Comparison of Source-Separated Municipal Solid Waste Compost and Solid Manure With and Without Fertilizer N

V. Rodd¹, P.Warman², P. Hicklenton³, K. Webb⁴, R. Halsey⁵, Barry Friesen⁶,
Pierre Breau⁷, Susan Antler⁸ and Tom Hennessey⁹

1. Agriculture and Agri-Food Canada,
Nappan Research Farm,
Nappan, Nova Scotia. B0L 1C0

2. Nova Scotia Agriculture College,
Truro. Nova Scotia, B2N 5E3

3. Agriculture and Agri-Food Canada.
Kentville Research Centre,
Kentville, Nova Scotia, B4N 1J5

4. Agriculture and Agri-Food Canada,
Truro, Nova Scotia, B2N 5E3

5. Halifax Regional Municipality,
2750 Dutch Village Road,
Halifax, Nova Scotia, B3L 4K3

6. Nova Scotia Department of Environment,
Halifax, Nova Scotia,

7. Solid Waste Management Committee of Lunenburg County,
Bridgewater, Nova Scotia, B4V 2W8

8. The Composting Council of Canada,
Toronto, Ontario, M6H 1P7

9. Miller Waste,
Markham, Ontario, L3R 9R8

Tables

1	2	3	4	5
6	7	8	9	10
11	12	13	14	15
16	17	18	19	20
21	22	23	24	25

Figure 1

Composting of source-separated municipal solid waste is an option currently being used by some municipalities in Nova Scotia as a mechanism to divert refuse from landfills. Only agricultural lands can accept the volume of compost that will be produced in the future. The purpose of this project is: 1) to determine the elemental mineralization kinetics of compost compared to manure, 2) to determine the requirement for supplemental N when using compost, and 3) to determine if there are any environmental consequences of using compost on agricultural lands.

Cereal boot stage (barley in 1996 and wheat in 1997) N , K, and Mn concentrations were in the manure than compost amended plots. Boot stage Na, Mg and Cu concentrations, however, tended to be higher in the compost amended plots. As the rate of manure addition increased concentration of N (barley and wheat), K (barley and wheat), Ca (wheat), Mn (barley), Cu (wheat), and Na (barley) increased. As the rate of compost addition increased, the concentration of Mg (barley and wheat) decreased while that of Cu (barley) and Na (barley) increased.

Compost and manure addition increased grain yield of both barley and wheat. Manure amended plots had a higher grain yield than compost amended plots and the yield increased with increased addition.

Generally, soil organic matter content, determined in the fall of 1996, increased with rate of addition of both organic amendments. Organic matter levels were higher in plots which had received compost.

The soil physical parameters, bulk density and resistance to penetration were higher in the manure than compost amended plots. Bulk density decreased with increased compost addition and the decrease appears to be related to the amount of carbon applied to the soil.

The growth of annual ryegrass, after two years of organics addition, was higher on the source-separated municipal solid waste compost than on the manure plots.

Introduction:

The cost plus the public outcry against locating landfills in their communities has resulted in municipalities reviewing other options. One of the most environmentally friendly is source- separation of the Waste followed by composting. Interest in this option was enhanced by the Canadian Council of the Ministers of the Environment which set as its target a 50% reduction in the amount of waste going to landfills by the year 2000. It has been estimated that 40-60% of the total waste stream could be composted. Thus, composting can extract a valuable material from the waste stream.

Currently, most of the compost produced in Nova Scotia is sold to the landscape trade. However, as more communities start producing compost, there will be increased pressure for application of this material to agricultural crop land. Farmers, especially organic growers have expressed interest in using source-separated municipal solid waste (SSMSW) compost. Traditional farmers have also expressed interest in this material as an amendment to alleviate soil constraints.

