An assessment of soil bacterial community structure and physicochemistry in two microtopographic locations of a palustrine forested wetland

We studied redoximorphic features, field indicators and bacterial communities of soils in hummocks and hollows of a palustrine forested wetland in Virginia. We hypothesized that presence of hydric soils, soil physicochemistry and soil bacterial community structure would differ between hummocks and hollows. We fingerprinted soils collected from different microtopographic locations using Length Heterogeneity Polymerase Chain Reaction (LH-PCR) to study their bacterial community structures. Two hummocks had silty/sandy loam soils with mean chroma values of > 4, showing no indication of ‘hydric soils’ (i.e., wetland soils). Two hollows, however, had clay loam soils with mean chroma values of 2 with gleying and redox concentrations observed, indicative of seasonally inundated wetlands. The soils of hollows also had higher organic matter content and soil moisture compared to the soils of hummocks (P < 0.05). Multidimensional scaling (MDS) and Analysis of similarity (ANOSIM) of the fingerprints revealed differences in soil microbial community structures between hummocks and hollows (Global R = 0.30, P < 0.01). The diversity measures of the fingerprints (Shannon’s H′) were also different by microtopography with higher diversity in hollows relative to hummocks (P < 0.05). LH-PCR proves to be a useful tool in examining bacterial community composition of wetland soils in this study. However, cloning and sequencing of specific community LH-PCR profiles of interest is necessary to fully characterize the community down to genus/species level. With species identities we should be able to not only better explain differences observed in the community profiles, but study their relations to hydrologic and/or physicochemical conditions of wetlands.     

Improvement of antioxidant and defense properties of Tomato (var. Pusa Rohini) by application of bioaugmented compost

Nutrient management practices play a significant role in improving the nutritional quality of tomato. The present study deals with the evaluation of compost prepared using Effective Microorganisms (EM), on antioxidant and defense enzyme activities of Tomato (Lycopersicon esculentum). A field experiment with five treatments (control, chemical fertilizer and EM compost alone and in combination) was conducted in randomized block design. An increment of 31.83% in tomato yield was recorded with the combined use of EM compost and half recommended dose of chemical fertilizers (N₅₀P₃₀K₂₅ + EM compost at the rate of 5 t ha⁻¹). Similarly, fruit quality was improved in terms of lycopene content (35.52%), antioxidant activity (24–63%) and defense enzymes activity (11–54%), in tomatoes in this treatment as compared to the application of recommended dose of fertilizers. Soil microbiological parameters also exhibited an increase of 7–31% in the enzyme activities in this treatment. Significant correlation among fruit quality parameters with soil microbiological activities reveals the positive impact of EM compost which may be adopted as an eco-friendly strategy for production of high quality edible products.     

Radioecological Risk Assessment of Low Selenium Concentrations through Genetic Fingerprints and Metabolic Profiling of Soil Bacterial Communities

In a context of environmental risk assessment of nuclear ⁷⁹Se radionuclide, the impact of low Se-selenite concentrations (0.008 and 8 mg kg⁻¹) on bacterial communities of two soils, a silty clay loam and a sandy soil, was investigated over a 6-month incubation time. This Se-selenite was partially labelled with ⁷⁵Se. The state of the Se-impacted bacterial communities was analyzed through total bacterial counts, DNA fingerprints (ARISA profiles) and metabolic profiling (carbon substrate utilization patterns). Furthermore, the genetic diversity of bacterial populations involved in Se volatilization was evaluated by tpm (thiopurine methyltransferase gene) profiling. Emissions of ⁷⁵Se and CaCl₂-extractable ⁷⁵Se were measured by γ-spectrometry and scintillation analysis. Se-selenite inputs changed transiently the substrate utilization patterns of bacterial communities but did not affect the other indicators. Se volatilization was at its highest level just after adding Se-selenite and for about 1 week. This volatilization was proportional to the added Se-selenite concentrations. It was 100-fold higher in silty clay loam, even though Se bioavailability was reduced in this soil. The soils were amended with crushed grass 3 months after the addition of Se-selenite. This organic amendment affected the organization of bacterial communities and increased the Se-volatilizing activities of both soils. Original soil organic carbon and bacterial diversity and activities seemed responsible for the different levels of Se emissions observed in soils. tpm lineages, encoding Se methyltransferases, were detected in both soils, confirming the broad distribution of tpm-harbouring bacteria and their probable role in the emissions of volatile Se. Five distinct groups of tpm were recorded per soil, with tpmI lineage being detected throughout the incubation period. This study demonstrates the ability of bacterial communities at volatilizing Se concentrations inferior to geochemical backgrounds and suggests that a probable transfer of nuclear Se will occur through volatilization after an environmental spill.     

