ORGANIC WASTE AMENDMENTS AS SOURCES OF CARBON AND FERTILITY FOR VEGETABLE

Waste amendments, such as food or yard waste, are abundant potential sources of C for soil organic matter and nutrients for crop production. A number of amendments, like gelatin waste and dehydrated food waste, remain relatively unstudied. For those amendments that have been extensively studied, like biosolids and paper waste, the conclusions about their effects on soil and crops are often conflicting, likely due to the varying experimental conditions. To address this gap in knowledge, I compared six waste amendments and their effects on soil quality and vegetable crop production to a mineral fertilizer control. In a two-year field trial (2013 and 2014) I compared the effects of paper fiber sludge/chicken manure (PF), biosolids/yard waste co-compost (BS), multi-source compost (MS), yard waste compost (YW), dehydrated food waste (FW), and gelatin waste (GW) against a mineral fertilizer (20-20-20). Three crops were included in the study: sweet corn (Zea mays cv. Applause and Brocade (2013) and Applause and Montauk (2014)), butternut squash (Cucurbita moschata cv. JWS 6823), and potatoes (Solanum tuberosum cv. Eva) for their physiological diversity and importance to the local economy. The experiment was conducted at the University of Rhode Island’s Greene H. Gardiner Crop Science Field Laboratory in Kingston, RI, and was laid out in a randomized block design (n=4). Waste amendments were applied to supply 10,000 kg C/ha over two seasons. Amendments were analyzed for pH, electrical conductivity (EC), total C, N and P content, organic matter (OM) content, moisture, density and heavy metals. Amendment effects on soil quality were assessed based on soil OM levels, bulk density, pH, and moisture. Soil samples were also tested for EC and heavy metals, two of the potential limiting factors for the use of waste amendments. Levels of inorganic N and potentially mineralizable N (PMN) were used to assess effects on soil fertility. Crop quality was assessed based on emergence and early growth, nutrient and heavy metal concentrations of tissue samples, and yield quantity and quality. Waste amendment properties, including pH, moisture, density, and OM content, varied between wastes, and year-to-year for the same waste, however none had problematically high EC or heavy metal levels. The nutrient (N, P, K) density of amendments was generally low, although GW contained considerable amounts of both N and P. Unique characteristics, like the presence of seashells in MS, affect estimates of carbon inputs and effects on soil pH, and are therefore important to note. Amendments did not significantly alter soil moisture or heavy metal concentrations, or increase EC to potentially problematic levels. Only MS significantly increased pH compared to the control, likely due to the presence of CaCO3 from seashells. Only FW produced a significant decrease in bulk density, compared to the control. Amendment with YW and BS significantly increased OM compared to the control, although effects were not consistent across crops. The organic N in waste amendments must be converted to inorganic forms to be plant-available. Waste amendment application was not a reliable way to increase late season inorganic N, or potentially mineralizable N (PMN), a measure of the organic N mineralized to inorganic forms, in comparison to the control. Although PF was the only amendment with a C:N ratio above 25:1, the threshold above which N immobilization is likely; inorganic N levels in plots amended with PF were not always significantly lower than the control. Potatoes from plots amended with PF had significantly lower emergence (2014) and were significantly shorter (2013 and 2014) compared to the control, indicating inhibition of early growth, although the same was not observed for corn or squash. Nutrient levels in plant tissue varied among treatment, but not consistently with application rates. Tissue levels of N, P, Ca, Mg, Mo, Cu, and Fe were all adequate for plant growth although concentrations of K, Mn, B, and Zn were deficient for some or all crops and treatments. There were no significant differences in corn cob tissue heavy metal levels among treatments (2014), indicating that short-term application of waste amendments does not increase corn ear heavy metal concentrations. Gelatin waste, BS, and FW produced yields comparable to the control for all crops. While YW, PF, and MS underperformed the control for corn and/or squash production, they performed as well as the control for potatoes. Paper fiber/chicken manure enhanced potato quality significantly in 2014. All waste amendments studied showed promise as effective replacements for mineral fertilizers, although not consistently for all crops. Although benefits to soil quality from application of waste amendments were limited, their application did not appear to be harmful or contribute problematic levels of salinity or heavy metals. Lastly, some waste amendments provided unique benefits such as increasing pH (MS) or improving potato quality (PF).

. Application rate of organic matter and C from amendments. Application rates were set to provide a cumulative application of ~10,000 kg C/ha over two years. ....43

INTRODUCTION
Conventional farming relies heavily on mineral fertilizers for the plant nutrients necessary for intensive production. The advantage of these fertilizers is that the nutrients can be balanced to meet crop needs and their release is predictable and reliable. However, synthetic sources of N (fixed by the Haber-Bosch process) are energy intensive to produce, prohibited by all organic certifying agencies and do not provide a source of carbon to build soil organic matter (Crews and Peoples, 2004).
Alternative sources of nutrients, including carbon-based materials like composts and manures, have historically been used for agriculture and new types of wastes are being considered for their potential as fertilizer replacements. These wastes can be from industrial processes like the manufacturing of paper or gelatin, or municipal sources such as sewage sludge, food waste, or yard waste.
The advantage of waste amendments as an alternative to mineral fertilizers is that, in addition to plant nutrients, they also provide carbon, a major component of soil organic matter. Soil organic matter is the key to soil quality because it controls moisture and nutrient retention and the density of the soil, all factors which can promote plant growth. In addition, waste amendments may be inexpensive and many are locally available, cutting down on the expense and environmental impacts of transportation. The use of wastes as agricultural amendments prevents the need to landfill or incinerate them, sequesters carbon in the soil and recycles nutrients that would otherwise be lost. Finally, unlike synthetic sources of nitrogen, these wastes have the potential to be approved for use in USDA Certified Organic agriculture (with the exception of biosolids which are prohibited) (USDA, 2015b).
Despite the advantages of their use in agriculture, many waste streams are not being taken advantage of. In the case of more novel amendments, such as gelatin and dehydrated food waste, this may be due to lack of data. In other cases it may be due to a stigma, as in the case of biosolids (processed human waste). Finally, unlike mineral fertilizers, the mineralization of N from organic wastes is less predictable and requires further study to ensure it meets crop needs and provides optimal yields.

Amendment Sources
Waste amendments originate from industrial (manufacturing processes) and municipal (sewage, yard waste) sources and represent a significant waste stream, only a portion of which is being recovered for beneficial use. For example, the U.S. paper industry generates 5.8 million tons of wastewater solids each year (Scott et al., 2000).
In addition, 6.9 million tons of biosolids were generated in the U.S. in 1998, and only 60% were used beneficially (Ozores-Hampton and Peach, 2002). An additional 33.8 million tons of yard waste (leaves and grass) and 36.4 million tons of food scraps were generated in the U.S. in 2012, only 21.3 million tons of which were recovered (EPA, 2014). Because of varying inputs and treatment methods, waste amendments differ in composition and consistency from year to year. Many of these characteristics, including nutrient content and ratios, pH, electrical conductivity and heavy metal content, impact their use as agricultural amendments.
Biosolids. Sewage sludge is a byproduct of centralized treatment of wastewater originating from households, industry and storm water runoff. Because it comes from human waste, it must be treated, stabilized, and disinfected by anaerobic or aerobic digestion, composting, or heat treatment before it can be used. The end product of these processes, referred to as biosolids, has a low C:N ratio (~10:1), and is therefore often co-composted with carbon-rich materials, including yard trimmings, to increase its C content (Ozores-Hampton and Peach, 2002), as is the case for the biosolids used in this study. Class A biosolids, as defined by EPA's 40 CFR Part 503 rule, contain no detectable level of pathogens and can be used for agricultural production (U.S. EPA, 1994).
Paper fiber sludge. Pulp and paper production, a major U.S. industry, generates a large amount of wastewater (USEPA, 2002). Treatment of this wastewater produces sludge of varying compositions and properties (Thompson et al., 2001).
While most of this sludge is disposed of in landfills, or by surface impoundment, some is used for land application (U.S. EPA, 2002).
Since the major U.S. source of fiber for paper is wood from trees, pulp mill waste sludge reflects the composition of wood fiber (Camberato et al., 2006;Thompson et al., 2001;U.S. EPA, 2002). Unlike pulp mill sludge, paper mill sludge contains only the cellulose portion of wood, along with additives and some heavy metals (Thompson et al., 2001). The growing trend of obtaining pulp from recovered paper requires a deinking stage, and sludge from this stage can contain ink residues (Camberato et al., 2006;U.S. EPA, 2002). In addition, sludge treatment can affect its composition. Primary sludge, which is treated by clarification, and deinking sludge tend to have high amounts of C but low plant nutrient levels. Secondary sludge, which undergoes further biological treatment, can have significant amounts of essential plant nutrients, including N, P and K (Camberato et al., 2006). The paper fiber used in this study was dewatered primary sludge from a mill that processes recycled paper.
Gelatin. Gelatin is manufactured from the skin and/or bones of pigs, cattle or fish, and used in the manufacture of photographic film, food, and pharmaceutical capsules (Roupas et al., 2007). Manufacturing gelatin involves removing the mineral portion of the bones, leaving behind "ossein", the organic portion, which contains collagen. The collagen is hydrolyzed into gelatin by liming, and filtered out, leaving behind a "filter cake," which is the waste used in this study (Geoff Kuter, pers. comm., Ag Resource Inc., February 27th, 2014). Compared to the other wastes used in this study, the gelatin waste was unique in that it had similar amounts of N and P (49 and 39 g/kg respectively). This could be problematic if the waste was applied to meet plant N needs because of the over application of P, which is discussed later.
Dehydrated food waste. I am not aware of any other published studies that have used this waste as an agricultural amendment although food waste is often used as a component of compost. The food waste used in this study is sourced from a restaurant. It is first ground, then dehydrated, and finally incubated for 18 h in an aerobic reactor, which reduces the waste volume by up to 90% (Global Enviro, 2011).
Although the food waste used had a similar N and P content to the biosolids compost used, it is only minimally composted and therefore the N and P may mineralize at a different rate from the more mature biosolids compost. The composition of the waste also reflects the restaurant it originates from and in this case it contained a large amount of mussel shells.
Compost. The two remaining waste amendments used in this study are composed in large part (multi-source compost) or entirely (yard waste) out of grass clippings, leaves, and brush. Many states are moving away from landfilling and incinerating yard waste, with some states outright banning the practice, and instead moving towards aerobic composting (Arsova et al., 2008). Leaves are often incorporated to provide bulk, preventing the composting process from becoming anaerobic (Michel et al., 1993).
While compost characteristics can vary widely depending on inputs and processing, the composts in this study were among the least nutrient dense of the materials used. While the multisource amendment had between 9-16 g/kg of N and 2-3 g/kg of P for 2013 and 2014 samples, the yard waste compost had 15-16 g/kg of N and 2 g/kg of P. Although neither had a high concentration of N, they both had C:N ratios below 15:1, indicating that the N present was unlikely to become immobilized in the soil during decomposition.

