湖南洞口县猪粪基质养殖蚯蚓以及蚯蚓土壤种植黑麦草测产试验

在洞口县杨林镇进行猪粪基质养殖蚯蚓和蚯蚓土壤种植黑麦草测产试验。试验结果:1) 养殖蚯蚓试验:60天猪粪基质pH 8.77,碱解氮0.71 g/kg,有效磷1.02 g/kg,速效钾1.92 g/kg,有机质22.32%,有效活菌数量5.21 × 108个/g。90天猪粪基质pH 8.87,碱解氮0.58 g/kg,有效磷0.91 g/kg,速效钾1.73 g/kg,有机质20.93%,有效活菌数量5.14 × 108个/g。60天猪粪基质比90天猪粪基质分别减少1.1%、增加22.4%、12.1%、11.0% (这3项差异显著P 2黑麦草鲜草最高产量达24,811 kg,较对照组(一般土壤种植)增产10,738 kg,增产76.3%,1 kg猪粪基质增产黑麦草鲜草10.47 kg。试验II组(90天猪粪基质)每667 m2黑麦草鲜草产量22,147 kg,较对照组增产8074 kg,增产57.4%,每667 m2施入猪粪基质1025 kg,1 kg猪粪基质增产黑麦草7.88 kg。60天猪粪基质较90天猪粪基质种植的黑麦草的产量高12.1%。结论:养殖蚯蚓60天猪粪基质较90天猪粪基质肥力高,其土壤种植的黑麦草的产量也高。并对培养蚯蚓土壤、蚯蚓改良修复土壤作用机理和用途进行了有益探索,为农业同行养殖蚯蚓和蚯蚓土壤利用方面提供参考。

蚯蚓生物积累表征土壤中芘的生物有效性研究

利用蚯蚓作为测试生物,引入蚯蚓-土壤积累因子(Earthworm-SoilAccumulationFactor,ESAF),就不同土壤中芘对蚯蚓的生物有效性进行了考察和研究。试验结果表明,蚯蚓在土壤中培养10d,体内积累芘的浓度达到平衡,积累浓度与土壤初始染毒浓度成显著正相关;土壤性质对土壤中芘的生物有效性具有非常重要的影响,土壤有机质、粘土矿含量越高,对芘的吸持能力越强,ESAF越小。

蚯蚓介导下镉胁迫对土壤理化性质和玉米生长的影响

为了探讨重金属如何驱动土壤动物的行为(垂直分布)进而影响土壤理化性质与作物生长,以赤子爱胜蚓为研究动物,利用室内模拟实验系统研究了镉胁迫下蚯蚓的生理响应、趋避行为及其对玉米生长的影响.结果表明,土壤镉污染影响了蚯蚓生理特征,总体上造成蚯蚓体内超氧化物歧化酶(SOD)活性下降而脂质过氧化产物(MDA)含量增加,这种不利效应导致蚯蚓作出了趋避响应,表现出向土壤深层分布的趋势.例如,处理第50 d,10 mg·kg^-1和30 mg·kg^-1镉处理组表层(0—10 cm)蚯蚓数量分别下降19.73%和22.17%,且其垂直分布与蚯蚓体内SOD活性显著负相关、与MDA含量显著正相关.蚯蚓垂直分布还改变了土壤有机质、碱解氮与速效磷含量,处理第50 d,30 mg·kg^-1镉处理组土壤中有机质、碱解氮、速效磷含量较对照组分别增加29.24%、15.50%、17.37%,且与蚯蚓分布数量极显著正相关.此外,玉米生物量和株高与土壤碱解氮、有机质、速效磷含量之间显著正相关.因此,土壤镉胁迫改变了蚯蚓的垂直分布,其行为变化改善了深层土壤营养状况(植物根系主要分布区),促进了玉米苗的生长,本研究成果可为镉污染对土壤生态系统的生态风险性评价提供新的实验依据和数据支撑.

设施菜田水肥管理模式下蚯蚓和土壤肥力状况的变化

通过田间定位试验,研究了设施有机菜田不同水肥（有机肥）管理模式下土壤蚯蚓密度和土壤基本肥力的变化及其关系,为有机菜田的合理灌溉培肥提供科学依据。结果表明：土壤湿度、孔隙度、有机碳、全氮、速效磷和速效钾含量均随有机肥施用量的增多而增加,增加幅度分别为4%~27%、6%~9%、19%~27%、19%~26%、141%~230%和74%~91%;有机肥处理土壤蚯蚓密度比不施肥处理显著提高43%~110%;相关分析表明,土壤蚯蚓密度与土壤生产力、土壤有机碳、全氮、速效磷和土壤孔隙度之间均呈极显著的正相关关系;土壤蚯蚓能够有效指示设施菜田土壤肥力状况,发挥重要的土壤生态功能;减量灌溉常规施肥为设施有机菜田的最佳水肥管理模式。

Effects of Arbuscular Mycorrhizal Fungi and Earthworm on Nematode Communities and Arsenic Uptake by Maize in Arsenic-Contaminated Soils

The influences of arbuscular mycorrhizal fungi (AMF,Acaulospora spp.and Glomus spp.) and rice straw and earthworms (RE,Eisenia foetida) on nematode communities and arsenic (As) uptake by maize (Zea mays L.) in Ascontaminated soils were examined in a field experiment conducted in Wujiang,Jiangsu Province,China.The experiment was designed as a 2 × 2 factorial with the factors of AMF (inoculated or uninoculated) and RE (added or not added).The results demonstrated that AMF inoculation led to significantly higher root colonization of AMF and root dry weight.Plants inoculated with both AMF and RE had the highest As concentrations in root.The number of total nematodes increased with AMF inoculation when RE was absent,and decreased with RE addition when AMF was inoculated.The improved abundance of nematodes with the AMF treatment implied that the tested AMF acted as food sources for fungivores.The abundances of omnivores-predators and plant parasites were reduced by earthworm activity.Twentyseven genera of nematodes were identified,with Filenchus dominant in all treatments.Trophic diversity,Shannon-Weaver diversity,Simpson dominance index,and species richness indicated higher species diversity,more proportionate species composition,evenly distributed species,and more food sources in the AMF,RE,and their interaction treatments.Maturity index showed a moderately disturbed environment due to As pollution.Besides enhancing plant uptake of contaminants,AMF and RE amendments could also improve soil health by restoring the structure of soil communities,as reflected by more stable nematode community structure.

