Composting as a Means of Disposal of Sheep Mortalities

Four studies explored the feasibility of year-round composting of lamb and mature sheep mortalities within the arid climate of the Canadian prairies. In all studies, a ratio of 2:1:1 (manure : mortalities : chopped straw) was maintained, although depth of the mortality layer within the bin, number of layers of mortalities per bin, age of animal (lamb or mature sheep) and time of year (summer or winter) were varied. Composting neonatal lambs in the spring/summer was successful whether a single layer (n=15 lambs, weight 99.7 kg) or two, separated layers of mortalities (n=41 lambs, weight 198 kg) were added to a 2.4 m³ open bin. Residual bone, wool and soft tissues were negligible after the lamb compost had completed one heating cycle. In contrast, composting mature sheep in the fall/winter was more difficult due to: (1) over wet manure (31% dry matter) resulting in continuous anaerobic decomposition of carcasses; (2) fat/grease accumulation when composting a layer of carcasses 71 cm in depth (weight of sheep 1020 kg). For mature sheep mortalities, 2 heating cycles were required to eliminate soft tissues and wool. As compost in all studies heated in excess of 60°C in the primary and/or secondary bin, bacterial isolates taken after the compost completed the secondary heating cycle were all innocuous species. Provided that compost is protected from excessive moisture and compost is aerated by turning into a secondary bin, a 2:1:1 (manure:mortalities:straw) ratio allowed for year-round composting of lamb and mature sheep mortalities.     

Inactivation of Giardia Cysts and Cryptosporidium Oocysts in Beef Feedlot Manure By Thermophilic Windrow Composting

Effects of composting manure on viability of Giardia cysts (GC) and Cryptosporidium cysts (CO) were determined in a two-year study with manure from feedlot cattle bedded on barley straw or woodchips. Each year, manure was deposited in 8 m × 2.5 m × 2 m windrows (one per bedding type) on a sheltered concrete pad. On day 0, porous bags containing 100 g of feces from confirmed Giardia- and Cryptosporidium-positive cattle (9 bags per retrieval day in Year 1; 3 per day in Year 2) were implanted in the windrows. Replicate bags were placed on the concrete pads as uncomposted controls. Windrow temperature and water content were measured and compost was turned mechanically twice each week. Fecal bags were retrieved and subsampled for enumerations of total and viable cysts and cysts after 1, 2, 3, 7, 10, 17, 24 and 31 days in 1998 and after 1, 2, 3, 7, 9, 16, 23, 30, 42, 56, 70 and 98 days in 1999. Windrow temperatures (TEMP) exceeded 55°C during the fourth week of composting, and remained above 50°C for 4 wk thereafter in 1999. Bedding material did not affect overall mean temperature in either year, but TEMP was higher with straw than with woodchip from day 10 to day 17 in 1998 (P < 0.05) and on day 16 and day 42 in 1999 (P < 0.10). In 1998, moisture content decreased from 62.2 to 43.2% during composting of woodchip manure and from 67.3 to 39.3% during composting of straw manure. In 1999, moisture content decreased from 61.0 to 31.8% for woodchip and from 64.5 to 28.6% for straw compost. Percentage of viable CO declined gradually over the 31 days in 1998. The following year revealed a rapid decline in viability of GC and CO once compost temperature exceeded 55°C and viabilities of GC and CO were reduced to zero after 42 days (straw compost) and after 56 days (woodchip compost). Exposure of CO and GC to temperatures > 55°C for a period of 15 days appears to be an effective method of inactivating Giardia cysts and Cryptosporidium cysts in feedlot manure.     

