical analysis showed that there was no significant difference in the Mehlich3-P concentration between the filter strip areas of the Old Pad and Control transects; suggesting that the downslope transport of phosphorus from the compost pad to the filter strip had not yet caused significant accumulation of phosphorus in the filter strip relative to the adjacent field. Leaching tests indicated that during the composting process, mature composts pose a greater potential as a source of NO^sub 3^-N leaching than the freshly-mixed composts. In contrast, the composting process and operation poses a greater potential as a source of PO^sub 4^-P during the early stages of composting than with older composts. Introduction

In many localized farm areas in the United States, there is an accumulation of nutrients in the soil as a result of over- application of manure that exceeds crop needs (Lander et al. 1998; Lanyon and Thompson 1996). Excess application of nitrogen and phosphorus to the soil enhances the potential movement of nitrate to ground water and phosphate in surface runoff creating an environmental problem. Nitrate can be toxic to both humans and livestock; whereas phosphate, though not directly toxic to humans, often causes advanced eutrophication of surface waters.

There is very little research that has investigated the composting process, facilities, and sites as potential sources of pollutants. The effects of large-scale and commercial composting sites and processes on surface and ground water quality, as well as the best management practices used to mitigate these effects, have not been fully explored and are not clearly known. In Pennsylvania, the conservation practice standard for composting (PA USDA-NRCS- NHCP Code 317) requires that the runoff from a compost facility shall be collected and treated in a vegetated filter strip area or in a constructed wetland. Krogmann and Woyczechowski (2000) suggested the use of vegetative filter strips for treatment of liquid by-products from a composting facility before release to surface waters. However, little information is readily available about the performance of filter strips that are specifically used in composting sites.

Neinaber and Ferguson (1992) measured the nitrate and chloride concentration of soil below a composting pad for beef cattle manure and below an adjacent cornfield. Prior to composting, the composting pad was part of the irrigated cornfield in which manure had been spread for several years. Soil samples were not taken before the composting operation and data were collected post facto. Their results indicated that there were elevated amounts of NO^sub 3^-N (20 ppm) and chloride (35 ppm) below a portion of a beef cattle feedlot converted to a compost pad as compared to the NO^sub 3^-N (< 5 ppm) and chloride (< 10 ppm) concentrations below an adjacent cornfield (3-m and 2.4-m depths, respectively), suggesting a potential for significant leaching beneath the compost pad. However, in comparing 3-yr old and 7-yr old pads, their results were inconclusive about the length of time a compost site could be used without creating nitrate and salinity problems.

Ballestero and Douglas (1996) also monitored the leachate beneath (0.60-, 0.91-, and 1.52-m depths) an open-windrow composting site (pad was well-drained Hinckley gravelly loam) for farm wastes (manure and barn bedding) and yard wastes (grass clippings and leaves) using suction lysimeters. They measured as much as 750 mg/L of NO^sub 3^-N at 0.60 m below the compost windrow. Results from these studies indicate that nitrogen loss (i.e., NO^sub 3^-N concentration in the leachate) is a function of the type of organic carbon and the nitrogen content of the compost mixture, along with bulk density and moisture content of the waste. Garrison et al., (2001) observed that high amounts of nitrogen losses at a composting site without impermeable linings were leached into the soil as indicated by high nitrogen soil accumulation beneath the pad.

The study reported herein was conducted to assess the amount of nitrogen and phosphorus that had moved beneath and downslope to an organic waste and manure composting site that had been operated for nearly 11 years. The specific objectives were to:l) assess the effectiveness of a compacted gravel compost pad in preventing the movement of nitrogen and phosphorus into and through the soil profile beneath the compost pad, and 2) evaluate the accumulation of nitrogen and phosphorus transported by surface runoff from the compost pad to a downslope filter strip. The results of this study would help identify the extent of N and P movement from a manure/ composting site operated on a compacted gravel pad in the humid northeast United States. In turn, this knowledge could be helpful in the design of efficient and effective control strategies for on- farm or commercial composting operations.

