Suppressiveness of 18 composts against 7 pathosystems: Variability in pathogen response

Compost is often reported as a substrate that is able to suppress soilborne plant pathogens, but suppression varies according to the type of compost and pathosystem. Reports often deal with a single pathogen while in reality crops are attacked by multiple plant pathogens. The goal of the present study was to evaluate the disease suppression ability of a wide range of composts for a range of plant pathogens. This study was conducted by a consortium of researchers from several European countries. Composts originated from different countries and source materials including green and yard waste, straw, bark, biowaste and municipal sewage. Suppressiveness of compost-amended (20% vol./vol.) peat-based potting soil was determined against Verticillium dahliae on eggplant, Rhizoctonia solani on cauliflower, Phytophthora nicotianae on tomato, Phytophthora cinnamomi on lupin and Cylindrocladium spathiphylli on Spathiphyllum sp., and of compost-amended loamy soil (20% vol./vol.) against R. solani on Pinus sylvestris and Fusarium oxysporum f. sp. lini on flax. From the 120 bioassays involving 18 composts and 7 pathosystems, significant disease suppression was found in 54% of the cases while only 3% of the cases showed significant disease enhancement. Pathogens were affected differently by the composts. In general, prediction of disease suppression was better when parameters derived from the compost mixes were used rather than those derived from the pure composts. Regression analyses of disease suppression of the individual pathogens with parameters of compost-amended peat-based mixes revealed the following groupings: (1) competition-sensitive: F. oxysporum and R. solani/cauliflower; (2) rhizosphere-affected: V. dahliae; (3) pH-related: P. nicotianae; and (4) specific/unknown: R. solani/pine, P. cinnamomi and C. spathiphylli. It was concluded that application of compost has in general a positive or no effect on disease suppression, and only rarely a disease stimulating effect.     

Microbial enrichment to enhance the disease suppressive activity of compost

Compost amended soil has been found to be suppressive against plant diseases in various cropping systems. The level and reproducibility of disease suppressive properties of compost might be increased by the addition of antagonists. In the present study, the establishment and suppressive activity of two fungal antagonists of soil-borne diseases was evaluated after their inoculation in potting soil and in compost produced from different types of organic waste and at different maturation stages. The fungal antagonists Verticillium biguttatum, a mycoparasite of Rhizoctonia solani, and a non-pathogenic isolate of Fusarium oxysporum antagonistic to fusarium wilt, survived at high levels (10³–10⁵ CFU g^–1) after 3 months incubation at room temperature in green waste compost and in potting soil. Their populations faded out in the organic household waste compost, especially in the matured product. In bioassays with R. solani on sugar beet and potato, the disease suppressiveness of compost increased or was similar after enrichment with V. biguttatum. The largest effects, however, were present in potting soil, which was very conducive for the disease as well as the antagonist. Similar results were found in the bioassay with F. oxysporum in carnation where enrichment with the antagonistic F. oxysporum had a positive or neutral effect. We foresee great potential for the application of antagonists in agriculture and horticulture through enrichment of compost or potting soil with antagonists or other beneficial micro-organisms.     

Effect of Compost Properties on Progress Rate of Verticillium dahliae Attack on Eggplant (Solanum melongena L.)

Several composts were tested for their capacity to moderate the effect of Verticillium dahliae Kleb. (VCG B4, VD) on eggplant (Solanum melongena) under greenhouse conditions. Eggplants plantlets were inoculated by immersing their roots in conidial suspension and then planted in pots filled with mixtures of compost or peat moss, mixed with perlite. Six composts and peat moss mixtures were tested, of which tomato waste compost suppressed V. dahliae, and turkey litter compost partially suppressed it. Reduced levels of symptoms and lower fungal colonization were detected in the xylem of eggplants planted in tomato waste compost, and these plants accumulated more dry matter and had higher chlorophyll content compared to other media. However, survival of conidia in tomato waste compost showed only a moderate decrease compared with a sharp decrease in other media, suggesting that conidial eradication cannot be proposed as the suppressiveness mechanism. γ irradiation of tomato waste compost and peat at 2.5 Mrad reduced microorganism density by four orders of magnitude, but irradiation of tomato waste compost did not reduce its suppressiveness of V. dahliae. Composts properties affected progress rate of VD in the xylem tissue of eggplant seedling. These properties could indicate both biotic and abiotic factors affecting the process.     

