Washington State University produces a manure-based compost of high pH (>8) and low N content (1%) by windrow composting campus wastes. Annual production at the four-acre facility is 18-20,000 cubic yards. In the interest of producing compost of higher N content and lower pH, ten experimental piles were constructed to investigate the effects of different feedstocks on the composting process, end quality, and agronomic performance. Biosolids and manure were compared at two rates of bedding both with and without coal ash. Compost temperature and inorganic N content during 96 days of active composting are reported along with end-product nutrient analysis and metal concentration. The composts behaved differently based on the N feedstock and level of bedding in the mix. Compost quality was influenced by the characteristics of the feedstocks. Applying the composts to an eroded hilltop (50 Mg/ha) increased winter wheat yield, but there were no differences among the ten composts.

Compost quality depends on the chemical composition and proportions of materials used to create the compost (Haug, 1993, Rynk, 1992). Operators can purchase feedstocks for custom mixes that are driven by specific end product quality or they simply make the best product possible with materials that are available. The Washington State University (WSU) compost facility was created to process wastes generated on campus. Feedstocks for the compost come from various sources on campus that would otherwise be diverted to waste streams at a considerable cost in tipping fees. The economic savings in reduced tipping fees finances the compost facility. Currently only campus wastes are used although future mixes that require purchased inputs may be considered if compost quality can be significantly improved. The compost yard is a four-acre facility on an asphalt pad and 18-20,000 cubic yards of compost are produced annually. Windrows are constructed with a front-end loader and turned with an over-the-row compost turner. Active composting typically lasts 12 weeks. The compost is a manure-based product of high pH (>8) and low N content (1%). In the spring of 1996, ten experimental piles were constructed at the Washington State University compost facility to investigate the effects of different feedstocks on the composting process, end quality, and agronomic performance. We were specifically interested in producing compost of higher N content and lower pH.

The three main ingredients in the standard compost mix include manure from the Animal Science beef and dairy units, stall bedding waste from Veterinary Medicine’s hospital, and coal ash from the University’s coal fired power plant. The usual compost mix is four parts manure, four parts bedding, one part coal ash and small quantities of greenhouse potting mix and food wastes. However, the quantity of different feedstocks varies throughout the year. Less manure is available during the summer months because the animals are out on pasture. Veterinary Medicine’s waste, mainly bedding, is used to make up the bulk of the summer piles. Summer piles may have two parts manure, six parts bedding and one part ash. Hence, they start with a much wider C:N ratio than the winter piles and have low N content. In the fall of 1995, the WSU Compost Committee discussed the option of including biosolids from the City of Pullman to provide a feedstock with greater N content and a disposal alternative to direct land application of biosolids.

As part of a cooperative study, we mixed ten experimental compost piles to compare biosolids and manure at two rates of bedding with and without ash. Two other piles with chipped tree limbs were included. We expected the biosolids to provide more N than the manure. Piles with more bedding or bulking agents were expected to have lower end quality than the piles constructed with a greater proportion of N-rich feedstocks. Coal ash is included in the university's compost (Beaver, 1994), but it is abrasive to the equipment and causes wear on the turner. Because WSU may eliminate their coal plant in the future, we wanted to evaluate the end product of coal ash-free compost produced with our equipment.

The objectives of this study were to evaluate the feedstocks used at the WSU Composting Facility. (1) We compared the end quality (nutrient content) of biosolids and manure-based compost mixes. (2) Different levels of bulking agents mimic the source availability of stocks throughout the year and enabled us to compare end quality of piles made with more bedding (less N enriched stock) to piles made with less bedding (more N enriched stock). Chipped limbs were examined as a replacement-bulking agent. (3) The source of heavy metals and micronutrients in compost was examined by comparing the chemical composition of the various composts. (4) The agronomic performance of the composts on eroded hilltops in the Palouse was also evaluated by measuring crop yield and soil pH.