Methods

Site Description

The site investigated in this study was used for composting food wastes, leaves, and manure from 1997 until summer 2001 and was operated and managed by the Organic Materials Processing and Education Center (OMPEC) at the Pennsylvania State University. The composting site was built according to USDA-NRCS standards for a waste stacking and handling pad (Houck and Graves 2001). Soil liners in composting pads should be at least 2 feet thick and compacted to achieve a permeability of no greater than 1 x 10^sup -9^ m/s (US EPA 1994). The permeability of the subsoil beneath the compost pad was not known after construction nor was measured in-situ in this present study. Prior to use for composting, the site was used for manure stacking from 1990 to the end of 1996. Nonetheless, this composting site provided an opportunity to investigate potential nitrate and phosphorus movement in a full-scale and commercial operation.

The compost pad was located in Centre County, Central Pennsylvania (approximately 40[degrees]48'50''N, 77[degrees]52'48'' W) on land owned by the Pennsylvania State University and about 1.6 kilometers northwest of the main campus. The compost pad was constructed of compacted gravel aggregate (~10-cm thick) placed on top of compacted subsoil originally mapped as Hagerstown silty loam soil). Hagerstown soils are well drained with moderate permeability (4.2 x 10^sup -6^ m/s to 2.1 x 10^sup -5^ m/s). The pad had a gentle slope (1-2%) allowing surface runoff to flow to a vegetated filter system (smooth brome grass and orchard grass) located immediately downslope (Figure 1). The vegetated filter strip (USDA-NRCS-NHCP Code 393) was designed to absorb and filter the nutrients from the surface runoff and prevent/minimize contamination of surface and groundwater (USDA-NRCS-NHCP 1999). The area adjacent to the compost pad (except the vegetated filter strip), received 168.4 kg urea fertilizer/ha in late April of each year as part of fertility program for the pasture. This adjacent area was pastured in the late summer or fall when rain or cool weather predominates. Hay was harvested from both the grass filter strip and pasture area.

FIGURE 1. The vegetative filter strip and pasture areas downslope of the compost pad. (View looking upslope toward the compost pad site.)

Soil Sampling Design and Method

Soil samples were taken in April 2001 from the old composting site and filter strip areas along two transectsontrol (outside of compost pad), Old Pad (manure stacking in 1990 through 1996 and compost pad from 1997 through summer 2001), and Extension pad (operated for composting from 1997 through 2001) (Figure 2). Each transect was divided into three sampling areas: within the pad, in an intermediate zone between the pad and the filter strip, and within the filter strip. In the Old Pad and Extension transects, there were six sampling points: two replicates in the pad itself, two replicates intermediate of the pad and the filter strip, and two replicates in the filter strips. During sample collection the compacted gravel (about 10-cm thick) was scraped off and was not included in the soil samples taken from the pad sampling area of the Old Pad and Extension transects. There was one sampling point in each sampling area of each of the two Control transects. FIGURE 2. Compost site field layout and sampling design showing locations of control, original pad, extension pad transects and pad, intermediate, and filter strip sampling zones (map not drawn to scale).

At each sampling point, hydraulically pushed soil cores were taken at four depths from the soil surface: D^sub 1^ = 0 to 10.0 cm, D^sub 2^ = 10.1 to 30.5 cm, D^sub 3^ = 30.6 to 61.0 cm, and D^sub 4^ = 61.1 to 91.4 cm. The soil core sample taken at each depth was thoroughly hand-mixed in a bucket, and samples (-100 g) were collected from the mixed soil and placed in zip-lock plastic bags during field collection. The collected soil samples were taken immediately after sampling to the Perm State Agricultural Analytical Services laboratory for physical and chemical analysis using standard soil analysis methods for nitrate (Griffin 1995), total nitrogen (Bremner 1996), and MehlichS-phosphorus (Wolf and Beegle 1995). In October 2001, soil samples were also taken in the control and old pad transects for a separate phosphorus analysis.

