Earthworm biomass and population structure are negatively associated with changes in organic residue nitrogen concentration during vermicomposting

Vermicomposting is an efficient and environmentally friendly technology to dispose of agricultural organic residues. The efficiency of organic residue decomposition during vermicomposting is directly affected by the biomass and population structure of earthworms. In this study, we investigated how the earthworm biomass and population structure responded to changes in the physicochemical properties of six types of organic residue (cattle dung, herbal waste, rice straw, soybean straw, garden waste, and tea residues) during vermicomposting. Each type of organic residues was placed in a pot with earthworms Eisenia fetida, and the physicochemical properties of the organic residues and earthworm growth dynamics were recorded at 0, 30, 60, and 90 d of vermicomposting. The biomass and population structure of earthworms were stable or increased in rice straw, garden waste, and cattle dung within 60 d of vermicomposting, whereas in tea residues and herb waste, very little earthworm activity (3 adults and 2 cocoons) was recorded on day 30. Among the physicochemical parameters, the substrate C/N ratio was negatively correlated with earthworm growth dynamics. Decomposing organic residues showed higher NH₄⁺-N and NH₃^--N concentrations but a lower total organic carbon content, which negatively affected earthworm growth and reproduction. We recommend that chemical properties of vermicomposting systems should be monitored regularly. At the threshold levels of decomposing organic residue NH₄⁺-N and NH₃^--N concentrations, earthworms should be removed and the vermicompost can be harvested. Small- and large-scale farmers thus need to monitor the physicochemical properties of vermicompost to sustain active earthworm populations.     

Effect of Woody Peat as an Additive on Maturity and Gaseous Emissions During Pig Manure Composting

Woody peat was used as an additive to compost with pig manure in 1.2 m³ composting reactors under aerobic conditions for a 77?days period to estimate the effect on the compost maturity and gaseous emissions (NH₃, N₂O, and CH₄). Pig manure was also composted with cornstalks (the traditional method) as a control treatment. The results showed that both cornstalks and woody peat composts reached the required maturity standard. Composting with woody peat as a bulking agent was found to reduced NH₃ emissions by 36% than the cornstalks amended treatment. Although CH₄ emission increased by adding woody peat, N₂O emission was considerably reduced, resulting in a slight decrease in total greenhouse gas emissions. More importantly, woody peat could reduce the losses of total carbon and total nitrogen, improve the compost quality as fertilizer.     

蚯蚓辅助堆肥处理蔬菜废弃物及其温室气体减排效果

蚯蚓辅助堆肥是近年兴起的处理有机废物的有效方法,为探明蚯蚓辅助堆肥法处理蔬菜废弃物的效果及其温室气体排放规律,该文以牛粪和新鲜番茄秧作为原料,在蚯蚓养殖场分别设置蚯蚓辅助堆肥和常规堆肥处理,对比研究了腐熟度指标变化和温室气体排放规律。结果表明:蚯蚓辅助堆肥堆垛温度较低,达不到无害化温度标准(50～55℃以上持续5～7d),但可满足蚯蚓生存需求,蚯蚓生物量在堆肥前期(0～10d)较低,为14.6×103～20.8×103条/m3,其后随着堆体温度的降低逐渐增长,至堆肥结束时达到90.2×103条/m3。综合pH值、电导率(EC)、碳氮比(C/N)、发芽率指数(GI)等腐熟度指标分析,蚯蚓辅助堆肥处理的腐熟度优于常规堆肥处理,并提前达到腐熟,堆肥周期缩短;蚯蚓辅助堆肥氮素损失较常规堆肥减少30.8%,CH4、NH3和N2O排放比常规堆肥分别减少12.8%、17.4%和46.1%,温室气体总量减排35.9%,因此蚯蚓辅助堆肥可有效降低堆肥过程中的氮素损失和温室气体排放量。研究结果可为有机固体废弃物循环利用和温室气体减排控制提供参考。     

Chemical and microbiological parameters for the characterisation of the stability and maturity of pruning waste compost

