Garden Waste Compost Research Articles

Composts of diverse green wastes improve the soil biological quality, but do not alleviate drought impact on lettuce (Lactuca sativa L.) growth

AbstractIntense soil cultivation and climate change have detrimental effects on soils. Solutions are needed to improve the biological quality and water holding capacity of agricultural soils. A greenhouse experiment was conducted to investigate the interactive effect of compost application and drought stress on a soil/plant system in order to determine the improvement of soil quality and plant growth and the alleviation of drought stress. Lettuce (Lactuca sativa L.) was grown under greenhouse conditions in a sandy soil with sufficient mineral fertilizer application to test the effect of five compost types (three made from municipal garden and park wastes with differing nutrient contents, one from municipal household waste, and one from farm plant residues) applied at 30 Mg ha−1 dry weight, with which we compared soil quality and plant growth to soil without compost application. Treatment pots were irrigated or subjected to drought conditions during the last 14 days of lettuce growth. Assays of potential N mineralization during 28 days, dehydrogenase and β‐glucosidase activities, and a phospholipid fatty acid (PLFA) analysis were performed to assess effects on soil biological quality. Gas exchange, leaf relative water content, biomass, nitrogen accumulation, and root tip growth of lettuce were measured to investigate compost and drought stress effects on lettuce physiology. All composts improved indices of soil biological quality significantly, except for fungal abundance, relative to soil without compost. The greatest increase was obtained from farm compost, which significantly increased potential nitrogen (N) mineralization and soil enzyme activities of β‐glucosidase and dehydrogenase by factors of 4, 2, and 43, respectively. Furthermore, soil with farm compost generally showed a higher abundance of soil microbial organisms compared with soil without compost, which could be related to its high cellulose and hemicellulose contents. The lowest abundance of microbial organisms was generally found in soil with garden and park waste compost with a medium nutrient content, which could be related to its low organic matter content. The beneficial effect of compost on soil biological quality did not lead to improved lettuce growth, which suggests that soil biological quality (ameliorated by compost application) is not important for a fast‐growing crop, such as lettuce, that is sufficiently fertilized. Drought stress reduced aboveground lettuce biomass, root tip growth, and the abundance of most soil microbial groups significantly, but compost in soil did not alleviate these negative effects. In conclusion, the farm compost made from grass–clover, straw, and vegetable residues is superior to garden and park waste and household waste composts in terms of beneficial effects on soil biological quality. Compost clearly improved soil biological quality, but did not influence lettuce's response to drought stress. The knowledge gained in this study is useful for producing tailor‐made compost with desired effects of improved soil biological quality.

Garden Waste Compost Tea: A Horticultural Alternative to Promote Plant Growth and Root Traits in Tomato (Solanum lycopersicum L.) Plants

The application of garden waste compost teas (CTs) in sustainable agriculture constitutes a biostimulant and environmentally friendly alternative. The purpose of this work was to study the physicochemical properties of three CTs prepared with different brewing processes (CT1, CT2, and CT3) immediately after extraction and six months later to determine whether those properties changed over time and evaluate the effect of CT application on tomato (Solanum lycopersicum L.) plant growth. The brewing process had a significant effect on the extracts’ chemical composition, while long-term storage did not lead to significant differences. The most energy-efficient CT was evaluated in a pot and in vitro assays by measuring plant growth parameters and root traits. CT1 directly supplied to the substrate increased the leaf number, plant height, and dry weight of tomato plants compared to the control and foliar treatments, whereas no significant differences were found among foliar treatments. In terms of the effects of CT application on root development, the results of the in vitro assays showed that CT supply enhanced the primary root length, lateral root number, and root fresh weight while decreasing shoot height and weight in 10-day-old tomato seedlings. From an agronomic standpoint, this study contributes new insights regarding the storage stability of CT and its impact on tomato plant growth.