Probably the biggest stumbling block to the utilization of SSMSW is the perception of contamination of the environment by heavy metals (Bourque 1995). He noted in recent years a shift in the compost feed material towards relatively clean organics coming from households. Current compost guidelines as proposed by the Canadian Council of Ministers 6f the Environment are more severe than the current guidelines for sewage sludge (Bourque, 1995). Generally, single application of SSMSW compost does not appear to deleteriously affect the environment (Frink and Sawhney 1994; Steffens et al 1992; Christoulas and Kapetanios 1992). Sims (1990) noted only slight differences in plant and soil concentrations of P, K, Ca, Mg, Cu, Cd,Cr, Ni, and Pb. It was suggested that when applied at agronomic rates with adequate amounts of supplemental N, compost could supply satisfactory plant growth and that concentrations of heavy metals should not limit its use. It should be noted that very few experiments have dealt with repeated application of the compost to land. Simard (1995) noted that soluble organics may complex with metals and greatly increase their bioavalability and movement in the soil profile. He also noted that very few experiments have been conducted where there was repeated application of compost to acidic soils. He suggested that the bioavailability of many metals would be orders of magnitude higher under these conditions. In Nova Scotia, Warman and Termeer (1995) found no phytotoxic effect from using sewage sludge compost in germination and seedling growth trials. Sawhney et al (1995) found, however, that increasing pH increased the concentration of Cd, Ni and Zn in compost leachates.

Decreased plant yield has been reported by various researchers (Sikora et al. 1980; Sims 1990; Christoulas and Kapetanios 1992; Spugnoli et al. 1993; Murillo et al. 1995). In the majority of the cases the yield decrease associated with application of compost was due to immobilization of N Sikora et al. 1980; Sims 1990; Christoulas and Kapetanios 1992; Murillo et al. 1995). Parker and Sommers (1993) indicated that the amounts of mineralizable nitrogen as a percentage of organic nitrogen were 25% for raw and primary sludges, 40% for waste activated sludges, 15% for anaerobically digested sludges, and 8% for composted sludges. Other researchers (Shiralipour McConnell 1993; Steffens et al. 1992; Maynard 1995) have found increased yields of wheat, barley and vegetables with compost addition. This suggests that mineralization from the compost was sufficient to meet crop requirements. Sikora and Azad (1993) applied N fertilizer and compost that 0, 25, 50, 75 and 100 % of the N was supplied by the compost. Though all treatments increased the yield of wheat, the highest yield was obtained when 50%of the N came from the compost and 50% from the fertilizer.

Compost has been found to beneficially affect soil physical properties. In compacted soils addition of compost has been found to improve soil structure (Avnimelech et al. 1992), resistance to penetration (Avnimelech et al. 1992), bulk density (Felton 1995), water holding capacity (Avnimelech et al. 1992; Felton 1995) and soil structure (Avnimelech et al. 1992). Hartley et al. (1994) noted a reduction in soil temperature at 50mm with surface mulches one of which was a compost. On a saline-sodic soil, SSMSW compost was reported to cause increased solubility of Ca which displaces Na on the exchange and improved soil structural stability (Avnimelech et al. 1992). They found that the yield had increased from nil to almost normal with gypsum and compost. Spugnoli et al. (1993) found that the compost treated soil was less compactable than the normal soil. In heavy structurally deficient soils, the addition of SSMSW compost increased yield by 10-20% over heavily fertilized corn and wheat (Avnimelech et al. 1993).

Thus, both from agronomic and food safety view points it is important to know how application of SSMSW compost will affect the availability of N and other minerals as well as heavy metals in cereals. The purpose of this project is: 1) to determine the elemental mineralization kinetics of compost compared to manure, 2) to determine the requirement for supplemental N when using compost, and 3) to determine if there are any environmental consequences of using compost on agricultural lands.

Materials and Methods:

In 1996, a split-split plot, split block factorial design with four replications was established. The main plots were manure (M) and SSMSW compost (C) applied at 0, 50, 100, and 150 kg of plant available N (PAN) ha^-1. PAN was assumed to be 15% and 50% of total N content of the compost and the manure, respectively. Fertilizer nitrogen (F) was applied at 0,50, 100 and 150kg N ha^-1 to each main plot of manure and compost. Compost, manure and fertilizer were also applied in 1997.