i. Heavy Metals
If waste amendments are to be recommended to farmers, we have to be aware of the risks associated with their use, including the potential to contribute heavy metals to the soil. Because heavy metals are toxic to humans and animals at elevated concentrations, the U.S. EPA (1994) has set upper limits for the amount of As, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Se, and Zn permitted in sewage sludge applied to agricultural land. These metals are a concern when any compost is applied to soil, not just those containing sewage sludge. Due to gaseous losses of C and N during the composting process, and retention of heavy metals, the concentration of heavy metals in composts are often higher than soil and can therefore increase soil concentrations when used as amendments Kirchmann, 2000a, 2000b;Smith, 2009).
Because of their long residence time in the soil, repeated additions of heavy metals from waste amendments may lead to their accumulation (Smith, 2009). This is a concern, not only because of contamination of the human food chain, but also because of the toxicity of heavy metals to plants and to soil microorganisms involved in carbon and nitrogen cycling (Giller et al., 1998;Khan et al., 2008).
Heavy metals can be present in soil in numerous forms, with varying levels of solubility and bioavailability. They may be bound in organic matter, or present in carbonates, oxides of iron and manganese, and sulfides (Giller et al., 1998). Soil properties, including pH, can have a strong influence on metal availability. For instance, for each unit decrease in pH, there is an approximate two-fold increase in the concentrations of Zn, Ni and Cd in the soil solution (Giller et al., 1998). The solubility of metals also influences their residence in the soil because, when metals become soluble, they can be lost both by leaching to groundwater and by increased plant uptake and crop removal (when part or all of the plant is harvested).
While aerobic composting of amendments generally increases binding of metals to stable forms of organic matter, which limits their bioavailability, amendments that include soluble organic matter increase metal leaching, possibly due to lowered pH and binding of metals to soluble organic compounds (Schwab et al., 2007;Smith, 2009). Thus, the accumulation of heavy metals in the soil is not just a function of the amount applied in waste amendments, but depends on other properties, including amendment pH, organic matter content and state of decomposition.
The presence and levels of heavy metals in waste amendments varies. A review of municipal solid waste (MSW) compost reported Cu, Zn, Ni, Cr, Cd, Mo, As, and Hg levels below EPA max concentrations but Pb and Se concentrations in some samples exceeded EPA limits (Hargreaves et al., 2008). Studies of sewage sludge reported detectable levels of Cd, Cr, Pb, Cu, Zn, and Ni, although none high enough to restrict land application (Casado-Vela et al., 2007;Da Silva et al., 2010). Similarly, the levels of Cd, Cr, Cu, Zn, and Ni detected in gelatin industry by-product and vegetable waste compost were not high enough to restrict land application (Da Silva et al., 2010).
Despite detectable levels of heavy metals in some waste amendments, they often have little effect on soil concentrations. Studies of soil amendment with sewage sludge and paper mill sludge reported no significant increases in soil concentrations (Aitken et al., 1998;Casado-Vela et al., 2007;Douglas et al., 2003). However, a review of MSW compost found that it can increase the soil concentrations of several heavy metals (Hargreaves et al., 2008).

ii. Salinity
Another concern about the addition of waste amendments to soil is increasing the concentration of soluble salts, which can increase the osmotic potential of the soil, making it harder for plants to obtain water. Furthermore, Na + can be toxic to plants at high concentrations, and can compete with K + for plant uptake (Sinha, 2004). Salinity problems are more likely in arid and semiarid regions where evaporation is high and there is not enough precipitation to flush out salts. Soil salinity is assessed by measuring the electrical conductivity (EC) of a saturated soil sample. The lower limit for a saline soil (a soil that contains enough soluble salts to adversely affect plant growth) is conventionally set at 4 mS/cm, however, due to varying plant sensitivities , adverse effects can begin as low as 1 mS/cm or as high as 8 mS/cm (Bernstein, 1975;Maas, 1984;Rhoades et al., 1999).
Studies conducted under greenhouse and humid field conditions (Maine and Quebec) have not identified a risk to crop productivity from excess soluble salts in paper sludge (Carpenter and Fernandez, 2000;Levy and Taylor, 2003;Simard et al., 1998). However, a different greenhouse experiment found that application of secondary pulp mill sludge led to significant increases in exchangeable Na, with Na saturation higher in amended soils than the level at which adverse impacts can become evident (Rato Nunes et al., 2008). Under greenhouse conditions salinity problems may be exaggerated by the lack of leaching from precipitation and higher temperatures for longer time periods.
In a review of municipal solid waste (MSW) compost, Hargreaves et al. (2008) reported compost EC levels ranging from 3.69 to 7.49 mS/cm. Application of MSW compost to soil at rates from 40 to 120 Mg/ha increased soil EC and, in some cases, inhibited plant growth. Two studies reported EC values for sewage sludge compost of 5.03 and 2.04 mS/cm (Casado-Vela et al., 2007;Perez-Murcia et al., 2006). A study conducted in a semi-arid region of Spain reported that increasing soil EC correlated with increasing compost application rate, although even at the highest rate (9 kg m 2 ), soil EC did not exceed 1.2 mS/cm (Casado-Vela et al., 2007). Reported EC levels for leaf compost have been low (0.6 mS/cm) (Maynard and Hill, 2000).

Soil Quality
i. Organic Matter The concentration of soil organic matter (SOM) is a key determinant of soil quality because it controls many properties, including cation exchange and waterholding capacity, nutrient retention, and bulk density. It is also a source of slowrelease plant nutrients as well as food and energy for soil microorganisms. Soil OM is, on average, about 58% carbon by mass (Howard and Howard, 1990).
Most studies have reported that the addition of paper mill sludge to soil increased soil OM levels (Rato Nunes et al., 2008). Douglas et al. (2003) reported a 60% increase in SOM in samples taken over a year after a single application of paper mill sludge (385 tons/ha). Gagnon et al. (2001) conducted a field trial on sandy loam using raw and composted pulp, and found that both similarly increased the total C content and C:N ratio of the soil, which can affect the mineralization of nutrients as discussed later. Finally, Zibilske et al. (2000) conducted a multiyear study on fine sandy loam soil and concluded that paper mill sludge, applied biennially, could compensate for decomposition losses due to conventional tillage, and allow for some C accumulation in soil.
In their review, Hargreaves et al. (2001) found MSW composts were generally high in OM, especially stable forms like humic acid. In addition, repeated application of MSW compost consistently increased soil OM levels. Ozores-Hampton et al.
(2011), after eight seasons of organic amendment application (biosolids or biosolids/yard waste co-compost), found that soil OM levels increased more than 200%.
Once added to soil, the rate at which waste amendments decompose will determine how long they effect SOM levels. The degradation rate of amendments is partly determined by the varying rates at which the organic compounds they are composed of (e.g. carbohydrates, amino acids, fatty acids, lignin) break down. The composting process will also affect the degradation rate of organic C compounds in amendments because labile organic compounds are mineralized during the composting process, leaving behind more resistant compounds (Bernal et al. 1998b). For example, levels of stable organic C were higher for composted food wastes than non-composted wastes (De Neve et al., 2003).

ii. Moisture
Raising the level of soil OM increases the water holding capacity of soil, by creating more small and medium-sized pores, and the amount of water available to plants, thereby reducing water stress during drought (Brady and Weil, 2008).
However, an increase in water holding capacity can cause delayed germination or rotting of seed in regions with wet springs (Maynard and Hill, 1994). Hargreaves et al. (2008) reported that application of MSW compost improved the water holding capacity of soil. Paper sludge also increased volumetric water content of soil (measured at field capacity for those studies that indicated water content); although this effect was short-lived, often disappearing by the second year after application (Aitken et al, 1998;Foley and Cooperband, 2002;Simard et al., 1998). Ozores-Hampton et al. (2011) reported that long-term application of biosolids and biosolids/yard waste compost significantly increased soil moisture at field capacity (-8 to -30 kPa). Water content was also higher at saturation (0 kPa) in amended plots than non-amended plots, although no difference was observed during drainage of gravitational water (-2 to -5 kPa).
iii. Bulk Density Due to their low density, the incorporation of waste amendments into soil can lower soil bulk density (the dry mass of a unit volume of soil, including pores), at least temporarily. Further, the addition of OM to soil increases aggregation, both by providing the carbon and energy for the biological processes involved in aggregation (e.g. production of polysaccharides), and by supplying organic polymers from decomposition to bind soil particles. Increased soil aggregation lowers bulk density, which allows plant roots to easily penetrate soil and access a greater volume of soil and nutrients (Brady and Weil 2008;Maynard and Hill, 1994).
Amendment with paper sludge increased the total pore space (by % volume) of clay soil and the proportion of macroaggregates (>250 µm), and lowered bulk density (Foley and Cooperband, 2002;Gagnon et al., 2001;Phillips et al., 1997;Zibilske et al., 2000). Long-term application of organic amendments (8 seasons of biosolids or biosolids/yard waste co-compost) also reduced soil bulk density compared to a non- iv. pH The pH of a soil, a measure of its acidity, is important to crop production because it affects the availability of both nutrients and toxic elements (e.g. aluminum), as well as the rate of microbial process that produce plant-available nutrients.
Although maximum nutrient availability differs, a pH of 5.5 to 7.0 is considered optimum for many agronomic crops. Plants also vary in their tolerance for acidity.
Due to the inherent acidity of New England soils, and the gradual acidification caused by natural and human-induced processes, local soils often require liming for optimum growth of many crops. Therefore, a waste amendment that could raise pH would provide an added benefit beyond increasing soil OM and fertility.
Since both the pulping and paper finishing processes increase the alkalinity of paper sludge (to a pH higher than 12.5) one would expect it to increase the pH of soil (Camberato et al., 2006;EPA, 2002). Some studies using paper sludge as a soil amendment reported increased pH (Rato Nunes et al., 2008;Aitken et al., 1998), whereas others reported no change (Douglas et al., 2003). The variability in results is likely due to the variability of sludge pH, as well as differences in the pH and buffering capacity of the soil it was applied to. A review of studies of MSW compost found that it increased soil pH, usually in proportion with application rate (Hargreaves et al., 2008).