Influence of Organic Amendments Based on Garden Waste for Microbial Community Growth in Coastal Saline Soil

Garden waste compost (GWC) has been applied as an amendment to improve the desalination efficiency, nutrient availability and diversity of the microbial community in coastal saline soil. Understanding the response of the microbial community to garden waste compost application is of great significance in coastal ecological restoration. Four treatments were established: CK, nonamended control; T1, application of 68 kg·m−3 garden waste compost; T2, application of 15 kg·m−3 bentonite; and T3, a mixture of garden waste compost and bentonite. In addition, soil physicochemical properties, soil enzymes, microbial biomass carbon and the soil microbial community were measured. The results show that T3 had a more significant effect on increasing soil enzymes, as well as microbial biomass carbon and nitrogen, urease, sucrase and dehydrogenase activities. Based on the relative abundance, microbial diversity and linear discriminant effect size (LEfSe) analyses, the amendments can be seen to have increased the microbial abundance and alpha diversity of the bacterial structure and also altered the microbial community structure. RDA and Pearson correlation analysis at the phylum level indicated that available nitrogen, total porosity, hydraulic conductivity, bulk density and EC were the primary determinants of microbial communities associated with this amendment. In conclusion, the application of garden waste compost enables more microorganisms to participate in the soil material cycle, indicating that garden waste composting is beneficial to the restoration of coastal soils.

Concentrations and Retention Efficiency of Tire Wear Particles from Road Runoff in Bioretention Cells

Bioretention cells are popular stormwater management systems for controlling peak runoff and improving runoff water quality. A case study on a functional large-scale bioretention cell and a laboratory column experiment was conducted to evaluate the concentrations and retention efficiency of bioretention cells towards tire wear particles (TWP). The presence of TWP was observed in all soil fractions (<50 µm, 50–100 µm, 100–500 µm, and >500 µm) of the functional bioretention cell. TWP concentrations were higher (30.9 ± 4.1 mg/g) close to the inlet to the bioretention cell than 5 m away (19.8 ± 2.4 mg/g), demonstrating the influence of the bioretention cell design. The column experiment showed a high retention efficiency of TWP (99.6 ± 0.5%) in engineered soil consisting of sand, silty-sand, and garden waste compost. This study confirmed that bioretention cells built with engineered soil effectively retained TWP > 25 µm in size, demonstrating their potential as control measures along roads.

Effects of Repeated Application of Organic Soil Amendments on Horticultural Soil Physicochemical Properties, Nitrogen Budget and Yield

Application of organic amendments to soil is commonplace in domestic gardening. However, a vast array of materials could be labelled as ‘compost’ by retailers and suppliers. We investigated six different amendments currently used, or available for use, in horticulture: composted bark, composted bracken, spent mushroom compost, composted horse manure, garden waste compost (at two different application rates), and peat. Using a controlled field experiment, we examined the physicochemical differences between the amendments, the subsequent effects on soil characteristics, and resultant yield and biometrics of Lavatera trimiestris. Amended soils resulted in a significantly different multivariate soil environment and N budget when compared to the unamended control. However, the effect on yield and plant biometrics (number of flowers, plant height, etc.) depended on the amendment used. Application of garden compost resulted in up to a five-fold increase in yield. However, there was no significant difference in yields in soils amended with composted bark or peat, when compared to the unamended control. This has implications, as there is increasing pressure to remove peat from products available to domestic gardeners. The variability in the different amendments investigated in our research, in addition to the variable effects on plant growth parameters, suggests that repeated use of a single amendment may not be best practise for gardeners.

Safety and efficiency of sewage sludge and garden waste compost as a soil amendment based on the field application in woodland

Sewage sludge (SS) and garden waste (GW) compost can be used as soil amendments to improve the soil environment. Studies done till date have been focused on the changes of harmful substances during sludge composting, but the safety and efficacy of SS and GW composting on woodland soil environment are still unclear. In the study, a field experiment was performed using to investigate the safety and efficacy of SS and GW compost as a soil amendment on woodland soil. Soil nutrients (such as nitrogen, phosphorus and potassium), organic matter and electrical conductivity were significantly increased after the addition of the SS and GW compost, while there were no significant changes in soil heavy metals content and soil enzyme activities. From these soil properties, it was found that SS and GW compost was safe and efficacious in improving the soil environment. The application of SS and GW compost had no significant effect on microbial diversity. Co-occurrence network analysis revealed that SS and GW compost efficaciously enhanced the interaction between bacterial communities, which proved that it was safe and efficacious. Furthermore, SS and GW compost enhanced ABC transporters and carbohydrate metabolism of bacterial community, while reduced the pathotroph action (such as the plant pathogen) and wood saprotrophs. Overall, these results proved the safety and efficacy of SS and GW compost as soil amendments after being added to the soil. This study contributes to the use of harmless treatments and reutilization processes of SS and GW.