Passively Aerated Composting of Straw-Rich Pig Manure: Effect of Compost Bed Porosity

Straw-rich manure from organic pig farming systems can be composted in passively aerated systems as the high application of straw results in a compost bed with good structure and porosity. The passively aerated composting process was simulated in one-dimensional reactors of 2 m³ for straw-rich manure with compost bed densities of 1100, 700 and 560 kg m^?3. Temperature profiles over the reactor height were monitored online and ammonia emissions were measured periodically. The composition of the compost bed over the reactor height was determined at the end of the composting process. The composting process strongly depends on the density of the compost bed. At a density of 1100 kg.m^?3, the porosity of the bed is too low to initiate natural convection, and aerobic degradation fails and anaerobic conditions may lead to emissions of methane and odorous compounds. At a density of 560 kg.m^?3, the porosity of the bed is high and the high rate of natural convection will keep the temperature low thereby preventing the removal of pathogens and weeds. Best results were observed at a density of 700 kg.m^?3 for which aerobic degradation and drying were adequate and temperatures were high enough to kill pathogens and weeds. On basis of the Ergun equation, which describes the airflow in porous media with internal heat generation, this corresponds to a compost bed permeability of 7×10^?8 m². It was also shown that it is possible to compost animal manures with a low C/N ratio without significant emissions of ammonia. This can be established by trapping the initial ammonia emissions in a straw filter, which is placed on top of the compost bed. Ammonia absorbed in the straw filter and in the compost bed were removed by nitrification and denitrification. The passively aerated composting system results in a compost bed which is highly heterogeneous with respect to temperature, oxygen level and its composition. It is proposed that in this way a highly diverse microbial community in the compost bed is established which can perform various microbial conversions. The extensive composting system is most promising for on-farm production of an organic fertilizer from straw-rich manure, since the costs of the process and the level of ammonia emissions were low.     

Valorization of Mediterranean Livestock Manures: Composting of Rabbit and Goat Manure and Quality Assessment of the Compost Obtained

The purpose of this work was to study the viability of the composting of goat (Capra aegagrus hircus) manure (GM) and rabbit (Oryctolagus cuniculus) manure (RM) and to evaluate the quality of the compost obtained. For this, a mixture of these manures was prepared at a goat/rabbit ratio of 44:56 (fresh-weight basis) and 50:50 (dry-weight basis). The mixture was composted by the Rutgers static pile composting system, with forced aeration and controlled temperature. Throughout the composting process, the temperature was monitored and physicochemical, chemical, and biological parameters were evaluated. The temperature evolution showed the suitable development of the composting process, with thermophilic values (>40 °C) maintained for more than 90 days. The finished compost had stabilized and humified organic matter. However, the pH (9.4) and the salinity (EC of 13.4 dS/m) could limit its potential agricultural use.     

Heat Inactivation of E. coli During Manure Composting

Contamination of food and water by microorganisms from animal manure has become an important issue in public health. Escherichia coli O157:H7 is one of several emerging pathogens of concern. In this research, we studied how the self-heating, thermophilic phase of composting influenced laboratory-grown vs. bovine-derived E. coli O157:H7 mortality, specifically the relationship between temperature, time at temperature, and pathogen survival. Composting experiments were conducted in laboratory-scale bioreactors operated in three temperature ranges: 40°C to 50°C, 50°C to 60°C, and greater than 60°C. We measured the effects of temperature and composting time on E. coli O157:H7 mortality. Laboratory-grown E. coli O157:H7, inoculated into the initial compost material, were not detected after approximately 300 degree days of heating. In several experiments where compost temperatures did not rise above 50°C, an initial decline of E. coli O157:H7 with subsequent regrowth was observed. E. coli O157:H7 in compost materials from infected cattle were not detected after approximately 180 degree days of heating. Numbers of total coliform bacteria declined with temperature similarly to those of E. coli O157: H7. The results of this research provide information for reducing or eliminating E. coli O157:H7 in animal wastes.     

Application rate and composting method affect the immediate and residual manure fertilizer value in a maize–rice–rice–maize cropping sequence on a degraded soil in northern Vietnam