i. Nitrogen
Nitrogen is essential for plant growth, and healthy plant foliage contains 2.5-4.0% N by weight. The C:N ratio of an amendment affects the release of N because microbes incorporate C and N into their biomass in a fixed ratio. Therefore, the application of amendments with a C:N ratio below 25:1 generally leads to the release of excess N into the soil, while addition of amendments with a C:N ratio above 25:1 favors the immobilization of N because soil microbes are forced to scavenge N from their surroundings, which depletes the pool of soluble N available to plants and can last for days to months (Brady and Weil, 2008). Nitrogen immobilization following the addition of composted sewage sludge (12.7:1 and 9:1) or gelatin waste (13.4:1) is unlikely due to their low C:N ratios (Casado-Vela et al., 2007;De Neve et al., 2003;Perez-Murcia et al., 2006).
Because of the low N content of woody plant tissue, the primary input in the paper-making process, pulp and paper-mill sludge are unlikely to contain enough N to satisfy plant needs (Allison and Murphy, 1963). Primary sludge has a C:N ratio ranging from 100 to 300:1 (high enough to cause N immobilization), while secondary sludge can have a C:N as low as 14:1, due to biological treatment (Camberato et al., 2006;Rato Nunes et al., 2008;Thompson et al., 2001). Although the degree of severity varied, studies of combined primary and secondary paper sludge and raw paper sludge application reported evidence of N immobilization in the soil (Carpenter and Fernandez, 2000;Simard et al., 1998).
In waste amendments most of the N is organic, which may not be fully mineralized into plant-available forms within the first season after application, further complicating prediction of N availability. When an amendment is added, soil conditions, including C:N ratio, temperature, and moisture, affect the rate of N mineralization. Immature compost may also have a high C:N ratio, which can cause initial N immobilization (Amlinger et al., 2003). First-year N availability for yard waste compost was 5% to 15%, with another 2% to 8% available the second year, while mean first year N availability of fresh biosolids was 37% (Amlinger et al., 2003;Gilmour et al., 2003). Estimates of first-year availability of N from MSW compost, made up primarily of kitchen and yard waste, ranged from 10 to 21% (Hargreaves et al., 2008). Due to low N availability and low N concentrations (below 40 g/kg), high application rates of MSW compost are often used (>50 Mg/ha) (Hargreaves et al., 2008). The effect of MSW compost on soil N levels varies; Hargreaves et al. (2008) reported that while some studies showed that application of MSW compost increased soil N levels, others found it to be less effective than mineral fertilizers.
When a large quantity of compost with a low N concentration is applied to meet plant N needs, it can lead to the over application of other nutrients, such as phosphorus. While the ratio of plant available N to P in many biosolids composts is 1:2, the ratio of N:P in many crops is between 7:1 and 10:1, leaving excess P to accumulate in the soil (Spargo et al., 2006). If excess P is lost by leaching it can stimulate algal growth in freshwater bodies and lead to eutrophication (Hargreaves et al., 2008).

ii. Phosphorus
Phosphorus is second only to nitrogen in its importance to plant growth. It is a component of nucleic acids, phospholipid membranes and adenosine triphosphate (ATP), the energy source for many biochemical processes. Healthy plant leaf tissue contains between 0.2 and 0.4% P by dry weight. Phosphorus is, however, more problematic than N because when P is added to soil it quickly becomes unavailable to plants due to adsorption to Ca (alkaline soils), or Fe Al (acid soils), and precipitation in association with Fe, Al, Mn, Ca or Mg (Brady and Weil, 2008).
The P content of paper sludge varies depending on its source. While primary sludge can have a P concentration of 1.6 g/kg, deinking sludge may only have ~0.1 g/kg, and secondary sludge can have 4.2 g /kg (Camberato et al., 2006). Application of sludge with C:P ratios of between 943:1 and 6,400:1 appeared to result in P immobilization, leading to reduced crop yields. The application of an organic substrate with a C:P ratio of greater than 300:1 is likely to cause microbial immobilization of soil P (Camberato et al., 2006). While Aitken et al. (2008) found no change in soil levels of extractable P after the addition of deinking sludge, other studies reported increased soil P (Rato Nunes et al., 2008;Simard et al., 1998). Rato Nunes et al. (2008) cautioned that increased pH (as high 7.6) and exchangeable Ca from the sludge may have limited the effects of increased P due to P adsorption.
Application of MSW composts (20 g P/kg) was reported to effectively increase soil P levels, with 10-50% P mineralization the first year. In fact, when MSW compost was applied at a rate of >200 Mg/ha to meet N needs, downward movement of P in the soil profile was reported, indicating a potential risk of leaching (Hargreaves et al., 2008). Ozores-Hampton et al. (2011) reported that after 8 seasons of applying organic amendments (biosolids, alone or co-composted with yard waste) soil P levels increased to more than 10 times the levels in the non-amended control.

i. Emergence
Rating emergence and initial growth of seedlings is a way to monitor for phytotoxicity and other unfavorable soil conditions caused by the addition of an amendment, such as changes to soil moisture, pH or bulk density. Levy and Taylor (2003) reported strong inhibition of germination for tomato seedlings grown in MSW compost, but no inhibition of seedlings grown in paper pulp mill solids. The inhibitory effect of MSW was observed when applied at very high concentrations, and was possibly due to its high pH (7.4). Douglas et al. (2003) reported poor establishment of ryegrass in plots amended with paper mill sludge, and subsequent significantly lower yields than other amendments, possibly due to the large volume of sludge applied to meet N needs. Perez-Murcia et al. (2006) did not report any reduction in germination of broccoli when composted sewage sludge and peat were used as a greenhouse growth media.
ii. Nutrient Uptake Although waste amendments may supply plant nutrients in sufficient amounts, rates of mineralization may be too low, or not timed to meet growth needs. Sampling of plant tissue is a way to assess nutrient status and determine fertilizer efficiency.
Application of MSW compost increased plant uptake of P in multiple crops, including potatoes (Hargreaves et al., 2008). The use of anaerobically digested liquid sewage sludge increased the uptake of both N and P in rye and sorghum-sudan forage (Kelling et al., 1977). However, Passoni and Borin (2009) found no significant difference in the total N concentration of crop biomass between three different composts made from food processing industry residues and municipal waste (200 kg N/ha) and a control (0 kg N/ha), possibly due to low N mineralization from composts.
Tissue analysis can also be used to monitor plant uptake of heavy metals. A review by Hargreaves et al. (2008) reported that amendment with MSW compost was iii. Yield Although the main goal of applying a fertilizer is to ensure sufficient plant nutrients to optimize crop yields, carbon-rich waste amendments have the potential to provide additional benefits which can improve yields. Because the nutrients in waste amendments must first be mineralized into plant available forms, their release may be slower and better timed to meet crop needs than the immediately available forms found in inorganic fertilizer, which are also prone to loss by leaching. In addition, if waste amendments increase soil OM levels, this may provide further benefits, including increased nutrient and moisture retention. Maynard and Hill (2000), in a study of onions grown with leaf compost, reported increased yields for some varieties.
In a different, long-term study, these authors reported yields in plots amended with leaf compost, lime, and fertilizer that were 25% higher than those amended with fertilizer and lime alone (Maynard and Hill, 1994). On the other hand, Chellemi and Rosskopf (2004) reported inconsistent yield responses to the addition of yard waste for pepper production.
Ozores-Hampton and Peach (2002), in a review of studies of biosolids and biosolid co-composts, found that, while co-composts generally increased vegetable yields, several studies showed no response, and others reported decreased yields.
Many studies have reported negative or neutral yield responses to application of paper sludge, including reduced yields on a commercial cereal farm and reduced barley yields, both after application of deinking sludge (Aitken et al., 1998;Simard et al., 1998). Foley and Cooperband (2002) found that there was no effect on potato yields the first year after paper mill sludge was applied. Yields of potatoes, sweet corn, and squash were lower in soil treated with MSW compost compared to fertilizer treated soils. However, studies of ryegrass, alfalfa, tomatoes, and strawberries, with application rates of 40 Mg/ha and higher, obtained equivalent or improved yields compared to controls (Hargreaves et al., 2008).
Waste amendments are abundant and a potential source of both nutrients and carbon for crop production. However, some amendments, like gelatin waste and dehydrated food waste, remain relatively unstudied. For those amendments that have been extensively studied, like biosolids and paper waste, the conclusions about their effects on soil and crops are often conflicting, likely due to the varying conditions of experiments. My project went beyond the scope of previous studies by comparing six waste amendments, both familiar and novel, to a mineral fertilizer control, and their effects on soil quality and crop production. Potatoes, sweet corn and winter squash were chosen as the crops for this study because of their importance to Rhode Island's economy (over $4.5 million/yr in sales), the quantity grown (over 1,300 acres), as well as their physiological diversity (USDA, 2013).