Estimation of bioavailability and potential risks of naphthalene in soils with solid phase microextraction

A series of batch experiments were conducted to observe the variations of bioavailability of naphthalene in different types of soil with indigenous microorganisms. Solid phase microextraction (SPME) was employed to estimate the bioavailability of naphthalene in the soils. Various soil properties were attained by artificially modifying soil organic matter (SOM) with the addition of bagasse compost and textures with the addition of original silt and clay to determine the correlation between the amount of biodegraded naphthalene after 300 h and the amount of extractable naphthalene by SPME. Experimental results indicated that the biodegradation rate increased from 0.30 (sandy loam) to 0.48 (silty loam) μg g⁻¹ h⁻¹ when soils had more silt/clay. In contrast, the biodegradation rate slightly decreased from 0.30 (1.3% SOM) to 0.20 (5.2% SOM) μg g⁻¹ h⁻¹ when the SOM was high. Distributions of naphthalene in soils after biodegradation were affected by the addition of bagasse compost. It showed that the bioavailability of naphthalene in soils decreased with an increase in SOM. Sequestration as measured by ultrasonic extractability evidently occurred within 4 months in aged soil samples. However, the amounts extracted by sonication after 4 and 16 months of aging did not statistically differ from each other. The SPME measurements correlated well with the amount of biodegraded naphthalene by indigenous microorganisms. Results of this study demonstrate that SPME is a promising method to estimate the bioremediation efficacy of naphthalene-contaminated soils with various properties.     

Spatial variability of soil nutrients and microbiological properties after the establishment of leguminous shrub Caragana microphylla Lam. plantation on sand dune in the Horqin Sandy Land of Northeast China

The objective of this study is to determine the spatial variability of nutrients, microbial biomass, and enzyme activities of soil due to the establishment of shrub plantation on moving sandy dunes, as part of an effort to understand the microenvironmental factors that control the soil microbiological properties. Caragana microphylla Lam., an indigenous leguminous shrub, is the dominant plant species used to control desertification in the semi-arid Horqin Sandy Land of Northeast China. In a 26-year-old C. microphylla plantation, soil samples were collected from three soil depths (0-5 cm, 5-10 cm, and 10-20 cm), three slope positions (windward slope, top slope, and leeward slope), and two microsites (under shrubs and between shrubs). The results showed significant differences in soil EC, nutrient content (except for total K), microbial biomass C and N, and the activities of dehydrogenase, urease, and protease at different slopes, soil depths, and microsites. Significant differences in pH at different microsites and slopes, soil moisture and polyphenol oxidase activity at different soil depths and slopes, and activities of phosphomonoesterase and nitrate reductase at different soil depths were also observed. The soil nutrient contents and microbiological activities were greater in the surface soil layer and decreased with the increase of soil depth. Soil organic C, total N, total P, available P and K, microbial biomass C and N, and the activities of enzymes tested (except for protease) under shrubs were higher than those in between shrubs. Furthermore, significant correlations among soil organic C, microbial biomass C and N, the activities of phosphomonoesterase, dehydrogenase, urease, protease, and nitrate reductase were observed, and correlations were also found among EC, total N, total P, available P and K, enzyme (except for polyphenol oxidase) activities, and microbial biomass C and N contents. These results suggest that microenvironmental factors (slope, soil depth and microsite) have significant influences on the spatial distribution of soil nutrients and microbiological properties when the C. microphylla sand-fixing plantation is established in the moving sand dunes in the Horqin Sandy Land.     