A field experiment was carried out in northern Vietnam to investigate the effects of adding different additives [rice (Oriza sativa L.) straw only, or rice straw with added lime, superphosphate (SSP), urea or a mixture of selected microorganism species] on nitrogen (N) losses and nutrient concentrations in manure composts. The composts and fresh manure were applied to a three-crop per year sequence (maize–rice–rice) on a degraded soil (Plinthic Acrisol/Plinthaquult) to investigate the effects of manure type on crop yield, N uptake and fertilizer value. Total N losses during composting with SSP were 20% of initial total N, while with other additives they were 30–35%. With SSP as a compost additive, 65–85% of the initial ammonium-N (NH₄-N) in the manure remained in the compost compared with 25% for microorganisms and 30% for lime. Nitrogen uptake efficiency (NUE) of fresh manure was lower than that of composted manure when applied to maize (Zea mays L.), but higher when applied to rice (Oriza sativa L.). The NUE of compost with SSP was generally higher than that of compost with straw only and lime. The mineral fertilizer equivalent (MFE) of manure types for maize decreased in the order: manure composted with SSP?>?manure composted with straw only and fresh manure?>?manure composted with lime. For rice, the corresponding order was: fresh manure?>?manure composted with SSP/microorganisms/urea?>?manure composted with lime/with straw alone. The MFE was higher when 5 tons manure ha^?1 were applied than when 10 tons manure ha^?1 were applied throughout the crop sequence. The residual effect of composted manures (determined in a fourth crop, with no manure applied) was generally 50% higher than that of fresh manure after one year of manure and compost application. Thus, addition of SSP during composting improved the field fertilizer value of composted pig manure the most.     

MSW Compost Reduces Nitrogen Volatilization During Dairy Manure Composting

Manures lose N through volatilization almost immediately after deposit. Attempts to control losses include the addition of a C source to stimulate nitrogen immobilization. Composting is a treatment process that recommends the addition of carbonaceous materials to achieve a C:N ratio of 30:1 to stimulate degradation and immobilize nitrogen. Dairies near cities may be able to reduce N loss from manures by composting with urban carbonaceous residues such as municipal solid waste (MSW) or MSW compost that, by themselves, have little agronomic value. Studies were conducted using a self-heating laboratory composter where dairy solids were mixed with MSW compost to determine the reduction of N loss during composting. One-to-one mixtures (v/v) of dairy manure solids and MSW compost were composted and NH₃ volatilization, CO₂ evolution and temperatures were compared to composting of manure alone. Addition of MSW compost resulted in increased CO₂ evolution and reduced N loss. Nitrogen loss from composting dairy manure alone was four to ten times greater than that from composting dairy manure mixed with MSW compost. Adjustment of the C:N ratio to 25 by adding MSW compost to manure appeared to be the major factor in reducing N losses.     

有机辅料对猪粪堆肥中氨气挥发的抑制效应及其影响因素分析

选取稻草、油菜秸秆和食用菌渣作为猪粪堆肥的有机辅料,研究三种堆肥体系中氨气挥发释放规律及其影响因素。结果表明,经过65 d的堆腐,稻草－猪粪、油菜秸秆－猪粪和菌渣－猪粪堆肥氨气挥发量分别为5.084、6.483和3.013 g/kg,是对照（纯猪粪）处理（7.836g/kg）的64.88%、82.74%和38.45%。从氨气的释放量和释放速率看,菌渣是一种较好的有机辅料。从氨气释放的时间变化特征看,稻草对猪粪堆肥氨气排放高峰期影响最为明显,主要表现为氨气前期猛烈释放且持续时间短,是猪粪快速腐熟技术优选的高效有机辅料。堆腐完成后,三种有机辅料均能减少水溶性NH4+-N的累积,增加水溶性NO3--N的含量,引起pH和EC值下降,提高堆肥全氮含量,促进堆肥有机物和粗纤维的降解,且以稻草和菌渣处理效果最为显著。     

Fate of Fusarium graminearum and Other Fusarium Species During Composting Of Beef Cattle Feedlot Manure

Fusarium head blight, caused by Fusarium graminearum, could potentially become a major concern for the cereal industry in Alberta, Canada. Infested feed grain in feedlot manure may act as a means of spreading the disease when manure is land applied. The ability of manure composting to eradicate the pathogen on infested grain (wheat, barley, corn) was evaluated. F. graminearum and other Fusarium spp. were rapidly eradicated from infested grains buried in compost windrows with no recovery after 2 d where windrow temperature attained 51°C. Under cooler windrow conditions (11.9 to 17.5°C), recovery of F. graminearum reached zero on Day 9 for corn (Zea mays L.), Day 14 for wheat (Triticum aestivum L.) and Day 22 for barley (Hordeum vulgare L.), showing that factors in addition to compost temperature may play a role in pathogen elimination. Composting represents an effective strategy in mitigating the dissemination of F. graminearum via manure should land application occur on fields that are subsequently used for grain production.     