The concentrations of nutrients (N and P) at the different locations, depths, and sampling times were compared, and an analysis of variance (ANOVA) was performed with the depths, sampling areas, and transects as independent variables using the SAS (Version 8) software. Tukey's test for multiple comparison of means was performed to determine significant differences between means at alpha = 0.05.

Laboratory Column Leaching of Composts

To determine the potential of the composts as source of nitrogen and phosphorus, compost samples from windrows were taken in Summer 2001 for laboratory leaching test in a setup based on the modified procedure described by Sharpley and Moyer (2000) and Li et al. (1997). Compost samples were placed in a 15.25-cm nominal diameter and 30.50-cm long PVC pipe columns for the leaching tests. The columns were filled with compost samples to a height of 25.4 cm (10'') equivalent to approximately 0.0046 m^sup 3^. The compost samples placed in the PVC pipe columns were leached using distilled and de-ionized (DDI) water. The DDI water was applied for 2.5 hours through a Mariotte bottle set at a constant flow equivalent to a 30- minute storm of 7 cm/hr (2.75 in/hr) intensity and 5-year return period in central PA (Sharpley and Moyer 2000). The windrows were made up of different ratios and mixes of compost feedstocks (food waste, manure, leaves, corn stalks, switch grass, etc.). The compost samples were not analyzed for chemical characterization immediately before the leaching test but previous analysis 2-3 weeks prior to leaching was used to characterize the samples.

Results and Discussion

Compost Leachate NO^sub 3^-N and PO^sub 4^-P Concentration

The mature compost was characterized by a low C:N ratio (~13) as compared with the high C:N ratio (~21) of the 2-week old compost (Table 1). Previous studies (i.e., Ballestero and Douglas 1996) indicated that leachate nutrient concentration is related to compost nutrient concentration. However, it was difficult to correlate the levels of nutrient in the leachate to the compost nutrient concentration since the composts were analyzed several weeks prior to leaching and no data was available for the 6-week and 14-week old composts. A forthcoming report from a related study will discuss the relationship of leachate nutrient levels to nutrient concentration of compost of different mixes and ages.

Results from the column leaching tests showed that NO^sub 3^-N and PO^sub 4^-P readily leach from compost and the concentrations in leachate vary for composts of different ages (Figure 3). The leachate NO^sub 3^-N concentration from the fresh (2-week old) compost was 2.17 mg/L and increased to 1300 mg/L from the mature compost. On the other hand, the PO^sub 4^-P concentration (135.2 mg/ L) of leachate was highest from the fresh compost compared with the PO^sub 4^-P concentration of leachate from older composts (17.6 to 39.4 mg/L). These results indicate that during the composting process mature compost poses a greater potential as a source of NO^sub 3^-N leaching than does the freshly mixed compost. In contrast, the composting process and operation poses a greater potential as a source of PO^sub 4^-P during the early stages of composting than with older composts. Furthermore, leachate is usually produced when water percolates through the compost material and it is not uncommon that more leachate is produced during high intensity rainfall. These findings therefore should be considered in the control strategies for composting operations.

TABLE 1.

Characterization of composts used in the leaching test.1,2

FIGURE 3. Concentrations of PO^sub 4^-P and NO^sub 3^-N in leachate from composts of different mix and ages. Vertical bars indicate standard error of the means for 3 samples.

Soil Nitrate and Total Nitrogen in the Surrounding the Compost Pad

In the Control transect, the average soil NO^sub 3^-N concentration at the soil surface was significantly greater (p = 0.02) than soil NO^sub 3^-N concentration at all the other depths across sampling locations, whereas there were no differences (p = 0.99) in soil NO^sub 3^-N concentrations among the three lower depths (10.1 to 30.5 cm, 30.6 to 61.0 cm, and 61.1 to 91.4 cm) (Figure 4). These results suggest that there was little accumulation of NO^sub 3^-N in the soil profile in the area surrounding the compost pad. The relatively high concentration of available NO^sub 3^-N at the soil surface compared with the amount of NO^sub 3^-N in the lower soil depths was most likely the result of organic nitrogen mineralization at the soil surface. The percent total nitrogen (Tot N) at the soil surface of the areas surrounding the compost pad was significantly higher (p < 0.01) than the Tot N in the lower depths (Figure 5). The total soil nitrogen is composed mostly of organic nitrogen since the NO^sub 3^ and ammonium (NH^sub 4^) concentrations of the soil samples were less than 100 ppm (0.01 %). Manure and fertilizer application on the pasture area during the spring season of each year could have also elevated the NO^sub 3^-N concentration at soil surface.