干旱胁迫对不同土壤基质下核桃楸幼苗的生理特性的影响

为探究不同土壤基质条件下核桃楸幼苗对干旱胁迫生理特性的响应,以两年生核桃楸幼苗为研究对象,在腐殖土、壤土和砂壤土三种基质条件下进行控水试验,水分梯度分别设置为CK(正常供水,80%田间持水量)、T1(轻度胁迫,60%田间持水量)、T2(中度胁迫,40%田间持水量)和T3(重度胁迫,20%田间持水量),测定幼苗叶片叶绿素、丙二醛、脯氨酸、抗氧化酶和光合指标。结果表明,随着胁迫程度的加深,叶绿素含量和Chla/b均呈逐渐降低的趋势(P<0.05),在胁迫60d时,T3处理下的叶绿素a(Chla)和叶绿素b(Chlb)分别比CK低65.41%和51.57%,3种基质中叶绿含量大小顺序为:腐殖土>壤土>砂壤土。随着胁迫程度的加深,叶片脯氨酸(Pro)、丙二醛(MDA)则呈逐渐升高的趋势(P<0.05),胁迫60d时,砂壤土中T3处理的Pro含量最高为83.37mg·g-1,比CK高86.32%。腐殖土中幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均随胁迫程度加深而升高,壤土中叶片SOD活性则呈先升高后降低的变化规律。3种土壤基质中核桃楸叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均随着胁迫程度的加深而降低,但不同基质中幼苗叶片的气孔限制和非气孔限制发生的时间不同,T3处理的叶片胞间CO2浓度(Ci)在腐殖土中是12:00时最低,而在壤土和砂壤土中则是10:00时最低。土壤全氮、全磷、渗透速率和蒸腾速率与叶绿素含量存在显著的正相关关系(P<0.05),土壤容重与叶绿素含量存在显著的负相关关系(P<0.05)。因此,土壤基质和干旱胁迫对核桃楸幼苗的生理生化和光合特性产生了显著的影响,重度胁迫对幼苗的叶绿素、渗透物质和酶体系产生了严重的损伤,同时降低了核桃楸幼苗的光合生产力。总体上,腐殖土中的幼苗有着较好的抗旱表现。     

Microbial DNA profiling by multiplex terminal restriction fragment length polymorphism for forensic comparison of soil and the influence of sample condition

Aims:  To evaluate: (i) the impact of air-drying on bacterial, archaeal and fungal soil DNA profiles and (ii) the potential use of multiplex-terminal restriction fragment length polymorphism (M-TRFLP) as a tool for forensic comparison of soil.
Methods and Results:  An M-TRFLP approach was used to profile bacterial, archaeal and fungal DNA profiles from five different soil sites. Air-drying soil significantly reduced the quantity of DNA but the number of operational taxanomic units (OTU) was unaffected. The impact of air-drying on soil DNA profiles was dependent on soil site and microbial primers. Fungal profiles were altered the least by air-drying. For prokaryotic profiles, air-drying altered the relative similarity/dissimilarity between soil sites. The M-TRFLP approach was more discriminatory compared with soil colour and single-taxa profiling, but did not significantly improve resolution between two similar soils.
Conclusions:  Of those tested, soil fungi were potentially the more robust target for application to soil forensic studies as they were altered less by air-drying and provided clear discrimination of soils from different sites. The M-TRFLP method demonstrated potential to achieve greater resolution, discriminating the soil sites based on both bacterial and fungal components.
Significance and Impact of the Study:  Soil DNA profiling has potential as a forensic tool, but sample condition and the appropriate selection of microbial target taxa must be considered.     

