Growth and reproduction of the vermicomposting earthwormPerionyx excavatus as influenced by food materials

An outdoor study was undertaken using polyethylene containers to assess the suitability of different organic residues, soybean straw (Glycine max L. Merril.), wheat straw (Triticum aestivum L.), maize stover (Zea mays L.), chickpea straw (citer arietinum L.) and city garbage, as food for the tropical epigeic earthwormPerionyx excavatus, and to assess the influence of this earthworm on the decomposition of these materials. Maize stover was found to be the most suitable of the food materials used. Population growth ofP. excavatus was enhanced by addition of these organic materials in the temperature range 24°-30°C, while the population was adversely affected above 30°C in a vermiculture system. Addition of earthworms accelerated the breakdown of residues, which ultimately resulted in a lowering of the C:N ratio, water-soluble carbon and carbohydrates, and increased ash percentage and cation exchange capacity compared with their respective controls.     

Effect of organic residue amendment on mineralization of sulfur in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of sulfur (S) in laboratory conditions of three rice soils (Joydebpur, Faridpur, and Thakurgaon), receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), and 3) pea vine (Pisum sativum L.). The organic residue (25 mg g^‐1) was added and mixed with soil and glass beads (1:1, soil to bead ratio) and placed into a Pyrex leaching tube. The soils were flooded and incubated at 35°C, after which they were leached with deionized water at 1, 2,4, 8, and 12 weeks for analysis of SO₄ and other chemical properties in the leachates. Potentially mineralizable S (S_o) and C (C_o) pools and first‐order rate constants (K_s for S and K_c for C) in soils amended with rice straw and pea vine under flooded conditions were estimated using an exponential equation. The S_o and K_s varied considerably among the soils and types of added organic residues, and their values in rice straw and pea vine ranged from 8.70 to 29.55 and 0.124 to 0.732 mg S kg^‐1 wk^‐1, respectively. Except for the Thakurgaon soil, the S_o and K_s values in Joydebpur and Faridpur soils were higher in the unamended treatments. Higher S_o values in the unamended soils were probably due to less microbial activity to mineralize organic S from organic residues. The results indicate that the amount of SO₄ in flooded soils amended with organic residues are dependent on soil type, nature of organic residues, and time of incubation. The C_o and K_c values under flooded incubation were higher in residue amended soils than in unamended soils. Pea vine treated soils had higher C_o and K_c values than the soils treated with rice straw.     

Soil fungal communities and enzyme activities in a sandy, highly weathered tropical soil treated with biochemically contrasting organic inputs

The regulative effect of long-term application of biochemically contrasting organic inputs such as rice straw (4.7 g?N; 6.5 g polyphenols), groundnut stover (22.8 g?N; 12.9 g polyphenols) and leaf litter of tamarind (13.6 g?N; 31.5 g polyphenols) and dipterocarp (5.7 g?N; 64.9 g polyphenols) on fungal decomposers was studied in a tropical sandy soil. Fungal decomposers were assayed by 18S rRNA gene-based community profiling and were combined with measurements of selected enzyme activities. Dipterocarp residue application depressed fungal abundance, but promoted specialized decomposers (e.g., Aspergillus fumigatus and Anguillospora longissima) with increases in polyphenol oxidase activity. The degree of functional redundancy for invertase and B-glucosidase activities was induced after the addition of easily decomposable rice straw and groundnut stover. Higher N availability in the tamarind treatment increased, in contrast to low N rice straw, fungal abundance (i.e., Fusarium oxysporum, Myceliopthora thermophila, and Aspergillus versicolor) and promoted invertase and B-glucosidase activities, while peroxidase activity was depressed. In addition, N availability seemed to regulate not only decomposing soil fungi, but also the abundance of protozoan decomposers whose actual contribution to N turnover in soils is still poorly understood. Prospective research should thus consider apart from studying decomposing fungi also protozoa and bacteria to better understand the microbially mediated degradation of complex organic materials in soils.     