Deciphering the Effects of Waste Amendments on Particulate Organic Carbon and Soil C-Mineralization Dynamics

It is important to understand the dynamics of soil carbon to study the effects of waste amendment inputs on soil organic carbon decomposition. The aim of this study was to evaluate the effect of waste amendment carbon input on the soil organic carbon (SOC) content, soil particulate organic carbon (POC) content and soil organic carbon mineralization rate dynamics. A 60-day experiment was carried out in the laboratory. The following treatments were compared: (1) CK: soil without amendments; (2) FW1: soil with food waste compost (soil/food waste compost = 100:1); (3) FW2: soil with food waste compost (soil/food waste compost = 100:2); (4) GW1: soil with garden waste compost (soil/garden waste compost = 100:0.84); (5) GW2: soil with garden waste compost (soil/garden waste compost = 100:1.67); (6) FGW1: soil amendments mixture (soil/food waste compost/garden waste compost = 100:0.5:0.42); (7) FGW2: soil amendments mixture (soil/food waste compost/garden waste compost = 100:1:0.84); the inputs of amendment carbon to FW1, GW1 and FGW1 were 2.92 g kg−1, the inputs of amendment carbon to FW2, GW2 and FGW2 were 5.84 g kg−1. The results showed that the addition of waste amendments increased the amount of cumulative mineralization from 95% to 262% and accelerated the rate of soil mineralization. After adding organic materials, the change in the soil organic carbon mineralization rate could be divided into two stages: the fast stage and the slow stage. The dividing point of the two stages was approximately 10 days. When equal amounts of waste amendment carbon were input to the soil, there was no significant difference in SOC between food waste and garden waste. However, SOC increased with the amount of amendment addition. However, for POC, there was no significant difference between the different amounts of carbon input to the garden waste compost treatments. SOC and POC were significantly correlated with the cumulative emissions of CO2.

Effects of Garden Waste Compost and Bentonite on Muddy Coastal Saline Soil

In order to effectively utilize resources and improve the amelioration effect of coastal saline soil, we studied the effects of applying garden waste compost and bentonite on highly saline coastal soil. Four treatments were established: a nonamended control; application of 68 kg·m−3 of garden waste compost; application of 15 kg·m−3 of bentonite; and mixed application of 68 kg·m−3 of garden waste compost and 15 kg·m−3 of bentonite. The results showed that the soil salinity of the three treatments was significantly lower than that of the nonamended control. The desalination effect of the mixed application was the best, and the salinity in the 0–20 and 20–40 cm soil layers decreased to 3.95 g·kg−1 and 3.82 g·kg−1, respectively. Application of both the garden waste compost alone and the mixed application significantly improved the physical and chemical properties of the soil. However, the mixed application had the best effect because of its ability to increase the total porosity, saturated hydraulic conductivity, and soil nutrient levels. The growth of Robinia pseudoacacia cv. Idaho in the mixed application treatment was also better than other treatments. Principal component analysis and comprehensive scores indicated that the addition of 68 kg·m−3 of garden waste compost and 15 kg·m−3 of bentonite was the optimal application.

The character and distribution of physical contaminants found in soil previously treated with mixed waste organic outputs and garden waste compost

The re-use of waste materials by application to land is an increasingly common practice around the world, but where municipal solid waste materials are applied, it is almost inevitable that physical contaminants such as glass and plastic will be added to the soil. In many jurisdictions, there are prescribed limits for the amounts of physical contaminants that may be present in these materials, but there is little information on whether these limits safeguard soil functional condition. Here, physical contamination of soil is described after varying rates of a mixed waste organic output (MWOO) and garden waste compost (GWC) were incorporated into field plots. At application rates of 100 and 200 t/ha, both treatments resulted in a coarsening of the topsoil particle size distribution, but only in the MWOO-treated soils were physical contaminants largely responsible for this. The physical contaminant particles present were found only to the depth of cultivation, and included glass, rigid and film plastics, and synthetic fibres. These contaminants were most commonly observed in the gravel and coarse sand-sized fractions, and in those soils treated with the highest rates of MWOO application. Physical contaminant particles acted as both enveloping and nucleating agents for mineral grains and organic matter, and blocked some pores. Although soil physical condition is usually improved by the incorporation of organic matter, the extent of pore blockage evident here suggests that soil physical functions such as water percolation may be affected as the organic matter is broken down and the soil undergoes natural re-consolidation.