Maturity indices for composted dairy and pig manures

Bulking agents and bedding materials used on farms for composting manures affect the time required for composts to mature. The effects of these materials on guidelines for the use of composted manures in potting mixes are not fully known. Several chemical and biological compost characteristics were mentioned and a cucumber plant growth greenhouse bioassay was performed on samples removed from windrows during composting of: (i) dairy manure amended with wheat straw; (ii) dairy manure amended with sawdust (mostly Quercus spp.); and (iii) pig manure amended with sawdust and shredded wood (mostly Quercus spp.). Dry weights of cucumber seedlings grown in fertilized and unfertilized potting mixes amended with composts (30%, v/v) having stability values of <1 mg CO₂-C g^-1 dw d⁻¹, did not differ significantly from those in a control peat mix. Only the most mature dairy manure-wheat straw compost samples consistently established sufficient N concentrations in cucumber shoots in unfertilized treatments. For the dairy manure-wheat straw compost, all possible subset regression analyses of compost characteristics versus cucumber plant dry weight revealed that any of several compost characteristics (electrical conductivity-EC, compost age, total N, organic C, C-to-N ratio, ash content, CO₂ respirometry, Solvita CO₂ index and the Solvita^® Compost Maturity Index) predicted growth of cucumber in the unfertilized treatments, and thus maturity. In contrast, at least two characteristics of the dairy manure-sawdust compost were required to predict growth of cucumber in the unfertilized treatments. Effective combinations were EC with compost age and the Solvita^® maturity index with total N. Even five compost characteristics did not satisfactorily predict growth of cucumber in the non-fertilized pig manure-wood compost. Nutrient analysis of cucumber shoots indicated N availability was the principal factor limiting growth in potting mixes amended with the dairy manure-sawdust compost, and even more so in the pig manure-wood compost even though the compost had been stabilized to a high degree (<1 mg CO₂-C g⁻¹ dw d⁻¹). Maturity of the composted manures, which implies a positive initial plant growth response of plants grown without fertilization, could not be predicted by compost characteristics alone unless the bulking agent or bedding type used for the production of the composts was also considered.     

Systemic Resistance Induced in Cucumber Against Pythium Root Rot by Source Separated Household Waste And Yard Trimmings Composts

Disease control with compost often is attributed to four factors including competition, antibiosis, parasitism and induced systemic resistance (ISR). Induction of systemic resistance by source separated household waste and yard trimmings compost against Pythium root rot of cucumber caused by Pythium ultimum was studied in a split-root bioassay. Split-root pairings were tested in root rot potting soil paired with potting soil, compost-amended potting soil suppressive to root rot paired with the potting soil, and compost-amended potting soil paired with the compost-amended potting soil. Only one side of the split roots was infested with P. ultimum. Root rot, based on dry and fresh root weights, was significantly reduced in split roots of plants produced in the conducive infested potting soil paired with the suppressive yard trimmings compost-amended mix. This suggested that systemic effects were induced in the roots by the suppressive compost against Pythium root rot. Growth of transplants germinated in the source separated household waste compost mix was significantly better than those germinated in the potting soil. Finally, root rot of plants germinated in the suppressive mix and then transplanted into the conducive mix was also significantly less severe than that of plants germinated in the conducive mix.     

Re-establishment of suppressiveness to soil- and air-borne diseases by re-inoculation of soil microbial communities

The aim of this study was to investigate the potentials and limitations in restoring soil suppressiveness in disturbed soils. Soils from three sites in UK and Switzerland (STC, REC, THE) differing in their level of suppressiveness to soil-borne and air-borne diseases were γ-irradiated and this soil matrix was re-inoculated with 1% (w/w) of either parent native soil or native soil from the other sites (‘soil inoculum’). Suppressiveness to air-borne and soil-borne diseases was quantified by means of the host-pathogen systems Lepidium sativum (cress)-Pythium ultimum, an oomycete causing root rot and seedling damping-off, and Arabidopsis thaliana-Hyaloperonospora parasitica, an oomycete causing downy mildew. Soil microbial biomass, activity and community structure, as determined by phospholipid fatty acid (PLFA) profiles, were measured in native, γ-irradiated, and re-inoculated soils. Both, L. sativum and A. thaliana were highly susceptible to the pathogens if grown on γ-irradiated soils. Re-inoculation completely restored suppressiveness of soils to the foliar pathogen H. parasitica, independently of soil matrix or soil inoculum, whereas suppressiveness to P. ultimum depended on the soil matrix and, to a lesser extent, on the soil inoculum. However, the soil with the highest inherent suppressiveness did not reach the initial level of suppressiveness after re-inoculation. In addition, native microbial populations as defined by microbial biomass, activity and community structure, could not be fully restored in re-inoculated soils. As for suppressiveness to P. ultimum, the soil matrix, rather than the source of soil inoculum was identified as the key factor for re-establishing the microbial community structure. Our data show that soils do not or only slowly fully recover from sterilisation by γ-irradiation, indicating that agricultural soil management practices such as soil fumigation or heat treatments frequently used in vegetable cropping should be avoided.     