Water-soluble organic materials in paddy soil ecosystem

Abstract

Column experiments were conducted to analyze the effect of the temperature on the amounts of organic materials in the leachate, especially organic acids and methane, from samples of the plow layer soil amended with rice straw. Total amount of inorganic carbon in the leachate during the 30-d period of incubation in relation to the temperature was 18°C < 25°C ≤ 30°C > 37°C > 45°C. Total amount of organic carbon in the leachate was signiicantly larger under 45°C incubation than that at other temperatures.

Acetic acid was the dominant organic acid in the leachate regardless of the temperature. Butylic and propionic acids were also present in large amounts in the early and the late period of incubation of temperatures ranging between 18 and 37°C, while only acetic acid was the dominant organic acid during the 30-d period of incubation at 45°C.

The total amount of methane in leachate during the 30-d period of incubation was very small at 18°C, while very large at 25, 30, and 37°C. It decreased nearly to one half at 45°C compared with that at 30°C. Based on the values of δ¹³CH₄ in the leachate, 3 different stages were recognized in the predominant processes of methane production in the submerged paddy soil amended with rice straw: the stage when methane production from CO₂-B₂ was predominant followed by the stages of methane production from acetic acid and from CO₂-H₂ in this order. The second stage coincided with the time of decrease of the organic acid contents in the leachate. Under 45°C incubation, methane production from CO₂-H₂ was predominant throughout the 30-d period of incubation.     

Vermicomposting of Vegetable Waste

? Vermicomposting is the degradation of organic waste through earthworm consumption, which converts the material into worm castings. Vermicomposting of vegetable waste was examined in order to identify suitable worm species and efficient levels of temperature and moisture. Laboratory experiments were conducted under controlled conditions using commonly available species: Pheretima sp.; Eisenia sp. and P. excavatus. Worms survived in the moisture range of 20-80 percent and the temperature range of 20°-40°C. Worm survival in decomposed and undecomposed organic wastes was also studied. Trials indicate that P. excavatus is the appropriate species for vegetable waste vermicomposting.     

Organic fertilizers derived from plant materials Part I: Turnover in soil at low and moderate temperatures

The aim was to investigate different organic fertilizers derived from plant materials with respect to their nitrogen and carbon turnover in soil in comparison with organic fertilizers derived from animal‐waste products. In a 64‐day incubation study at 5°C and 15°C, the following fertilizers were used: coarse faba bean–seed meal (Vicia faba L.), coarse meals of yellow and white lupin seeds (Lupinus albus L. and Lupinus luteus L.), Phytoperls^® (waste products of maize [Zea mays L.] processing), coarse meal of castor cake (Ricinus communis L.) as a widely used organic fertilizer, and horn meal as a reference fertilizer‐derived from animal waste products. At 15°C, horn meal showed the highest apparent net N mineralization of fertilizer‐derived N, followed by castor cake and the two lupin meals. At 5°C, apparent net N mineralization of fertilizer‐derived N from horn meal and coarse meal of yellow lupin seeds was nearly identical, followed by castor‐cake meal. Net N mineralization from legume‐seed meals showed no or even a negative temperature response, at least temporarily. In contrast, the other fertilizers showed a positive temperature response of net N mineralization. The content in recalcitrant structural components and the decoupling of decomposition of N‐rich and C‐rich tissue components in time are discussed as controlling factors of fertilizer‐N turnover at low temperature. Microbial residues seem to be an important temporary sink of fertilizer‐derived C and N. Legume‐seed meals induced considerable N‐priming effects. Temperature induced differences in the decomposition of total fertilizer C, indicated by changes in the sum of cumulative CO₂‐C evolution, total K₂SO₄‐soluble organic C and microbial‐biomass C were much smaller than indicated by cumulative CO₂‐C evolution alone. Our results indicate that legume‐seed meals have the potential to replace horn meal and castor‐cake meal in organic vegetable production, especially when soil temperatures in early spring are still low.     