Ten experimental compost piles were constructed on 3 April 1996 to compare different rates of biosolids, manure, bedding, ash, and wood chips feedstocks. The unreplicated treatments were arranged in a 2x2x3 factorial design with N source, ash, and bedding rates as factors. The two N sources were biosolids and manure. Ash was either present or absent. The three bedding rates were high, low, and low plus chipped tree limbs (50% of each). The high rate was two thirds bedding and one third N source. The low bedding rate was half bedding and half N source by volume. The design was unbalanced because there were no piles with chips and without ash.

The piles were mixed on a volume basis (Table 1) with a front-end loader. Dry weights were estimated based on the average feedstock weight per scoop of the front-end loader and moisture content of the feedstocks. Given the moisture and density differences of the stock material, there was a large range in concentrations on a dry weight basis (Table 1). Predicting initial N content of the mixes from the estimated mass and measured N content of the feedstocks did not correspond to the initial N concentration from the day 0 sampling after mixing. This precluded obtaining a mass balance for N in the piles.

The anaerobic-digested biosolids came from the City of Pullman’s waste treatment facility. The manure comes from the University’s beef units and dairy. The dairy manure is dewatered before the solids are trucked to the compost yard. It contains kiln-dried woodchips that are used for bedding and is referred to as separated solids. Manure from the beef units is not separated prior to composting. Bedding comes from stalls at the University’s Veterinary Medicine hospital. It is mostly straw and kiln-dried wood chips, but occasionally spoiled hay or other animal feed may be mixed in. The manure content of this bedding is very low. Chipped tree limbs are not a normal feedstock for the University’s compost facility. They were included in this trial because wood chips are thought to increase porosity and may facilitate air movement into piles. More oxygen may hasten the composting process and/or produce a different end product. The chipping, however, was unsatisfactory because many large diameter sticks passed through the chipper. Large sticks remaining in the end product from would require screening the compost, a process not currently done at the composting facility. The chemical properties of the stocks are presented in Table 2.

Piles were approximately 17-26 cubic meters in size and had initial dry weights ranging from 10.2 to 15.7 Mg. Piles were turned with a self-propelled straddle windrow turner (Fronteir - Brookings, OR) 25 times between 3 April and 8 July (96 days). Temperature was recorded prior to each turning.

Samples were taken for analysis immediately after turning. A sample was a composite of ten grab samples taken from the piles. Compost pH and EC were measured on a 1:5 wet compost to water mix (Rynk, 1992). Ammonium- and nitrate-N were extracted with 0.1M MgSO₄ (1:10) and measured with ion selective electrodes (Orion Research, Inc. Beverly, MA). Inorganic N, pH, and electrical conductivity in the composts were measured at two-week intervals for 96 days.

Samples from the feedstocks, and initial (day 0) and final (day 96) compost samples were taken to the University of Idaho testing laboratory for analysis (Table 5). The most probable number of coliform and E. coli was assayed immediately upon receipt of moist samples. The remaining portion of the samples were dried, ground, and screened (<2mm) for elemental analysis. Total cations were measured after digestion with nitric/hydrochloric acid by ICP spectroscopy (EPA Method 3050-6010). Mercury was measured by ICP-cold water vapor following EPA Method 7470. Available P and K were extracted with sodium acetate and determined by colorimetric analysis and ICP. Total C and N were measured using a Leco CHN 600 analyzer.

Data was analyzed with a modified analysis of variance using the GLM procedure in SAS statistical software package. Nitrogen source, bedding rate, ash, and N source X bedding interaction were estimated. Ash interaction and third order interaction were used to estimate error. Significant main effects were separated with LSD at the p=0.05 level.

