Garden Compost Research Articles

Adaptation of the Biobed Composition for Chlorpyrifos Degradation to Southern Europe Conditions

Biobeds developed in Sweden bind and degrade pesticides from point sources. The objective of this work was to adapt the biobed to Italian operating conditions, for example, to identify organic materials as effective as those in the original Swedish composition. The capacity of urban and garden composts alone or mixed with citrus peel or straw to degrade chlorpyrifos and its metabolite TCP was compared to the typical Swedish biomix consisting of straw, peat, and soil. A tendency for higher 14C-chlorpyrifos mineralization and lower TCP levels was observed in the biomixes with garden compost alone or amended with straw. In a second trial, a high correlation of lower TCP with increasing levels of straw in typical Swedish biomixes was observed. Straw stimulates production of lignin-degrading enzymes such as manganese peroxidase (MnP), and further trials with pure MnP showed that this enzyme degrades TCP. Materials with an active lignin-degrading microflora are a prerequisite for effective dissipation of chlorpyrifos and non-accumulation of TCP. Thus, lignocellulosic materials as straw and garden composts should be present in biomixes to be used under Italian conditions.

Structural and developmental studies of Chlamydomyzium oviparasiticum from Rhabditis nematodes and in culture

The oomycete ( Peronosporomycete) Chlamydomyzium oviparasiticum, previously recorded as a parasite of rotifer eggs, was found infecting Rhabditis nematodes in a sample of rotting garden compost. For the first time C. oviparasiticum was cultured in liquid media, which enabled more detailed studies of zoospore behaviour and facilitated the use of confocal microscopy. Rhabditis nematodes were successfully re-infected from liquid-cultured inoculum. Light (including video) microscopy and transmission electron microscopy were used to document details of thallus development, zoospore release and resting spore morphology to enable comparison with other oomycete species. This species showed several significant saprolegnialian characters such as the ‘achlyoid’ pattern of spore formation, centrifugal cleavage and structured encystment vesicles. In contrast, spore release into a transient vesicle was a peronosporalean characteristic. The thick-walled resting spores showed relatively poor cytoplasmic preservation and had a thick multi-layered wall. It was still not possible to unequivocably decide whether these were chlamydospores or parthenogenically formed oospores. The phylogenetic significance of these observations is discussed.

The lipolytic activity of Thermomyces lanuginosus strains isolated from different natural sources

Abstract The ability of 144 Thermomyces lanuginosus wild strains isolated from biohumus, mushroom and garden composts, decayed leaves, hazelnuts, and raw coffee beans to hydrolyze synthetic (tributyrin, Tween 20, Tween 40, Tween 60, and Tween 80) and natural fatty substrates (sunflower, soybean, rapeseed and corn oil) was evaluated, and whether the lipolytic activity depended on the isolation source determined. All strains incubated at 55 °C on solid media containing 1% synthetic and 15% natural fatty substrates hydrolyzed both types of substrate. Mean lipolytic activity on natural substrates was significantly higher than on synthetic substrates. The highest mean activity index was noted after growth on sunflower oil, followed by soybean oil and tributyrin; indices on other fatty substrates were low. Strains isolated from raw coffee beans showed the highest mean index, followed by those from biohumus and garden compost; the lowest index being for strains isolated from hazelnuts. Thus, the lipolytic activity index depended on the specific fatty substrate and the source of the isolates.

In situ and in vitro suppressive effect of agricultural composts and their water extracts on some phytopathogenic fungi

In situ and in vitro experiments were carried out to determine the effect of various composts (leafy fruit compost (LFC), garden compost (GC), and crops compost (CC)) and their water extract on Pythium debaryanum, Fusarium oxysporum f.sp. lycopersici, Sclerotium bataticola. Compost water extract (CWE) of LFC, GC, and CC were found to contain Bacillus spp., Micrococcus spp., Staphylococcus spp. and Corynebacterium spp., and the fungi Aspergillus spp., Rhizopus spp., and Drechslera spp., and various Actinomycetes. In situ results indicated considerable decrease in fungal growth around the unautoclaved compost especially in the case of S. bataticola and F. oxysporum f.sp. lycopersici, compared to the autoclaved compost. In vitro tests showed that concentration of CWE at 5, 10 and 15% (v/v) suppressed the hyphal growth of S. bataticola by 83% using 5% CC and by 94.4% using 5% LFC or 10% GC, and F. oxysporum f.sp. lycopersici by 94.4% using either composts. CWE of GC decreased fungal dry weight of F. oxysporum f.sp. lycopersici by 97.7%, P. debaryanum by 92.8%, and S. bataticola by 84.4%; CC decreased F. oxysporum f.sp. lycopersici by 94%, P. debaryanum by 86.2%, and S. bataticola by 63.3%, while CWE of LFC was the least effective against the tested fungi. CWE produced clear inhibition zones against all the tested fungi. Microflora found in CWE have an important role in suppressing the growth of tested fungi. CWE contained neither antibiotics nor siderophores. The presence of protease, chitinase, lipase and β-1,3 glucanase (lysogenic enzymes) in CWE indicates a possible role in fungal degradation.