The fate of a genetically modified Pseudomonas strain and its transgene during the composting of poultry manure

The fate of the genetically modified (GM) Pseudomonas chlororaphis strain 3732 RN-L11 and its transgene (lacZ insert) during composting of chicken manure was studied using plate count and nested polymerase chain reaction (PCR) methods. The detection sensitivity of the nested PCR method was 165 copies of the modified gene per gram of moist compost or soil. Compost microcosms consisted of a 100-g mixture of chicken manure and peat, whereas soil microcosms were 100-g samples of sandy clay loam. Each microcosm was inoculated with 4 x 1010 CFU of P. chlororaphis RN-L11. In controlled temperature studies, neither P. chlororaphis RN-L11 nor its transgene could be detected in compost microcosms after incubation temperature was elevated to 45 degrees C or above for one or more days. In contrast, in the compost microcosms incubated at 23 degrees C, the target organism was not detected by the plate count method after 6 days, but its transgene was detectable for at least 45 days. In compost bins, the target organism was not recovered from compost microcosms or soil microcosms at different levels in the bins for 29 days. However, the transgene was detected in 8 of the 9 soil microcosms and in only 1 of the 9 compost microcosms. The compost microcosm in which transgene was detected was at the lower level of the bin where temperatures remained below 45 degrees C. The findings indicated that composting of organic wastes could be used to reduce or degrade heat sensitive GM microorganisms and their transgenes.     

N uptake and N status in ponderosa pine as affected by soil compaction and forest floor removal

Soil compaction and forest floor removal influence fundamental soil processes that control forest productivity and sustainability. We investigated effects of soil compaction and forest floor removal on tree growth, N uptake and N status in ponderosa pine. Factorial combinations of soil compaction (non-compacted and compacted) and forest floor removal (forest floor present and no forest floor) were applied to three different surface soil textures. For studying N uptake, four trees from every treatment were ¹⁵N labeled with 130.6 mg m^–2 of ¹⁵N. Tree responses to compaction were dependent on the forest floor removal level. In loam and clay soils, non-compacted+no forest floor was beneficial to tree growth. Tree growth was depressed with compaction+no forest floor in clay soil. In sandy loam soil, compaction+no forest floor showed the best tree growth. No N deficiency was found in any soil type but a graphical method suggested correlation between N status and tree growth. In loam and clay soils, compaction+forest floor present increased N uptake. Nitrogen uptake was explained significantly by potential N mineralization in loam and clay soils. In sandy loam soil, the effects of compaction and forest floor removal were more complex, with the N uptake improved in the compaction+no forest floor treatment and reduced under compaction+forest floor present. Soil compaction may have influenced N tracer uptake because of improved unsaturated flow and root-soil contact. However, N immobilization may have restricted N uptake in compaction+forest floor present in the sandy loam soil. The study illustrates how soil properties and site preparation can potentially interact to affect N dynamics and forest productivity.     

Soil composition affects the nesting behavior of blue-tailed bee-eaters (Merops philippinus) on Kinmen Island

The blue-tailed bee-eater (Merops philippinus) is a summer migrant that breeds on Kinmen Island, located off the west coast of Taiwan, about 5 km from the southern coast of mainland China. The aim of this study was to investigate why blue-tailed bee-eaters build their nests in sandy loam and sandy clay loam, but not in clay loam. Soil chemical and physical properties, and mineralogical composition were measured for the different soil types. Clay loam had a significantly lower pH, Na, and base saturation than did sandy loam or sandy clay loam. Clay loam had a significantly higher N, cation-exchange capacity (CEC), K, and free iron (Fe_d) and aluminum oxide (Al_d) contents than the other soil types. Clay loam had significantly lower sand and higher clay content, and higher bulk density and penetration resistance than the other soil types. The correlation coefficients (r ²) between penetration resistance and Fe_d, Al_d, and clay contents were 0.997, 0.848, and 0.779, respectively. Soil strength and compaction are important criteria for bee-eaters nesting-site selection. The lower pH of clay loam would enhance the exchangeable Al and acidity, further increasing the soil aggregation. Thus, it might prevent the bee-eaters from excavating nesting burrows.     