Composting of pruning waste, leaves and grass clippings was monitored by different parameters. A windrow composting pile, having the dimensions 2.5 m (height) x 30 m (length) was establish. The maturation of pruning waste compost was accompanied by a decline in NH₄ ⁺-N concentration, water soluble C (WSC) and an increase in NO₃ ^–-N content. Both organic matter (OM) content and total N (TN) losses during composting followed a first-order kinetic equation. These results were in agreement with the microbiological activity measured either by the CO₂ respiration or dehydrogenase (DH-ase) activity during the process. Statistically significant correlations were found between DH-ase activity, easily biodegradable organic C forms, NH₄ ⁺-N and NO₃ ^–-N concentrations and organic matter content and N losses. For this reason, DH-ase activity and the CO₂ evolution could be used as good indicators of pruning waste compost maturity. In contrast, humification parameters data from the organic matter fractionation did not agree with the initially expected values and did not contribute to the assessment of compost maturity. Neither the cation exchange capacity nor the germination index showed a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.     

Effect of Adding Flue Gas Desulphurization Gypsum on the Transformation and Fate of Nitrogen during Composting

The objective of this study was to investigate the effect of adding flue gas desulphurization gypsum (FGDG) on the transformation and fate of nitrogen during co-composting of dairy manure and pressmud of a sugar refinery. The ammonia absorption of FGDG was investigated. The changes in compost temperature, pH, electrical conductivity (EC), moisture, organic matter, the C/N ratio, Kjeldahl N, NH₄⁺-N, NO₂^?-N, NO₃^?-N were assessed. The addition of FGDG did not significantly affect compost temperature, pH, EC, moisture, and organic matter degradation. However, the addition of FGDG significantly increased the NH₄⁺-N content in the compost during the thermophilic phase, and the NH₄⁺-N maximal content in the compost with FGDG (CP+G) was 59.9% more than that in the compost without FGDG (CP–G). FGDG was thought to create the formation of (NH₄)₂SO₄ and the cation exchange between NH₄⁺ and Ca²⁺. The NO₂^?-N content in the CP+G peaked on day 15, and was not observed in the CP–G. In the final compost products, the NO₃^?-N concentration in the CP–G was more than that in the CP+G, which was 1451 (CP–G) and 1109 mg·kg^?1 (CP+G) dry material. This might be due to the NO₂^? accumulation in the CP+G, which accelerated N loss in the form of N₂O. There is a strong correlation between N₂O emission and NO₂^?-N accumulation in the composting process. Compared with the original N content in the compost mixture, the N loss in CP–G and CP+G were 15.0 and 10.8%, respectively. These results revealed that NH₄⁺-N conservation effect was improved during the thermophilic phase and the total N loss was mitigated by adding FGDG into composting materials. FGDG could be utilized as a potential amendment to conserve nitrogen during composting.     

Influence of earthworm culture on fertilization potential and biological activities of vermicomposts prepared from different plant wastes

The present investigation was aimed to analyze influence of earthworm culture on nutritive status, microbial population, and enzymatic activities of composts prepared by utilizing different plant wastes. Vermicomposts were prepared from different types of leaves litter of horticulture and forest plant species by modified vermicomposting process at a farm unit. Initial thermophilic decomposition of waste load using cow‐dung slurry was done in the separate beds. The culture of Eisenia fetida was used for vermicomposting in specially designed vermibeds at the farm unit. The physico‐chemical characteristics, enzyme activities (oxido‐reductases and hydrolases), and microbial population (bacteria, fungi, free‐living nitrogen‐fixing bacteria, actinomycetes, Bacillus, Pseudomonas, phosphate‐solubilizing bacteria and fungi) of vermicomposts were found significantly higher (p < 0.05) than those of control (without earthworm inoculum). The study quantified significant contributions of earthworm culture to physico‐chemical, enzymatic, and microbiological properties of vermicompost and confirmed superior fertilization potential of vermicompost for organic farming. The agronomic utility of vermicompost was assessed on yellow mustard plant in a pot experiment. Pot soil was amended with different ratios (5%, 10%, 20%) of vermicompost and normal compost (without earthworm inoculum). Effects of these amendments on the growth of Brassica comprestis L. were studied. The significant differences (p < 0.05) in the growth of plant were observed among vermicompost‐, compost‐amended soil, and control. Vermicompost increased the root and shoot lengths, numbers of branches and leaves per plant, fresh and dry weights per plant, numbers of pods and flowers, and biochemical properties of plant leaf significantly, especially in 20% amendment. These results proved better fertilization potential of vermicompost over non‐earthworm‐inoculated compost.     