Objectives
The objective of this project was to study the use of waste amendments for crop production. Their success as sources of carbon and nutrients for crops was assessed based on their effects on soil quality and fertility as well as crop yield and quality. In a two-year field trial I studied the effects of (1) paper fiber sludge/chicken manure, (2) biosolids/yard waste co-compost, (3) multi-source compost, (4) yard waste compost, (5) dehydrated food waste and (6) gelatin waste on production of sweet corn, winter squash and potatoes.

Soil quality
i. Organic matter, moisture, bulk density.
Amendments will increase SOM and moisture retention relative to the control and decrease bulk density. Large additions of C-rich amendments have been shown to increase the C content of soil, a major component of SOM, which in turn increases water holding capacity and reduces bulk density (Gregorich et al., 1994;Haynes and Naidu, 1998;Khaleel et al., 1981).

ii. pH
Amendments with a high pH will raise soil pH. Paper fiber sludge and municipal solid waste compost have been reported to increase soil pH (Aitken et al., 1998;Hargreaves et al., 2008;Rato Nunes et al., 2008).
Amendments high in organic C and N will lower soil pH. Sources of acidity from C and N cycles include decomposition of organic matter which releases CO2 which, when combined with soil water, can form carbonic acid (H2CO3), and oxidation of ammonia which releases H + (Bolan and Hedley, 2005).
iii. Electrical conductivity Amendments with high EC will raise soil EC temporarily but the effect will be short lived. Due to the large quantities added, amendments with high EC could raise soil EC but this effect will be only temporary as salts are leached out by rain and irrigation.

iv. Heavy metals
Amendments that contain heavy metals will raise soil heavy metal levels.
When added to the soil, heavy metals will be retained by binding to OM or associating with carbonates, oxides of iron and manganese or sulfides. This increase, however, may not be significant enough to be detectable by my analysis method.

Soil fertility
i. Ammonium, nitrate Early season inorganic N levels will be lowest in plots amended with materials with a C:N ratio >25:1. Application of amendments with a C:N ratio >25:1 causes immobilization of N by soil microbes, which can last for days to months (Brady and Weil, 2008).
Later season soil inorganic N levels will be higher in waste amended plots than fertilizer amended plots due to dynamics of organic N mineralization.
Because N applied in mineral fertilizer is subject to plant uptake and loss by leaching or volatilization soon after application, side-dressing with additional N later in the season is often recommended (Hazard and Howell,2007) . However, organic N in wastes is slowly mineralized as organic matter decomposes, leading to a slower release of N and higher later season N levels, which may be better timed to meet crop needs and eliminate the need for side-dressing.
ii. Potentially mineralizable N PMN will be higher in waste amended plots than control plots. PMN represents organic N mineralized under ideal conditions. Addition of organic N in waste amendments provides a larger pool of N available for mineralization than is present in control plots.

Crop quality
i. Emergence/initial growth Emergence and initial growth will be delayed in plots amended with high (>25:1) C:N ratio materials relative to the control. The addition of wastes with a high C:N ratio leads to N immobilization by soil microorganisms, which can in turn lead to an insufficient supply of N needed for early plant growth.
Emergence/initial growth in waste amended plots will be higher than control plots. Provided they are a source of sufficient N, waste amended plots will have higher seedling emergence and early growth due to soil conditions favorable for seedling emergence (e.g. increased moisture and lower bulk density due to increased SOM).
ii. Tissue nutrient levels Adequate levels of plant nutrients will be present in tissue samples for plots that received recommended nutrient application rates. Nutrients from amendment application will be sufficient for plants to reach tissue nutrient levels associated with normal plant growth.
Tissue levels of heavy metals will not reflect increases in soil heavy metal levels (from the addition of wastes) due to low bioavailability. Plants can absorb non-essential elements from the soil, some of which are toxic (Peralta-Videa et al., 2009). However, heavy metals bind to organic matter, both in the soil and waste amendments themselves, as well as from associations with carbonates, oxides of iron and manganese or sulfide, all of which reduces their bioavailability (Giller et al., 1998;Shober et al., 2003).

iii. Yield
Waste amended plots will achieve yields comparable to control plots. The waste amendments in this study have sufficient plant nutrients and are added at a high enough rate to achieve comparable yields to mineral fertilizers.

Project Overview
I conducted a two-year field experiment, at the University of Rhode Island's Greene H. Gardiner Crop Science Field Laboratory in Kingston, RI during the growing seasons of 2013 and 2014, to study the suitability of municipal and industrial waste amendments as sources of carbon and nutrients for sustainable vegetable production. I evaluated 6 waste amendments against a mineral fertilizer control: (1) paper fiber sludge/chicken manure, (2) biosolids/yard waste co-compost, (3) multisource compost, (4) yard waste compost, (5) dehydrated food waste, and (6) gelatin waste. I collected data on soil fertility, soil quality and crop quality for three crops: sweet corn (Zea mays cv. Applause and Brocade (2013) and Applause and Montauk (2014)), butternut squash (Cucurbita moschata cv. JWS 6823), and potatoes (Solanum tuberosum cv. Eva). Amendments were applied at a rate sufficient to supply 10,000 kg organic C/ha over two seasons.
Amendments were analyzed for pH, EC, total C, N and P content, OM content, moisture, and total elements/heavy metals. Amendment effects on soil quality were assessed based on determination of OM levels, bulk density, pH, and soil moisture.
Soil samples were also tested for salinity (EC) and heavy metals (As, Cd, Cr, Cu, Pb, Hg, Mo, Ni, Se and Zn), two of the potential limiting factors for the use of waste amendments. Soil fertility effects were evaluated by measuring levels of ammonium, nitrate, and potentially mineralizable N (PMN). Crop quality was assessed based on tissue levels of macro and micro nutrients as well as heavy metals, ratings of crop emergence and early growth, and yield. The field was prepared by mowing the cover crop and then incorporating the residue by disc harrow. The 84 experimental plots, measuring 4.6 m × 4.6 m, were laid out with crops and amendments arranged in a randomized block design (n=4) ( Figure   1). Amendments were applied in late-April 2013 and late May 2014, at a rate sufficient to supply 10,000 kg organic C/ha over two seasons (Table 1). Application rates were determined using the total C (dry wt.) and moisture content of each amendment to determine the wet weight need to supply the specified rate of C. Wet weights were then converted to volume using amendment bulk density to determine the number of 5-gallon buckets needed per plot. Buckets of amendments were spread on the surface of each plot, evenly distributed with rakes and incorporated by disc

Amendment Characterization
Amendment were delivered or picked up in the spring of 2013 and 2014. The biosolids/yard waste, yard waste and multisource compost were from Rhode Island.
The dehydrated food waste was from a restaurant in New York, the gelatin waste was from a Massachusetts facility and the paper fiber was from a resource management company based in New Hampshire. Amendments were stored in piles under tarps until application. All amendments were applied as delivered with the exception of the gelatin waste which arrived in large filter cakes and had to be broken up through a screen by hand before application.
For both 2013 and 2014 amendments, three subsamples were collected from each amendment pile, combined and analyzed for pH, EC, total C, N and P content, OM, moisture, bulk density and macro and micro nutrients/heavy metals. The 2014 amendment samples were also analyzed for NH4, NO3 and P2O5.
Organic matter. Amendment organic matter content was measured by loss-onignition at 550°C for 5 hours (Gugino et al., 2009).

Moisture.
The gravimetric water content of the amendments was determined by drying at 105°C for a minimum of 24 hours. Results were reported as mass of water per mass of dry amendment (Topp, 1993).
Bulk density. Amendment bulk density was determined from the dry weight of amendment samples (dried at 105°C for a minimum of 24 hours) taken with a 1,006 cubic centimeter corer (Culley, 1993). Bulk density measurements were based on one sample per amendment.

Elemental analysis. Amendment macro and micro nutrients and heavy metals
were measured by X-ray fluorescence with a Niton XL3r600 XRF Analyzer (Thermo  (Helrich, 1990). Ammonium and nitrate were extracted using a 1:10 ratio of amendment to 1 N KCl and analyzed by ICP (Gugino et al., 2009).

Soil Quality
Amendment effects on soil quality were based on changes to OM levels, bulk density, pH, and soil moisture. Soil samples were also tested for EC and heavy metal Testing methods for soil organic matter, pH, moisture, EC and heavy metals were the same as for amendments (see previous section).
Bulk density. Soil bulk density was determined from the dry weight of the soil (dried at 105°C for a minimum of 24 hours) from a 185 cubic centimeter corer (Culley, 1993). Bulk density measurements were based on one 10 cm sample per plot.

Soil Fertility
Soil fertility was assessed by measuring levels of inorganic N (NH4 and NO3) and potentially mineralizable N (PMN). The sampling dates were the same as for soil quality testing.

Potentially mineralizable N.
Soil PMN was determined from the difference in soil ammonium concentration before and after a 7-day anaerobic incubation at 30°C (Gugino et al., 2009). Ammonium concentration was determined colorimetrically as described above.