Effect of organic residue amendment on mineralization of nitrogen in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), or 3) pea vine (Pisum sativum L.). The organic residue (25 mg straw g^‐1 soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH₄‐N, NO₃‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (N_o) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw N_o values and pea vine, respectively, than the control. The K_N values for unamended soils ranged from 0.35 to 0.52 mg N kg^‐1 wk^‐1 and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg^‐1 wk^‐1. The lower N_o and K_N values in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.     

Mineralization of physically fractionated rotten plant residues under upland conditions

A well-rotten mixture of rice straw and calcium cyanamide (rice straw compost prepared indoors) was separated physically into four fractions using a combination of methods which involved sieving, sedimentation and centrifugation. The four fractions obtained were Fl-3 (>0.043 mm), F4 (sedimented at 4°C), F5 (sedimented by centrifugation at 10⁴ × g for 10 min) and F6 (supernatant). The air-dried and pulverized fractions were mixed with upland soils and incubated for 4 weeks at 30°C under upland conditions. The amount of nitrogen mineralized in each fraction was determined, In a red yellow soil, 11.2% of the organic nitrogen present in the unfractionated, air-dried sample was mineralized, compared with 6.8% in volcanic ash soil. The contribution of fraction F5 to the total amount of mineralized nitrogen in wet compost was the highest, followed by F6. Fraction Fl-3 showed immobilization of inorganic nitrogen in both soil types. On the other hand, fractionated samples obtained after air-drying the wet compost showed no immobilization for Fl-3, although the values obtained for other fractions were similar to those obtained for the corresponding fractions of wet compost.

Well-rotten plant residues such as rice straw (compost prepared outdoors), Timothy and Ladino clover were air-dried, then separated into fractions and analyzed for elementary composition as well as inorganic nitrogen content using the same procedures. Although the amounts of mineralized nitrogen were higher in fractions F5 and F6 compared with other fractions, the values were much lower compared with those of undecomposed plant residues.

It was found that the amount of organic nitrogen mineralized in soil was affected not only by the C/N ratio of the plant residues but also by the differences in characteristics or properties of the plant materials and soils.     

Long-term effects of temperature on carbon mineralisation processes

The long-term effects of temperature on soil C mineralisation were investigated in two experiments using ¹⁴C labelled wheat straw incubated in organic soils from five coniferous forests located in different climate zones of Western Europe. In the first experiment, samples were incubated in the laboratory at 4, 10, 16, 23 or 30°C, with constant moisture, and the loss of ¹⁴C was monitored for 550 days. Double negative exponential functions fitted to the ¹⁴C loss data at different temperatures were used to define the relative proportions of labile and recalcitrant components in the original straw. The estimated proportions of these constituents were related to incubation temperatures with the amount of C reflecting the labile fraction increasing with increasing temperature. In the second experiment samples mixed with the labelled straw were incubated at 4, 16 or 30°C until the same percentage of ¹⁴C loss was reached. The samples were then incubated again at a common temperature for 30 days and CO₂ production was measured to assess the lability of the remaining material. For all the soils, the amount of readily decomposed material was higher in samples conditioned at 4° than at 30°C. It was concluded that in addition to temperature controlling rates of C mineralisation in soil it also affects the processes of decomposition so that material produced at higher temperatures was more recalcitrant than at lower temperatures.     

Effects of Temperature,Moisture, and Chemical Composition of Organic Substrates on C Mineralization in Soils

Laboratory experiments were conducted to (i) study the influence of chemical composition of organic substrates (green manure, rice straw, wheat straw, and farmyard manure) and temperature on carbon (C) mineralization under flooded and nonflooded moisture conditions, (ii) study the relationship between C mineralization and chemical composition of organic materials, and (iii) model C mineralization kinetics under different temperature and moisture conditions. The proportion of added C mineralized under nonflooded conditions ranged between 45 and 66% at 35 °C compared to 18 to 42% at 15 °C. Flooding the soil reduced the proportion of added C mineralized, which ranged between 25 to 47% at 35 °C and 6 to 20% at 15 °C. Water-soluble components, cellulose, lignin, and nitrogen content of the organic source significantly influenced C mineralization. Temperature sensitivity of decomposition depended on the quality of the organic substrate with relatively less decomposable farmyard manure (FYM) being more sensitive (Q₁₀ ?3.0) than the easily decomposable green manure (Q₁₀ ?2.5). A first-order monocomponent model that is based on relative rate of mineralization and includes a parameter for speed of aging best described C mineralization under both the temperature and moisture conditions. It was concluded that FYM with preponderance of recalcitrant components and low decomposability provides greater C sequestration potential than green manure and crop residues.     