Effect of Compost Age and Concentration Of Pig Slurry on Plant Growth

Shredded straw of Miscanthus ogiformis Honda ‘Giganteus’ was composted with addition of water or aqueous solutions with 3, 10, 30 or 100% pig slurry. After 3, 6, 9, 12 and 15 months of composting the composts were tested as pot plant growth substrates for Hedera helix L. in comparison with enriched and nonenriched peat substrates. During the first week of composting temperatures rose to higher levels with stronger pig slurry solution except for the compost made with 100% pig slurry solution which suffered from oxygen depletion. Plants grown in compost substrates made with M. ogiformis and 10 or 30% pig slurry solution produced the same shoot lengths and dry matter as plants grown in enriched or nonenriched peat substrates. Plants in compost substrates made with water or 3% pig slurry solution produced slightly shorter shoots and less dry matter. Many plants in the compost substrate made with 100% pig slurry solution failed to grow, and for the remaining plants in that treatment, shoot and dry matter production was very low at all five ages of compost. Nutrient concentrations were suboptimal for compost substrates made with water or 3% pig slurry solution, near optimal with 10% pig slurry solution, above recommended concentrations with 30% pig slurry solution and supraoptimal with 100% pig slurry solution. The pig slurry concentration had little effect on water retention in 6 months old compost substrates while in older compost substrates increasing pig slurry concentration increased the water retention capacity. In six month old compost substrates water retention was lower than in peat substrates while in 12 months old composts the water retention was greater in the compost substrates than in the peat substrates. Total porosity was above 92% and similar for all substrates. Air volume was greater in compost substrates than in peat substrates. It is concluded that compost substrates made of Miscanthus ogiformis straw and diluted pig slurry can be used successfully as a substitute for peat substrates. An aqueous solution of 10 to 30% pig slurry solution added as nitrogen source before composting is optimal. Three months of composting is sufficient for optimal plant growth.     

Response of soil microbial communities to compost amendments

Soil organic matter is considered as a major component of soil quality because it contributes directly or indirectly to many physical, chemical and biological properties. Thus, soil amendment with composts is an agricultural practice commonly used to improve soil quality and also to manage organic wastes. We evaluated in laboratory scale experiments the response of the soilborne microflora to the newly created soil environments resulting from the addition of three different composts in two different agricultural soils under controlled conditions. At a global level, total microbial densities were determined by classical plate count methods and global microbial activities were assessed by measuring basal respiration and substrate induced respiration (SIR). Soil suppressiveness to Rhizoctonia solani diseases was measured through bioassays performed in greenhouses. At a community level, the modifications of the metabolic and molecular structures of bacterial and fungal communities were assessed. Bacterial community level physiological profiles (CLPP) were determined using Biolog™ GN microtiter plates. Bacterial and fungal community structures were investigated using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting. Data sets were analyzed using analysis of variance and ordination methods of multivariate data. The impact of organic amendments on soil characteristics differed with the nature of the composts and the soil types. French and English spent mushroom composts altered all the biological parameters evaluated in the clayey soil and/or in the sandy silty clay soil, while green waste compost did not modify either bacterial and fungal densities, SIR values nor soil suppressiveness in any of the soils. The changes in bacterial T-RFLP fingerprints caused by compost amendments were not related to the changes in CLPP, suggesting the functional redundancy of soil microorganisms. Assessing the density, the activity and the structure of the soil microflora allowed us not only to detect the impact of compost amendment on soil microorganisms, but also to evaluate its effect at a functional level through the variation of soil disease suppressiveness. Differences in disease suppressiveness were related to differences in chemical composition, in availability of nutrients at short term and in microbial composition due to both incorporation and stimulation of microorganisms by the compost amendments.     