Effects of biochar,earthworms, and litter addition on soil microbial activity and abundance in a temperate agricultural soil

Biochar application to arable soils could be effective for soil C sequestration and mitigation of greenhouse gas (GHG) emissions. Soil microorganisms and fauna are the major contributors to GHG emissions from soil, but their interactions with biochar are poorly understood. We investigated the effects of biochar and its interaction with earthworms on soil microbial activity, abundance, and community composition in an incubation experiment with an arable soil with and without N-rich litter addition. After 37 days of incubation, biochar significantly reduced CO₂ (up to 43 %) and N₂O (up to 42 %), as well as NH₄ ⁺-N and NO₃ ^?-N concentrations, compared to the control soils. Concurrently, in the treatments with litter, biochar increased microbial biomass and the soil microbial community composition shifted to higher fungal-to-bacterial ratios. Without litter, all microbial groups were positively affected by biochar × earthworm interactions suggesting better living conditions for soil microorganisms in biochar-containing cast aggregates after the earthworm gut passage. However, assimilation of biochar-C by earthworms was negligible, indicating no direct benefit for the earthworms from biochar uptake. Biochar strongly reduced the metabolic quotient qCO₂ and suppressed the degradation of native SOC, resulting in large negative priming effects (up to 68 %). We conclude that the biochar amendment altered microbial activity, abundance, and community composition, inducing a more efficient microbial community with reduced emissions of CO₂ and N₂O. Earthworms affected soil microorganisms only in the presence of biochar, highlighting the need for further research on the interactions of biochar with soil fauna.     

Relating Compost Measures of Stability And Maturity to Plant Growth

Assessment of compost maturity is important for successful use of composts in agricultural and horticultural production. We assessed the “maturity” of four different sawdust-based composts. We composted sawdust with either cannery waste (CW), duck manure (DM), dairy (heifer) manure (HM) or potato culls (PC) for approximately one year. Windrows were turned weekly for the first 60 days of composting, covered for four winter months and then turned monthly for six more months. We measured compost microbial respiration (CO₂ loss), total C and N, C:N ratio, water soluble NO₃-N and NH₄-N, dissolved organic carbon (DOC), pH and electrical conductivity at selected dates over 370 days. Compost effects on ryegrass biomass and N uptake were evaluated in a greenhouse study. We related compost variables to ryegrass growth and N uptake using regression analysis. All composts maintained high respiration rates during the first 60 days of composting. Ammonium-N concentrations declined within the first 60 days of composting, while NO₃-N concentrations did not increase until 200+ days. After 250+ days, DM and PC composts produced significantly more ryegrass biomass than either CW or HM composts. Total C, microbial respiration and water-extractable NO₃-N were good predictors of compost stability/maturity, or compost resistance to change, while dissolved organic carbon, C:N ratio and EC were not. The compost NO₃-N/CO₂-C ratio was calculated as a parameter reflecting the increase in net N mineralization and the decrease in respiration rate. At ratio values >8 mg NO₃-N/mg CO₂-C/day, ryegrass growth and N uptake were at their maximum for three of the four composts, suggesting the ratio has potential as a useful index of compost maturity.     