The Effects of Goat Manure,Sewage Sludge And Effective Microorganisms on the Composting of Pine Bark

This study investigated the cocomposting of pine bark with goat manure or sewage sludge, with or without inoculated effective microorganisms (EM). Composting was done for 90 days and parameters monitored over this period included temperature, pH, electrical conductivity (EC), C/N ratio, inorganic N, as well as tannin content. Changes in temperature, pH and EC during composting were consistent with those generally observed with other composting systems. The parameters were influenced by the feedstock materials used but were not affected by inoculation with effective microorganisms. The highest temperature measured from pine bark-goat manure composts was 60°C but much lower maximum temperatures of 40°C and 30°C were observed for pine bark sewage sludge and pine bark alone composts, respectively. The C/N ratios of the composts decreased with composting time. Ammonium levels decreased while nitrate levels increased with composting time. Tannin levels generally decreased with composting time but the extent of decrease depended on the contents of the composting mixtures. The trends observed showed that temperature, pH, EC, C/N ratio, tannin levels, and inorganic NH₄-N and NO₃-N were reliable parameters for monitoring the co-composting of pine bark with goat manure or sewage sludge. The pine bark-goat manure compost had more desirable nutritional properties than the pine bark and pine bark-sewage sludge composts. It had high CEC, near neutral pH, low C/N ratio, and high amounts of inorganic N and bases (K, Ca, and Mg) while pine bark compost had the least amounts of nutrients, was acidic, and had high C/N ratio and low CEC. The final tannin content of the pine bark-goat manure compost was below the 20 g/kg upper threshold level for horticultural potting media, implying that its use as a growing medium would not cause toxicity to plants.     

蜉金龟堆肥和自然堆肥类胡敏酸的表征及特性研究

分别用焦磷酸钠和氢氧化钠浸提新鲜牛粪、蜉金龟堆肥(APCM)和自然堆肥(腐熟牛粪)产物中的类胡敏酸,采用元素组成、红外光谱及差热分析研究了其结构特征。元素分析结果表明,蜉金龟堆肥焦磷酸钠浸提物——类胡敏酸(NaHLA)的芳香性低于新鲜牛粪和自然堆肥,而碳水化合物及氮元素含量增加。蜉金龟堆肥氢氧化钠浸提物——类胡敏酸(PAHLA)的碳水化合物和氮元素含量也高于新鲜牛粪和自然堆肥,而自然堆肥PAHLA的芳香性略低于新鲜牛粪和蜉金龟堆肥。红外光谱分析结果表明,与自然堆肥NaHLA相比,蜉金龟堆肥NaHLA中羧酸脂类化合物、酮类化合物、脂肪族化合物及碳水化合物有所增加。与新鲜牛粪PAHLA相比,蜉金龟堆肥和自然堆肥PAHLA的碳水化合物、脂肪族化合物、酚类化合物及纤维素酯类减少,同时蜉金龟堆肥PAHLA的酰胺化合物在蜉金龟消化过程中被其吸收。差热分析结果表明,自然堆肥NaHLA的热稳定性高于新鲜牛粪和蜉金龟堆肥,而蜉金龟堆肥NaHLA的脂族化合物、外围官能团和分子内部芳香结构含量较高,分子结构较复杂。蜉金龟堆肥PAHLA存在两个放热峰,而新鲜牛粪和自然堆肥的中温放热峰消失。综上,蜉金龟堆肥和自然堆肥采用两种提取液浸提出类胡敏酸的结构特征存在差异性。     

Residual Effects of Novel versus Traditional Organic Amendments for Rain-fed No-till Barley: Yield,Nutrient Uptake,and N2O Emissions