Efficiency of garden waste compost teas on tomato growth and its suppressiveness against soilborne pathogens

ABSTRACT: The use of compost teas is of great interest to sustainable agriculture. Aerated compost tea (ACT) and aerated vermicompost tea (AVT) originating from garden waste have been analytically characterized and tested in vitro and in vivo on tomato plants to determine their suppressive effect on Rhizoctonia solani and Fusarium oxysporum f. sp. lycopersici. The nitrogen (N, 3840 ppm) and potassium superoxide (K2O, 5800 ppm) contents were relevant in ACT. Both ACT and AVT were shown to contain indoleacetic acid IAA (80 - 20 mg L−1), salicylic acid (5.85 - 1.33 ng L−1) and humic acids (190 - 140 mg L−1). Direct confrontation assays against the pathogens showed that ACT had a high suppressive effect on F. oxysporum f. sp. lycopersici (relative growth of the pathogen [RG]: 12 %) and AVT had a high suppressive effect on R. solani (RG: 18 %). These suppressive effects have been confirmed by tests performed in vitro and on potted tomato plants. Results of plants growth assays showed that both teas can be applied, in their concentrated forms, to the growth medium. The analysis of the growth effect of the teas on tomato plants clearly indicated that both ACT and AVT, when applied weekly, produce a positive effect on shoot and root dry weight (dry weights were tripled), chlorophyll content and stem diameter compared to untreated plants. These results support the use of ACT and AVT as potential alternatives to the application of synthetic fungicides, and as plant promoters in crop production, for attaining environmental sustainability for farming and food safety.

Deriving Environmental Life Cycle Inventory Factors for Land Application of Garden Waste Products Under Northern European Conditions

The amount of waste which is being recycled is increasing in Europe. Garden waste is increasingly composted and land applied. However, composting to full maturity requires resources in terms of space, equipment and labour. Alternatives could include a simple shredding, or composting for a shorter time. Finally, an option could be to remove trunks and large branches which are not easy to compost and incinerate them to recover energy. In order to assess these options and the associated environmental impacts, it is necessary to have good estimates of emissions and other inventory factors during the different steps of the life cycle of the compost products. Especially, the impacts occurring after land application are difficult to estimate. The objective of the current paper is to estimate environmental inventory factors for land application of four garden waste products: shredded garden waste, shredded garden waste after removal of the woody fraction, immature garden waste compost and mature garden waste compost. Soil incubations of the materials were conducted in order to assess the carbon (C) and nitrogen (N) dynamics occurring after incorporation in soil. Subsequently, the results were used to calibrate the mineralisation kinetics of the materials in the agroecosystem model Daisy. Subsequently, the model was used to simulate C and N dynamics under different environmental conditions and emissions to the environment and used to derive inventory factors. Nine soil and climate combinations were included in the simulation study to cover local conditions commonly found in Northern Europe. The degradability of the garden waste products increased when the woody fraction of garden waste was removed and generally the degradability of the product was decreased by composting. All four products showed initial immobilisation of N in soil, but it was clear that removal of the woody fraction and composting reduced the length and severity of the immobilisation phase. The approach taken in the current paper using soil incubations to estimate decomposition parameters for the materials and subsequently an agroecosystem model to extrapolate the observations proved efficient at estimating inventory factors under various environmental conditions and fertilisation levels. Under low N availability conditions, the harvest factor, which estimates the fraction of N harvested in response to application of an amount of compost ranged between 0.10 and 0.18 for a sandy loam soil and medium precipitation conditions for Northern European while it ranged from negative values to 0.12 under conditions of ample N supply. These results were also clearly reflected in the emission factors for N leaching to the groundwater and losses to surface water, which were higher under high N availability than under low. The harvest factor, emission factors for ammonia, N leaching to ground water and loss to surface water proved to be very dependent on the local conditions like the soil type, precipitation regime and general fertilisation level, whereas the biochemical composition of the materials was of less importance for these factors. In contrast, the C sequestration factor was almost unaffected by the environmental conditions but depended to a large extent on the degradability of the added material.

