Volume 5 Special Issue 2 2011
Compost III

ISBN 978-4-903313-84-9

How to reference: Avilés M, Borrero C, Trillas MI (2011) Review on compost as an inducer of disease suppression in plants grown in soilless culture. In: Ferrer AS (Ed) Compost III. Dynamic Soil, Dynamic Plant 5 (Special Issue 2), 1-11

Guest Editor

Antoni Sánchez Ferrer
Departament d'Enginyeria Química, Escola Tècnica Superior d'Enginyeria, Universitat Autònoma de Barcelona, Barcelona, Spain

www.uab.cat/departament/enginyeria-quimica/

Issue infomation

CONTENTS AND ABSTRACTS

Manuel Avilés, Celia Borrero, Mª Isabel Trillas (Spain) Review on Compost as an Inducer of Disease Suppression in Plants Grown in Soilless Culture (pp 1-11)

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Invited Review: The soil/substrate that supports plant roots and provides water and nutrients to plants is often considered a hostile environment that harbours plant pathogens. Moreover, the most common strategy used to control risk of disease from the soil is the eradication or minimization of soil pathogens regardless of the presence of other organisms. Consequently, the extensive use of physical/chemical biocides generates a soil/substrate microbiological vacuum which makes it more susceptible to reinfestation by pathogens, increases disease incidence and in some cases enhances fungal resistance. In Europe, legislation on plant protection products has been re-evaluated since 1991 (Directives 1991/414 and 2009/128), leading to a drastic reduction in the use of chemical compounds. A reduction in fungicides that effectively combat disease is achieved with the use of suppressive composts in pot plants. Suppressive composts similar to suppressive soils are examples of natural biological control of disease as the result or a more or less complex three-way interaction between microorganisms in the composts, plant pathogens, and plants. The roles of the physical properties and chemical composition of composts are also important in the suppressive effect, not only because they are responsible for the type and quantity of microorganisms established, but also because of their effects on pathogens, plant root health and leaf nutrient status. The two classic modes of action of microorganisms involved in the suppression of soil-borne plant pathogens (general and specific suppression) can be defined in composts. In specific suppression, only one or a few species are involved; while in contrast, a great diversity of microorganisms working together as a nutrient sink contributes to general suppression. A third mode of action is also induced by microorganisms in composts: systemic resistance, similar to challenge inoculation with a pathogen or beneficial organism.

Mª del Carmen Vargas-García, Mª José López, Francisca Suárez-Estrella, Gema Guisado, Joaquín Moreno (Spain) Bioremediation of Heavy Metal-polluted Environments through Compost Amendments and Composting Processes (pp 12-24)

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Invited Review: Pollution is a non-desirable consequence of most of anthropogenic activities. Contaminants accumulate in waters, sediments and, above all, soils, showing a high potential for causing damages in the ecosystems. Among these pollutants, heavy metals present the special feature of being non biodegradable, which makes them persistent in the environment. Moreover, this fact determines the nature of the technologies used for the reclamation of the polluted environments, since extraction and stabilization or immobilization are the only viable strategies. The former are generally carried out ex situ, resulting in high costs and negative affectation of the polluted area. On the contrary, stabilization techniques can be carried out in situ, which made them economically more attractive, although they are more time consuming and tend to cause some uncertainty. Stabilization or immobilization are containment technologies based on the use of plants and/or soil amendments in the polluted environment to reduce metal toxicity by metal fixation in the soil as a hardly-available forms. In this last case, the input of organic matter causes a double effect on both the physico-chemical properties and the associated microbiota of the polluted area, which in turn contribute to alter the physical form of heavy metals and reduce their mobility and bioavailability. Among the different materials tested, compost has been referenced as one of the most valuable substrates for the reclamation of heavy metal-polluted areas. Compost increases the chemical status of the soil, promotes microbial populations and their activity and favors the re-establishment of vegetation. Composting may also be a useful strategy for heavy metal-polluted soils remediation, although available information regarding this is scarce. A better understanding of mechanisms of action and the promoted effects is needed for its implementation as a usual technique for the reclamation of heavy metal-polluted areas, both in relation to composting and compost amendments.