The manure and compost were applied to give similar PAN as 1996. It was assumed that 15% of the total N applied in 1996 would be the amount of residual PAN available to the 1997 crop (Smith and Peterson 1982). Compost was assumed to have negligible residual N fertility. The dry mass of compost and manure applied is contained in Table 1. The amendments were incorporated into the soil by rotovation and the plots were rolled. Various chemical parameters of the manure and compost are contained in Table 2. The compost produced from SSMSW had higher concentrations of copper, zinc, and molybdenum than allowed for in the CCME guidelines for class 1 compost (Table 2). The concentrations of mercury and cadmium in the SSMSW compost were slightly higher than the CCME guidelines, however, given the natural variation in these determinations, they probably were not significantly higher than the guidelines.

Chapais barley and Belvedere wheat were seeded on 27 May 1996 at 130 kg ha^-1 and 29 May 1997 at 135 kg ha^-1, respectively, with an International 5100 double disk drill.

At boot stage, 20 stems from each plot were cut, dried at 70C, ground in a Wiley Mill to pass through a 2mm stainless steel screen and analyzed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), and boron(B). Selected compost and manure samples were analyzed for cobalt (Co), chromium (Cr), cadmium (Cd), nickel (Ni), and lead (Pb) from a nitric acid digest. In 1997 the chlorophyll content of the wheat was also determined at boot stage with a chlorophyll meter.

Plots were harvested with a Hege plot combine and the samples were dried, deawned, cleaned and ground.

Soil chemical properties organic matter (OM), pH, and Mechlic 3 extractable nutrients were determined in the fall of 1996 and 1997. Soil NO₃-N and NH₄-N contents where determined at planting, boot stage, and after harvest. The soil physical parameters, surface bulk density (Db) and soil resistance to penetration (SRP), to a depth of 45 cm were determined in the fall of both years.

In 1998, the plots were seeded to Aubade annual ryegrass on May 6^th to monitor the residual effects of SSMSW compost and manure. At the time of preparation of this report, data was still being gathered from the 1998 season, thus, only yield and worm data are presented. The yield of annual ryegrass was determined by harvesting the plots with a Haldrup forage harvester; subsamples were taken for dry matter determination and used for subsequent analysis. Worm populations were monitored on October 19^th, 1998 on plots which had received the following treatments; 0M0F, 0C0F, I50M0F, 150C0F, 0C150F, 0M15O0F, 150M150F, and l50C150F. A solution of 50ml formaldehyde in 2L of water was applied to 0.36 m²quadrants which were placed at random within the plots. Worms were removed from the surface with tweezers, categorized as being mature or immature, counted and weighed.

Results and Discussion:

Cereal Boot Stage

Except for barley boot stage Na concentration in 1996, the interaction between the type of organic addition, rate of addition of PAN and rate of addition of fertilizer N was not significant and thus not presented.