FIGURE 4. Soil NO^sub 3^-N nitrogen concentrations at different depths and sampling zones along the control transect. Horizontal lines indicate range for 2 samples (1 sampling location x 2 transects).

FIGURE 5. Percent total nitrogen (% Tot N) of soils at different depths and sampling zones along the Old Pad and Control transects. Horizontal lines indicate standard error of the mean (4 samples for the Old Pad and 2 samples for Control).

Soil NO^sub 3^-N concentrations were not significantly different (p = 0.50) between the locations in the Control transect across all depths, thereby showing the homogeneity of the soil around the pad (Figure 4). The amount of NO^sub 3^-N (7.6 to 17.4 ppm) at the soil surface (0 to 10 cm) at this study site was slightly less than the surface soil NO^sub 3^-N content (12.5 to 50 ppm) normal for pasture areas in Pennsylvania (L. E. Lanyon, personal communication, University Park, Pennsylvania, 13 January 2003).

There was no significant difference (p = 0.20) in the soil NO^sub 3^-N concentrations in the soil surface layer between the pad, intermediate, and filter strip areas of the Old Pad, Extension, and Control transects. No difference in NO^sub 3^-N concentrations suggests that there was little or no NO^sub 3^-N surface movement from the pad to the filter strip area in the Old Pad and Extension transects. Rather, it appears that most leachate nitrate from the compost likely infiltrated through the gravel pad and entered the soil beneath the pad.

Soil Nitrate and Total Nitrogen Beneath the Compost Pad

Soil NO^sub 3^-N concentrations under the Old Pad were greater than the soil NO^sub 3^-N concentrations at the same depths under the Control (Figure 6). The average soil NO^sub 3^-N concentration at D^sub 3^ (38 ppm in the 30.6 to 61.0 cm layer) and D^sub 4^ (44 ppm in the 61.1 to 91.4 cm layer) of the Old Pad transect were significantly greater (D^sub 3^: p = 0.019 and D^sub 4^: p = 0.004) than the average soil NO^sub 3^-N contents (about 2 ppm) in the same depth layers of the Control transect. These results were obtained despite the lower total nitrogen percentage (and consequently organic N) of the soils at lower depths (Figure 5); and the effect of organic nitrogen mineralization can be neglected.

This result was similar with the findings of Neinaber and Ferguson (1992) where they measured elevated amounts of soil NO^sub 3^-N (20 ppm) three meters below a compost pad for beef cattle manure as compared to less than 5 ppm NO^sub 3^-N for a control area. These results indicate that there was downward movement and accumulation of NO^sub 3^-N beneath the manure/composting pad area. Previous studies by Richard and Chadsey (1990), Neinaber and Ferguson (1992), and Douglas and Ballestero (1995) also indicated the downward movement of NO^sub 3^-N below open windrow composting sites without gravel pads.