Amelioration of an acid ultisol by agricultural by‐products

Ultisols are widely distributed in the subtropical regions of China as well as in the world. High acidity of Ultisols limits plant growth and reduces crop yields. Amelioration of an acid Ultisol was investigated by incorporating the residues of canola (Brassica campestris L.), wheat (Triticum aestivum L.), rice (Oryza sativa), corn (Zea mays), soybean (Glycine max), peanut (Arachis hypogaea), faba bean (Vicia faba L.) and pea (Pisum sativum) and Chinese milk vetch (Astragalus sinicus L.) shoots after incubation of the agricultural by‐products for a maximum of 75 days, soil pH was increased by each of the plant materials. The degree of amelioration of the soil acidity by the plant materials was found to depend on the ash alkalinity and N content of the materials; the legumes of higher ash alkalinities and lower N contents, such as peanut straw and faba bean straw, led to the largest increases in soil pH, while the legumes of higher N contents showed less amelioration of the acidity to a certain degree, because of the release of protons during nitrification of NH from mineralisation of organic N. The non‐leguminous materials have medium amelioration effects and increased soil pH by 0·42–0·56 units at the end of incubation. The incorporation of the plant materials also increased exchangeable base status and reduced exchangeable Al, and thus decreased the toxicity of Al in the soil. This study demonstrates that plant materials, especially crop residues, can be used as amendments for acidic soils to restore degraded land in subtropical regions. Copyright © 2010 John Wiley & Sons, Ltd.     

Co-accumulation of microbial residues and particulate organic matter in the surface layer of a no-till Oxisol under different crops

In the absence of significant mechanical disturbance such as under permanent no-till (NT), crop type should be a prominent factor controlling soil organic C (SOC) pools. Microbial cell residues have been shown to be influenced by plant species and are believed to contribute significantly to soil organic matter formation. We performed a study to investigate the co-accumulation of microbial cell wall residues (glucosamine, GlcN and muramic acid, MurN) and organic C (total and particle-size fractions) in the surface layer (0- to 5-cm depth) of an Oxisol after 7 yr under NT, as affected by different crop types. SOC content associated with pigeon pea [Cajanus cajan (L.) Millsp.] was 20% and 18% higher than that with corn (Zea mays L.) or sunflower (Helianthus annuus L.), respectively. The highest particulate organic C (POC) content in soil was also found under pigeon pea, which showed values 54, 46, and 48% higher than under corn, sunflower, and oilseed radish (Raphanus sativus L. var. oleiformis Pers.), respectively. Changes in POC explained most of the variation in SOC. The positive impact of pigeon pea on POC and SOC was attributed to rapid decomposition of its residues, due to their low C/N ratio, followed by selective preservation of lignin-rich particulate organic matter. The accrual of POC was closely associated with the accumulation of fungal and bacterial cell wall residues. This may be due to preferential feeding of fungi and bacteria on recently deposited plant-derived C sources present in the form of particulate organic matter. This observation is consistent with a recent model suggesting that microbial residues play a greater role in the formation of SOC than previously considered. We emphasize that this effect was mediated by the accumulation of POC and influenced by crop type.     