Crop Quality
Crop quality was based on tissue samples levels of macro and micro nutrients as well as heavy metals, crop emergence, early growth, and yield quantity and quality.  (Miller, 1998).
Critical nutrient levels (the lower limit for adequate growth) were based on Maynard and Hochmuth (2007) for pumpkins (most recent mature leaf, 8 weeks after seeding), sweet corn (most recent mature leaf, just prior to tasseling), and potatoes (most recent mature leaf, 1 st blossom stage). These levels represent the closest approximation for the stage of maturity at which tissue samples were taken and although the most recent mature leaf was sampled for potato and squash, corn samples were taken from the 5 th leaf down (per Univ. Conn. instructions).
Five Montauk corn ears (including husk and cob) per plot were also collected in 2014 and analyzed for heavy metals by the same method used for soil samples. Yield. Potatoes were harvested from a 3 x 3 m area in the center of each plot.
They were washed and sorted into three categories of quality: "A" (marketable), "B" (potentially usable for secondary market like processing) and "C" (culls) based on appearance. The potatoes were weighted by category and total yield (all three categories) was calculated on a per plot basis.
Squash were harvested from a 3 x 3 m area in the center of each plot. They were washed and sorted into marketable and culls based on appearance. Both categories were weighted and counted, and total yield (marketable + culls) was calculated on a per plot basis. The fraction of total yield that was culled was calculated on the basis of weight and number of fruit culled. Amendment pH was less consistent than EC ( Table 2). The mineral fertilizer (2014) and gelatin waste (2013) were the most acidic (4.6 and 4.9, respectively), the chicken manure (2014) was neutral (7.0), and the dehydrated food waste was consistently acid in 2013 and 2014 (5.5). The yard waste compost (6.5 and 6.7) and paper fiber (6.9 and 6.4) were only slightly acidic and consistent between years. The pH of the multisource compost hovered right around neutral (6.7 and 7.1). Finally, the biosolids/yard waste co-compost had the least consistent pH, varying from 5.1 in 2013 to 7.9 in 2014.
The organic matter content of the waste amendments varied among amendments and year-to-year for the same amendment (Table 2). In 2013, the OM content of the amendments followed the order: Multisource compost < yard waste compost < dehydrated food waste < biosolids/yard waste co-compost < chicken manure < gelatin waste < paper fiber. The order was the same in 2014, with the exception of dehydrated food waste which had a slightly higher OM content than the biosolids/yard waste co-compost. The proportion of C in amendment OM varied, with the lowest values observed for paper fiber and chicken manure (40-50%), biosolids/yard waste cocompost, gelatin waste and yard waste in the middle (50-60%), and the highest values observed for dehydrated food waste and multisource compost (75-85%) ( Figure 2).  Both the dehydrated food waste and the multisource compost contained a considerable amount of seashells. Because shells are denser (1.7 g/cm 3 ) than organic matter, and are primarily CaCO3 (12% C), they could be responsible for the high percent of C in OM for these amendments (Manohara et al., 2014). While the C contribution from shells is reflected in the total C measurement of the amendments due to the high combustion temperature, the CaCO3 from the shells would be unlikely to begin decomposing during heating in the muffle furnace to measure OM. Although the loss-on-ignition procedure heats the samples to 550°C, Mohamed et al. (2012) found that the CaCO3 in cockle shells does not begin to decompose until 700°C.
Therefore, the percent of OM that is C is likely overestimated by the methods used here. The C present in the shells as CaCO3 would not function the same as the rest of the C in the waste materials because the large pieces of shell would break down very slowly, therefore very little of this C would initially be available to soil microorganisms.
To determine how seashells affected the C content of amendments, samples of the dehydrated food waste and multisource compost (2014) were treated with 6N HCl.
The samples were mixed with the acid, dried (105°C for a minimum of 24 hours), ground, and analyzed for total C and N by solid phase analysis. The total C content of the acid-treated samples was subtracted from the C content of the untreated samples to determine the amount of C lost (from CaCO3). While there was only 15.5% less C in dehydrated food waste samples after acid treatment, there was 47.4% less C in the multisource compost samples. Because C from CaCO3 is not available to microorganisms, the multisource compost will contribute almost 50% less C to microbial processes than total C values indicate. Without shells the C:N ratio of the multisource compost decreases from 9:1 to 5:1, which could result in higher inorganic N availability than expected. This highlights the importance of distinguishing between organic and inorganic sources of C when interpreting amendment test results.
Although they were not determined quantitatively, some textural properties of the amendments were unique. The biosolids/yard waste co-compost was a mixture of very fine organic material and larger pieces that resembled bark mulch. The yard waste compost also resembled bark mulch, although the pieces were consistently larger. The multisource compost was unique from the other composts because it included pieces of clam shells. This is reflected in a higher bulk density than the other two composts (Table 3). The dehydrated food waste was finely ground and contained pieces of mussel shells. Because the paper fiber was not composted, and was made entirely of recycled paper, it had a very different appearnce and texture from the rest of the material: it had a very low density (0.22 g/cm 3 ) and contained foreign materials, including pieces of plastic. Finally, the gelatin waste arrived in large filter cakes and had the texture of cheesecake. It had to be pushed through a sieve by hand to break it up into smaller pieces before it could be applied.
Physical charactersitics of waste amendments, like texture and moisture, are important for practical and aesthetic reasons. Texture can effect the rate of decomposition: aerobic breakdown of materials depends on both access; the smaller the particle size the more surface area available to microorganisms, and also availability of oxygen; if particles are too small it can lead to compaction and prevent airflow (Ahmad et al., 2007). Particle size also influences the ability of a farmer to spread the materials, while the requirements for specific pieces of equipment vary, a consistent texture is preferable (Alexander, 1997). Although amendments in this study were spread by hand, the gelatin waste could not have been spread by many types of equipment (like a cone spreader) without being first broken up by hand. Amendment moisture content is also a consideration: excess moisture adds unnecessarily to shipping costs but materials that are too dry may be dusty or hydrophobic (Ozores-Hampton et al., 1998). For this study, the paper fiber that was delivered was over half water by weight, while the other amendments were drier (Table 3). There are also aesthetic considerations: a farmer or gardener might object to materials that contain large quanities of shell (dehydrated food waste and multisource compost) or foreign material (plastic in paper fiber). The amendments were also tested for their heavy metal content (Mo, Pb, Se, As, Hg, Zn, Cu, Ni, Cr and Cd). None of the amendments exceeded the ceiling limits for heavy metal concentrations outlined by the U.S. EPA (1994) for land application of biosolids (Appendix 1). All concentrations were also below the more restrictive levels established for exceptional quality biosolids with the exception of the yard waste compost in 2014, which slightly exceeded the limit for As.

Plant Nutrients
Waste amendments were tested for their total N, P and K content. Several of the amendments studied had N contents comparable to or exceeding commercial organic fertilizers such as chicken manure (Table 4). The gelatin waste had the highest N concentration (49 g/kg), exceeding that for the chicken manure (45 g/kg) used in the paper fiber blend. The dehydrated food waste and biosolids both contained > 30 g N/kg. The multisource compost, paper fiber and yard waste compost all contained < 17 g N/kg.
Although the multisource compost and yard waste compost had low N contents, their C:N ratios were <15:1, while the C:N ratio of the paper fiber was between 57:1 and 74:1, well above the threshold for N immobilization (25:1) ( Table   4). Even when blended with a composted chicken manure product (C:N = 8:1) at the rate recommended by the provider of the paper fiber (7 parts paper to 1 part chicken manure), the C:N ratio of the blend (>50:1) was still high enough to result in N immobilization.
Most of the N present in waste amendments is organic N; however, some is present in inorganic forms (NH4 and NO3) (Figure 3). Unlike organic N, these forms are available for immediate plant uptake, and nitrate is susceptible to loss by leaching.
The paper fiber/chicken manure blend had the highest fraction of N in inorganic forms (4.5%), followed by the biosolids/yard waste co-compost (3%), and the multisource compost (2.6%). The yard waste compost, gelatin waste and dehydrated food waste all had 1% or less of their N content in inorganic forms. Most of the waste amendments are not significant sources of P (Table 4).
Although the dehydrated food waste, yard waste compost and multisource compost had P concentrations of 2-3 g/kg, the paper fiber had <1 g P/kg. The biosolid/yard waste co-compost had a slightly higher concentration (4-6 g P/kg). The gelatin waste was unique because it had a P content approaching its N content (39 g P/kg), which could lead to over application of P if it were applied to meet crop N needs. Unlike mineral fertilizers, not all of the P in waste amendments is plantavailable. For example, the plant-availability of P from biosolids ranged from nearly 0% to 100%, depending on how the wastewater was treated (Elliot et al., 2005).
Therefore, a measure of plant-available-P is necessary when applying amendments to meet crop nutrient needs. For this study, the amount of available-P in the waste amendments was measured using a neutral ammonium citrate (NAC) extraction. The portion of the total P that was plant-available (according to this method) varied between 53% (multisource compost) up to 111% (paper fiber/chicken manure mix) ( Figure 4). However, Elliot et al. (2005) reported that, for biosolids, the amount of available-P extracted by the NAC method was not statistically different from the total P extracted by strong acid digestion, and sometimes even exceeded it (as seen in this study). Further, they reported that there was no correlation between plant-availability of biosolids P and the amount extracted by NAC. They concluded that NAC extraction was not useful for testing plant-availability of P in biosolids. The waste amendments used in this study also contained varying amounts of K (Table 4). The gelatin waste contained almost none (<1 g/kg) and the paper fiber also contained very little (<5 g/kg). The biosolids/yard waste co-compost, dehydrated food waste, multisource compost, and yard waste compost all contained between 10 and 30 g/kg of K. These are all low in comparison to the chicken manure (62 g/kg) and fertilizer (166 g/kg).