The soil NO^sub 3^-N concentrations within the soil profile in the Extension transect (7.0 to 14.5 ppm) were greater than the soil NO^sub 3^-N concentration for the same depths in the Control transects (2.0 to 10.9 ppm) (Figure 6), but the difference was not statistically significant (p = 0.95). Furthermore, in the Extension transect, the average soil NO^sub 3^-N concentration (15.0 ppm) at D (30.6 to 61.0 cm layer) was slightly but not significantly greater (p = 0.88) than the average soil NO^sub 3^-N concentrations at the other depths (14.5 ppm, 9.0 ppm, and 7.0 ppm for D^sub 1,^ D^sub 2^, and D^sub 4^, respectively). In the Extension pad area the soil nitrates showed concentrations (15 ppm) at the D^sub 3^depth that were comparable to concentrations in the surface layer (14.5 ppm). D^sub 2^ and D^sub 4^ also showed concentrations (9.0 ppm and 7.0 ppm, respectively) that were greater than the concentrations (3.5 ppm and 2.2 ppm) in the Control tran sect at the respective depths. These observations indicate that there was downward movement of NO^sub 3^-N beneath the Extension pad but this downward movement had not yet caused significant accumulation of soil NO^sub 3^-N beneath the extension transect relative to the control transect. FIGURE 6. Soil nitrate nitrogen (NO^sub 3^-N) concentrations at various depths beneath the composting/manure pad in the Old Pad, Extension, and Control transects. Horizontal lines indicate standard error of the mean for 4 samples (2 sampling locations x 2 transects).

The difference in soil NO^sub 3^-N concentrations below the extension and the Old Pad transects was likely due to the length of time that each portion of the pad was used and the type of operation employed on the pad. It should be noted that the extension pad had been used for composting for about 4 years prior to soil sampling and the Old Pad had been used for manure stacking (7 years) and composting (4 years) prior to soil sampling. Based on these observations, it is apparent that if the composting operation continued in a manner similar to that used during the 1997 through 2001 period significant accumulation of NO^sub 3^-N beneath the Extension pad would occur after a few years. Results obtained by Neinaber and Ferguson (1992) showed that there was accumulation of NO^sub 3^-N from the soil surface down to the 3.0 m depth with increasing composting operation time (3- and 7 years).

Soil Test Phosphorus (STP) Along the Old Pad Transect

For the Old Pad transects the STP (Mehlich3-P) mean concentration (97.7 ppm) at the soil surface (0 to 10 cm) was significantly greater (p < 0.001) than the mean STP concentrations for all the other depths (greatest mean concentration of 26.3 ppm) across sampling areas (Figure 7). Furthermore, there was no significant difference (p = 0.57 to 0.99) in the mean STP concentrations between the three deeper samples (10.1 to 30.5 cm, 30.6 to 61.0 cm, and 61.1 to 91.4 cm). This indicates that, unlike NO^sub 3^-N, there was little movement or accumulation of phosphorus into and within the soil profile. According to Hansen et al. (2002), the most common pathway of phosphorus transport is through soil erosion and surface runoff. Phosphorus is readily adsorbed to soil and is not nearly as mobile in solution as is NO^sub 3^-N. The concentration of STP (~ 40 ppm) at the soil surface (0 to 10 cm) in the pad area was less than in the intermediate (-120 ppm, p = 0.029) and the filter strip (~ 140 ppm, p = 0.002) areas.

FIGURE 7. Soil test phosphorus concentrations using the Mehlich3 method at different depths and sampling zones along the Old Pad and Control transects, April 2001. Horizontal lines indicate standard error of the mean (4 samples for the Old Pad and 2 samples for Control).

These results suggest that there was accumulation of phosphorus due to surface transport and movement of phosphorus from the compost pad downslope to the intermediate area and to the filter strip. However, statistical analysis showed that there's no significant difference in the STP between the filter strip areas of the Old Pad and Control transects. The same results were found between the intermediate areas of the Old pad and Control transects. These findings further suggest that there was downslope transport of phosphorus from the compost pad to the filter strip but this downslope movement had not yet caused statistically significant accumulation of phosphorus in the filter strip relative to the control transect.

The STP concentrations of the surface soil samples taken in October 2001 from the area immediately upslope from the compost pad ranged from 11 to 28 ppm. The phosphorus concentrations (< 30 ppm) at this location represent the background (without manure and fertilizer application) phosphorus levels and were comparable with the STP (~ 35 ppm) at the surface of the compost pad (Figure 8). These comparable STP concentrations indicate that there was little or no accumulation of phosphorus in the soil profile beneath the compost pad area.