Assessment of farm soil, biochar, compost and weathered pine mulch to mitigate methane emissions.

Previous studies have demonstrated the effective utility of volcanic pumice soil to mitigate both high and low levels of methane (CH4) emissions through the activity of both γ-proteobacterial (type I) and α-proteobacterial (type II) aerobic methanotrophs. However, the limited availability of volcanic pumice soil necessitates the assessment of other farm soils and potentially suitable, economical and widely available biofilter materials. The potential biofilter materials, viz. farm soil (isolated from a dairy farm effluent pond bank area), pine biochar, garden waste compost and weathered pine bark mulch, were inoculated with a small amount of volcanic pumice soil. Simultaneously, a similar set-up of potential biofilter materials without inoculum was studied to understand the effect of the inoculum on the ability of these materials to oxidise CH4 and their effect on methanotroph growth and activity. These materials were incubated at 25°C with periodic feeding of CH4, and flasks were aerated with air (O2) to support methanotroph growth and activity by maintaining aerobic conditions. The efficiency of CH4 removal was monitored over 6months. All materials supported the growth and activity of methanotrophs. However, the efficiency of CH4 removal by all the materials tested fluctuated between no or low removal (0-40%) and high removal phases (>90%), indicating biological disturbances rather than physico-chemical changes. Among all the treatments, CH4 removal was consistently high (>80%) in the inoculated farm soil and inoculated biochar, and these were more resilient to changes in the methanotroph community. The CH4 removal from inoculated farm soil and inoculated biochar was further enhanced (up to 99%) by the addition of a nutrient solution. Our results showed that (i) farm soil and biochar can be used as a biofilter material by inoculating with an active methanotroph community, (ii) an abundant population of α-proteobacterial methanotrophs is essential for effective and stable CH4 removal and (iii) addition of nutrients enhances the growth and activity of methanotrophs in the biofilter materials. Further studies are underway to assess the feasibility of these materials at small plot and field scales.

Erratum to: Potential of Fusarium wilt-inducing chlamydospores, in vitro behaviour in root exudates and physiology of tomato in biochar and compost amended soil

Biochars are recognised for their ability to improve soil functions and to stimulate plant defense mechanisms. We evaluated the response of Fusarium oxysporum f. sp. lycopersici chlamydospores to tomato plants grown in biochar and compost amended soil to get a deeper insight into the tomato-Fusarium pathosystem. Wood chips and green waste biochar in combination with compost (‘WCBcomp and GWBcomp’ respectively) were studied for their ability to suppress the Fusarium chlamydospores infectivity. Plant growth parameters and in vitro effects on chlamydospores were determined. The ‘GWBcomp’ soil amendment stimulated plants growth and gaseous exchange rates and had a suppressive effect on the chlamydospore infectivity in comparison with the ‘WCBcomp’ treatment and the treatment containing compost only. The germination rate of chlamydospores was unaffected by the source of root exudates, whereas the mycelial growth was significantly higher in root exudates from chlamydospore inoculated plants grown in ‘WCBcomp’ amended soil unlike to ‘GWBcomp’ amended soil. Overall, our findings indicate that both biochars had a variable effect on chlamydospores. We conclude that soil amendment with garden waste biochar and compost exhibit a great potential in suppressing Fusarium chlamydospore infectivity and alleviating pathogen–induced physiological stress in tomato plants.