Maturity and Stability Evaluation of Composted Yard Trimmings

The objective of this research was to evaluate a variety of stability and maturity indices for yard trimmings compost produced in the Puget Sound region of western Washington State. Compost samples were collected periodically during a 133-d composting cycle at a commercial composting facility, showing that indices of compost respiration rate were sensitive indicators of compost quality. All respiration rate indices identified a period of high respiration rates during active composting (first 27 d), and a period of relatively stable respiration rates during the latter part of curing (70 to 133 d). Chemical tests of compost solids showed less promise as maturity indicators, but provided valuable information on final compost quality. Mature yard trimmings compost had a C:N of 12, an NH₄-N to NO₃-N ratio of less than 4, a cation exchange capacity (CEC) of 400 cmol per kg of compost-C, and a pH between 6.5 and Seed germination tests and sensory tests (color and odor) were of limited value in assessing compost maturity. Fully-cured compost produced with forced aeration had a Solvita CO₂ test value of 6 to 7 and a respiration rate via the alkaline trap method of 2 mg CO₂-C g compost-C^?1 d^?1. It reheated less than 2°C in an insulated Dewar flask in a 7 d incubation. Further evaluation and calibration of respiration test protocols for compost quality assurance testing programs are recommended.     

Composting of Source-Separated Household Organics At Different Oxygen Levels: Gaining an Understanding of the Emission Dynamics

Source-separated household organics were composted in a reactor at three oxygen levels, 16%, 2.5% and 1% in the compost gas. Short-chained fatty acids were initially present in the compost material, and were also produced during the mesophilic phase at all three oxygen levels. This indicated that partial anaerobic conditions existed. No NH₃ emissions occurred during the mesophilic phase due to acidic conditions. Composting at 2.5% and 1% O₂ concentrations prolonged the mesophilic phase and reduced the microbial activity as compared to 16% O₂. This led to delayed and decreased emissions of NH₃. Nitrous oxide was not formed during thermophilic conditions. Methane, which was measured at 2.5% and 1% O₂, was only found during thermophilic conditions. The emission of methane indicates that anaerobic conditions occurred during the thermophilic phase. The main reactions regulating pH during composting were outlined involving the ion species VFA, NH₄⁺/NH₃ and CO₂/HCO₃^?/CO₃^2?.     

Maturity Tests for Composts — Verification Of a Test Scheme for Assessing Maturity

Increased recycling of organic wastes has raised concern about the quality of compost end products. In addition to the limit values for heavy metals and impurities including weeds and pathogens, the quality criteria for compost products should also include criteria for maturity. There is a tremendous number of maturity assays, developed earlier by several authors, and recommended to be used to evaluate maturity of composts. Because no such single test alone reliably demonstrates the complex properties occurring during maturization of compost, we developed a fast and easy-to-use two-phase test scheme for the assessment of maturity. In the first phase the degradation phase e.g. stability of compost samples is evaluated by using a carbon dioxide evolution test and/or determination of the NO₃-N/NH₄-N ratio by simple test strips. In the second phase, the toxicity of the compost is evaluated by a plant growth test, germination tests and/or the Flash bioluminescence test. Eleven plants composting sewage sludge, source-separated biowaste, manure or a combination of these raw materials were sampled after 1-3 weeks of composting and when the compost was considered “ready for use”. Chemical and physical analyses were considered useful as additional information when evaluating maturity especially when the results were not conclusively clear. This fast and easy-to-use test scheme was designed especially for the composting plant operators and official laboratories responsible for evaluating compost quality.     

Treatment of Source-Separated Human Feces via Lactic Acid Fermentation Combined with Thermophilic Composting

Human feces from urine diverting dry toilets can serve as valuable soil conditioners. For a successful agricultural application, an efficient pathogen reduction needs to be ensured, with no negative effects on plants. This study assessed the efficiency of lacto-fermentation combined with thermophilic composting on pathogen removal from human feces and the post-treatment effects on germination and growth of radish (Raphanus sativus) and tomatoes (Lycopersicum esculentum) compared to lacto-fermentation combined with vermi-composting and the control. The NH₄⁺-N/NO₃^?-N ratio of 3.0 and 3.6, respectively, suggested the obtained compost and vermi-compost was not yet mature. A complete reduction in the concentration of all investigated bacterial indicators (i.e., coliforms, Escherichia coli, Enterococcus faecalis, and Clostridium perfringens) from 5–7 log CFU g^?1 to below detection limit (<3 log CFU g^?1) was achieved after lacto-fermentation combined with thermophilic composting. Lacto-fermentation combined with vermi-composting also contributed to pathogen die-off, but coliform bacteria were reduced to only 5 log CFU g^?1. Fertilization of seeds of radish by compost obtained after lacto-fermentation combined with thermophilic composting led to a higher germination index than by the vermicast obtained by lacto-fermentation and vermi-composting (90% versus 84%). Moreover, significantly bigger average fruit weight and total biomass per tomato plant (p < 0.05) were obtained after compost amendment compared to vermicast or the control.     