Soil samples obtained from the intermediate area in October 2001 (mean = 219 ppm) were higher in STP concentrations than samples from the same area obtained in April 2001 (mean = 116 ppm). This difference was not significantly different (p = 0.54) because of the large variances in October samples. Thus, we could not determine whether the difference was due to continued surface transport of phosphorus from the pad to the intermediate area, or due to sampling and spatial variability. It should be noted that the "intermediate" area does not receive fertilizer; while the pasture area adjacent to the compost pad site does.

FIGURE 8. Soil test phosphorus concentrations using the MehlichS method at the soil surface of the Old Pad transect for samples collected in April and October 2001. Vertical lines indicate standard error of the mean for 4 samples.

Summary and Conclusions

This study was conducted to evaluate the potential movement of nitrogen and phosphorus from an un-covered manure stacking and composting site in operation from 1990 to 2001. The movement and accumulation of NO^sub 3^-N beneath the old composting pad (compost operation from 1997 to 2001) could not be fully attributed to the composting process because the manure stacking operations (1990- 1996) on the pad preceding the composting operation undoubtedly contributed to the movement and accumulation of NO^sub 3^-N.

The data indicate that a conventionally-designed and compacted gravel pad (as commonly used for a manure stacking and/or composting operation) does not prevent downward leaching of NO^sub 3^-N. Leaching of NO^sub 3^-N under the extension pad was evident (elevated soil NO^sub 3^-N as compared to the control transect but not statistically significant at alpha = 0.05) and suggests that continued composting operations will, at some point in time, result in significant accumulation of NO^sub 3^-N nitrogen beneath a compacted gravel pad.

The NO^sub 3^-N concentrations at the soil surface for the sampling locations of the Old Pad and extension transects were similar. There was no significant difference (p > 0.95) in the NO^sub 3^-N concentrations among the four depths at each of the intermediate and filter strip areas (downslope of the pad) of the Old Pad transects. Similar results were also found in the Extension transects. Results indicate that there was little or no accumulation in the filter strip areas of the Old Pad and Extension transects, suggesting little surface movement and transport of NO^sub 3^-N from the pad downslope to the filter strip.

The Melich3-P concentrations of the soil upslope of the pad area were comparable with the soil Melich3P concentrations in the pad area for the various soil depths. This result showed that there was little or no phosphorus accumulation in the soil profile beneath the compost pad. The amount of available phosphorus along the soil surface of the Old Pad transect was greater in the filter strip and intermediate area than in the pad zone indicating that surface runoff and downslope transport of phosphorus from the compost site occurred. However, this downslope transport of phosphorus from the compost pad to the filter strip had not yet caused statistically significant accumulation of phosphorus in the filter strip relative to the Control transect.

Leaching tests indicated that during the composting process, mature composts pose a greater potential as a source of NO^sub 3^-N leaching than the fresh composts. In contrast, the composting process and operation poses a greater potential as a source of PO^sub 4^-P during the early stages of composting than with older composts. It was difficult to correlate the levels of nutrient in the leachate to the compost nutrient concentration. A forthcoming report from a related study will discuss the relationship of leachate nutrient levels to nutrient concentration of compost of different mixes and ages. Another limitation of this study was that the permeability of the compacted subsoil was not measured. While the pad was constructed according to standards, the results would have been more useful if the permeability of the subsoil for the different sampling points were known.

References

Ballestero, T. P. and E. M. Douglas. 1996. Comparison between nitrogen fluxes from composting farm wastes and composting yard waste. Transactions of the ASAE 39(5): 1709-1715.

Bremner, J.M. 1996. Nitrogen-Total, p. 1085-1121. In Methods of Soil Analysis, Part 3. Chemical Methods. Soil Science Society of America Book Series #5, ed. D.L. Sparks. Madison, WI: American Society of Agronomy.