Potential of Fusarium wilt-inducing chlamydospores, in vitro behaviour in root exudates and physiology of tomato in biochar and compost amended soil

Biochars are recognised for their ability to improve soil functions and to stimulate plant defense mechanisms. We evaluated the response of Fusarium oxysporum f. sp. lycopersici chlamydospores to tomato plants grown in biochar and compost amended soil to get a deeper insight into the tomato-Fusarium pathosystem. Wood chips and green waste biochar in combination with compost (‘WCBcomp and GWBcomp’ respectively) were studied for their ability to suppress the Fusarium chlamydospores infectivity. Plant growth parameters and in vitro effects on chlamydospores were determined. The ‘GWBcomp’ soil amendment stimulated plants growth and gaseous exchange rates and had a suppressive effect on the chlamydospore infectivity in comparison with the ‘WCBcomp’ treatment and the treatment containing compost only. The germination rate of chlamydospores was unaffected by the source of root exudates, whereas the mycelial growth was significantly higher in root exudates from chlamydospore inoculated plants grown in ‘WCBcomp’ amended soil unlike to ‘GWBcomp’ amended soil. Overall, our findings indicate that both biochars had a variable effect on chlamydospores. We conclude that soil amendment with garden waste biochar and compost exhibit a great potential in suppressing Fusarium chlamydospore infectivity and alleviating pathogen–induced physiological stress in tomato plants.

Agricultural and Forestry Waste Composts as Substitutes for Peat in Potting Media: Effects on Root Growth and Fractal Features of New Guinea impatiens (Impatiens hawkeri)

Peat is widely used as a growth substrate in horticultural soilless cultivation, but it is an expensive and non-renewable resource. The objective of the present study was to assess the feasibility of using peat substitutes in the production of New Guinea impatiens (Impatiens hawkeri) by selecting garden waste compost, mushroom residue compost, soil, and peat as the media. No significant difference had been observed in total root length, root tips, and root fractal dimension at prophase when using 100 % peat substrate with garden waste compost and peat mixed in a 1:1 treatment, whereas at a later period, the 1:1 mixture resulted in faster growth rate. Root fractal dimension and root abundance improved to different degrees when using garden waste compost and mushroom residue compost as substitutes; moreover, using garden waste compost contributed to maintain root growth, whereas mushroom residue compost was effective for generating fibrous roots. Hence, the results suggested that (1) garden waste compost could be ideal substitutes for peat in New Guinea impatiens production and have great potential during the later period of root growth and (2) a box-counting fractal model could be used for the study of plant root morphology and architecture as well as being an effective method for analyzing root geometry and functional properties quantitatively.

Determination of the Physical, Chemical, and Hydraulic Characteristics of Locally Available Materials for Formulating Extensive Green Roof Substrates

Several locally available materials were tested to create an optimized growth substrate for arid and semiarid Mediterranean extensive green roofs. The study involved a four-step screening procedure. At the first step, 10 different materials were tested including pumice (Pum), crushed tiles grade 1–2 mm (T1–2), 2–4 mm (T2–4), 5–8 mm (T5–8), 5–16 mm (T5–16), and 4–22 mm (T4–22); crushed bricks of either 2–4 mm (B2–4) or 2–8 mm (B2–8); a thermally treated clay (TC); and zeolite (Zeo). All materials were tested for their particle size distribution, pH, and electrical conductivity (EC). The results were compared for compliance with existing guidelines for extensive green roof construction. From the first step, the most promising materials were shown to include Pum, Zeo, T5–8, T5–16, and TC, which were then used at the second stage to develop mixtures between them. Tests at the second stage included particle size distribution and moisture potential curves. Pumice mixed with TC provided the best compliance with existing guidelines in relation to particle size distribution, and it significantly increased moisture content compared with the mixes of Pum with T5–8 and T5–16. As a result, from the second screening step, the best performing substrate was Pum mixed with TC and Zeo. The third stage involved the selection of the most appropriate organic amendment of the growing substrate. Three composts having different composition and sphagnum peat were analyzed for their chemical and physical characteristics. The composts were a) garden waste compost (GWC), b) olive (Olea europaea L.) mill waste compost (OMWC), and c) grape (Vitis vinifera L.) marc compost (GMC). It was found that the peat-amended substrate retained increased moisture content compared with the compost-amended substrates. The fourth and final stage involved the evaluation of the environmental impact of the final mix with the four different organic amendments based on their first flush nitrate nitrogen (NO3−-N) leaching potential. It was found that GWC and OMWC exhibited increased NO3−-N leaching that initially reached 160 and 92 mg·L−1 of NO3−-N for OMWC and GWC, respectively. By contrast, peat and GMC exhibited minimal NO3−-N leaching that was slightly above the maximum contaminant level of 10 mg·L−1 of NO3−-N (17.3 and 14.6 mg·L−1 of NO3−N for peat and GMC, respectively). The latter was very brief and lasted only for the first 100 and 50 mL of effluent volume for peat and GMC, respectively.