Tomato Fusarium wilt suppressiveness. The relationship between the organic plant growth media and their microbial communities as characterised by Biolog

Fusarium wilts are economically important diseases for which there are no effective chemical control measures. Biological control strategies are becoming efficient alternatives for controlling this disease. The suppressiveness to Fusarium oxysporum f. sp. lycopersici race 1 of grape marc compost and cork compost was evaluated in comparison to peat by using a susceptible cultivar of tomato (Lycopersicon esculentum cv. Marmande). Based on community level physiological profiles, different community structures were evident among the plant growth media evaluated. The peat microbial community, growth medium conducive to wilt, used mostly sugars, while those associated with both composts, the very suppressive grape marc and the moderately suppressive cork, used mostly carboxylic acids, amino acids, amines, phenolic compounds and polymers.     

Microbial recolonization and suppression of Rhizoctonia solani in a bedding-plant potting mix amended with recycled mix before aerated-steam treatment

Summary Some South Australian bedding-plant nurseries add recycled potting mix to fresh potting mix before aerated-steam treatment in an attempt to decrease fungal root diseases. To test the hypothesis that this addition of recycled potting mix affects microbial colonization and, consequently, the disease-suppressiveness of mixes treated with aerated steam, recycled potting mix was added to or withheld from fresh potting mix. The mixes were then treated with aerated steam at 60°C for 35 min or not treated. Their recolonization by actinomycetes, heat-resistant organisms, pseudomonads, and fungi was followed for 25 days. The addition of recycled potting mix frequently increased the numbers of actinomycetes and heat-resistant microbes recovered from the mixes, whether treated with steam or not, but decreased the numbers of aerobic bacteria. Fungal populations were rarely influenced by the addition of recycled potting mix. Pseudomonad populations dropped to undetectable levels after the aerated-steam treatment and failed to reach levels comparable to those in treatments without steam during the next 25 days. Organisms from each group were tested for in vitro antagonism to Rhizoctonia solani Kühn (AG-8). The proportion of inhibitory organisms varied with the microbial group, the mix treatment, and the time since mix treatment. Where aerated-steam treatment was applied, the addition of recycled potting mix rarely affected the development of Rhizoctonia disease symptoms on seedlings of Celosia argentea. The potential for improving the suppressiveness of aerated-steam-treated nursery mixes via microbial inoculation is discussed.     

Comparative Study on Biowaste Definition: Effects on Biowaste Collection,Composting Process and Compost Quality

A comparative study was run during 13 months on two biowaste definitions involving both lab tests and field surveys. A narrow biowaste definition, allowing only biogenic wastes (kitchen and garden waste) and referred to as ‘Biowaste,’ was compared to a broad biowaste definition, referred to as ‘Biowaste Plus’ and including man-made products, such as nonrecyclable wastepaper and diapers. Two similar test areas, each with about 425 inhabitants, were defined in a semiurban area north of Antwerp. During the entire test period, the amount of curbside waste (i.e., biowaste and restwaste or ‘grey waste’), was continuously measured and analyzed regularly (twice per season) for composition. At the start, middle and end of the test, the population of each test area was surveyed. Bench-scale aerobic composting experiments were run to evaluate the influence of both biowaste definitions on the composting process and the compost end product.

The introduction of source separated waste collection resulted in an overall landfill diversion rate of 43 percent for the (narrow) ‘Biowaste’ definition and 46 percent for the (broad) ‘Biowaste Plus’ definition. The contamination of biowaste with restwaste was low for both definitions (about three percent). Assuming that the collection and the appropriate disposal of organics could be improved to 95 percent efficiency (compared to about 60 percent currently), the landfill diversion rate could be increased to 59 percent for the ‘Biowaste’ and 74 percent for the ‘Biowaste Plus’ definition. Whereas the average sorting efficiency of separately collected organics was about 61 percent; 49 percent for nonrecyclable paper; and as low as 20 percent for certain categories of nonrecyclable paper (e.g., nonrecyclable cardboard packages). Apparently more education or a better systém of recognition and identification is needed to improve the collection efficiency of man-made compostables. Indeed, for easily recognizable products such as diapers, the sorting efficiency was as high as 70 percent.