Evaluation of maturity of poultry manure compost by phospholipid fatty acids analysis

To study the influence of the physical properties of compost feedstock on some characteristics associated with maturity, two types of compost were made from poultry manure, rice husk, and rice bran. The bulk density of one type (PMC) was always higher than that of another type (NMC) during composting. In the case of PMC, the change in temperature, decrease in NH₄⁺, appearance of NO₃^–, and increase in germination indices (GI) with Japanese Komatsuna (Brassica campestris cv. Osome) were all more delayed than in NMC. As the composting process progressed, the proportion of branched (iso-, anteiso-, 10Me-) and saturated phospholipid fatty acids (PLFA) [BRANCHED FAMES (fatty acid methyl esters), biomarkers for gram-positive bacteria] gradually increased, then reached plateau. The high proportion of BRANCHED FAMES was maintained over a long storage period. The straight hydroxyl and saturated PLFAs (SOH-FAMES) initially increased, then disappeared with the progress of composting. The increase in BRANCHED FAMES and the decrease in SOH-FAMES were more delayed in PMC than NMC. The day on which the proportion of BRANCHED FAMES reached plateau and the proportion of SOH-FAMES dipped below 2 mol% coincided with the maturity stage based on the changes of physicochemical characteristics and GI. The composition of BRANCHED FAMES showed highly positive and negative correlation with GI and NH₄⁺, respectively. In the case of SOH-FAMES, inverse correlations were observed. This indicates that the proportion of BRANCHED FAMES and/or SOH-FAMES can be used as a tool for evaluating the maturity of poultry manure compost.     

Evaluation of maturity and stability parameters of composts prepared from farm wastes

A composting experiment was carried out to study changes in physical [color, odor, temperature, organic matter (OM) loss], chemical [C:N ratio, water-soluble organic carbon (C_w):organic N (N_org) ratio, NH₄ ⁺-N and NO₃ ^?-N, humic acid (HA):fulvic acid (FA) ratio, humification index (HI) and cation-exchange capacity (CEC):total organic carbon (TOC) ratio)] and biological [seed germination index (GI)] parameters to assess compost maturity and stability over a period of 150 days. Five composts were prepared using a mixture of different farm wastes with or without enrichment of N, rock phosphate (RP) and microorganism (MO) inoculation. All the composts appeared to change to a granular and dark grey color without foul odor, and attained a constant temperature with no measurable changes (ambient level) at 120 days of composting. Correlation analysis showed that the optimal values of the selected parameters for our experimental conditions are as follows: organic matter loss > 42%, C:N ratio < 15, HA:FA ratio > 1.9, HI > 30%, CEC:TOC ratio > 1.7 and C_w:N_org ratio < 0.55. Composts enriched with N + RP or N + RP + MO matured at 150 and 120 days, respectively, whereas composts without any enrichment or enrichment with N or RP + MO did not mature even at 150 days of composting.     

堆肥反应器中硫磺对牛粪好氧堆肥的保氮效果研究

利用堆肥反应器严格控制堆肥条件,以牛粪和蘑菇渣为原料进行好氧堆肥,在堆肥过程中添加硫磺粉,研究硫磺对堆肥温度、pH、氮素转化、硫素转化和保氮效果的影响。结果表明,堆肥中添加0.5%硫磺粉（T1）对堆肥温度没有显著影响,高温期（≥50℃）维持5.5 d; 而添加1.0%硫磺粉(T2)能快速升温,但堆肥高温期维持时间4.6 d。添加不同量的硫磺粉均能显著降低堆肥pH,与CK比较差异显著。添加硫磺粉能大幅度增加铵态氮含量,至堆肥结束时,T1和T2处理铵态氮含量分别是CK处理的15倍和24倍,差异极显著; 还增加了堆肥有效硫含量,至堆肥结束T1和T2有效硫含量分别较堆肥初始增加35.7%和77.1%。整个堆肥过程总氮（TN）含量呈增加的趋势,堆肥结束时CK、T1和T2处理的TN含量分别达15.8、16.5和16.9 g/kg,T1和T2分别比CK处理增加4.4%和7.0%。说明在牛粪好氧堆肥中添加0.5%或1.0%硫磺粉,均可起到一定的保氮作用,可大幅度提高堆肥铵态氮和有效硫的含量,改善了堆肥养分品质; 而且添加1.0%硫磺粉效果好于0.5%硫磺粉。但是添加1.0%硫磺粉缩短了堆肥高温期,降低了种子发芽指数,不利于堆肥的无害化进程。     