After 96 days of composting (8 July 1996), the ten compost piles were moved to an outdoor, uncovered holding pad. Piles were not disturbed until 10 October 1996 when used in the field study. The experimental design of the agronomic study was a completely randomized block with three blocks. Plots were laid out along three eroded ridgetops in a field near the WSU campus managed by the Department of Crop and Soil Sciences. Each block contained eleven treatments including a non-compost control and the ten composts. Plot size was 7 by 15 m with 3-m buffers between plots. Compost was applied with manure wagons on 10 and11 October 1996. The rate of application was approximately 70 Mg/ha on a dry weight basis. After application, the land was moldboard plowed, disked, harrowed and seeded to winter wheat. The entire field was fertilized with recommended levels of N and P based on soil test results.

On 21 May 1997 soil inorganic N, pH, EC and moisture were measured from 0-15 cm samples. Inorganic N was extracted with 2M KCl and analyzed colorimetrically on an Alpkem autoanalyzer (Alpkem Corp. Clackamas, OR). Soil pH was measured on a 1:1 soil to water slurry. The winter wheat was harvested with a small plot combine from a 7.5 m² area.

Soil properties and yield data were statistically analyzed using SAS (SAS Inst., Cary, North Carolina). An ANOVA was performed for compost treatments and meaningful contrasts were constructed. Compost vs. none compares all ten composts to the control. Manure vs. biosolids compares five biosolids composts to the five manure composts. Ash vs. no ash compares four no ash composts with four ash composts (compost with chips not included). Low vs. high bedding contrasts four low bedding composts to four high bedding composts (chip composts eliminated).

This pilot study was the first time biosolids were included in a compost mix at the Washington State University compost facility. The total coliform and E. coli numbers after initial mixing ranged from10³ - 10⁶ colony forming units per gram dry compost (Table 3). All of the compost piles had temperatures greater than 55 C within the first two weeks of composting (Figure 1). For aerated windrow composting, fifteen consecutive days with temperature above 55 C and five turnings are required for adequate reduction in pathogens for Class A use (USEPA, 1993). Some of the biosolids mixes with low bedding did not meet the temperature requirement initially, and some did so only after reheating. After 96 days of composting, however, total coliform counts were less than 10² and there were no E. coli detected in any of the piles (Table 4).

The moisture content of the piles was between 55 and 70% initially (data not shown). Moisture was fairly constant until day 23 (24 April 96) when it rained 45mm increasing the moisture in the piles. Temperature in the biosolids piles with low bedding or chips dropped below 30 C (Figure 1) because of poor internal drainage and aeration. By day 42 ambient temperature rose and the piles began drying. On day 96 the piles had approximately 45% moisture. The reheating of the biosolids piles with low bedding or chips corresponded to the drying of the piles and rise in ambient temperature (Figure 1). The biosolids piles with high bedding and all manure piles maintained higher temperatures throughout this time period. Throughout the composting period, all manure piles had similar temperatures. Biosolid piles with high bedding had temperatures between the biosolid with low bedding and the manure piles. The overall lower temperature of biosolids treatments may reflect less available energy since energy was consumed during the anaerobic digestion process prior to the biosolids being composted.

The normal feedstocks at the WSU composting facility, manure, bedding and coal ash are all alkaline with pH greater than 8.5 (Table 2). During composting, the pH increased in the manure piles and decreased in the biosolids piles (Figure 2). Piles with manure as main source of N, had end pH values greater than 8.7 while the average pH of the biosolids piles was 7.3. As discussed below, nitrification in the biosolids composts may contribute to the lower pH values. On average, ash in the compost increased the final pH by 0.2 units for manure and 0.5 units for biosolids (Table 4). Therefore, coal ash does not appreciably contribute to the high pH of the WSU compost. Campbell et al. (1997) found that the final pH of biosolids compost was lower than that of a yard waste compost. The authors presumed that acidic wood chips added to the biosolids compost were responsible.