Changes in the soil C and N contents,C decomposition and N mineralization potentials in a rice paddy after long-term application of inorganic fertilizers and organic matter

A long-term experiment on combined inorganic fertilizers and organic matter in paddy rice (Oryza sativa L.) cultivation began in May 1982 in Yamagata, northeastern Japan. In 2012, after the 31^st harvest, soil samples were collected from five fertilizer treatments [(1) PK, (2) NPK, (3) NPK + 6 Mg ha^?1 rice straw (RS), (4) NPK + 10 Mg ha^?1 rice straw compost (CM1), and (5) NPK + 30 Mg ha^?1 rice straw compost (CM3)], at five soil depths (0–5, 5–10, 10–15, 15–20 and 20–25 cm), to assess the changes in soil organic carbon (SOC) content and carbon (C) decomposition potential, total nitrogen (TN) content and nitrogen (N) mineralization potential resulting from long-term organic matter addition. The C decomposition potential was assessed based on the methane (CH₄) and carbon dioxide (CO₂) produced, while the N mineralization potential was determined from the potassium chloride (KCl)-extractable ammonium-nitrogen (NH₄⁺-N), after 2, 4, 6 and 8 weeks of anaerobic incubation at 30°C in the laboratory. Compared to NPK treatment, SOC in the total 0–25 cm layer increased by 67.3, 21.0 and10.8%, and TN increased by 64.2, 19.7 and 10.6%, in CM3, RS and CM1, respectively, and SOC and TN showed a slight reduction in the PK treatment by 5.2 and 5.7%, respectively. Applying rice straw compost (10 Mg ha^?1) instead of rice straw (6 Mg ha^?1) to rice paddies reduced methane production by about 19% after the soils were measured under 8 weeks of anaerobic incubation at 30°C. Soil carbon decomposition potential (Co) and nitrogen mineralization potential (No) were highly correlated with the SOC and TN contents. The mean ratio of Co/No was 4.49, lower than the mean ratio of SOC/TN (13.49) for all treatments, which indicated that the easily decomposed organic matter was from soil microbial biomass and soil proteins.     

Growth and reproduction of Perionyx excavatus (Perr.) (Megascolecidae) as factors in organic waste management

 The life cycle of Perionyx excavatus has been studied and the potential of this epigeic earthworm species for breaking down and processing organic wastes is well known. Understanding of its optimal environmental requirements is required in order to optimize and accelerate the vermicomposting process. The rates of growth and reproduction of P. excavatus, on a variety of organic wastes, were evaluated in these experiments. The time of maturation and the rates of growth of this species, under various population density pressures and temperatures between 15  °C and 30  °C, were also assessed. Increasing temperatures up to 30  °C accelerated the growth of earthworms and lessened the time to sexual maturity. However, the highest rates of reproduction occurred at 25  °C both in cattle solids and sewage sludge. The mean time to egg hatching decreased and the degree of hatching success increased with increasing temperature. Earthworms grew at similar rates in cattle solids, pig solids and aerobically digested sewage sludge, but the earthworms did not grow well in horse solids and grew only poorly in turkey wastes. The maximum individual growth rates as a function of earthworm population and the maximum earthworm weights as a function of time with a constant food supply at four different temperatures were assessed. Received: 16 July 1997     

Mineralization and microbial biomass formation in upland soil amended with some tropical plant residues at different temperatures

A model experiment was carried out at 15, 25, and 35°C to investigate the changes in microbial biomass and the pattern of mineralization in upland soil during 8 weeks following the addition of 8 organic materials including 6 tropical plant residues, ipil ipil (Leucaena leucocephala), azolla (Azolla pinnata), water hyacinth (Eichhornia crassipes), dhaincha (Sesbania rostrata), cowpea (Vigna unguiculata), and sunhemp (Crotalaria juncea). The amounts of CO₂-C evolved and inorganic N produced at 35°C were about 2 times larger than those at 15°C. At any temperature, the flush decomposition of C was observed within the first week and thereafter the rate of mineralization became relatively slow. A negative correlation was observed between inorganic N and C/N ratios of the added organic materials. The relationships between the amounts of cellulose or cellulose plus hemicellulose and the amount of mineralized N of the added organic materials were also negative.

The changes in the microbial biomass were affected by temperatures. The amount of biomass C and N was maximum after 42 d of incubation at 15°C, and after 7 d at 25 and 35°C, and thereafter decreased. The rate of biomass decline was slower at 15°C and faster at 35°C than at 25°C. Regardless of the temperatures, the addition of organic materials enhanced microbial biomass formation throughout the incubation periods.     