Quantification of nitrogen excretion rates for three lumbricid earthworms using 15N

 Nitrogen excretion rates of ¹⁵N-labeled earthworms and contributions of ¹⁵N excretion products to organic (dissolved organic N) and inorganic (NH₄-N, NO₃-N) soil N pools were determined at 10  °C and 18  °C under laboratory conditions. Juvenile and adult Lumbricus terrestris L., pre-clitellate and adult Aporrectodea tuberculata (Eisen), and adult Lumbricus rubellus (Hoffmeister) were labeled with ¹⁵N by providing earthworms with ¹⁵N-labeled organic substrates for 5–6 weeks. The quantity of ¹⁵N excreted in unlabeled soil was measured after 48 h, and daily N excretion rates were calculated. N excretion rates ranged from 274.4 to 744 μg N g^–1 earthworm fresh weight day^–1, with a daily turnover of 0.3–0.9% of earthworm tissue N. The N excretion rates of juvenile L. terrestris were significantly lower than adult L. terrestris, and there was no difference in the N excretion rates of pre-clitellate and adult A. tuberculata. Extractable N pools, particularly NH₄-N, were greater in soils incubated with earthworms for 48 h than soils incubated without earthworms. Between 13 and 40% of excreted ¹⁵N was found in the ¹⁵N-mineral N (NH₄-N+NO₃-N) pool, and 13–23% was in the ¹⁵N-DON pool. Other fates of excreted ¹⁵N may have been incorporation in microbial biomass, chemical or physical protection in non-extractable N forms, or gaseous N losses. Earthworm excretion rates were combined with earthworm biomass measurements to estimate N flux from earthworm populations through excretion. Annual earthworm excretion was estimated at 41.5 kg N ha^–1 in an inorganically-fertilized corn agroecosystem, and was equivalent to 22% of crop N uptake. Our results suggest that the earthworms could contribute significantly to N cycling in corn agroecosystems through excretion processes. Received: 12 April 1999     

二氧化锰对微好氧堆肥腐熟、温室气体及臭气排放的影响

为探究锰矿物添加对微好氧堆肥过程腐熟、温室气体和臭气排放的影响,以由厨余垃圾、水稻秸秆、羊粪和尾菜组成的多元混合物料堆肥为研究对象,共设3个处理,采用间歇通风方式,将通风速率为0.14 L/（kg·min）设置为好氧堆肥对照（CK）,速率为0.06 L/（kg·min）为微好氧处理（T1）,添加二氧化锰（MnO₂）的微好氧处理为T2。结果表明：多元废弃物好氧或微好氧堆肥在堆制70 d后均能腐熟,但T2处理腐熟度显著高于T1。微好氧处理T1、T2减少了26.47%～30.29%的NH₃和33.19%～38.60%的N₂O的排放,总温室效应减少了29.26%～31.38%。臭气的排放集中在前14 d,T1、T2处理的H₂S和VOCs的释放量显著增加了320.35%～501.04%和39.82%～53.63%。因此,微好氧堆肥可达到减排目的,但却加剧臭气的排放;MnO₂可提高促进堆肥腐熟,降低温室气体和臭气的排放。     