Ackmez Mudhoo, Romeela Mohee (Mauritius) Fate of Heavy Metals Exposed to Composting Environments and Composts (pp 25-35)

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Invited Review: Heavy metal remediation of contaminated aqueous streams and soils is of great environmental concern. When present in excessive concentrations, heavy metals can become extremely toxic to the receiving bodies and pose serious health threats. Composting as a bioremediation technique offers the possibility to render less harmless various heavy metal contaminants using the natural biological activity of composting matrices due to the presence of bacteria, actinomycetes and lignolytic fungi. This review article presents an outlook on the speciation, immobilization mechanisms, uptake and fate of heavy metals present during the composting processes and when exposed to composts by essentially revisiting the essential biochemical and microbiological aspects of the composting process, and assessing the application of composting/composts in influencing the speciation and fate of heavy metals.

María Teresa Barral, Remigio Paradelo (Spain) A Review on the Use of Phytotoxicity as a Compost Quality Indicator (pp 36-44)

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Invited Review: Given the common use of compost in agriculture, forestry, landscaping and environmental restoration, it is essential that it is perfectly compatible with plant growth and, if possible, that it increases production and quality of plant biomass. It is therefore necessary to evaluate the absence of phytotoxic substances in the compost, which not only informs about its quality, but also on the proper handling of the composting process. Procedures for assessing the phytotoxicity as an indicator of compost maturity can be grouped into two types: a) seed germination and seedling elongation tests with extracts of compost; b) direct seeding tests on substrates made wholly or partly by compost. For the compost to be considered mature, the results of germination and elongation, or plant biomass, should be at least 80-90% of those obtained in a control. These tests have proven to be sensitive to various toxins, such as salts, organic acids, ammonia, or metals, and can be used to evaluate the process conditions and the degree of stabilization of organic matter, and the suitability of the raw materials. However, the great variability in testing methods make difficult the comparison and interpretation of results, so it is necessary to advance in the standardization of procedures and determine phytotoxicity thresholds for potential phytotoxic compounds in compost.

Steel Hanne, Bert Wim (Belgium) Biodiversity of Compost Mesofauna and its Potential as an Indicator of the Composting Process Status (pp 45-50)

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Invited Mini-Review: One of the key issues in compost research is to assess the quality and maturity of the compost. Biological parameters, especially based on mesofauna, have multiple advantages for monitoring a given system. The mesofauna of compost includes Isopoda, Myriapoda, Acari, Collembola, Oligochaeta, Tardigrada, Hexapoda, and Nematoda. This wide spectrum of organisms forms a complex and rapidly changing community. Up to the present, none of the dynamics, in relation to the composting process, of these taxa have been thoroughly investigated. However, from the mesofauna, only nematodes possess the necessary attributes to be potentially useful ecological indicators in compost. They occur in any compost pile that is investigated and in virtually all stages of the compost process. Compost nematodes can be placed into at least three functional or trophic groups. They occupy key positions in the compost food web and have a rapid respond to changes in the microbial activity that is translated in the proportion of functional (feeding) groups within a nematode community. Furthermore, there is a clear relationship between structure and function: the feeding behavior is easily deduced from the structure of the mouth cavity and pharynx. Thus, evaluation and interpretation of the abundance and function of nematode faunal assemblages or community structures offers an in situ assessment of the compost process.

Gabriele Alfano, Giuseppe Lustrato, Giancarlo Ranalli (Italy) From the Soil into the Soil - A Closed Cycle of Olive Oil Residues. Future Scenarios and Perspectives (pp 51-57)

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Invited Mini-Review: Olive cultivation plays a key role in southern Europe and in Mediterranean areas in terms of economy and culture. Currently, the potential profit from olive cultivation and olive oil production is increasing. This is particularly true in countries where production is characterized by modern, high-density, specialized cultivation, such as in those of the southern Mediterranean. However, one of the factors that hinders the development and profitability of the olive sector is the huge amount of waste produced every year by small and medium-sized olive mills. Olive wastes have been widely viewed as pollutants due to the presence of antimicrobial and phytotoxic compounds, mainly polyphenols. However, it has been proved that the composting process can provide bioremediation of such wastes, avoiding the harmful effects on the soil that can be caused by the spreading of untreated wastes. Composting has been proved to be an effective way to transform olive wastes into valuable, high-quality agricultural amendments and fertilizers particularly suitable for organic farming systems. Composting has also proved to be highly-adaptable so as to suit various countries and their respective, widely-varying production conditions. Moreover, the closed-cycle of composted olive oil residues has been shown to be an environmentally and economically-sustainable process, which could represent a low cost solution for the management and the recycling of olive waste and an additional form of income. Thus, olive waste composting could contribute to increase the competitiveness and the profit of the olive oil industry, and especially for small and medium sized olive farms and mills which are the most affected by the global market competition.