Biosolids piles had more inorganic N by the end of the composting process than the manure based composts (Table 4). The N dynamics of the biosolid piles followed the typical scenario where initially high ammonium levels dropped rapidly (data not shown) and equilibrated at low levels, while nitrate concentration increased (Figure 3). By the end of active composting, biosolids piles had more inorganic N than the manure piles and the percentage, as nitrate was appreciably higher (Table 4). This may indicate that the biosolid piles were more mature than the manure piles at that time. Since nitrification is an acid producing reaction, the higher nitrate concentration may explain the lower pH of the biosolids composts (Figure 2). In the Campbell et al. (1997) study, nitrate concentration of their biosolids compost was also over ten times higher than the yard waste compost which may suggest nitrification contributed to the low pH of their biosolids compost.

Nitrification may be inhibited by the high pH in the manure piles as suggested from the relatively high levels of ammonium to nitrate (Table 4). Conversely, low nitrate in the manure piles may reflect immobilization as the microorganisms are processing the compost, although the C:N ratio of the manure and biosolids composts are similar at day 96 (Table 4). Because of the high pH and high ammonium levels in the piles, volatilization may be a pathway of N loss during the composting process (Mahimairaja et al., 1994). Other researchers have measured high N losses from ammonia volatilization (Mahimairaja et al., 1994; Martins and Dewes, 1992). During composting we expect N concentration to increase as the organic matter is oxidized releasing carbon dioxide.
 
 

The total N concentration within most piles increased from day 0 to day 96 as expected, however, in biosolids with low bedding piles (with or without ash or chips) N concentration decreased (Tables 3 and 4). Biosolids feedstock was very homogenous, so it is unlikely that the N in the biosolids was underestimated. It is possible that biosolids may have been underrepresented in the initial sample since the compost mixes were initially heterogeneous. However, it is more probable that N was lost during composting in these piles though either ammonia volatilization or through denitrification. Mahimairaja et al. (1994) found adding carbonaceous materials reduced N loss by immobilizing ammonium. Later these researchers found composting poultry manure with C-rich bedding also reduced denitrification 60-80% (Mahimairaja et al., 1995). Our piles that decreased in N concentration were the ones that the temperature dropped to less than 30 C (Figure 1). These biosolids and low bedding piles were poorly aerated, a condition that favors denitrification. Since these piles were constructed with less C-rich feedstocks than the other piles, they may have had more denitrification because they lacked C-rich bedding that immobilizes available N early in the composting process. This observation is similar to the results of Mahimairaja et al. (1995). In our biosolids piles, clumps of biosolids could also create anaerobic microsites favoring denitrification. In the high bedding biosolids piles N increased from day zero to day 96, presumably from a more aerobic environment favorable for immobilization of available N from added C.

Although piles with ash had less nitrate at day 96 than their respective comparison without ash (Table 4), differences were not statistically significant. Lower nitrate concentration in the ash piles is probably a dilution effect resulting from adding the N-impoverished ash.

The C concentration of the piles decreased during composting, but the decrease in the manure piles was greater than in the biosolids piles (Tables 3 & 4). Available energy from the C compounds in the biosolids are used by anaerobic organisms during primary and secondary treatment of the biosolids. Carbon is the only element that should decrease in concentration during composting unless there are volatile losses of other elements. There was minimal leaching from the compost facility and losses to wind transport were considered insignificant. The final content of the compost reflected the various feedstocks and the chemical composition of the feedstocks used in the mix.

The compost sample taken on day 0 after one turning was fairly heterogeneous. The proportion of feedstocks in the piles may not be adequately represented in the initial sample. Processing the samples for analysis in the lab may have further biased the relative contribution of the various feedstocks. For example, many of the larger wood chips did not grind well or pass through the screen in the lab, and, therefore were not included in the analysis. By day 96, 25 turnings later, the compost was more homogeneous and the analyses were more representative of the compost composition.

Both manure and biosolids feedstocks were enriched with nutrients compared to the bedding. Biosolids composts were enriched in P, S, NO₃-N, Ca and Mg and depleted in K, NH₄-N, and Na relative to manure-based composts at day 96. The pH and EC of biosolids composts were also lower than manure composts. Both had similar C and total N content.