Mineralization and changes in microbial biomass in water-saturated soil amended with some tropical plant residues

An incubation experiment was conducted in the laboratory at 25 and 35°C during 56 d to analyze the mineralization patterns and the changes in microbial biomass in water-saturated soils amended with 6 types of organic materials (O.M.) including residues from 4 tropical plants. C and N mineralization in amended and non-amended soils was influenced by the temperature, A significantly positive correlation was observed between C mineralization and the amount of hexoses of the amended O.M. regardless of the period of incubation. A negative relationship between the N mineralized from amended O.M. and C/N ratios and the amounts of cellulose plus hemicellulose of the added O.M. was observed during the period of maximum mineralization on the 49th day at 25°C. The critical C/N ratio value for N mineralization and immobilization was observed in dhaincha (15.7) and cowpea (22.0).

The pattern of changes in microbial biomass C and N was almost similar at both 25 and 35°C. The amount of biomass C and N gradually increased up to a period of 28 to 42 d and thereafter decreased gradually. A significant increase in the amount of biomass C and N was observed in O.M. amended soils over the control. The contribution of rice straw and cowpea to biomass C formation was significantly larger than that of other O.M. at the end of incubation (56 d). In the case of biomass N, the contribution of rice straw was significantly larger than that of other O.M. except for azolla at 25°C and cowpea at 35°C. The significant contribution of rice straw and cowpea to biomass formation suggests that microbial biomass remaining in soil on the 56th day had been influenced by the combination of a larger amount of cellulose plus hemicellulose and higher C/N ratio in plant residues.     

Decomposition of Organic Matter with Previous Cadmium Adsorption in Soils

Decomposition of organic matter with previous Cd adsorption (thereafter referred to as OMACd) in soils and in water was studied in order to clarify the mechanism of Cd-induced inhibition of organic matter decomposition in soil. Two types of organic materials (sludge, rice straw) with or without previous Cd adsorption were mixed with a Gley soil or a Light-colored Andosol in a proportion of 1%. In the soils amended with the Cd-free organic materials, a CdCl₂ solution was added to the soils. The decomposition of the organic matter was examined by measuring the CO₂ evolution for 4 weeks at 28°C. Although the same amount of Cd was added to the soils, the decomposition of OMACd was inhibited to a greater extent than that in the soils to which a CdCl₂ solution had been added.

Furthermore the decomposition of sludge with previous Cd adsorption (thereafter referred to as SACd) in water after inoculation of soil microorganisms was investigated. Although the control sludge without Cd was markedly decomposed at 30°C during 4 weeks, SACd was not appreciably decomposed. These results suggest that OMACd cannot be readily decomposed by microorganisms.     

Decomposition of different organic materials in soils

Laboratory experiments were conducted to evaluate organic C mineralization of various organic materials added to soils. A soil sample was mixed with organic material to approximate a field application of 9 g organic C kg^-1 soil (0.9% or 50 Mg ha^-1). The organic materials used were four crop residues [corn (Zea mays L.), soybean (Glycine max L. Merr.), sorghum (Sorghum vulgare Pers.), and alfalfa (Medicago sativa L.)], four animal manures [chicken (Gallus domesticus), pig (Sus scrofa), horse (Equus caballus), and cow (Bos taurus)] and four sewage sludges [Correctionville (Imhoff tank), Charles City (holding tank), Davenport (secondary digester), and Keokuk (primary digester)]. The soil-organic material mixture was incubated under aerobic conditions at room temperature (20±2°C) for 30 days. The CO₂ evolved was collected in standard KOH solution by continuously passing CO₂-free air over the soil. Results showed that, in general, the amounts of CO₂-C released mereased rapidly initially, but the pattern differed among the organic materials used. More than 50% of the total CO₂ produced in 30 days of incubation was evolved in the first 6 days. Expressed as percentages of organic C added, the amounts of CO₂ evolved ranged from 27% with corn to 58% with alfalfa. The corresponding percentages for animal manures ranged from 21 to 62% with horse and pig manures, respectively, and for sewage sludges they ranged from 10 to 39% for Charles City and Keokuk sludges. All CO₂ evolution data conformed well to a first-order kinetic model. Potentially, readily mineralizable organic C values and first-order rate constants (k) of the organic matter-treated soils ranged from 1.422 g C kg^-1 soil with ak value of 0.0784 day^-1 to 6.253 g C kg^-1 soil with ak value of 0.0300 day^-1. The half-lives of the C remaining in soils ranged from 39 to 54 days for plant materials. The corresponding half-lives for the C remaining from animal manures and sewage sludges ranged from 37 to 169 days and from 39 to 330 days, respectively.     