Soil types with different texture affects development of Rhizoctonia root rot of wheat seedlings

The effect of different soil textures, sandy (97.5% sand, 1.6% silt, 0.9% clay), loamy sand (77% sand, 11% silt, 12% clay) and a sandy clay loam (69% sand, 7% silt, 24% clay), on root rot of wheat caused by Rhizoctonia solani Kühn Anastomosis Group (AG) 8 was studied under glasshouse conditions. The reduction in root and shoot biomass following inoculation with AG-8 was greater in sand than in loamy sand or sandy clay loam. Dry root weight of wheat in the sand, loamy sand and sandy clay loam soils infested with AG-8 was 91%, 55% and 28% less than in control uninfested soils. There was greater moisture retention in the loamy sand and sandy clay loam soils as compared to the sand in the upper 10–20 cm. Root penetration resistance was greater in loamy sand and sandy clay loam than in sand. Root growth in the uninfested soil column was faster in the sand than in the loamy sand and sandy clay loam soils, the roots in the sandy soil being thinner than in the other two soils. Radial spread of the pathogen in these soils in seedling trays was twice as fast in the sand in comparison to the loamy sand which in turn was more than twice that in the sandy clay loam soil. There was no evidence that differences among soils in pathogenicity or soil spread of the pathogen was related to their nutrient status. This behaviour may be related to the severity of the disease in fields with sandy soils as compared to those with loam or clay soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同类型土壤上种植的不同面筋含量冬小麦品种灌浆期间籽粒中淀粉分支酶活性变化

种植在粘土、壤土和沙土中的3个面筋含量高、中、低的冬小麦品种灌浆期间籽粒中淀粉分支酶(SBE)活性变化均呈单峰曲线,开花后20 d达到峰值.面筋含量高的品种在粘土和沙土上种植的SBE活性较高,而面筋含量中等和较低的品种在粘土和壤土中种植的SBE活性较高.     

温度对不同粘粒含量稻田土壤有机碳矿化的影响

模拟了亚热带地区3种不同粘粒含量的水稻土(砂壤土、壤粘土、粉粘土)在5种温度(10、15、20、25和30℃)下的有机碳(SOC)矿化特征,分析SOC矿化对温度变化的响应.结果表明:在160d的培养期内,温度对3种水稻土SOC矿化量的影响有一定差异,30℃时砂壤土、壤粘土和粉粘土SOC矿化量分别是10℃时的3.5、5.2和4.7倍.在较低温度(≤20℃)下,SOC矿化速度较低且相对稳定;在较高温度(≥25℃)下,前期SOC矿化速度较高,随着培养时间的延长逐渐降低,并趋于稳定.3种水稻土SOC矿化的温度系数(Q10)随培养时间出现波动,砂壤土的Q10平均值最低,为1.92,壤粘土和粉粘土的Q10平均值较接近,分别为2.37和2.32;3种土壤矿化速率常数(k)与温度呈极显著的指数相关(P<0.01).3种水稻土有机碳矿化对温度变化的响应敏感度依次为壤粘土>粉粘土>砂壤土.     

Quantification and correlation of vesicular-arbuscular mycorrhizal propagules with soil properties of some mollisols of northern India

The populations of vesicular-arbuscular mycorrhizae (VAM) propagules by the most probable number method in some mollisols and their correlations with some important soil properties were determined. On average, the six soils, Phoolbagh clay loam, Beni silty clay loam, Haldi loam, Nagla loam, Khamia sandy loam and Patherchatta sandy loam contained 4.9, 4.0, 7.9, 7.9, 3.3 and 13.0 propagules/g soil, respectively, i.e. none of the soils was found to be high in VAM. The size of the VAM population was compared to soil properties such as pH, organic carbon, sand content, available phosphorus and available potassium, cation-exchange capacity, silt and clay contents. A significant positive correlation (r=0.586) was only found with available soil phosphorus (P<0.05) and a significant negative correlation (r=-0.555) with soil clay content (P<0.05).Directorate research paper series No. 7862     