At the start of composting, piles with ash had less C, N, P, K, NH₄-N, and NO₃-N than those without ash. Because ash comprised 30% by weight of the piles and had lower concentration of these elements than either of the N sources, the decrease in concentration was probably a dilution effect. At the end of composting, piles with ash had about 75% of the C, N, P, K, NH₄-N, NO₃-N, the same amount of S, Zn and Cu, and a higher concentration of metals than the piles without ash. Chipped limbs had higher Co, Cr, Fe, Mo, Mn, Ni, Pb, Zn, Ba, and lower Na and K than the bedding and the difference in the composts made with chips vs. low bedding followed the same trend.

Heavy metal composition of the composts was typical of other compost produced in the west (Campbell et al., 1997). Arsenic and Selenium were not determined on composts for this study. With the exception of molybdenum, all ten composts were within the Grade AA category for heavy metals as recommended by the Washington State Department of Ecology (1994). More detailed studies on the heavy metal composition and plant uptake of metals from the typical WSU compost have been completed (Cox, D. B. M.S. Thesis, WSU, 1998) and will be published.

In early spring 1997, the wheat within the field plots with compost was more robust and darker green than the wheat in the alleys. Both the plots and alleys were fertilized the previous fall prior to seeding. In spring, surface soil nitrate levels were low (Figure 4), but contrasts showed less soil nitrate in control plots than in the compost plots for 0-15 cm (Table 5) indicating net N mineralization from the composts. In another trial with WSU, manure-based compost (Cox, D.B. M.S. thesis, 1998), N was immobilized when the compost was added (112 Mg/ha) without additional N fertilizer. In our study the added N fertilizer probably prevented net N immobilization.

Compost increased yield from 5.1 Mg/ha in the control plots to 5.8 Mg/ha in the compost plots (Figure 4). Ash did not affect yield. There were no statistical yield differences between the biosolids and manure-based composts (Table 5). In a greenhouse trial, Chen et al. (1996) found increased plant biomass and N uptake from biosolids compost relative to manure compost when no additional N fertilizer was added. Their biosolids compost contained ten times more mineral N than their manure compost. Our biosolids composts also had ten times more nitrate than the manure composts. Had we not fertilized we may have seen yield differences from the two composts.

Composts made with low bedding had higher yield than the high bedding composts (6.0 vs. 5.5 Mg/ha - Table 5 and Figure 4). Low bedding composts were mixed with more N-enriched stock (either manure or biosolid) than were the high bedding composts. However, the N concentrations of the finished composts were similar for both low and high bedding piles (Table 4). Since the field was fertilized adequately in addition to the compost application, yield differences from compost application may relate to moisture, water retention, or other more favorable physical soil properties rather than nutrients. Cox (M.S. Thesis, WSU, 1998) found adding WSU compost to an eroded hilltop (110 Mg/ha) increased water stable aggregation and decreased soil bulk density and soil impedance (two measures of soil compaction).

There was no change in soil pH (0-15 cm) from applying 70 Mg/ha compost with pH ranging from 6.7 to 9.2 (data not shown). Cox (M.S. Thesis, WSU, 1998) also found no change in soil pH from a single 110 Mg/ha application of WSU compost. At another research trial, located 3 miles from our study, soil pH increased from 5.7 to 6.6 from a single 224 Mg/ha application of the typical WSU product. The increase in soil pH is still evident three years later. The WSU compost used in these other studies was most similar to the manure + ash low bedding compost in our study.

The composts had different chemical compositions that reflect the various feedstocks used to construct the piles. All composts heated significantly for adequate reduction in pathogens. However, temperature in biosolids composts with low bulking agents was reduced markely after a rainfall event. After 96 days, total coliform counts were less than 10² and no E. coli were found.