Extremes of rubbish

Extremophile bacteria found in hot springs might one day provide the basis for high-tech garden compost. Such bacterial fermentation could digest all sorts of rubbish under the right conditions.

The effect of aging biosolids on the availability of cadmium and zinc in soil

SummaryA major concern with the safe re‐use of biosolids on land is the potential for release of metals from organic matter in the biosolids, due to decomposition proceeding as biosolids age. To quantify the effects of biosolid aging on Cd and Zn bioavailability, two sewage sludges (Lagoon sludge and Filtered sludge) and a garden compost were incubated at 25°C and 35°C for 100 days. Changes in availability of Cd and Zn were determined using isotope dilution principles, with the materials being labelled with carrier‐free 109Cd and 65Zn. We determined isotopically exchangeable metal pools (E values) and plant available metal pools (L values) by measuring specific activities of Cd and Zn in soil extracts and in wheat plants, respectively. Changes in carbon content over time were determined using 13C‐NMR spectroscopy and chemical extraction methods, and related to changes in availability of metal pools as determined by isotopic procedures.Hot‐water‐extractable carbon content, assumed to represent easily decomposable organic matter, decreased during the 100 days by 80–190 mg kg−1. The Compost and Lagoon sludge showed no change in L values for Cd or Zn with time, but in the Filtered sludge the L values for Cd and Zn increased significantly, by 43% and 56%, respectively. The isotopically exchangeable pools of Cd and Zn did not change with incubation treatment of the biosolids.These data indicate that the potential for metal release from biosolids as organic matter decomposes depends to a large extent on the biosolid composition.

EVALUATION OF ORGANIC LANDSCAPE MULCHES: COMPOSITION AND NUTRIENT RELEASE CHARACTERISTICS

Summary A 12 month field experiment was undertaken on a sandy loam soil to investigate nutrient content and nutrient release characteristics of six organic landscape mulches; cocoa shells, coarse conifer bark chips, wood chips, garden compost, horse manure and finely ground conifer bark. Comparisons were made against black polythene mulch and a bare earth control. Mulch treatments were applied to bare soil plots, left for 12 months and then cleared before sowing a crop of agricultural mustard (Sinapis alba L.). Soil analysis was carried out at the start and end of the experiment, fresh and dry masses of the aerial portion of the mustard crop were determined and their nutrient contents assessed. Initial mulch pH was not a good indicator of how that mulch would affect the underlying soil pH over time. After 12 months the organic mulches had either no significant effect on soil pH or increased it slightly relative to unamended soil. In contrast, initial nutrient content of the organic mulches proved to be a useful indicator of their impact on available nutrient levels in the soil and of their relative benefits to plant growth. Horse manure, garden compost and cocoa shell mulches, with low C:N ratios and high potassium content resulted in significant increases in soil nutrients and supported the highest yields. After twelve months, no evidence of nitrogen immobilisation or growth suppression under the wood or bark-based mulches was observed. None of the mulches had a significant effect on the underlying soil organic matter content during the experiment.

Nitrogen transfer from grey municipal solid waste to high quality compost

Ammonia was transferred from an anaerobically digested mixed waste at high pH (due to addition of 10% CaO) to an actively nitrifying, high quality mature vegetable–fruit–garden compost. After 5 days indirect contact with the anaerobic compost, by laying a sieve in-between the two materials, the recipient aerobic compost exhibited a rapid increase in NH 4 +–N concentration, followed by a subsequent decrease due to nitrification. The nitrifying activity (ammonium oxidation rate) was 94 mg NO 2 −-N/kg DW·d in the treated aerobic compost. In the non-treated aerobic compost, the activity was 22 mg NO 2 −-N/kg DW·d. The treated aerobic compost contained 967 mg NO 3 −-N/kg DW. In the control aerobic compost, the amount was 291 mg NO 3 −-N/kg-DW. The treated aerobic compost can serve as a readily available N source to ensure rapid crop development. This methodology increases the agricultural value of the compost for areas where industrial fertilisers may not be advisable or available.