Organic amendments recycle nutrients, but N₂O emissions are both environmental and agronomic concerns. We conducted a 4-year field experiment to determine no-till barley (Hordeum vulgare L.) yield and nutrient uptake and soil N₂O emissions following a single application of six amendment treatments: (1) no amendment (Check); (2) synthetic N fertilizer (Fert); (3) fresh beef cattle feedlot manure (ManureF); (4) beef cattle feedlot manure compost (CompostR); (5) beef cattle feedlot manure composted with cattle mortalities (CompostM); and (6) separated solids from anaerobically digested cattle feedlot manure (ADM). Barley grown in Year 1 (2006), Year 2 (2007), and Year 4 (2009) (with Year 3 (2008) under fallow) had higher grain yields from ManureF (4.73 Mg ha^?1) in Year 2 and ADM (6.30 Mg ha^?1) in Year 4 (p < 0.05) than other treatments. The grain N and P contents were not affected (p > 0.05), but N uptake over 3 years (112.8 kg N ha^?1 yr^?1), and P uptake in Year 1 (19.1 kg ha^?1 yr^?1) and Year 2 (14.3 kg ha^?1 yr^?1) from ManureF, were higher (p < 0.05×) than other treatments. The cumulative N₂O emissions from ManureF in Year 1 (1.488 kg N ha^?1) and from ADM in Year 2 (1.072 kg N ha^?1) were higher (p < 0.05) than other treatments while the fraction of applied N emitted as N₂O was small (0.00 to 0.79%) and not affected by treatment. However, the percentages of applied N emitted as N₂O from compost and ADM were similar to synthetic fertilizer and livestock manure.     

Mass and Nutrient Losses During the Composting Of Dairy Manure Amended with Sawdust or Straw

Composting has become an increasingly popular manure management method for dairy farmers. However, the design of composting systems for farmers has been hindered by the limited amount of information on the quantities and volumes of compost produced relative to farm size and manure generated, and the impact of amendments on water, dry matter, volume and nitrogen losses during the composting process. Amendment type can affect the free air space, decomposition rate, temperature, C:N ratio and oxygen levels during composting. Amendments also initially increase the amount of material that must be handled. A better understanding of amendment effects should help farmers optimize, and potentially reduce costs associated with composting. In this study, freestall dairy manure (83% moisture) was amended with either hardwood sawdust or straw and composted for 110-155 days in turned windrows in four replicated trials that began on different dates. Initial C:N ratios of the windrows ranged from 25:1 to 50:1 due to variations in the source and N-content of the manure. Results showed that starting windrow volume for straw amended composts was 2.1 to 2.6 times greater than for sawdust amendment. Straw amended composts had low initial bulk densities with high free air space values of 75-93%. This led to lower temperatures and near ambient interstitial oxygen concentrations during composting. While all sawdust-amended composts self-heated to temperatures >55°C within 10 days, maintained these levels for more than 60 days and met EPA and USDA pathogen reduction guidelines, only two of the four straw amended windrows reached 55°C and none met the guidelines. In addition, sawdust amendment resulted in much lower windrow oxygen concentrations (< 5%) during the first 60 days. Both types of compost were stable after 100 days as indicated by CO₂ evolution rates <0.5 mg CO₂-C/g VS/d. Both types of amendments also led to extensive manure volume and weight reductions even after the weight of the added amendments were considered. However, moisture management proved critical in attaining reductions in manure weight during composting. Straw amendment resulted in greater volume decreases than sawdust amendment due to greater changes in bulk density and free air space. Through composting, farmers can reduce the volume and weights of material to be hauled by 50 to 80% based on equivalent nitrogen values of the stabilized compost as compared to unamended, uncomposted dairy manure. The initial total manure nitrogen lost during composting ranged from 7% to 38%. P and K losses were from 14 to 39% and from 1 to 38%, respectively. There was a significant negative correlation between C:N ratio and nitrogen loss (R₂=0.78) and carbon loss (R₂=0.86) during composting. An initial C:N ratio of greater than 40 is recommended to minimize nitrogen loss during dairy manure composting with sawdust or straw amendments.     