Biosolids composts contained appreciably more inorganic N, especially nitrate, after 96 of composting, as compared to as manure composts. The lower pH values in the biosolids composts reflected the acid produced during nitrification.

Total C and C:N ratio decreased more in the manure piles than in the biosolids piles. There was apparently more readily degradable C substrate in the manure piles. The biosolids piles with low bedding (high percent of biosolids) did not heat like the other piles at low ambient temperatures because these piles were too dense and wet. Future mixes should not contain as much biosolids as attempted in this trial (more than 40% by volume).

Biosolids composts were enriched in P, S, N, Ca and Mg relative to manure-based composts. And biosolids piles had less ammonium, K, Na, and lower pH and EC than manure composts. Both had similar C and N content. Composts with ash were lower in N EC, K, P, C, N, Zn, and Mn relative to composts without ash. Ash increased pH, Ca, and most metals. Adding wood chips did not have a significant effect on composting and resulted in a product that would require screening for most end users.

Although the ten composts had a range of differences in their chemical composition, they did not affect yield or soil properties differently. Adding compost increased yield of winter wheat, although low bedding composts (more N feedstock) increased yield more than the high bedding composts (less N feedstock).

Beaver, T. 1994. Pilot study of coal ash compost. Compost Science and Utilization. 2(3):18-21.

Chen, L. W.A. Dick, J.G. Streeter, and H.A.J. Hoitink. 1996. Ryegrass utilization of nutrients released from composted biosolids and cow manure. Compost Science and Utilization 4(1):73-83.

Cox, D.B. 1998. Effect of compost, coal ash, and straw amendments on restoring quality of eroded palouse soil. M.S. Thesis. Washington State University. Pullman, WA.

Haug, R.T. 1993. The practical handbook of compost engineering. Lewis Publishers. Boca Raton, FL.

Mahimairaja, S., N.S. Bolan, M.J. Hedley, and A.N. Macgregor. 1994. Losses and transformation of nitrogen during composting of poultry manure with different amendments: an incubation experiment. Bioresource Technology 47:265-273.

Mahimairaja, S., N.S. Bolan, and M.J. Hedley. 1995. Denitrification losses from fresh and composted manures. Soil Biol. Biochem. 27:1223-1225.

Martins, O. and T. Dewes. 1992. Loss of nitrogenous compounds during composting of animal wastes. Bioresource Technology 42:103-111.

Rynk, R. 1992. On-farm Composting Handbook (NRAES_54). Northeast Regional Agricultural Engineering Service. Ithaca, NY.

USEPA. Feb. 19, 1993. Standards for the use and disposal of sewage sludge. 40 CFR Part 503. Federal Register.

Washington State Department of Ecology. 1994. Interim guidelines for compost quality. Solid waste Service Program Publication #94-38. Washington State Department of Ecology, Olympia.

† Bedding and wood chips mixed in equal proportions on both per volume and per weight basis
 
 

Table 2. Chemical characteristics of feedstocks used at WSU Compost Facility.
 

		Manure	Biosolids	Bedding	Chips	Ash*
Properties	Total coliform CFU g-1	2200	1700	23	16000	nd
	E.coli CFU g-1	2200	500	23	3	nd
	PH	8.55	7.95	8.62	5.67	8.76†
	EC (dS/m)	2.83	1.54	2.71	0.41	0.97†
	C (%)	41	22	45	45	13
	N (%)	1.14	2.27	0.70	0.73	0.27
	C:N	36	10	64	62	48
	NH4+-N (mg/kg)	4102	5855	4135	104	146†
	NO3 --N (mg/kg)	63	83	48	8	17†
Total elements (mg/kg)
	Ca	14000	31000	14000	18000	25790
	Cd	0.89	3.60	1.00	1.60	3.0
	Co	7.0	11.0	4.8	11.0	nd
	Cr	9	43	5	44	66.5
	Cu	21	140	15	22	71.5
	Fe	9800	16000	3500	7700	11140
	K	18000	3500	12000	4700	1476
	Mg	5300	10000	3400	3500	4833
	Mn	280	830	120	270	69
	Mo	4.1	18.0	5.1	14.0	nd
	Na	2200	1700	1400	450	5408
	Ni	14.0	33.0	8.2	38.0	nd
	P	2500	7000	1500	1400	1587
	Pb	33	80	23	89	67
	S	2900	6900	1900	1100	5688
	Zn	65	250	43	90	166
	Ba	94	610	74	250	nd
	Be	0.29	1.50	0.23	0.29	nd