Thu Ha Nguyen, Haruo Shindo (Japan) Assessment of Long-term Compost Application on Organic Nitrogen Composition of Whole Soils and Their Particle Size Fractions (pp 58-62)

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Original Research Paper: We assessed the effects of long-term compost application on organic N composition of whole soils and their particle size fractions in a field subjected mainly to double cropping. Soil samples were collected from two plots: (a) F plot, only chemical fertilizers; (b) F+C plot, chemical fertilizers plus compost. Soil was divided into five fractions, coarse sand-sized aggregate (CSA), medium sand-sized aggregate (MSA), fine sand-sized aggregate (FSA), silt-sized aggregate (SIA) and clay-sized aggregate (CLA) fractions. Then CSA, MSA and FSA fractions were subdivided into “decayed plants” (DP) and “mineral particles” (MP). The amounts of total N and different forms of organic N in the whole soil and size fractions were much larger in the F+C plot than in the F plot. In the whole soil, the percentage distribution of non-hydrolysable N to total N was markedly increased by compost application while the other forms of N were generally maintained or reduced. In the size fractions, the percentage distribution of total N and different organic forms of N in the CSA-DP, MSA-DP and FSA-DP fractions were increased by compost application while their distribution degree in the CSA-MP, MSA-MP, FSA-MP were less affected. The application induced an increase in distribution values of total N and amino sugar-N in the SIA fraction while the other forms of organic N tended to maintain or decline. In the CLA fraction, the distribution values of total N and forms of organic N were decreased by the application. However, the amounts and percentage distribution of total N and organic N forms were the highest in the CLA fraction. The findings indicate that in the F and F+C plots, CLA fraction merit close attention as an important reservoir of various organic N.

Ena Smidt, Johannes Tintner, Katharina Böhm, Erwin Binner (Austria) Transformation of Biogenic Waste Materials through Anaerobic Digestion and Subsequent Composting of the Residues – A Case Study (pp 63-69)

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Original Research Paper: Anaerobic digestion of biogenic waste materials has become an important strategy for energy supply and organic matter stabilization. This study focuses on the characterization of input materials, digestates and composted digestates throughout the processes. Changes of the materials due to both anaerobic degradation/composting and annual variation under actual conditions were revealed using the example of the Viennese biogas plant. Besides the comprehensive characterization by infrared spectroscopic and thermo-analytical investigations, biological activity, nutrients and heavy metals were determined. Lab-scale composting experiments with digestates and different bulking agents were performed in order to assess the influence on humification that is considered a quality criterion.

Vandana Chummun, Ackmez Mudhoo, Romeela Mohee (Mauritius) Process Dynamics and Parameter Variations during Co-Composting of Mixed Vegetables, Broiler Litter, Cow Dung and Textile Sludge (pp 70-81)

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Original Research Paper: The co–composting behaviours of a mixture of vegetable wastes and three other different substrates (broiler litter, cow dung and textile sludge) were investigated through the evolution of temperature, respiration rate (RR), pH, volatile solids (VS), electrical conductivity (EC), moisture content (MC), bulk density (BD) and free air space (FAS) for 32 days. The three experimental mixes were set up separately in three 200L in–vessel rotary batch composters. The mass of vegetable wastes was kept fixed at 10 kg in all mixes but the amount of other substrates varied, and bagasse (10 kg) was used as bulking agent. 10 kg broiler litter, 17 kg cow dung and 36 kg textile sludge were added to Mix 1, Mix 2 and Mix 3 respectively. The average initial C/N ratio and initial wet MC were 24.0 and 53.2, 32.1 and 66.4% and 33.3 and 65.7% for Mixes 1, 2 and 3, respectively. Temperature peaks were recorded on day 2 for Mix 1 at 68.9 and 49.2°C on day 4 for Mix 2 and 68.5°C on day 4 for Mix 3. The average matrix temperatures for all mixes remained above the threshold of 55°C for an average period of 4 days. An increase in wet BD of 84.64% was noted for Mix 1, 57.12% for Mix 2, and 34.28% for Mix 3. The VS typically reduced from 72.35 to 55.9% in Mix 1, 72.27 to 62.10% in Mix 2, and from 66.11 to 58.39% in Mix 3, indicating that adequate microbial degradation of the organic fractions had taken place in the mixes. The average RR peaked at 73 mg CO₂.C/day on day 2 for Mix 1 and decreased to 10.9 mg CO₂.C/day on day 32. The corresponding peak and final stable values for Mixes 2 and 3 were 54.2 mg CO₂.C/day and 14.0 mg CO₂.C/day on day 32, and 50.2 mg CO₂.C/day and 14.5 mg CO₂.C/day on day 32. The typical temperature trends obtained for all mixes supported that the major composting stages had taken place but the different pH, EC, VS and temporal RR variations highlighted that the microbial decomposition rates were dependent on the nature of the substrates.