The acceptance and goodwill of the population was significantly higher for the ‘Biowaste Plus’ definition, especially in the summer months. The yearly, overall composition of the total curbside waste (biowaste and restwaste combined) was 17 percent kitchen organics, 47 percent yard waste, four percent recyclable paper, 13 percent nonrecyclable paper and 19 percent noncompostables. It must be mentioned that glass, paper and large yard waste were collected separately by a voluntary bring-system. Biowaste Plus typically contained 16.0 percent paper (of which 2.9 percent was recyclable) versus 2.0 percent for Biowaste (0.3 percent recyclable).

The ‘Biowaste Plus’ definition resulted in improvements for the aerobic composting process due to easier moisture control, better aeration and a more tempered pH evolution. A significant difference was seen for NH₃ and corresponding odor emission, both being much lower with ‘Biowaste Plus.’ The quality of the compost produced was similar and acceptable for both biowaste definitions, according to existing standards (VLACO in Flanders and RAL in Germany).     

添加不同辅料对污泥堆肥腐熟度及气体排放的影响

选择玉米秸秆和木本泥炭两种辅料添加至脱水污泥中进行联合好氧堆肥,研究了秸秆和木本泥炭作为添加剂对污泥堆肥腐熟度和堆肥过程中气体排放(NH_3、CH_4和N_2O)的影响。两种辅料添加量均为初始物料的15%,堆肥在60 L的密闭反应器中共持续35 d。研究结果表明,秸秆作为添加剂与污泥联合堆肥,堆肥产品可以达到卫生标准和腐熟标准。添加秸秆处理整个堆肥过程中累积NH_3、CH_4和N_2O排放量分别为2.2、0.14和0.09 g/kg,NH_3和CH_4排放主要发生在堆肥的升温期和高温期,N_2O排放主要发生在堆肥的后腐熟阶段。添加木本泥炭作为添加剂不能成功启动堆肥,整个堆置过程中未检测到NH_3和CH_4排放,但是在堆肥前期有大量N_2O产生。对于添加秸秆的处理,CH_4、N_2O和NH_3对总温室气体排放的贡献率分别为45%,36%和19%,CH_4所占比重最高。     

粉煤灰和钢渣处理多种金属污染的酸性土壤，金属有效性的衰减研究

The objectives of this work were to determine the potential mineralization of various organic pollutants that are likely found in compostable materials during composting, and to evaluate the participation of the microflora of the thermophilic and maturation composting phases in pollutant mineralization. Four composts were used: a biowaste compost (BioW), a municipal solid waste compost (MSW), a green waste compost (GW) and a co-compost of green waste and sludge (GW+S). In each composting plant, two samples were withdrawn: one in the thermophilic phase (fresh compost) and one in the maturation phase (mature compost) to have the microflora of thermophilic and maturation phases active, respectively. The mineralization of 5 organic pollutants, 3 polycyclic aromatic hydrocarbons (PAHs) (i.e., phenanthrene, fluoranthene and benzo(a)pyrene), 1 herbicide (dicamba) and 1 polychlorinated biphenyl (PCB, congener 52), was measured in a laboratory setting during incubations at 60 ℃ in fresh composts and at 28 ℃ in mature composts. All molecules were 14 C-labeled, which allowed the mineralization of the molecules to be measured by trapping of produced 14CO2 in NaOH. Their volatilization was also measured by trapping molecules on glass wool impregnated with paraffin oil. Mineralization of the organic molecules was only observed when the maturation microflora was present in the mature composts or when it was inoculated into the fresh compost. Phenanthrene mineralization of up to 60% in the fresh GW+S compost was the only exception. Mineralization of PAH decreased when the complexity of the PAH molecules increased. Mineralization of phenanthrene and fluoranthene reached 50%-70% in all mature composts. Benzo(a)pyrene was mineralized (30%) only in the MSW mature compost. Dicamba was moderately mineralized (30%-40%). Finally, no PCB mineralization was detected, but 20% of the PCB had volatilized after 12 d at 60 ℃. No clear difference was observed in the degrading capacity of the different composts, and the major difference was the larger mineralizing capacity of the maturation microflora compared with the thermophilic microflora.     