Winter Wheat Yield,Quality, and Nitrogen Removal Following Compost- or Manure-Fertilized Sugarbeet

To efficiently use nitrogen (N) while protecting water quality, one must know how a second-year crop, without further N fertilization, responds in years following a manure application. In an Idaho field study of winter wheat (Triticum aestivum L.) following organically fertilized sugarbeet (Beta vulgaris L.), we determined the residual (second-year) effects of fall-applied solid dairy manure, either stockpiled or composted, on wheat yield, biomass N, protein, and grain N removal. Along with a no-N control and urea (202 kg N ha^?1), first-year treatments included compost (218 and 435 kg estimated available N ha^?1) and manure (140 and 280 kg available N ha^?1). All materials were incorporated into a Greenleaf silt loam (Xeric Calciargid) at Parma in fall 2002 and 2003 prior to planting first-year sugarbeet. Second-year wheat grain yield was similar among urea and organic N sources that applied optimal amounts of plant-available N to the preceding year’s sugarbeet, thus revealing no measurable second-year advantage for organic over conventional N sources. Both organic amendments applied at high rates to the preceding year’s sugarbeet produced greater wheat yields (compost in 2004 and manure in 2005) than urea applied at optimal N rates. On average, second-year wheat biomass took up 49% of the inorganic N remaining in organically fertilized soil after sugarbeet harvest. Applying compost or manure at greater than optimum rates for sugarbeet may increase second-year wheat yield but increase N losses as well.

Abbreviations CNS, carbon–nitrogen–sulfur     

Liming effects of beef cattle feedlot manure or compost

Abstract

Soil pH can be increased by manure or compost application because feed rations usually contain calcium carbonate. This study was conducted from 1992 to 1996 to evaluate effects of phosphorus (P) and nitrogen (N)‐based manure and compost application management strategies on soil pH level. Composted and uncomposted beef cattle (Bos taunts) feedlot manure was applied to supply N or P needs of corn (Zea mays L.) for either a one‐ or two‐year period. Phosphorus‐based manure or compost treatments also received additional fertilizer N (ammonium nitrate) to provide for a total of 151‐kg available N ha^‐1 yr^‐1. Fertilized and unfertilized checks also were included. Manure and composted manure contained about 9 g CaCO₃kg^‐1 resulting in application rates of up to 1730 kg CaCO₃ ha^‐1 in 4 years. The surface soil (0–150 mm) pH was significantly decreased with ammonium nitrate application compared to soil in the unfertilized check or to soil receiving manure or compost. Soil pH was significantly increased with the N‐based management strategy compared with the soil original level. In contrast, 4 yr of P‐based manure and compost application strategy maintained soil pH at the original level. Nitrogen‐based applications resulted in higher soil pH than P‐based. Beef cattle feedlot manure and compost can be good sources of CaCO₃ for soils requiring lime addition.     

Effective cation exchange capacity of manure compost of varying maturity stages determined by the saturation‐displacement method

Abstract

The effective cation exchange capacity (ECEC) of manure composts, at the start and during the composting process, were determined. During this study we developed a new saturation‐displacement principle based method for compost samples. It was clearly demonstrated that ECEC of manure compost, as analyzed from three successive composting series, profoundly increased as compost matured. In addition, the ECEC values were highly repeatable, due to the proper mixing of the matrix with the saturation, washing, and displacement solutions, as well as to the preventing of any matrix losses with the separation of the matrix from those solutions with careful centrifugation‐filtration procedure.     

Composting of Tropical Toxic Weed Lantana camera L. Biomass and Its Suitability for Agronomic Applications

ABSTRACT

Lantana camara is an evergreen, which is the most notorious toxic weed of the terrestrial ecosystem. It is native to subtropical and tropical America, but a few taxa are indigenous to tropical Asia and Africa. An enormous quantity of green foliage is produced by this weed, which cannot be used as livestock feed due to its toxic properties. Management through utilization seems the only sustainable option for this problem. In this study, the composting of Lantana biomass was done and changes in chemical characteristics of waste biomass were measured. The composting caused decreases in pH, organic carbon, C:N ratio _totK and _totC by 2.0-, 1.25-, 1.66-, and 19-fold, respectively, but increases in electrical conductivity (EC), ash content, _totN, _totP, _totZn, and _totMg of 2.0-, 1.11-, 3.36-, 1.76-, 1.28-, and 1.70-fold, respectively. The C/N ratio (20.1) and soil respiration rate (47.12–66.20 mg CO₂-C/100 g) suggested the compost maturity at 52 days. The high bacterial (38.67 CFU × 10^?7 g^?1), fungal (30.0 CFU × 10^?3 g^?1), and actinomycetes (32.0 CFU × 10^?5 g^?1) population in composted material suggested the suitability of compost for agronomic purposes. Phytotoxity measured through compost:water extract and compost pot trial suggested the germination index (GI) in the ranges of 52.3%–122.3% and 74.5%–166.9%, respectively. The high ranges of chlorophyll, protein, and carotenoids in seedling than control suggested the non-toxicity of ready materials. Results suggested that composting can be a potential technology to manage Lantana biomass for sustainable land fertility management programs.     