Yaswaree Mihilall, Ackmez Mudhoo, Romeela Mohee (Mauritius) Development of a New Substrate for the Cultivation of the Pleurotus sajor–caju Mushroom through Controlled Composting (pp 82-92)

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Original Research Paper: The in-vessel composting of a substrate, around 60 kg, composed of 18 kg of green banana leaves (Musa paradisiaca) (B), 18 kg green grass (Stenotaphrum dimidiatum) (G), 15 kg mixed cardboard waste (C) and 4 kg untreated pinewood shavings (W), was carried out. Oxygen was provided by active aeration with the airflow kept at 540 ± 24 L/h. The average temperature monitored over the 23 days, was 46.2°C with a maximum of 56.5°C on day 8. The final composted BGCW mix had a moisture content (MC) of 42.3%, wet bulk density (BD_w) 186.0 kg/m³ and particle size ranged from 26.67 mm to 4.699 mm, water holding capacity (WHC) 572.77%, porosity 53.18%, pH 7.94, electrical conductivity (EC) 1.18 dS/m and volatile solids content (VS) 78.7%. The nutrient content for the BGCW compost was 1.72% for nitrogen, 0.11% for phosphorus and 1.36% for potassium, totalizing to a sum of 3.19% as compared to bagasse, 0.001% for nitrogen, 0.003% for phosphorus and 0.006% for potassium. The BGCW compost along with bagasse were packed, in heat resistant bags, 750 g each, and pasteurised at 70°C for 4 h. The total yield of fructifications harvested from the three pickings was 950.30 g for bagasse and 810.60 g for the BGCW compost. The average biological efficiency on bagasse was 42.23 ± 4.4% as compared to the BGCW compost (36.03 ± 5.3%). The difference in yield could be primarily explained by higher fibre content in bagasse (47.3 ± 2.4%) as compared to the BGCW compost (40.5 ± 2.3%). It is envisaged that the BGCW compost was supplemented to bagasse for the cultivation of the Pleurotus sajor−caju mushroom.

Miguel A. Sánchez-Monedero, Marialuz Cayuela, Nuria Serramiá, Concepción García-Ortiz Civantos, Antonia Fernández-Hernández, Asunción Roig (Spain) Emission of CO₂, CH₄ and N₂O during Composting of Two-Phase Olive Mill Wastes: A Four-Year Study (pp 93-97)

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Original Research Paper: A four-year monitoring program was performed to quantify the emission of the three most important greenhouse gases (GHG), CO₂, CH₄ and N₂O, emitted during composting of two-phase olive mill wastes (TPOMW). A composting pile was prepared with typical agroindustrial wastes generated from olive oil mills: TPOMW and olive tree prunings, used as bulking agent, enriched with urea as N source. The study was performed during four consecutive years in order to obtain a wide set of experimental data to evaluate the effect of the variability of the raw material characteristics and the performance of the composting plant on GHG emissions. Biogenic CO₂ was the main gas generated during TPOMW composting. The range of CO₂ emission exhibited low interannual variation regardless the operational conditions at the composting plant. The improvement of the composting operations (better control of pile moisture and improved aeration) reduced the amount of CH₄ and N₂O emitted from the pile by reducing the formation of anaerobic spots within the pile. The control of the CH₄ and N₂O emissions reduced the contribution of TPOMW composting to climate change, expressed as kg of CO₂ equivalents.