* 1993 coal ash sample

** nd - not determined

† measured on 1996 sample taken at same time as other stocks
 
 

Table 3. Analysis of compost piles after initial turning, day 0 (3 April 1996).
 

	————————————Manure——————————					———————————Biosolids———————————
	——High bedding——		——Low bedding——		Low+chips	——High bedding——		——Low bedding——		Low+chips
	ash	no ash	ash	no ash	ash	ash	no ash	ash	no ash	ash
Coliforms CFU g-1	16000	3000	230000	16000	16000	5000	16000	92000	3000000	16000
E.coli CFU g-1	700	3000	230000	5000	700	1700	5000	92000	2300000	3000
pH	8.43	8.45	8.27	8.38	8.15	8.33	8.09	8.01	7.93	7.43
EC (dS/m)	2.60	2.65	2.66	3.01	2.48	2.55	2.34	2.17	2.12	1.87
C (%)	37	42	40	42	31	32	41	34	39	25
N (%)	0.63	1.01	0.96	0.97	0.73	0.89	1.24	1.40	1.91	1.60
C:N	59	42	42	43	42	36	33	24	20	16
NO3-N (mg/kg)	34	49	37	41	34	33	47	39	49	20
NH4-N (mg/kg)	2105	3685	2887	3380	2661	2788	4413	3487	4898	2178
Total cations - EPA 3050 (mg/kg)
Ca	25000	16000	22000	12000	23000	26000	19000	27000	18000	28000
Cd	2.2	1.8	2.2	1.3	2.0	1.6	1.8	2.5	1.9	2.7
Co	8.6	7.8	7.6	5.5	11.0	8.7	7.5	9.2	5.6	13.0
Cr	28	11	22	16	33	20	16	27	14	69
Cu	33	22	31	22	30	37	61	69	79	98
Fe	12000	6500	9400	4900	12000	11000	9100	12000	8300	17000
K	8600	13000	12000	14000	8300	8800	11000	5700	8700	5200
Mg	4900	3300	7100	4400	5200	5800	4200	8200	4400	6500
Mn	110	160	130	140	150	200	430	380	570	570
Mo	11	11	6	5	12	11	11	14	4	18
Na	3000	1700	2600	1800	2500	2500	1600	2400	1400	2400
Ni	26	15	18	13	29	20	16	24	17	57
P	1600	2000	2000	2100	1600	2100	3900	3700	4700	4800
Pb	45	41	46	30	38	36	34	68	27	61
S	2900	2200	2800	2100	2800	3000	3800	4500	4300	5500
Zn	78	58	68	61	79	110	130	140	170	190
Ba	660	140	380	95	480	510	270	560	240	660
Be	1.80	0.49	1.30	0.38	1.40	1.40	0.56	1.70	0.41	1.50

 
 
 

Table 4. Compost analysis of the ten experimental piles on day 96 (8 July 1996).
 