Application Rates
Amendments were applied to provide ~10,000 kg/ha of C over the two years of the study, with the exception of the mineral fertilizer control, which was not a significant source of C (Table 5). Gelatin waste was not applied in 2014, as the 2013 application had exceeded the total C required. Table 5. Application rate of organic matter and C from amendments. Application rates were set to provide a cumulative application of ~10,000 kg C/ha over two years. BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF/CM = paper fiber/chicken manure, YW = yard waste. Because application rates were based on amendment C content, and the nutrient density of the amendments varied, application rates of N, P, and K also varied Although enough N was applied in waste-amended plots to meet crop needs, it was applied mostly as organic N (Figure 3), which is not mineralized completely into plant-available forms in the first growing season. Estimates of first-year N availability from yard waste and municipal solid waste composts range from 5-21% (Amlinger et al., 2003;Hargreaves et al., 2008). Although data on inorganic N release is available for many composts, similar data are not available for novel amendments such as gelatin waste and dehydrated food waste. The mineralization rates for these amendments are potentially higher because they have not been composted and likely contain more rapidly decomposable compounds. Because N mineralization rates depend on a wide variety of factors, including soil conditions, it is difficult to predict if the N applied from waste amendments (and N mineralized from existing soil OM) will be sufficient to meet crop needs.
The recommended agronomic P and K application rates vary based on crop needs; however, they are also dependent on existing soil P and K levels. When P is added to acid soil, like the field in this study (pH generally <6.0), it quickly becomes bound in Fe and Al compounds with very low solubility and therefore low plant availability. To compensate for low plant availability, farmers often over apply P, resulting in excess buildup in the soil. Once this buildup has occurred, if soil tests indicate optimum to above-optimum soil P levels, little to no P addition is recommended (Hazard and and Howell, 2014).
Because P uptake is slow in cold soils, a small addition is recommended even for soils with optimum P levels. These rates range from 20 kg P/ha for sweet corn and squash to 29 kg/P ha for potatoes (Hazzard and Howell, 2014). The results of soil tests from March 2013 (UConn Soil Laboratory), before establishment of experimental plots, indicated that soil P levels were already optimum, indicating further additions of P would be unlikely to increase yields (Hazzard and Howell, 2014). All amendment application rates were at least 29 kg P/ha, with the exception of the gelatin waste plots in 2014, which did not receive any additional amendment after a large addition (904 kg P/ha) in 2013. Recommended application rates of K are also dependent on existing soil levels.

Figure 5.
Although excess K does not have the same potential as N and P to cause environmental problems, like eutrophication, excess K will be taken up by plants, beyond what they need, and may depress uptake of Ca and Mg, causing nutritional imbalances in the plant (Brady and Weil, 2008).
Unlike P levels, soil tests indicated that K levels were below optimum in March 2013. For soils with below-optimum K levels, additions of 112 kg K/ha for sweet corn, 139 kg K/ha for winter squash, and 186 kg K/ha for potatoes are recommended (Hazzard and Howell, 2014). All plots received the recommended rate of K for winter squash and sweet corn with the exception of the gelatin waste plots and control plots. Because of the very low K content of the gelatin waste these plots Amendments were also sources of Ca and Mg (Table 6).

Electrical Conductivity
Reduction of crop yield due to soil salinity was unlikely at the EC levels found in this study. Yield losses for sensitive crops begin at EC levels of ~1 mS/cm, corn and potatoes yield losses are likely above 1.7 mS/cm, while squash tolerances are higher (Maas, 1984). The highest EC levels found in this study (0.587 mS/cm) were observed in control potato plots, immediately after amendment in 2014 ( Figure 6). As hypothesized, the increase in salinity due to amendment application was temporary, and all soil EC levels had fallen sharply by the next sampling date (two months later).
These results suggest that the amendments used in this study, applied at or below the rates used, will not contribute problematic levels of salts to the soil.   (Figure 7). The pH for MS treatment was significantly higher than all other treatments in August 2013 potato plots, and all months and crops sampled in 2014. Although this compost had a higher pH (6.7-7.1) than the soil, it did not have the highest pH of the amendments used in the study (Table 2). It did, however, contain a significant amount of seashells, which are made primarily of CaCO3. Calcium carbonate is used to neutralize soil acidity, and therefore could have been responsible for the higher pH in these plots. Crushed oyster shells and clam processing wastes have previously been shown to increase soil pH (Lee et al., 2008;Owen et al., 2008). These results indicate that amendments containing seashells may provide the additional benefit of raising soil pH.
I anticipated that waste amendments, which are high in organic C and/or N, would lower soil pH, due to the release of acidity from the decomposition of organic matter and oxidation of ammonia (Bolan and Hedley, 2005). The results did not support this hypothesis for all amendments. The soil pH of plots amended with PF and GW was never significantly lower than the control, and plots amended with FW were only significantly lower in corn plots in September 2013. It appears that acidity released from application of these wastes was similar to the acidity produced by conversion of urea and NH4 from the control fertilizer. As stated earlier, the pH of plots amended with MS was consistently higher, potentially due to the acid neutralizing effect of shells. However, the pH of plots treated with YW and BS was often significantly lower than the control in 2014. This is not likely due to the pH of the amendments alone, since the 2014 YW treatment had a pH of 6.7 and the 2014 BS treatment had a pH of 7.9, the highest of all the amendments applied. Instead, the low pH was likely related to processes that release acidity such as decomposition of organic matter, or oxidation of N or S. These results indicate that some waste amendments have the potential to significantly lower pH in comparison to a mineral fertilizer.

Bulk Density
Plots which received waste amendments were expected to have lower bulk density, because of the low density of the amendments themselves, and the addition of OM which provides the energy for biological processes involved in aggregation, as well as organic polymers from decomposition that bind soil particles (Brady and Weil, 2008). Most waste amended plots had lower bulk density than the control treatment, although only plots amended with FW were significantly lower. The exception was MS amended plots, which had a higher mean bulk density than the control, although not significantly (Figure 8).
Changes in soil bulk density were likely not due to the incorporation of amendments with lower bulk density alone. While MS raised bulk density, and FW decreased it, compared to the control, FW itself had a higher bulk density than MS (0.65 and 0.54 g/cm 3 respectively) ( Table 3). While both FW and MS contained seashells, which are dense (1.7 g/cm 3 ), MS contained more (15.5 vs. 47.4% of total C from shells) (Manohara et al., 2014). Because the C from shells is less available to soil microorganisms, and MS was already composted, it may have provided less of the products involved in aggregation (C for energy and polymers from decomposition).
With the exception of MS, results indicate that the waste amendments tested have the potential to lower bulk density, especially FW. Low bulk density is desirable because it allows plant roots to more easily penetrate the soil and increases pore space which allow movement of gases and water (Brady and Weil 2008).

Organic Matter
Despite large additions of organic matter to plots amended with waste materials, and no addition of OM to control plots, there was no significant variation in soil OM between treatments for any of the crops or months tested for both 2013 and 2014 (Data not shown). This could be due, in part, to a systematic variation in OM in the field where the experiment was located. The pattern of variation became evident when values of OM from the May 2013 soil samples (post-amendment) were plotted against their location in the field, measured as a distance from the west end of the field ( Figure 9). There was a strong positive correlation between OM content (%) and field position: as distance from the west edge of the field increased, the OM content of the soil increased by almost two percentage points over 60 m. This variation was large enough to obscure the increase in OM of <1 percentage point that could be expected from even the highest amendment rates in this study (22,000 kg/ha OM addition in PF plots over 2 years).
To compensate for the preexisting gradient of OM in the experimental plots, I used four data points from plots that had not received any OM additions (two outside plots and the two control plots) to estimate the slope of the existing OM gradient. This value was used to calculate the background level of OM for each plot, based on distance from the west edge of the field, which was subtracted from all my results to eliminate the pre-existing variation. This left a value which represented the change in soil OM during the study, due to the application of treatments ( Figure 10).
There were no significant differences in the change in OM between treatments in 2013. Some of these values were negative, likely because the slope estimate was    receiving no addition of OM, could be explained by higher biomass production in these plots. Lower OM levels in waste amended plots could be the result of increased mineralization of existing soil OM due to increases in microbial biomass from the addition of large amounts of organic matter. While this phenomenon, known as the priming effect, has been reported following the addition of fresh organic matter to soil, its mechanisms are poorly understood (Fontaine et al., 2003). This could explain the low OM levels at the end of the study in some GW and FW plots.
The statistically significant effect of BS and YW on soil OM may be due to the type of organic compounds they contained. Both BS and the YW were composted, a process which leaves behind the organic compounds most resistant to breakdown (Bernal et al., 1998b;De Neve et al., 2003). Higher concentrations of resistant organic compounds could explain why BS and YW had a significant effect on OM levels while other non-composted wastes (PF, GW, and FW) did not. Although MS was also composted, almost 50% of its C was from an inorganic source, and therefore less likely to contribute to soil OM, as discussed previously.
Despite the short duration of this study, it appears that the addition of some of these amendments may have been enough to offset losses of OM due to cultivation (Lal, 2004). Furthermore, use of composted amendments, such as YW, may increase soil OM levels in comparison to a mineral fertilizer, which could increase carbon sequestration and benefits to soil quality associated with organic matter, such as increased nutrient and moisture retention, and lower bulk density.

Moisture
Soil gravimetric water content did not vary significantly by treatment for any months or crops sampled in either 2013 or 2014 ( Figure 11). Based on the soil type (silt loam) and an average OM content of 6%, the wilting point for soil at the experiment site is approximately 14.3% and field capacity is 33.0% (gravimetric water content) (Saxton and Rawls, 2006). The only soil samples with moisture content below 14.3% were taken on 8/29/14, after most crop growth had ceased. No samples were at field capacity (33.0%), the point at which water has ceased draining from macro pores, usually 1-3 days after irrigation or rain, likely because samples were not taken soon after any rain or irrigation events.
These results do not support my hypothesis that the addition of waste amendments would increase soil moisture retention due to increased organic matter.
However, because OM is the driving force behind moisture retention, and there was no significant variation in OM, one would not expect a variation in moisture either. The lack of significant variation between treatments which received waste amendments and the control is possibly due to the underlying gradient in soil OM (Figure 9), which resulted in a large variation between replicates and obscured treatment effects.
Although there was no evidence of a benefit in terms of moisture retention from applying waste amendments, there was also no negative effect.