Assessment of Microbial Communities In Decomposition of Specified Risk Material Using a Passively Aerated Laboratory-Scale Composter

The occurrence of bovine spongiform encephalopathy (BSE) in Canada has resulted in the implementation of regulations to remove specified risk material (SRM) from the food chain. SRM includes the distal ileum of all cattle, and the skull, brain, trigeminal ganglia, eyes, palatine tonsils, and spinal cord and dorsal root ganglia of cattle ≥30 months of age. Composting may be a viable alternative to rendering for SRM disposal. In our study, two bulking agents, barley straw and wood shavings, were composted with beef manure along with SRM in passively aerated, laboratory-scale composters. Both composts heated rapidly, exceeding 55°C after 3 days with oxygen declining in the early composting stage with wood-shaving compost, but returning to near-original levels after 5 days. During composting the two matrices differed (P <0.05) only in water content, TC and bulk density. In the final compost, water content, TC and C/N ratio were higher (P < 0.05), while EC was lower (P < 0.05) in the wood shavings as compared to the straw compost. Approximately 50% of SRM was decomposed after 15 days of composting, with 30% of SRM being decomposed within the first 5 days. Phospholipid fatty acid (PLFA) profiles were used to characterize the microbial communities and showed that Gram positive bacteria were predominant in compost at day 5, a point that coincided with a rapid increase in temperature. Gram negative bacteria and anaerobes declined at day 5 but populations recovered by day 15. Fungi appeared to be suppressed as temperatures exceeded 55°C and did not appear to recover over the remainder of the composting period, with the exception of the straw compost at day 15. On day 5, Actinomycetes increased in the straw compost, but declined in the wood shavings compost, with this group increasing in both types of compost at day 15. Although temporal changes were evident, compost matrices or depth within the composter did not obviously influence microbial communities. Decomposition of SRM also did not differ between compost matrices or with depth in the composters. These results suggest that SRM decompose rapidly during composting and that both mesophilic and thermophilic microbial communities play a role in its decomposition.     

Nitrogen mineralization from an organically managed soil and nitrogen accumulation in lettuce

The potential of an organically managed Cambic Arenosol to supply nitrogen (N) from either an applied commercial organic fertilizer (granulated hen manure), a compost produced on‐farm, or four different mixtures of both fertilizers was studied in a laboratory incubation and a pot experiment with lettuce. In the incubation experiment, a significant higher apparent N mineralization occurred after hen‐manure application (53.4% of the organic N applied) compared to compost (4.5%) or mixed‐fertilizer application (8.7% to 16.7%). The apparent N mineralization in a mixed treatment consisting of compost and half rate of hen manure (15.4% of the organic N applied) was significantly higher than that estimated based on the N mineralization for compost and hen‐manure treatments (7.6%), proving that a combined application of both fertilizers enhanced organic‐N mineralization when compared to separate fertilizer supply. In the pot experiment, a higher lettuce fresh‐matter yield was obtained with hen manure (1.9 kg m^–2) than with compost (1.7 kg m^–2) or unfertilized control treatment (1.3 kg m^–2). Combined application of compost with only a half rate of hen manure led to yields (2.0 kg m^–2) equal to those obtained with only hen manure. A good correlation was observed between the N‐mineralization incubation data and the N accumulated by lettuce plants in the pot experiment (r = 0.983). Hence, in the organic production of baby‐leaf lettuce, a mixture of compost and hen manure appears to be a good fertilization alternative, since it allows a reduction by half of the typical amount of commercial fertilizer usually applied (granulated hen manure), cutting fertilization costs, and providing an amount of available N that allows maintaining lettuce yields.