	————————————Manure——————————					———————————Biosolids———————————
	——High bedding——		——Low bedding——		Low+chips	——High bedding——		——Low bedding——		Low+chips
	ash	no ash	ash	no ash	ash	ash	no ash	ash	no ash	ash
Coliforms CFU g-1	0	2	0	2	24	1	2	4	300	30
E.coli CFU g-1	0	0	0	0	0	0	0	0	0	0
pH	8.9	8.7	9.2	9.0	9.0	7.7	7.3	7.3	6.7	7.4
EC (dS/m)	2.5	2.9	2.7	3.3	2.4	2.4	2.8	2.2	2.8	2.0
C (%)	25	35	26	37	24	26	36	29	35	24
N (%)	1.14	1.5	1.22	1.48	1.23	1.36	1.73	0.96	1.69	1.24
C:N	22	23	21	25	20	19	21	30	21	19
NO3-N (mg/kg)	77	130	171	190	108	1530	2786	912	2124	746
NH4-N (mg/kg)	477	693	683	908	565	335	530	295	353	195
available P (g/kg)	0.93	1.60	1.42	1.44	1.13	1.43	2.21	1.52	2.27	1.50
available K (g/kg)	8.44	13.40	10.90	6.12	8.54	5.56	8.28	4.85	6.41	3.53
Total cations - EPA 3050 (mg/kg)
Ca	28000	20000	28000	21000	26000	30000	22000	32000	23000	29000
Cd	1.8	1.3	1.8	1.3	2.0	2.1	1.8	3.1	2.6	2.8
Co	8.0	8.4	9.1	7.9	10.0	10.0	8.0	11.0	9.8	11.0
Cr	21	17	23	18	24	23	18	31	22	42
Cu	36	32	36	32	39	66	75	110	120	91
Fe	9800	8700	11000	8900	12000	13000	10000	15000	12000	16000
K	12000	17000	15000	21000	13000	8800	12000	7500	9200	6200
Mg	6600	5900	7600	6500	7300	7600	6200	8400	6800	8000
Mn	160	270	220	290	200	410	540	650	850	580
Mo	11	8	10	7	12	13	13	12	14	19
Na	3400	2300	3300	2800	3200	2600	1800	2800	1600	2500
Ni	19	15	20	16	20	21	17	25	19	33
P	2300	3400	2500	3900	2700	3900	5200	6100	7600	5000
Pb	48	31	45	27	47	45	36	70	50	61
S	3700	3200	3400	3600	3800	4400	4400	6100	5800	5400
Zn	100	90	103	100	110	140	160	210	240	190
Ba	520	180	450	190	480	520	310	690	380	570
Be	1.80	0.59	1.50	0.59	1.50	1.50	0.71	1.70	0.75	1.50
ICP cold vapor (mg/kg)
Hg	0.073	0.049	0.063	0.045	0.092	0.290	0.087	0.490	0.740	0.360

Coliforms and E. coli by most probable number technique; Trace micro element screen (Al - As) by EPA 3050; C, H, N by combustion LECO, Corp.; Hg - EPA 7470; Available P and K - sodium acetate extract
 
 

Table 5. Winter wheat yield, soil nitrate N and contrasts of compost treatments.
 

Field treatmentYield (kg/ha)	Soil nitrate (mg N/kg)
none	5.05	1.2
manure +ash, high bedding	5.39	2.2
manure, high bedding	5.61	2.1
biosolids +ash, high bedding	5.73	3.1
biosolids, high bedding	5.34	2.0
biosolids +ash, chips +low bedding	5.76	3.8
manure +ash, chips +low bedding	5.86	2.8
manure + ash, low bedding	6.27	3.2
manure, low bedding	6.13	2.5
biosolids +ash, low bedding	5.86	1.7
biosolids, low bedding	5.88	3.4
Contrast	Yield - p value	Soil nitrate-N -p value
compost vs. none	0.02	0.04
biosolids vs. manure	ns	ns
ash vs. no ash	ns	ns
low vs. high bedding	0.01	ns
chips vs. high bedding	ns	0.04
chips vs. low bedding	ns	ns

*ns non-significant contrast.
 
 

Figure 1. Compost temperatures in the (a) low bedding and (b) high bedding piles. Solids lines represent daily minimum and maximum ambient temperatures recorded at the Pullman-Moscow Regional Airport located three kilometers from the composting facility.