Effects of municipal waste compost and sewage sludge on proton binding behavior of humic acids from Portuguese sandy and clay loam soils

The effects of amendment with municipal solid waste compost (MSWC) and sewage sludge (SS) on acid-base properties of soil humic acids (HAs) were investigated. For this purpose, HAs were isolated from MSWC and SS and two different Portuguese soils, one sandy and the other clay loam, either unamended or amended with MSWC or SS at a rate of 60 t ha(-1), and analysed by potentiometric titrations at various ionic strengths (0.01, 0.05, 0.1 and 0.3M) over the pH range from 3.5 to 10.5. All titration data were fitted with the NICA-Donnan model and the variations of model parameters between the various HA samples were discussed. The HAs from MSWC and SS had lower acidic functional group contents and higher proton binding affinities than the control soil HAs. Amending soils with MSWC and SS determined a decrease of acidic functional group contents and an increase on proton binding affinities of soil HAs. These effects were more evident in SS-amended soil HAs than in MSWC-amended soil HAs, and in clay loam soil HA than in sandy soil HA.     

汞污染对水稻土微生物和酶活性的影响

通过盆栽试验,研究了两种水稻土中不同汞处理的微生物学和酶学效应.结果表明：水稻收获后,除部分土壤的呼吸强度和代谢商随汞处理浓度的增加而持续增加外,不同浓度汞处理后土壤微生物量碳、呼吸强度、土壤脲酶、酸性磷酸酶和脱氢酶均表现为在低浓度汞处理(<2 mg Hg·kg^-1)时升高,而在高浓度汞处理(≥2 mg Hg·kg^-1)时则下降.土壤微生物商是对汞处理比较敏感的微生物学指标.黄红壤不同浓度汞处理的土壤酶活性大于小粉土.对重金属生态剂量ED₅₀进行分析表明,汞对小粉土脲酶活性和黄红壤磷酸酶活性的生态毒性均较强.     

Nutrients and antinutrient constituents of Amaranthus caudatus L. Cultivated on different soils

This study investigated variations in the concentration of nutrients, antinutrients and mineral content of Amaranthus caudatus harvested from different soil types at various stages of maturity. Four out the five soils namely; sandy clay loam, silty clay loam, clayey loam and loam were experimentally formulated from primary particles of silt, clay and sand in line with the United State Department of Agriculture’s (USDA) soil triangle protocol. The unfractionated soil was used as the control. After harvesting at pre-flowering (61 days after planting), flowering (71 days after planting) and post-flowering (91 days after planting) stages, nutrient and antinutrient analyses were carried out following Association of Official Analytical Chemists (AOAC) and other referenced methods while the Inductively Coupled Plasma- Optical Emission Spectrometer was used to determine mineral compositions of the plant samples. The results of the study revealed that particle size and physicochemical properties of the soil influenced the number of minerals deposited in plant tissues. It was further observed that the nutritional properties of the plant change as plant ages. For an optimal yield of vitamins A and E, clayey loam proved to be the best soil particularly when A. caudatus is harvested before flowering but for vitamin C, sandy clayey loam yielded the highest output at the same stage. Similarly, clayey loam and loam soils yielded the highest proximate compositions at flowering and pre-flowering; however, mineral elements (micro and macro) were highest in control and loam soils.     