Heavy Metals
Soil samples from corn plots taken on 5/18/13 and 6/2/14 were tested for Mo, Pb, Se, As, Hg, Zn, Cu, Ni, Cr and Cd. Levels of Cd, Ni, and Mo were below detection limit for both years. There no were statistical differences between treatments for any of the metals in either year ( Figure 12).
I expected that amendments high in heavy metals would raise soil levels, although the increase might be below the level of detection. None of the amendments exceeded the ceiling concentrations for heavy metals established by the U.S. EPA (1994) for land application of biosolids, although 2014 YW exceeded the more restrictive guidelines for As (Appendix 1). The lack of a statistical difference in soil heavy metal levels indicates that short-term application of these wastes will not significantly raise levels in comparison to a mineral fertilizer. Studies of short-term application of composted sewage sludge and paper-mill sludge did not find any significant increase in soil heavy metals (Casado-Vela et al., 2007;Douglas et al., 2003) Because heavy metals are retained in the soil by binding to OM or by reacting with carbonates, oxides of iron and manganese or sulfides, long term-application of wastes could still lead to accumulation in the soil. Mantovi et al. (2005) found that 12 years of biosolids application significantly increased Zn and Cu in the soil while Schroder et al. (2008) reported significant increases in Cd, Cu, Pb, Mo and Zn after 13 years of application of biosolids. Although long-term application may increase soil heavy metal levels, they may not reach a problematic level. A model of application of the wastes used in this study found that it would take more than 24 years of yearly application for soil heavy metal levels to exceed federal limits (Bercaw et al., 2014). . Levels of Cd, Ni and Mo were below detection limit. There were no significant differences between any treatments. BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table  11 for Fisher's LSD results.

Inorganic Nitrogen
The application of amendments with a C:N ratio > 25:1 was expected to cause early season immobilization of N as soil microbes decomposed the excess C. The PF amendment was the only treatment with a C:N ratio above this threshold, even after blending with chicken manure. Despite receiving less total N than all other treatments (except the control) in 2013, and having the highest C:N ratio (66:1), the PF plots did not have the lowest inorganic N (NO3 and NH4) levels for any months or crops in 2013 ( Figure 13). YW plots often had lower inorganic N levels, despite receiving more total N in the form of a waste with a lower C:N ratio, although differences were not significant.
In 2014 PF was, once again, the only amendment with a C:N ratio above the threshold likely to cause N immobilization (51:1), and PF plots received the lowest amount of total N (with the exception of the control). Although PF plots had the lowest soil inorganic N levels for all crops at the June and July sampling dates, for August, September and October sampling dates YW plots were generally the lowest.
These results suggest that C:N ratio alone is not a reliable indicator of N availability from waste amendments.
I expected that soil inorganic N levels, later in the season (after July 1st) would be higher in waste amended plots than control plots. Inorganic N from mineral fertilizers is subject to plant uptake or loss by leaching or volatilization soon after application, therefore side-dressing with additional N later in the season in recommended (Hazard and Howell, 2007). Because the organic N in wastes is expected to mineralize slowly throughout the season as organic matter decompose, side-dressing later in the season may be unnecessary. However, results did not show that all waste amendments were better sources of late season inorganic N than the control. In 2013, only plots amended with GW consistently had inorganic N levels that were significantly higher than control plots. However, plots amended with GW received a much higher rate of total N (1,140 kg N/ha) compared to control plots which received mineral fertilizer (112 kg N/ha). Although plots amended with MS and FW also received large applications of total N (763 and 428 kg N/ha respectively), they did not consistently have late season inorganic N levels significantly higher than the control. In 2014, only plots amended with FW consistently had late season inorganic N significantly higher than the control. In both 2013 and 2014, plots amended with PF, YW and BS never had significantly higher inorganic N than the control plots, despite receiving more total N ( Figure 5).
Although most waste amended plots did not have significantly higher lateseason inorganic N levels compared to the control, side-dressing would have been unlikely to improve yields for most treatments. In New England, yield responses are unlikely above a threshold of 20-25 µg NO3/g soil for corn and 25-30 µg NO3/g soil for butternut squash and other long season vegetables (Hazard and Howell, 2007). In 2013 total soil inorganic N levels (NH4 and NO3) for all plots were below this level on June 24th, however, by August 14th they were all above 25 µg inorganic N/g soil. In 2014 samples taken on June 30th were consistently above this level for all crops except plots amended with PF and YW.
Despite receiving more total N, YW was a poorer source of inorganic N than the control. Additionally, plots amended with YW had the lowest inorganic N levels more often than PF did, despite having a much lower C:N ratio (13:1 for YW vs. 51 to 66:1 for PF). While C:N ratio has often been relied on as an indicator of potential N availability, studies have found that N mineralization is also related to factors not represented by this ratio such as the type of carbon containing compounds, alkyl-C content, water-soluble fraction, and uric acid content of a material (Cabrera et al., 2005). Although pH and salinity can effect N mineralization, YW did not have an exceptionally high or low pH (6.5-6.7), or high salinity (1.8-4.0 mS/cm). While, YW had slightly higher heavy metal levels, particularly Pb and As, compared to the other wastes in this study, heavy metals have been shown to both increase and decrease N mineralization (Cabrera et al., 2005) (Appendix 1).

Potentially Mineralizable Nitrogen
Potentially mineralizable nitrogen (PMN) is a measure of the organic N that is mineralized to inorganic forms during a 7-day incubation and takes into account immobilization caused by excess C. Although PMN and inorganic N levels are based on soil samples taken on the same date, PMN values represent the inorganic N that could become available in the seven days following sampling (under ideal conditions), and do not include the inorganic N present at the time of sampling.
I predicted that PMN would be higher in waste amended plots, which received organic N, than control plots, which did not. In 2013, control plots did not have the lowest PMN for any months or crops sampled, and only plots amended with GW had significantly higher PMN than control plots. In 2014, there was often no significant variation in PMN between any treatments. However, when there were significant variations, some or all of the waste amendments had significantly higher PMN than the control plots. These results indicate that waste amendments can increase PMN in comparison to a mineral fertilizer control, although not reliably.
Because PMN is calculated by subtracting the NH4 present at the beginning of incubation from the amount present at the end, PMN values can be negative if more inorganic N was immobilized by soil microbes than was mineralized. The largest negative values were seen in June 2014 samples taken after amendment application in plots amended with BS and the control fertilizer ( Figure 14).This would be expected for control plots, because no organic N was added and recent tillage likely accelerated decomposition by breaking down plant residue in the soil and increasing microbial access to oxygen, causing soil microbes to immobilize some of the inorganic N present. Negative PMN values in plots amended with BS could be due to the maturity of the compost. Bernal et al. (1998a) found that a mixture of raw sewage sludge and cotton waste caused the most immobilization when added to soil, once the materials had reached the end of the active phase of composting they caused less immobilization (2 days), and mature compost did not cause any immobilization. However, this does not explain why plots amended with FW, which is not fully composted, had the highest PMN in corn and potato plots from the same month.  Table 13 for Fisher's LSD results.

Emergence and Early Growth
I hypothesized that emergence and early growth could be enhanced or inhibited by amendment effects on soil moisture, OM, bulk density and N availability. Plots amended with PF had significantly lower emergence of potatoes than the control in 2014, as well as significantly shorter plants in both 2013 and 2014 (Figures 16, 17 and   18). The negative influence of PF on emergence and early growth of potatoes may be associated with its high C:N ratio (51:1). However, this effect was not seen in corn and squash which were planted later. Plots amended with YW and PF had significantly shorter potato plants than the control in both 2013 and 2014, and plots amended with FW and GW also had significantly shorter potato plants in 2014.
No waste amendments had significantly higher emergence than the control, and only GW corn plots had significantly taller plants than the control (2013) ( Figures   15, 16, 17 and 18). The significantly taller corn plants in plots amended with GW could be due to the large addition (1,140 kg/ha) of N in those plots. The lack of significant improvement in emergence or early growth in waste-amended plots, in combination with a lack of statistical difference in soil OM or moisture, does not support the hypothesis that improved soil conditions from waste amendments would improve germination and early growth. Furthermore, lower emergence in PF potato plots indicates that PF may have an inhibitory effect on early growth of potatoes.
While Levy and Taylor (2003) reported inhibition of seedlings grown in municipal solid waste compost, but not paper pulp mill solids, Roe et al. (1997) found that seedling emergence was delayed when grown in composts made from biosolids and yard trimmings compared to a sandy soil. Emergence was also delayed and early seedling growth was inhibited when grown in the same compost with the addition of mixed waste paper.

Tissue Nutrients
Nitrogen. Tissue N levels did not, as hypothesized, reflect N application rates.
Despite the largest N application in 2013 (1,140 kg N/ha), corn tissue from plots amended with GW had the lowest N levels, although not significantly lower than the control ( Figure 19). Although squash tissue (2013) from plots amended with GW had the highest N concentrations, they were not significantly different than the control.
While N application rates also varied in 2014, levels of N in corn tissue did not. Potato tissue samples from control plots had significantly higher N than tissue from plots amended with GW, BS, PF and YW. The same was true for squash tissue samples from plots amended with YW and PF, despite higher total N application rates than the control for all waste amended plots except GW, which was not amended in 2014. No amendment yielded tissue samples that were consistently higher in N than the control across all crops and years sampled, despite higher N application rates. All tissue N levels were considered adequate, which indicates all amendments provided sufficient N (Maynard and Hochmuth, 2007).  (14) Potato (14) Squash (14) Tissue  Table 14 for Fisher's LSD results.

Phosphorus.
As was the case with N, tissue P did not reflect P application rates. Despite cumulative P application rates that varied from 59 to 904 kg/ha, tissue P levels only varied significantly in 2014 for potatoes ( Figure 20). Potato tissue samples from plots amended with PF had the highest P, despite receiving the lowest total application of P over the two years of the study. In addition to the lack of significant variation, all tissue P levels were considered adequate for crop growth, which suggests that P applications, in combination with existing soil P levels, were sufficient to meet crop needs (Maynard and Hochmuth, 2007).