Mariane Domeizel, Antoine Khalil, Pascale Prudent (France) Biodegradability of Seven Mediterranean Plants in a Composting Environment (pp 98-103)

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Original Research Paper: This study proposes to evaluate the biodegradability of branches and leaves from 7 Mediterranean plants: palm tree, olive tree, cypress, pine, bay tree, mimosa and plane tree. The chemical approach to biodegradability of each sample has been compared to its biochemical composition. During the first 5 days, biodegradation kinetics can be divided into 2 prevalent stages: the first one with a slow rate and the second with a fast rate. The difference between these 2 stages is more dependent on the plant’s species than its different parts (leaves or branches). The study also confirms the role of lignin and the importance of granulometry in the biodegradation of green waste and the efficacy of the decomposing process in composting.

Antonis A. Zorpas (Cyprus) Metals Selectivity from Natural Zeolite in Sewage Sludge Compost. A Function of Temperature and Contact Time (pp 104-112)

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Original Research Paper: It is well known that the application of Natural Zeolite in sewage sludge compost processes has the ability (a) to remove and/or uptake heavy metals in significant levels and not let them past to the groundwater, (b) to take up all the metals, which are bound to the most mobile forms while the rest remain to an inert forms. Hence, there are a lot of studies that show the selectivity of natural zeolite in metals, which are presented, in liquid waste or liquid prepared samples in laboratories but no research was carried out, for the selectivity of metals from zeolite in the process of sewage sludge compost. The paper focuses on the determination of the selectivity of heavy metals from natural zeolites in the first steps of the composting process, which the substrate is unstable. A number of experiments were carried out in different conditions in order to indicate how the temperature (20, 40 and 60°C) of composting and the contact time (1 - 30 d) of the clinoptilolite affected the uptake of the heavy metals. The selectivity series for the removal of heavy metals is different from temperature to temperature and from day to day. The optimum result was carried out in 30 d and for 60 ± 2°C. In those conditions 70% of Cd, 67% of Cr and Mn, 62% of Co, 46% of Zn, 43% of Ni, 41% of Pb, 37% of Fe and 27% of Cu were taken up from clinoptilolite. The results are very useful for the determination of the best conditions of the composting of a heavy polluted waste with zeolites.

Dimitrios Komilis, Eleni Timotheatou (Greece) Bioremediation of a Diesel-contaminated Soil: Effect of Compost Addition (pp 113-119)

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Original Research Paper: Organic waste derived compost is usually viewed as a soil amendment. However, mature and stable composts can be used as a media to aid in the bioremediation of hazardous wastes. The goal of this study was to investigate the effect of compost addition on the degradation of a diesel-contaminated soil. A municipal solid waste-derived compost and an olive pulp-derived compost were used in this study. The former compost was more stable than the latter. A total of 18 experiments were performed in 1 L manometric respirometers and the biodegradation process was followed through measurements of net O₂ consumption and net CO₂ generation for 170 days. Results of the work showed that the addition of both composts increased the net respiration activity due to the degradation of diesel in the compost amended samples. The addition of municipal solid waste compost at a ratio of 2: 1 (dry soil: dry compost) led to the highest net microbial activity and the highest diesel removal (94%). The olive pulp-derived compost resulted in the highest net microbial activity when added at a ratio of 5: 1 but with a diesel removal of approximately 73%. The diesel contaminated soil alone had a low microbial respiration activity and a relatively high diesel removal (84%).

Philip R. Warman (Canada) Effect of Ruminant, MSW and Biosolids Composts and Their Teas on Some Berry Crops, Vegetables and Soil Fertility (pp 120-126)

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Original Research Paper: Two types of non-aerated compost teas were made from their respective mature composts and used as sole fertility amendments in separate experiments for beans, sweet corn, greenhouse tomatoes, strawberries and blackberries grown in a relatively infertile Gibraltar sandy loam at Boutiliers Point, Nova Scotia. The teas were made from municipal solid waste (MSWC) and biosolids composts (BC). Each crop was grown using compost or compost tea in experiments as long as six years; in each experiment, compost applications were based on crop N requirements and were applied once or twice based upon their respective total N content. Compost tea applications, however, were normally based on weekly or bi-monthly spray applications to cover the surfaces of the leaves or as a soil drench and continued until the plants blossomed. Vegetable and berry yields were taken when cobs, beans or fruit matured, thus, multiple pickings each year. Leaf tissue and/or Mehlich-3 extractable levels of at least 10 soil elements were taken at the recommended time for each crop. The yield results indicated the compost and tea treatments produced equivalent berry or cob yields for the blackberry, strawberry and sweet corn experiments. Snap bean yields were highest with the MSWC and lowest with an organic fertilizer blend, while tomato fruit yields for soybean, BC and BC tea treatments were greater than the control. There were few effects of treatments on soil fertility or leaf tissue samples and non-significant correlation between the results of the Mehlich-3 extracts and tissue elemental content. The MSWC and its high tea spray had some effect on soil or tissue Na, likely because Na is the most soluble element in the tea treatments. Since Na is not essential for plant growth, there is a concern that increasing Na additions could affect K absorption and plant growth. Potentially toxic trace elements did not accumulate in any of the treated plants.