Douglas, E.M. and T.P. Ballestero. 1995. Nitrogen transport and fate at farm and yard waste composting facility. NABEC Paper No. 9507. Presented at the annual Northeast Department of Agricultural and Biosystems Engineering/Bio-Engineering Conference (NABEC), July 30- August 21995. Bar-Harbour, Maine: American Society of Agricultural Engineers.

Garrison, M.V., T.L. Richard, S.M. Tiquia, and M.S. Honeyman. 2001. Nutrient losses from unlined bedded swine hoop structures and an associated windrow composting site. ASAE Paper No. 012238. ASAE, St. Joseph, Michigan. Griffin, G. 1995. Recommended soil nitrate-N tests. In Recommended Soil Testing Procedures for the Northeastern United States, Northeast Regional Bulletin #49, eds. J. Thomas Sims and A. Wolf, 17-24. Newark, Delaware: Agricultural Experiment Station, University of Delaware.

Hansen, N.C., T.C. Daniel, A.N. Sharpley, and J.L. Lemunyon. The fate and transport of phosphorus in agricultural systems. Journal of Soil and Water Conservation 57(6): 408-416.

Houck, N.J. and R.E. Graves. 2001. Composting Operations. Project Report No 01-01. University Park, PA: Pennsylvania State University - Organic Materials Processing and Education Center. Available at http://www. age.psu.edu/extension/ompec/CompostingOps0101. pdf. Accessed on October 27, 2006.

Krogmann, U. and H. Woyczechowski. 2000. Selected characteristics of leachate, condensate and runoff released during composting of biogenic waste. Waste Management and Research 18(3): 235-248.

Lander, C.H., D. Moffitt, and K. Alt. 1998. Nutrients available from livestock manure relative to crop growth requirements. Resource Assessment and Strategic Planning Working Paper 98-1. Washington, DC: USDA, Natural Resources Conservation Service. Available at http:/ /www.nrcs.usda.gov/technical/land/pubs/nlweb.html. Accessed on October 27, 2006.

Lanyon, L.E. and P.B. Thompson. 1996. Changes in farm production. In Proceedings, Animal Agriculture and the Environment Conference, ed. M. Sailus, 15-23. Ithaca, New York: NRAES.

Neinaber, J.A. and R. B. Ferguson. 1992. Nitrate movement beneath a beef cattle manure composting site. ASAE Paper No. 92-2619. St. Joseph, Michigan: ASAE.

Richard, T. and M. Chadsey. 1990. Environmental impacts of yard waste composting. Biocycle 31(4): 42-46.

SAS. 2001. SAS Version 8. Documentation available at http:// v8doc.sas.com/sashtml. Accessed on October 27, 2006.

USDA-NRCS-NHCP. 1999. National Handbook of Conservation Practices, Conservation Practice Standard Code 393 (Filter Strip). Washington, DC: USDA Natural Resources Conservation Service. Available at ftp://ftpfc.sc.egov.usda.gov/NHQ/practice-standards/ standards. Accessed on October 27,2006.

U.S. EPA. 1994. Composting yard trimmings and municipal solid waste. EPA530-R-94-003. Washington, DC: U.S. Environmental Protection Agency. Available at http://www.epa.gov/epaoswer/non-hw/ compost/ cytmsw.pdf. Accessed on October 27, 2006.

Wolf, A.M. and D.B. Beegle. 1995. Recommended soil tests for macronutrients: phosphorus, potassium, calcium, and magnesium. In Recommended Soil Testing Procedures for the Northeastern United States, Northeast Regional Bulletin #49, eds. J. Thomas Sims and A. Wolf, 25-34. Newark, DE: Agricultural Experiment Station, University of Delaware.

R.B. Confesor1, J.M. Hamlett2, R.D. Shannon2, and R.E. Graves2

1. Department of Agricultural and Resource Economics, Oregon State University, Corvallis, Oregon

2. Department of Agricultural and Biological Engineering, Agricultural Engineering Building,

The Pennsylvania State University, University Park, Pennsylvania=

Copyright J.G. Press Inc. Spring 2007

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