Cereal boot stage (barley and wheat) N , K, and Mn concentrations were higher in the manure than the SSMSW compost amended plots (Tables 3, and 4). Boot stage Mg, Cu, and Na concentrations, however, tended to be higher in the plots amended with compost (Tables 4, 5, and 6). As the rate of manure addition increased, the concentration of N (Table 3; barley and wheat), K (Table 3; barley and wheat), Ca (Table 4; wheat), Mn (Table 4; barley), Cu (Table 5; wheat), and Na (Table 6; barley) increased. As the rate of compost addition increased, the concentration of Mg (Table 4; barley and wheat) decreased, while that of Cu (Table 5; barley) and Na (Table 6; barley) increased. The trend was for fertilizer addition to increase the concentration of N (Table 3; barley and wheat), K (Table 3; barley and wheat), Ca (Table 4; barley and wheat), Mg (Table 4; barley and wheat), Mn (Table 4; barley and wheat), Cu (Table 5; barley and wheat), Zn (Table 5; barley and wheat), B (Table 5; wheat), Na (Table 6; barley and wheat); and Fe (Table 6; wheat). The interaction between fertilizer N addition and type of organic addition was significant for the concentration of N (Table 3; barley), P (Table 3; barley and wheat), Mg (Table 4; wheat), Mn (Table 4; barley and wheat), Cu (Table 5; barley) and Na (Table 6; barley and wheat) in boot stage tissue. The addition of fertilizer N increased the cereal boot stage concentrations of N and Mn in the manure plots relative to the compost plots. Fertilizer N, however, tended to increase the plant boot stage concentration of Mg. Cu, and Na in the compost plots to a greater extent. Generally, the nutrient concentrations tended to be at the low end of the normal range (Table 7). The high K concentrations, in the plots which had received manure were the exception. The high K concentrations may cause a problem with grass tetany if the barley and wheat were harvested as forage. Presently, the greatest barriers to
N greater utilization of SSMSW compost on agricultural lands is the CCME guideline of 100 mg Cu kg^-1 and 500 mg Zn kg^-1. In this study, the copper and zinc concentrations in the compost exceeded N the CCME guidelines both years (Table 2). Although appreciable amounts of copper and zinc were applied in both years the boot stage concentrations were at the low end of reported literature values for barley (Table 7). The copper concentrations in barley and wheat at the highest rate of compost addition were less than 1.13 mg kg^-1greater than where no compost had been applied. Based on N extrapolation of the 1995 data (be aware that extrapolation can lead to some errors), it would appear that there is approximately a 1 mg/kg increase in Cu concentration with every 100 tonnes of compost N applied. Thus, in order for the Cu concentrations to raise to 15 mg kg¹, the mid point of the Cu range, it would appear that 1000 tonnes of compost ha^-1 would need to be applied. This is out of the agronomic range of application. Thus, from an agronomic view point, it appears that the CCME guidelines of 100 mg Cu kg^-1 needs to be reassessed. It should also be noted that increased compost addition did not significantly increase the concentration of zinc in barley or wheat. The concentration of zinc in wheat boot stage tissue, at the highest rate of compost addition, was only 3.9 mg kg^-1 greater than where no compost had been applied. Accounting for the 101 tonnes of compost that had been applied in the previous year plus, the amount of zinc taken off in the barley grain, the amount of compost derived Zn would have been 114,632g ha^-1. Extrapolation indicates that the amount of compost derived Zn needed to increase the cereal tissue Zn concentration to 42mg kg^-1, the midpoint of the sufficiency range, would be 558463g ha^-1. Thus, even if SSMSW compost N had a zinc concentration of l000mg kg^-1or 1g kg^-1 approximately 558 tonnes of dry compost would have to be applied. This is five times the quantity applied in this agronomic trial. Application of such quantities are out of the normal agronomic range of application. Thus, it would appear that the CCME guidelines for Zn concentration in compost should be reassessed.

Generally, increased addition of SSMSW compost did not appear to influence boot stage tissue heavy metal concentrations (Table 8). The Cd concentrations in boot stage barley increased with SSMSW compost application. However, at the highest level of compost addition, the barley boot stage concentrations were less than those which had received the highest rate of manure addition. The highest wheat boot stage Co concentration was from plots amended with manure at 150 kg PAN ha^-1. Thus, from a heavy metals uptake stand point, there does not appear to be any detrimental effect of using SSMSW compost in this agricultural application.