Effect of Soluble Nutrient Content in Wood on its Susceptibility to Soft Rot and Bacterial Attack in Ground Test

Summary The objective of the study was to investigate whether soluble sugars and nitrogenous compounds in wood have an impact on susceptibility of wood to decay in ground contact, which is important in the field of test methodology and standardization. Kiln drying of Scots pine planks caused a distinct gradient of low-molecular weight (LMW) sugars and nitrogenous compounds in the 0–2 mm zone at the surface of the timber, whereas the deeper zones had constant and low contents of soluble substances. Strips, containing different content of soluble nutrients, were cut and exposed in two types of soil; the former one being rich in soft rot fungi, the latter one being rich in soft rot fungi and bacteria. The strips rich in nutrients showed an average of 16 % of mass loss whereas samples poorer in nutrients were less affected (8–9 %) after 120 days of exposure in the soil rich in soft rot fungi. A pure culture test with the soft rot fungus Phialophora mutabilis confirmed the above-mentioned observation. The result is in favour of taking samples with approximately equal content of soluble nutrients to decrease the variability of test results, e.g., mass losses. The garden compost, rich in both soft rot fungi and bacteria, caused severe mass loss (40–48 %) of the strips after 120 days of exposure. No difference in the mass losses of the samples was measured. The choice of test soil as well as the nutrient status of the samples can lead to completely different results and, consequently, conclusions.

Supercritical fluid extraction of chlorpyrifos and 3,5,6-trichloro-2-pyridinol from garden compost

A method was developed for the simultaneous supercritical carbon dioxide extraction of chlorpyrifos and its primary degradate, 3,5,6-trichloro-2-pyridinol (TCP), from garden compost. In situ derivatization with N,O-bis(trimethylsilyl)trifluoracetamide was necessary for extraction of TCP. Recoveries for TCP and chlorpyrifos were quantitative for spiked compost samples. Sodium chloride was used as the packing material in extractions with in situ derivatization. Optimum results were obtained for air-dried samples containing 4–7% moisture. No sample cleanup was required prior to analysis by GC–flame ionization detection. The effects of compost moisture content and ageing were investigated for chlorpyrifos recovery. No significantly negative effect on recovery for up to 20% (w/w) moisture for chlorpyrifos was observed. Effects of ageing showed a decrease in extraction efficiency over time with 52% recovery after 10 days.

An experimental ecological study of a garden compost heap

A quantitative survey of the fauna of a garden compost heap showed it to be similar to that of soil and leaf litter. The greatest biomasses of animals identified were earthworms, molluscs, and woodlice respectively. Animals were most abundant in the upper levels. The addition of various groups of animals to experimental composts allowed the direct estimation of their effect upon primary decomposition and of their role in the compost heap. Microbial populations played by far the greatest role in primary decomposition; earthworms and enchytraeids had smaller but significant roles. The addition of other animals had no significant effect.

Staining reactions for the detection of hemicellulose-degrading bacteria

The use of dye-polysaccharide interactions in visualizing zones of polymer hydrolysis has been used to facilitate the detection of hemicellulolytic activity. Grams iodine was particularly effective in confirming the degradation of hemicellulosic pentosans and some α-glucans, whereas Congo Red and Trypan Blue interacted strongly with the β-d-glucans tested. Organisms, selectively isolated from garden compost, that produced iodinevisualized zones of hydrolysis all possessed xylanase activity; this enzyme was not detected in the isolates that failed to produce hydrolysis zones. Post-incubation staining with Grams iodine will therefore expedite the detection and unambiguous enumeration of hemicellulolytic isolates on enrichment culture.

Staining reactions for the detection of hemicellulose-degrading bacteria

The use of dye-polysaccharide interactions in visualizing zones of polymer hydrolysis has been used to facilitate the detection of hemicellulolytic activity. Grams iodine was particularly effective in confirming the degradation of hemicellulosic pentosans and some α-glucans, whereas Congo Red and Trypan Blue interacted strongly with the β-d-glucans tested. Organisms, selectively isolated from garden compost, that produced iodinevisualized zones of hydrolysis all possessed xylanase activity; this enzyme was not detected in the isolates that failed to produce hydrolysis zones. Post-incubation staining with Grams iodine will therefore expedite the detection and unambiguous enumeration of hemicellulolytic isolates on enrichment culture.

Nitrite production by a thermophilic bacterium

Attempts to isolate thermophilic nitrifiers from two central Australian desert soils and two hot-house soils were unsuccessful. A suspected nitrifier isolated from garden compost was identified as B. stearothermophilus, and was later shown to have no nitrifying ability, but produced nitrite by the reduction of nitrate present in the compost.