蚯蚓-蚯蚓粪分离-收获工艺与关键部件试验

蚯蚓堆肥是实现农业有机固体废弃物减量化、无害化、资源化和增值化的生物处理技术之一。蚯蚓堆肥结束后,如何将成熟活体蚯蚓从大量堆肥物料中快速分离收获,是目前规模化蚯蚓堆肥亟需解决的难题之一。为实现蚯蚓体快速、高效、稳定的分离和收获,该研究提出了蚯蚓堆肥产物3步分离收获工艺方法,并针对此工艺中的动态斜面分离收获关键部件和工艺参数开展了试验研究。在此基础上,结合力学分析、EDEM离散元仿真模拟揭示了蚯蚓分离关键过程中的动力学机制。结果表明：本研究所提出的分离工艺可较好实现蚯蚓、蚯蚓粪的分离和集中收获,动态斜面在蚯蚓-蚯蚓粪分离过程中起关键作用,利用了蚯蚓体表液膜接触粘附摩擦特性强,易粘附于斜面,而动态斜面作用下蚯蚓粪滚动摩擦力小的特性,蚯蚓与蚯蚓粪抛落于动态斜面后因受力差异导致两者呈相反方向运动,实现分离。蚯蚓-蚯蚓粪分离收获的最优参数组合为安装锥形分离器下,分离收获斜面速度50 mm/s、倾角为30°。基于此工艺方法处置蚯蚓粪-蚯蚓混合物料10 kg耗时55.36 s,在蚯蚓收获区的蚯蚓收获率为（81.50±5.55）%,蚯蚓粪含杂率接近于0,物料总收获率为（96.56±1.79）%。研究结...     

Effects of activated charcoal and tannin added to compost and to soil on carbon dioxide,nitrous oxide and ammonia volatilization

Given high mineralization rates of soil organic matter addition of organic fertilizers such as compost and manure is a particularly important component of soil fertility management under irrigated subtropical conditions as in Oman. However, such applications are often accompanied by high leaching and volatilization losses of N. Two experiments were therefore conducted to quantify the effects of additions of activated charcoal and tannin either to compost in the field or directly to the soil. In the compost experiment, activated charcoal and tannins were added to compost made from goat manure and plant material at a rate of either 0.5 t activated charcoal ha^?1, 0.8 t tannin extract ha^?1, or 0.6 t activated charcoal and tannin ha^?1 in a mixed application. Subsequently, emissions of CO₂, N₂O, and NH₃ volatilization were determined for 69 d of composting. The results were verified in a 20‐d soil incubation experiment in which C and N emissions from a soil amended with goat manure (equivalent to 135 kg N ha^?1) and additional amendments of either 3 t activated charcoal ha^?1, or 2 t tannin extract ha^?1, or the sum of both additives were determined. While activated charcoal failed to affect the measured parameters, both experiments showed that peaks of gaseous CO₂ and N emission were reduced and/or occurred at different times when tannin was applied to compost and soil. Application of tannins to compost reduced cumulative gaseous C emissions by 40% and of N by 36% compared with the non‐amended compost. Tannins applied directly to the soil reduced emission of N₂O by 17% and volatilization of NH₃ by 51% compared to the control. However, emissions of all gases increased in compost amended with activated charcoal, and the organic C concentration of the activated charcoal amended soil increased significantly compared to the control. Based on these results, tannins appear to be a promising amendment to reduce gaseous emissions from composts, particularly under subtropical conditions.     

Chemical,Physical and Biological Criteria for Maturity in Composts for Organic Farming

Properties of organic farming composts were examined during the composting process: pH, electrical conductivity, C/N ratio, total N content, NH₄₊ content, NO_3?content, ash content, and organic matter content. In addition to these properties the respiration rate, microbial population counts, hydrolysis of Fluorescein Diacetate (FDA) and the activity of the enzyme amidase were studied. Composts at several stages of maturity were incubated in soil, and their N mineralization rates were measured. The end of the thermophilic stage was characterized by irreversible decrease in pile temperature to under 55°C, followed by stabilization of the chemical properties. This stage in the composting process is also characterized by decrease in CO₂ evolution rate, changes in microbial populations and specific patterns in FDA hydrolysis and amidase activity. Based on this evidence, we suggest that biological parameters can be considered as indicators for compost maturity.