Horticultural Characteristics Of Licorice Waste Compost

Licorice (Glycyrrhiza glabra L.) is a leguminous herbaceous perennial. Its root extracts are commonly used for medicinal uses and as a flavoring agent in the food and tobacco industries. After extraction, about 10,000 tones of licorice root residues are accumulated in Israel annually with no recycling outlet. The objectives of the current research were to develop a reliable protocol for licorice root wastes composting, to test the use of licorice compost as a peat substitute in growing media and to study its suppressiveness against Fusarium oxysporum f. sp. melonis (FOM) – the causal agent of Fusarium wilt of melon (Cucumis melo L.). Licorice root wastes were cocomposted using temperature controlled forced aeration with the coarse fraction of separated cow manure, in order to enrich both its nutrients content and microbial population. Thermophilic conditions prevailed in the pile for 90 days and the compost stabilized and reached ambient temperature 110 days from start. The physical characteristics of the resulted compost were comparable to that of peat. Nutrient content was high and salinity was relatively low. No phytotoxicity was found in the compost extract, based on the cress germination test. Tomato plants grown in compost showed enhanced development as compared to peat. The number of surviving FOM spores incubated in the compost declined faster then in peat. Fusarium infested melon plants survived much better if planted in the licorice compost, as compared to peat. It is concluded that licorice compost can serve as a peat substitute with preferable qualities.     

Poultry Residual Composts: Materials Balance and Crop Response

This paper discusses compost production yields as a percent of raw product mix using poultry litter, poultry processing plant dissolved air flotation skimmings, sawdust, wood chips and ground yard debris. Three different mixes were used and identified as Mixes 1, 2 and 3. Mixes 1 and 2 were produced using windrows and a windrow turner and Mix 3 was made using a covered in-channel compost turner. Mixes 1 and 2 were poultry litter compost with a screened mass yield of 80 and 77 percent, respectively. Mix 3 was a dissolved air flotation compost with a screened mass yield of 40 percent. Results from plant experiments show poultry litter compost can be used successfully in potting mixes for poinsettia and chrysanthemum production. A compost produced from dissolved air flotation skimmings, a poultry processing waste, can be used in field corn production but had little influence in the production of soybeans.     

Storage method affects disease suppression of flax wilt induced by composts

Compost can have a disease suppressive effect, but compost research is constrained by the fact that repetition of experiments with a similar batch of compost is impossible, since storage affects the organic material including the microbial communities. The objective of this study was to test the hypothesis that differential changes in microbial community structure and associated microbial activities after various storage methods (drying, freezing and cooling) lead to differential changes in the disease suppressive ability of compost material with respect to Fusarium oxysporum f. sp. lini induced by mixes of composts with peat substrate (20/80%, vol./vol.). A significant (P<0.0001) storage method × compost interaction was found with respect to suppression of Fusarium wilt of flax, indicating that the effect of storage type on disease suppression is compost-dependent. For seven composts storage had no (13 cases) or a significantly positive effect (eight cases) on disease suppression and for 1 compost there was a significant negative effect of storage on disease suppression. Significant changes in microbial activity and 16S-rDNA DGGE banding patterns of the composts were observed as a result of all tested ways of storage and these changes could be related to changes in disease suppression: relatively strong changes in microbial activity and bacterial composition due to storage had a relatively strong effect on disease suppression. The cool storage treatment (4 °C) resulted in the least deviation in disease suppression from the fresh compost, although the freezing treatment gave the most reliable results with the lowest standard deviation.     

Effects of Compost Source and Timing of Fertigation Initiation on Growth of Potted Poinsettia

Treatment combinations of four poinsettia (Euphorbia pulcherrima) cultivars, 20 substrates, and three fertigation treatments were evaluated in a completely randomized block design. Poinsettia cultivars included ‘V-14 Glory’, ‘Red Sails’, ‘Lilo Pink’, and ‘Annette Hegg Top White’. The compost substrates were compost:peat:perlite blended (by vol.) at 2:3:3, 1:1:1, and 2:1:1 ratios. Sunshine Mix 1 and Pro Gro 300S were used as controls. Composts tested were those prepared from crab offal, lime and polymer-dewatered biosolids, municipal solid waste (MSW), yard waste, and poultry litter. Fertigation treatments were initiated on the week of potting, delayed one or two week after potting and applied once per week. Controls produced premium quality plants. Composts prepared from poultry litter, yard waste, polymer-dewatered biosolids, crab offal, and MSW produced good quality plants. Plant width in 25 percent compost treatments were greater than those in 50 percent compost treatments. Total number of branches, plant height, canopy diameter, and plant grade on plants treated with fertilizer on the first week were only three percent greater than in treatments where fertilizer application was delayed one or two weeks.     