Mathava Kumar (India), Jih-Gaw Lin (Taiwan) Co-composting of Food Waste and Green Waste in Pilot-Scale Systems: In-vessel and Windrow Investigations (pp 127-133)

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Original Research Paper: The two largest constituents of municipal solid waste are food waste and green waste. These two wastes have enormous quantity of nutrients and other resources; this can be used for plant growth/land application after some degree of treatment. This study discusses the adept schemes for successful co-composting of food waste and green waste in pilot-scale systems via in-vessel and windrow systems. Furthermore, this study describes the effect of moisture content and controlled seeding of microorganisms on the windrow composting system.

Suzelle Barrington, Michael Schwalb, Rebecca Chin, Carrie Rosewear (Canada) Selecting Community Composting Centre Bulking Agent for Sanitization and Minimal N Losses (pp 134-143)

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Original Research Paper: As opposed to landfilling which is affordable but not without environmental issues, community composting to recycle food waste (FW) can reduce collection and transportation costs. Nevertheless, community composting centres (CCC) require proper planning to be affordable and good management for a sanitary product and minimal greenhouse gas and ammonia emissions. The objective of the project was therefore to determine the best CCC composting recipe optimizing BA usage and operating costs, and limiting N losses. This objective was met with: laboratory composters testing six duplicate combinations of BA (cereal residue pellets (CRP) alone, CRP with wood chips (WC), and CRP with WC and shredded paper (P)) and two C:N ratios (16-17 and 32-38), and then; using the two best laboratory recipes (CRP alone and CRP with WC) at a C:N of 35-38, test their performance for three years at a CCC in downtown Montreal, Canada. Composting efficiency was evaluated by measuring: the temperature regime during the active phase, and; the loss of mass, carbon and nitrogen (N) during both the active and maturation phases. The laboratory experiment demonstrated that: high C:N ratios minimise N volatilisation while still providing sanitizing thermophilic temperatures; as BA, CRP alone produced a longer thermophilic period and the highest loss of dry mass, organic carbon and N while P shortened the thermophilic period for the high C:N ratio. The CCC tests demonstrated that despite the variation in FW and BA properties over three years, both BA combinations provided sufficient free air space (FAS) for proper compost aeration; thermophilic temperatures were reached when the CCC attendant received the proper training and took the proper precautions to sufficiently aerate the reactor; the best compost recipe of 71% FW, 21% CRP and 8% WC (wet mass) generated sanitizing thermophilic temperatures during five days while minimising N losses.

Filipe Pedra (Portugal), Alfredo Polo (Spain), Corina Carranca, Alexandra Ribeiro, Hermínia Domingues (Portugal) Kinetic Models Fitted to Nitrogen Mineralization Potential in Soils Amended with Municipal Compost and Urban Sewage Sludge (pp 144-146)

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Short Communication: An experimental incubation was conducted to study and describe the dynamics and kinetics of nitrogen (N) mineralization, using six different kinetic models, on two different soils, amended with municipal solid waste compost (MSWC) and sewage sludge (SS). For this purpose, a pot experiment was carried out, under semi-controlled conditions and without crop, in a complete randomised block design, with application of seven levels of organic amendments (0, 15, 30 and 60 t ha^-1 for both MSWC and SS). The two contrasting texture soils were an Haplic Podzol (PZha) and a Calcic Vertisol (VRcc). The soil samples were collected at the end of 1^st, 2^nd, 3^th, 4^th and 8^th weeks and mineral N was measured. The kinetic models applied showed a lower fitting for the PZha soil than to the VRcc soil. However, for both soils the best determination coefficients were obtained with the simple and the double exponential models. The results suggested that to choose the model that better fits N mineralization data soil texture must be considered and soils should be modeled separately.