The Influence of Bulking Material Type and Volume On In-house Composting in High-Rise,Caged Layer Facilities

In-house composting involves treating manure where it accumulates on the floor of high-rise, caged layer facilities. This process produces a partially composted material and can aid in house fly (Musca domestica L.) control by generating temperatures in the thermophilic range (≥43°C). Two trials were conducted to determine the effect of material volume and the use of previously composted material (starter) or wheat (Triticum aestivum L.) straw as bulking agents on compost temperatures and material properties. In Trial 1, starter combined with wheat straw or wheat straw alone were added to separate quadrants in a layer building, formed into windrows, and turned biweekly. Temperatures were consistently higher with the starter treatment, but both treatments followed a distinct pattern where temperatures peaked on the day of turning and declined rapidly thereafter. The starter treatment had higher initial volume (0.19 m³ m^?1 row) than straw alone (0.13 m³ m^?1 row), and maintained proportionately higher volumes throughout the trial. Volume in both treatments increased linearly with time and was correlated with peak compost temperature on the day of turning. Regression analysis indicated that a critical volume of 0.18 m³ m^?1 row was required to consistently achieve compost temperatures ≥43°C. In a second trial, starter alone was compared to wheat straw at two rates. Volumes for all treatments initially ranged from 0.20 to 0.28 m³ m^?1 row and increased linearly throughout the trial. Temperatures consistently exceeded 43°C on the day of turning. Analysis of the materials from both trials indicated that starter or straw had little effect on %moisture, %carbon, %nitrogen, or carbon:nitrogen ratio of composting materials beyond the first week after windrow establishment. These results indicate that material volume is more important than the use of starter or straw materials as bulking agents to achieve in-house composting temperatures ≥ 43°C.     

Food and habitat preferences of the earthworm Lumbricus terrestris L. for cover crops

Some of the widely used cover crops in temperate agroecosystems (including species of the Brassicaceae and Poaceae) have been shown to exhibit allelopathic effects. In particular, various Brassicaceae have been reported to act as biofumigants against a variety of soil-borne pests through the release of i.a. isothiocyanates (ITC) from glucosinolate precursors. Although these allelochemicals may potentially reduce the need for application of synthetic pesticides, their effects on beneficial soil ecosystem engineers such as earthworms (Lumbricidae) have not been assessed yet.Food choice chambers were used to assess short-term food preferences of Lumbricus terrestris L. for lacy phacelia (Phacelia tanacetifolia BENTH.), the Poaceae Italian ryegrass (Lolium multiflorum LAM.) and oats (Avena sativa L.), and the Brassicaceae yellow mustard (Sinapis alba L.) and rapeseed (Brassica napus L.) while litter bags were used to study long-term litter preference under field conditions. Habitat preference of L. terrestris was determined through simple habitat preference units.Ryegrass residues were a preferred food resource, both in fresh and partly decomposed state, over mustard, phacelia or rapeseed residues, and these were in turn more fed on than oats. Litter disappeared at a fast and variable rate from litter bags under field conditions. No clear relationships with residue C:N ratio were observed. Habitats in which living oat plants were present were avoided in comparison to habitats with bare soil or yellow mustard plants.In conclusion, brassicaceous cover crops are not preferred nor avoided by L. terrestris compared to the other cover crops in this study. Decreased ITC release and earthworm exposure under field conditions may further lower the risk of harmful effects, but further research on the long-term impact is needed.