Allergic bronchopulmonary aspergillosis in garden waste (compost) collectors--occupational implications

The separation of rotting garden material from general domestic waste and its collection for processing in industrial composting sites is a relatively new industry in the UK. Two cases of allergic bronchopulmonary aspergillosis and the results of health surveillance are described in a team of 28 garden waste (compost) collectors. A few cases of extrinsic allergic alveolitis due to Aspergillus fumigatus have previously been reported in compost workers. In the absence of any guidance from research and to prevent similar cases of a potentially serious illness, we advise that new starters to the job of collecting or processing compost are screened for asthma and aspergillus sensitivity, cystic fibrosis, bronchiectasis and immunodeficiency if their exposure to high levels of Aspergillus sp cannot be controlled. Annual health surveillance for these workers is also recommended.

Addition of a fine-textured soil to compost to reduce nutrient leaching in a sandy soil

Compost addition to soil can increase nutrient availability, but if added to sandy soils, nutrients can be rapidly leached. Clay added to compost could increase nutrient retention and reduce nutrient leaching due to binding to the clay. An incubation experiment was conducted to assess the effect of addition of a fine-textured soil (34% clay) to garden waste compost on nutrient availability and leaching in a sandy soil. The sandy soil was non-amended or amended with compost only, at a rate 27.3 g kg–1, or with a mixture of compost and 5% or 20% (w/w) of fine-textured soil. Two additional treatments included sandy soil amended with only the fine-textured soil at rates similar to those added with compost. Soil, compost, and fine-textured soil were mixed and packed to a bulk density of 1.22 g cm–3. Soil respiration was measured over 23 days. On days 1, 5, and 23, the soils were leached with 50 mL reverse-osmosis water, and the following parameters were measured in the leachate: water-soluble organic carbon (OC), inorganic nitrogen (N), and phosphorus (P); water-soluble OC and available N and P were measured in the soil after leaching. Compost increased nutrient availability and leaching compared with the non-amended control. Addition of the fine-textured soil to compost reduced cumulative respiration and N and P leaching, with the effect more pronounced at 20% (w/w). Addition of the fine-textured soil alone had no effect on nutrient availability and leaching because of the low nutrient concentration in this soil. This study showed that addition of fine-textured soil to compost can reduce N and P leaching, which could enhance and prolong the positive effects of compost on soil fertility.

Testing a Biofilter Cover Design to Mitigate Dairy Effluent Pond Methane Emissions

Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.

Compost Amendment to Sandy Soil Affects Soil Properties and Greenhouse Tomato Productivity

Sandy soils, with low productivity, could be improved by compost application to sustain crop production. This study aimed to examine the effect of three compost types (vegetable, fruit and yard waste compost, garden waste compost, and spent mushroom compost) on basic properties of a loamy sand and greenhouse tomato productivity. Disturbed and intact soil samples were taken from a decade-long compost field experiment on loamy sand with three compost types at application rate of 30 m3 ha−1 yr−1 (7.5 ton ha−1 yr−1). The soils were characterized for chemical and physical properties. Tomato was planted in a greenhouse using soil samples from the field and vegetative and yield parameters (plant height, stem diameter, leaf number, and fruit yield), water productivity, and harvest index were evaluated. All compost types significantly increased soil total carbon, total nitrogen, pH, electrical conductivity and significantly decreased bulk density, with no effect on plant available water compared to the control. Fresh and dry fruit weights were significantly increased after compost addition. Plant height, leaf number, stem diameter, and total biomass did not significantly improve after compost addition. Spent mushroom compost had greater effect in improving tomato productivity. A decade-long application of composts on loamy sand improved basic chemical and physical properties which were reflected in increased fruit yield in tomato. Since no negative effect of compost was observed, we suggest that sandy soils may serve as a safe end use option for these composts and potentially support crop growth.