Effect of Soil Texture on the Distribution and Infectivity of Neoaplectana carpocapsae (Nematoda: Steinernematidae)

The vertical migration of N. carpocapsae infective juveniles applied to the soil surface or introduced 14 cm below the soil surface was studied in four different soil types (pure silica sand, coarse sandy loam, silty clay loam, and clay). The percentage of juveniles able to migrate and infect wax moth pupae placed in the soil decreased as the percentage of clay and silt increased. Most nematodes placed on the soil surface remained within 2 cm of the surface, but some penetrated to a depth of 10 cm in pure silica sand and coarse sandy loam to infect pupae. Some pupae at the same depth were also infected with nematodes in silty clay loam soil. In pure silica sand and coarse sandy loam, nematodes introduced 14 cm below the soil surface were able to infect wax moth pupae located between 4 and 24 cm. Movement was least in clay soil and limited in silty clay loam. Nematodes showed a tendency to disperse upwards from the point of application. In all cases the number of migrating nematodes was greatest when wax moth pupae were present.     

Persistence of Viruses in Desert Soils Amended with Anaerobically Digested Sewage Sludge

Pima County, Ariz., is currently investigating the potential benefits of land application of sewage sludge. To assess risks associated with the presence of pathogenic enteric viruses present in the sludge, laboratory studies were conducted to measure the inactivation rate (k = log₁₀ reduction per day) of poliovirus type 1 and bacteriophages MS2 and PRD-1 in two sludge-amended desert agricultural soils (Brazito Sandy Loam and Pima Clay Loam). Under constant moisture (approximately -0.05 × 10⁵ Pa for both soils) and temperatures of 15, 27, and 40°C, the main factors controlling the inactivation of these viruses were soil temperature and texture. As the temperature increased from 15 to 40°C, the inactivation rate increased significantly for poliovirus and MS2, whereas, for PRD-1, a significant increase in the inactivation rate was observed only at 40°C. Clay loam soils afforded more protection to all three viruses than sandy soils. At 15°C, the inactivation rate for MS2 ranged from 0.366 to 0.394 log₁₀ reduction per day in clay loam and sandy loam soils, respectively. At 27°C, this rate increased to 0.629 log₁₀ reduction per day in clay loam soil and to 0.652 in sandy loam soil. A similar trend was observed for poliovirus at 15°C (k = 0.064 log₁₀ reduction per day, clay loam; k = 0.095 log₁₀ reduction per day, sandy loam) and 27°C (k = 0.133 log₁₀ reduction per day, clay loam; k = 0.154 log₁₀ reduction per day, sandy loam). Neither MS2 nor poliovirus was recovered after 24 h at 40°C. No reduction of PRD-1 was observed after 28 days at 15°C and after 16 days at 27°C. At 40°C, the inactivation rates were 0.208 log₁₀ reduction per day in amended clay loam soil and 0.282 log₁₀ reduction per day in sandy loam soil. Evaporation to less than 5% soil moisture completely inactivated all three viruses within 7 days at 15°C, within 3 days at 27°C, and within 2 days at 40°C regardless of soil type. This suggests that a combination of high soil temperature and rapid loss of soil moisture will significantly reduce risks caused by viruses in sludge.     

Control of Late Blight (Phytophthora capsici ) in Pepper Plant with a Compost Containing Multitude of Chitinase-producing Bacteria

Compost sustaining a multitude of chitinase-producing bacteria was evaluated in a greenhouse study as a soil amendment for the control of late blight (Phytophthora capsici L.) in pepper (Capsicum annuum L.). Microbial population and exogenous enzyme activity were measured in the rhizosphere and correlated to the growth and health of pepper plant. Rice straw was composted with and without a chitin source, after having been inoculated with an aliquot of coastal area soil containing a known titer of chitinase-producing bacteria. P. capsici inoculated plants cultivated in chitin compost-amended soil exhibited significantly higher root and shoot weights and lower root mortality than plants grown in pathogen-inoculated control compost. Chitinase and β-1,3-glucanase activities in rhizosphere of plants grown in chitin compost-amended soil were twice that seen in soil amended with control compost. Colony forming units of chitinase-producing bacteria isolated from rhizosphere of plants grown in chitin compost-amended soil were 10³ times as prevalent as bacteria in control compost. These results indicate that increasing the population of chitinase-producing bacteria and soil enzyme activities in rhizosphere by compost amendment could alleviate pathogenic effects of P. capsici.