Crop (year)
Corn (13) Squash (13) Corn (14) Potato (14) Squash (14) Tissue P (mg/kg)  Table 15 for Fisher's LSD results. Potassium. Like N and P, tissue K concentrations did not reflect application rates. Despite control plots receiving the lowest K application rates (after only GW), no amendments yielded tissue samples with significantly higher K ( Figure 21). Plots amended with GW, which received almost no K (<8 kg/ha cumulative), had significantly lower tissue K than the control for all three crops in 2014. However, there were no significant differences in 2013. Tissue K levels were deficient for corn from GW and control treatments 2013, and all treatments in 2014 (Maynard and Hochmuth, 2007). No squash tissue samples were considered deficient although 2014 potato samples from GW treatments were.
Crop ( (Maynard and Hochmuth, 2007). BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 16 for Fisher's LSD results. but also because it protects cells against toxic elements, and can be lost by leaching, erosion and crop removal, a waste amendment that provided Ca would be beneficial (Brady and Weil, 2008). Although cumulative Ca application rates ranged from 0 to 8,270 kg/ha, tissue Ca concentrations only varied significantly for corn (Table 6 and more Ca than the mineral fertilizer, and tissue samples from waste amended plots generally had higher concentrations, tissue Ca levels did not always reflect the rates at which Ca was applied. Tissue Ca levels were adequate or higher for all treatments (Maynard and Hochmuth, 2007).
While plots amended with MS, PF, BS and YW received Mn, plots amended with FW and GW did not, and control plots received only minimal Mn (<1 kg/ha/yr) ( Table 6).
Tissue Mn rates did not, however, reflect these application rates. Plots amended with MS had lower tissue concentrations of Mn than GW and FW plots for all three crops in 2014, despite receiving more Mn (Figure 23). Plots amended with FW had significantly higher corn and potato tissue Mn than the control in 2014, despite no application of Mn. Tissue samples from all treatments were deficient for Mn for some or all of the crops or years tested (Maynard and Hochmuth, 2007). The availability of Mn in the soil solution can be effected not only by application rates, but also by soil pH, as Mn becomes less available at high pH (Hochmuth et al., 2012). This could explain the low concentrations of Mn from plots amended with MS, despite high application rates, as these plots generally had the highest pH.  (14) Potato (14) Squash (14) Tissue Mn ( (Maynard and Hochmuth, 2007). BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 18 for Fisher's LSD results.

Other Nutrients
Although application rates of Mg and Mo are not known, there was significant variation in tissue levels of both (Figure 24 and 25). However, all tissue concentrations of Mg and Mo were sufficient, therefore application rates, in combination with existing levels, were adequate (Maynard and Hochmuth, 2007). Tissue B concentrations were deficient for corn (2013 and 2014) and potatoes (2014) for all treatments ( Figure 26) (Maynard and Hochmuth, 2007). While corn yields may have been negatively affected by B deficiency, there was no significant variation in corn tissue levels, so all treatments were likely effected similarly. Although there was significant variation in potato tissue B levels, no treatment was significantly different than the control. All squash tissue B levels were adequate.
There was no significant variation in tissue Al, Cu, Fe, Na, Pb, or (Maynard and Hochmuth, 2007). BS = biosolids/yard waste cocompost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 19 for Fisher's LSD results.  (14) Potato (14) Squash (14) Tissue Mo (mg/kg)  (Maynard and Hochmuth, 2007). BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 20 for Fisher's LSD results.  (14) Potato (14) Squash (14) Tissue B (mg/kg)  (Maynard and Hochmuth, 2007). BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 21 for Fisher's LSD results. There were no statistical differences between treatments for any of the metals tested ( Figure 27). I hypothesized that increases in soil heavy metal levels would not be reflected in tissue heavy metal levels because of low metal bioavailability. Although there were no statistical differences in tissue heavy metal levels, there were also no statistical differences in soil levels. These results suggest that short-term use of these waste amendments, at similar rates, will not lead to significantly higher levels of heavy metals in corn ears when compared to mineral fertilizer grown corn. Levels of Cd, Ni, Pb, As, and Ag were below detection. There were no significant differences between treatments for any heavy metal. BS = biosolids/yard waste cocompost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste. See Table 22 for Fisher's LSD results.

Yield
Although I hypothesized that waste amended plots would achieve yields comparable to control plots, some did not. Squash. In 2014 plots amended with YW, PF, and MS yielded significantly less butternut squash (by weight) than the control, and the plots amended with YW and PF had significantly smaller squash than the control in both years (Figure 29 and 30). Compared to the control, plots amended with YW, PF, and MS received equivalent or higher rates of N, P, and K; the exception was PF which received ~30 kg P/ha, which was less than the control (49 kg P/ha) but more than the recommended rate for butternut squash of 20 kg P/ha (Hazzard and Howell, 2014).
While some squash tissue samples were deficient in Mn, this may not explain the significant difference in yield between the control and plots amended with YW, PF, and MS. This is because, in 2014, YW treatments had significantly higher tissue Mn than control plots and although PF and MS had lower levels, they were not significantly different.
Squash were considered unmarketable based on disease, insect, and/or animal damage and the fraction of total harvest culled was calculated ( Figure 31). While there were no statistical differences in the fraction culled by weight in either year, a significantly higher number of squash were culled in 2013 from plots amended with GW compared to all other treatments.

Potato.
No amendment produced significantly lower potato yield than the control in either year ( Figure 32). The quality of potato yield was determined by separating them into three categories: "A" (marketable), "B" (potentially usable for secondary market like processing) and "C" (culls). Potatoes were placed in the "B" or cull category because of mechanical damage, disease or insect damage (including wire worm, the larvae of click beetles, Coleoptera Elateridae). While plots amended with PF produced a lower total weight of potatoes than the control in both years, although not significantly, the potatoes harvested were of significantly better quality than the control in 2014, e.g. a higher proportion of firsts and fewer seconds ( Figure 33). This was in spite of an overall drop in quality in 2014, when all treatments yielded a lower proportion of firsts and high proportion of seconds compared to 2013, due to increased incidence of disease and pests. This indicates that the PF amendment may have contributed to lower disease and/or pest pressure. Suppression of Rhizoctonia solani and snap bean root rot (Pythium spp. and Aphanomyces euteiches) have been reported after amendment with composted and raw paper fiber (Croteau and Zibilske, 1998;Rotenberg et al., 2007). Although amendment with composted paper fiber reduced symptoms of bacterial speck (Pseudomonas syringae pv. tomato) in tomatoes and thale cress (Arabidopsis thaliana), non-composted paper fiber did not (Vallad et al., 2003 (14) Montauk (14) Weight per ear ( Figure 33. Mean potato quality, measured as the percent of total harvest that were firsts, seconds and culls, by weight, for plots in 2013 and 2014 (n=4). Treatments with the same letter were not significantly different. Each year and category was analyzed separately (LSDs for 2013: Firsts = 13.853%, Seconds = 12.86%, Culls = 10.497%, LSDs for 2014: Firsts = 22.25%, Seconds = 18.361%, Culls = 8.2573%). BS = biosolids/yard waste co-compost, CN = mineral fertilizer control, FW = dehydrated food waste, MS = multisource compost, GW = gelatin waste, PF = paper fiber/chicken manure, YW = yard waste.

CONCLUSIONS
Waste amendments may be effective sources of plant nutrients, and their use as fertilizers for vegetable production could provide both a productive means of disposal and a potential source of carbon to build soil organic matter and improve soil quality.

Amendment qualities.
While the amendments used in this study had consistent electrical conductivity from year to year, and were all lower than the control fertilizer, their pH was more variable. Unlike mineral fertilizers, waste amendments contain a large proportion of OM, although this proportion varied from amendment to amendment, as did the fraction of OM that was C. Both FW and MS contained seashells, which affected estimates of the fraction of OM present as C. Furthermore, because the C from seashells would not be as available to soil microorganisms as organic C, affecting C:N ratios, this alters expected N availability.
Waste amendments also varied in texture, density and moisture content, which affect their decomposition in the soil, and can present practical issues, such as transportation problems and the need for specialized spreading equipment. While none of the wastes contained heavy metal concentrations that exceeded the U.S. EPA's (1994) ceiling levels for land application of biosolids, the As content of YW (2014) exceeded more restrictive limits for exceptional quality biosolids.
The nutrient densities of waste amendments also differed. While most contained moderate to low N, GW contained more N than the commercial chicken manure product that was used in this study. All wastes had a C:N ratio below 25:1, the threshold above which N immobilization is likely, except the paper fiber, even after blending with a higher N product (chicken manure). Unlike mineral fertilizers, most N in the waste amendments was organic (>95%). Amendments were not significant sources of P, except GW, which contained almost equal parts N and P. This could lead to the over application of P if GW were applied to meet crop N needs. Finally, wastes contained varying amounts of K but were all low in comparison to the mineral fertilizer used.
Soil quality. The soil EC did not exceed 1 mS/cm, the level that may affect sensitive crops, regardless of treatment. Multisource compost was the only amendment to significantly increase pH compared to the control, likely due to the CaCO3 from seashells. In contrast, at the rates used in this study, BS and YW have the potential to lower pH in comparison to a mineral fertilizer. Multisource compost increased bulk density in comparison to the control, although not significantly, whereas FW significantly decreased bulk density. Yard waste and BS were the only amendments to significantly increase OM compared to the control, although the effect was not consistent across crops. Waste amendments did not affect soil moisture or heavy metal levels.
Soil fertility. Waste amendments were expected to be better sources of late season inorganic N, due the slow mineralization of organic N, but this was not the case for most amendments. Application of waste amendments also did not reliably increase potentially mineralizable N in comparison to the control. Although PF was the only amendment with a C:N ratio above 25:1, the threshold above which N immobilization is likely, inorganic N levels in plots amended with PF were not always significantly lower than the control, or the lowest among waste-amended plots, indicating amendment C:N ratio is not a reliable predictor of N availability. PF potatoes were of significantly better quality than the control, indicating a potential reduction in insect and/or disease damage.
All the waste amendments showed promise as effective replacements for mineral fertilizers for at least one crop. While some treatments resulted in deficient levels of nutrients in tissue samples, there was no clear connection between deficiencies and reduced yields. Application of waste amendments did not have negative effects on soil quality. While most amendments did not appear to increase soil OM or improve quality in the short duration of this study, longer term applications of waste amendments may have more significant effects. Lastly, some waste amendments provided unique benefits such as increasing pH (MS) or improving potato quality (PF).