Grain

The concentrations of N (Table 9; barley and wheat), and Mn (Table 11; barley) in the grain were higher in the plots amended with manure than with SSMSW compost. However, the Na concentration (Table 12; barley) was higher in the compost amended plots. The interaction between type of organic amendment and rate of amendment addition was significant for the concentration of N (Table 9; barley), P (Table 9; barley), K (Table 10; barley), Mg (Table 10; barley), and Cu (Table 11; wheat), and Na (Table 12; barley) in the grain. Although the interaction was statistically significant, trends were not discernible for Mn and Cu concentrations. The concentration of N in the grain tended to increase with organic amendment addition; especially in the manure amended plots. Grain P concentration, however, tended to decrease with the addition of the organics. The grain K concentration increased with increased manure addition while the grain Na concentration increased with increased compost addition. The grain Ca concentration tended to increase with increased addition of both types of organics. The stringent CCME guidelines for the concentration of Cu and Zn in SSMSW compost presently appears to be the greatest barrier to increased utilization of SSMSW compost in agricultural systems. It should be noted that grain Cu concentrations were well within the maximum tolerable limits for livestock (Table 13). Thus, from an animal health view point there does not appear to be any problem with Cu and Zn concentrations in the compost three and two times higher, respectively, than the CCME guidelines. The addition of fertilizer N increased the concentration of N (Table 9; barley and wheat), Ca (Table 10; barley and wheat) Mn (Table 11; barley and wheat), Cu (Table 11; barley), and Zn (Table 11; barley) in the grain. The addition of fertilizer N, however, decreased the concentrations of P (Table 9; wheat), K (Table 10; wheat), Mg (Table 10; wheat) in the grain. Generally, there was no interaction between type of organic amendment and fertilizer N for the mineral concentrations in the grain (Tables 9-12). Except for the high Ni concentration in the manure plots amended with 150 kg PAN ha-¹ there does not appear to be any significant effect of compost on grain heavy metal concentrations (Table 14). Thus, it appears that addition of SSMSW compost did not detrimentally affect the quality of the grain produced.

Increased compost and manure addition increased grain yield of both barley and wheat (Table 9); the trend was most apparent for manure. Addition of fertilizer N also increased the yield of barley and wheat (Table 9). The smaller yield increase with compost, compared to manure, suggests that mineralization of N from compost was not sufficient to meet the N nutritional requirements of the barley and wheat. This was further collaborated by soil N (Tables 15-18)and chlorophyll data (Table 19).

Annual Ryegrass Yield

The yield of annual ryegrass tended to be higher, Cut 1 (P=0.087) and Cut 3 (P=0.026) where SSMSW compost had been applied previously (Table 15). The suggests that the residual nutrient availability from the SSMSW compost was greater than that of manure. This is in contrast to the cereal results from the two years of application. The lack of significant difference between SSMSW compost and manure for Cut 2 and Total yield was probably due in part to the drought conditions prevalent at that time of the year. The residual effect of the organics on the yield of annual ryegrass tended to increase as application rate increased (SSMSW compost and manure-Cut 1; SSMSW compost- Cut 3). The residual effect of fertilizer N in Cut 1 increased as the rate increased for the SSMSW amended plots but not the manure.
 

Soil N Concentration

Soil NH₄-N concentrations in the 0-15 cm depth interval were higher under the manure amended plots in the spring of 1996 and increased with rate of manure addition (Table 16). This was not unexpected since NH₄-N was not detected during analysis of the compost. That spring, addition of N fertilizer also increased NH₄-N concentration; the highest concentration NH₄in the soil occurred in the manure amended plots which had also received the highest rate of fertilizer N. At the other samplings, there was no effect of any of the treatments, and by the fall of 1996 and 1997, the NH₄-N concentration had decreased to nondetectible levels. There was no effect of any of the treatments on NH₄-N concentrations in the soil at the 15-30cm depth interval (Table 17).

Generally, soil N0₃-N concentrations increased with increased manure addition in the spring of 1996 but tended to be unaffected by increased compost addition (Tables 18 and 19). In the spring of 1997, there appeared to be no effect, at either soil depth interval, of increased application of the organic amendments on soil N0₃-N status. Although in both years spring soil N0₃-N concentrations increased with fertilizer N addition, there was no interaction between increased fertilizer N application and the type of organic amendment. Boot stage N0₃-N concentrations, at both soil depths, were higher under the manure than the compost amended plots. In fact soil N0₃-N concentrations tended to increase with increased addition of manure and decline with increased addition of compost. In both years, at boot stage, the application of fertilizer N increased soil N0₃-N concentrations. The interaction between type of organic amendment and fertilizer N addition was significant for the 0-15 cm depth interval in 1997 and in both years for the 15-30 cm soil depth interval. Where the interaction was significant, fertilizer N increased the soil N0₃-N to a greater extent in the manure rather than the compost plots. Generally the trends for soil N0₃-N concentration, after harvest in the fall, were similar to that of the boot stage; the exceptions being the lack of interaction between type of organic amendment and fertilizer N (both soil depths in 1997) and lack of significant difference between SSMSW compost and manure (0-15cm soil depth 1997). Chlorophyll readings taken at boot stage in 1997 showed trends similar to that found for N0₃-N (Table 20).