Microbial community shifts in Pythium ultimum-inoculated suppressive substrates

In this study, the role of compost amendments for the biocontrol of Pythium ultimum was evaluated in bioassays with cucumber (Cucumis sativa L. variety “Chinesische Schlangen”). The addition of compost to the peat-based growing substrates resulted in a significant reduction of disease symptoms of cucumber plants in the presence of P. ultimum compared to pure substrate. Microbial community composition of compost-amended substrates and with different levels of P. ultimum inoculum (0, 5‰) was analyzed by polymerase-chain-reaction-based techniques. To detect and compare dominant bacterial and fungal representatives of suppressive substrate mixes with different pathogen inoculum, 16S and 18S rRNA clone libraries were established. Phylogenetic analysis of the 16S rRNA clones revealed Actinobacteria and α-Proteobacteria to be the prominent classes in the presence of P. ultimum, which are not part of the dominant microflora in the mixes without the pathogen. 18S rRNA sequences for the Pythium-inoculated compost supplemented samples were dominated by Chytridiomycota and Sordariomycetes, whereas in uncontaminated soil–compost mixes, a large part of the sequences were related to Homobasidiomycetes. Thus, it is assumed that the presence of P. ultimum induces distinct shifts in microbial communities favoring to groups known to comprise potential biocontrol agents.     

木本泥炭添加比例对猪粪堆肥腐熟度和污染及温室气体排放的影响

针对当前猪粪好氧堆肥过程中存在的腐熟度低、氮素损失严重、污染气体排放量大等问题,该研究以木本泥炭作为添加剂与猪粪进行联合堆肥,研究了不同木本泥炭添加量(添加比例依次为占物料湿基质量的5%、10%、15%和20%的4个处理)对猪粪好氧堆肥产品腐熟度和堆肥过程中CH4、NH3和H2S等污染气体排放变化的影响。结果表明:在猪粪堆肥中添加木本泥炭作为调理材料,堆体可成功启动升温,在第2~4天堆体可进入高温期,并持续7 d以上,达到无害化卫生标准;经28 d好氧堆肥以后,堆肥产品p H值为8.0左右,电导率值为1.47~1.82 m S/cm,发芽指数均大于80%,达到腐熟标准;木本泥炭添加量增加至15%以上时,有机质分解程度高,物料干质量降解率达22%左右,28 d堆体含水率下降35%左右,CH4、NH3和H2S排放量分别减少82.12%~89.48%、53.47%~63.31%、50.98%~62.76%,总温室气体排放当量减少70.34%~83.26%,堆体总氮损失减少率达44%~63%,保氮效果显著。因此,建议木本泥炭用作猪粪堆肥添加剂的最优添加量为15%~20%(以物料总湿重计)。     

碳源调理剂对黄瓜秧堆肥进程和碳氮养分损失的影响

由于中国蔬菜产地的黄瓜秧无害化处理与循环利用缺乏针对性的使用技术,这类废弃资源多成为当地的环境污染源。该文以黄瓜秧为原料(空白对照,CK)进行高温好氧堆肥,并在此基础上设置2组处理,即把玉米秸秆(CS)和木本泥炭(WP)作为辅助碳源调理剂,按照C/N比为25添加到物料中。通过对比分析不同处理的CO2和氨气的排放速率和累积量、物料损失率、有机质含量、p H值、电导率(EC)、发芽指数等指标,研究外加碳源对黄瓜秧堆肥过程和碳氮氧分损失的影响,以期实现对黄瓜秧堆肥化进程进行工艺优化,并降低碳氮元素以气态形式的损失,进而减少温室气体排放。结果表明:玉米秸秆和木本泥炭作为外加碳源调理剂,可以减少物料损失量,加速堆肥腐熟进程,其中尤以玉米秸秆效果更佳。但是,玉米秸秆的添加会增加整个堆肥过程中有机质的降解和CO2的排放强度,提高累积排放量(100g/kg),而木本泥炭会减少有机质的降解总量和CO2的累积排放量(77g/kg);玉米秸秆和木本泥炭都有利于控制堆肥过程中氨气的排放,且作用时间和机理不同。综合考虑堆肥进程和气体损失,木本泥炭作为碳源调理剂的改良效果更优于秸秆,应进一步研究两者联合使用的效果。