Soil Chemical and Physical Properties

In both years, plots which had received compost had higher soil organic matter levels (Table 21; barley and wheat), pH (Table 21), Ca content (Table 22), Mg content (Table 22), and concentration of Cu (Table 23), Zn (Table 23) and B (Table 23) than those which had received manure. Soil organic matter content (barley and wheat), pH (wheat), Cu concentration (barley and wheat) and Zn concentration (barley and wheat) increased with increased application of compost, but tended to remain constant with increased application of the manure. The reason for the increase in soil organic matter levels with compost compared to manure was probably due to the much higher application rates of the compost. Addition of fertilizer N tended to lower soil pH and increase the content of soil P (Table 21). Although the effect of increased addition of fertilizer N was statistically significant for the concentration of soil Mg (Table 22; wheat), and Zn (Table 23; wheat), trends were not discernible.

Soil resistance to penetration and surface soil bulk density were lower in the SSMSW compost plots than the manure plots (Table 24). Bulk density tended to decrease with increased application of the organic amendments; the effect being greatest with the SSMSW compost. This was due to the higher amount of carbon applied to the soil with the compost amendments (Fig. 1). Soil penetration resistance, however, did not appear to be affected by the rate of application of the organic amendments in either year. Although the interaction between type of organic amendment and rate of fertilizer N addition was significant for the barley in 1996, trends were not discernible.

Worms

Mature worm populations and biomass tended not to be affected by organic or fertilizer addition (Table 25). The immature worm population, total worm population, and immature worm biomass were, on average, higher in the SSMSW compost amended plots than in the manure. Although the number of immature worms in the soil increased with rate of organic addition there was no interaction between the type of organic amendment and the rate of addition. Fertilizer nitrogen addition also did not appear to influence worm numbers or biomass. The lack of differentiation between SSMSW compost and manure with respect to the mature worm population and mature and total worm biomass may be because of worm mortality from rototilling of the plots prior to seeding.

Conclusions:

There does not appear to be any deleterious affect from an environmental and food safety view point of using source-separated municipal solid waste compost on cereals. Heavy metal concentrations where no higher with compost than manure applications. Even though copper and zinc concentrations were approximately three and two times higher, respectively, than the Canadian Council of Ministers of the Environment, the concentrations of these nutrients in cereal tissue were at the low end of the plant sufficiency range and those in the grain were well within the maximum tolerable limit for livestock feed. The addition of compost, at the rates used in this experiment, appears to have improved soil physical properties and increased the macro-biota. However, source- separated solid waste compost did not appear to be able to supply the nitrogen nutritional requirements of barley and wheat when applied in the seeding year. It is proposed that these plots be maintained, cropped to forage, to determine the subsequent release of N, and other minerals including heavy metals, and the influence of SSMSW compost on soil macro-biota. Nitrogen, and other minerals including heavy metals, may be more available to plants in years subsequent to application. Thus, it is imperative that these plots be maintained and monitored to further assess the benefits and risks of using source-separated municipal solid waste compost.

Acknowledgements

Financial support from the Composting Council of Canada, Millar Waste, the Solid Waste Management Committee of Lunenburg County, the Halifax Regional Municipality, the Centre for Composting Technology and Agriculture and Agri-Food Canada Matching Investment Program, and input from the Nova Scotia Department of Environment is gratefully acknowledged. The technical assistance of Sam Henley, Janice Goodwin, Betty Anne Hoe g, Lisa Gowan, Karla Thomas, Jason Wilson, Jason Wells, Sharron Sorrenson, Teressa Hauser and Tanya McKenzie is also gratefully acknowledged

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