Topsoil as Affected by Dung Deposition Under Resting Places of Red Howler Monkey (Alouatta seniculus)

The short-term influence of dung deposition and the further redistribution of dung by dung beetles were studied under a resting place of the red howler monkey （Alouatta seniculus） living in tropical ralnforests of South America. Monkey dung was experimentally clumped on the field in a place used by troops of howler monkeys for resting in the Nouragues Reserve Station, French Guiana. Dung-treated plots were sampled serially over three weeks and compared with controls located in their immediate vicinity. The composition of the soil matrix （top 10 cm） was studied in successive microlayers using an optical method. Under the influence of dung beetle activity, the topsoil became more homogeneous by losing its litter, its content in earthworm faeces increased in the course of time, and surface mineral deposits were penetrated by roots. The results were interpreted in the light of present knowledge on the effects of soil animal activity on plant growth and survival of seedlings.

Fertigation with Wastewater and Vermicompost: Soil Biochemical and Agronomic Implications

To study how wastewater(WW) and different organic sources(humic substances or vermicompost) affected soil chemical and biochemical fertility and agronomic productivity in field-grown melon, an experiment arranged in a randomized complete block design with three replications was conducted with the following treatments: three different mixtures of irrigation water(100% WW, 50% WW with 50% groundwater, and 100% groundwater) and, for each WW treatment, four different organic fertilization treatments of control without organic matter application(CK), vermicompost used as surface mulch(SM), vermicompost incorporated into the soil(VC),and humic substances extracted by vermicompost(HS). Chemical and biochemical results indicated an improvement in soil fertility,suggested by the increase in soil organic carbon and nutrient(nitrate and macro- and microelements) contents and in soil microbial activities(hydrolytic and oxidative enzymes), in particular in the VC treatments. In addition, even soil potential metabolism was stimulated by WW combined with organic treatments, as highlighted by the increase in the metabolic(dehydrogenase activity/watersoluble carbon) and nitrification indices(NO-3and NH+4). Melon productivity confirmed these results, with the highest yield and melon quality in the VC treatments irrigated with 100% WW. In conclusion, the combined use of WW and organic amendment,recovering both mineral and organic nutrients from these kinds of recycled materials, was effective in the improvement of soil quality and crop productivity.

Effects of Epigeic Earthworms on Decomposition of Wheat Straw and Nutrient Cycling in Agricultural Soils in a Reclaimed Salinity Area:A Microcosm Study

Earthworms, one of the most important macroinvertebrates in terrestrial ecosystems of temperate zones, exert important influ- ences on soil functions. A laboratory microcosm study was conducted to evaluate the influence of the earthworm Eisenia fetida on wheat straw decomposition and nutrient cycling in an agricultural soil in a reclaimed salinity area of the North China Plain. Each microcosm was simulated by thoroughly mixing wheat straw into the soil and incubated for 120 d with earthworms added at 3 different densities as treatments： control with no earthworms, regular density （RD） with two earthworms, and increased density （ID） with six earthworms. The results showed that there was no depletion of carbon and nitrogen pools in the presence of the earthworms. Basal soil respiration rates and metabolic quotient increased with the increase in earthworm density during the initial and middle part of the incubation period. In contrast, concentrations of microbial biomass carbon and microbial biomass quotient decreased in the presence of earthworms. Earthworm activity stimulated the transfer of microbial biomass carbon to dissolved organic carbon and could lead to a smaller, but more metabolically active microbial biomass. Concentrations of inorganic nitrogen and NO^-N increased significantly with the increase in earthworm density at the end of the incubation （P ~ 0.05）, resulting in a large pool of inorganic nitrogen available for plant uptake. Cumulative net nitrogen mineralization rates were three times higher in the ID treatment than the RD treatment.

Effects of Earthworms and Ryegrass on the Removal of Fluoranthene from Soil

Earthworms can promote the bioremediation of contaminated soils through enhancing plant growth and microorganism development. The individual and combined effects of earthworms and ryegrass （Lolium multifloram Lain.） on the removM of fiuoranthene from a sandy-loam alluvial soil were investigated in a 70-d microcosm experiment. The experiment was set up in a complete factorial design with treatments in four replicates： without earthworms or ryegrass （control, CK）, with earthworms only （E）, with ryegrass only （P）, and with both earthworms and ryegrass （EP）. The residual fluoranthene, microbial biomass C, and polyphenol oxidase activity in the soil changed significantly （P 〈 0.01） with time. In general, the residual concentration of fluoranthene in the soil decreased sharply from 71.8-88.7 to 31.7-37.4 mg kg-1 in 14 d, and then decreased gradually to 19.7-30.5 mg kg-1 on the 70th d. The flu- oranthene concentration left in the soil was the least with both earthworms and ryegrass, compared to the other treatments at the end of the experiment. Half-life times of fluoranthene in the E, P, and EP treatments were 17.8%-36.3% smaller than that of CK. More fluoranthene was absorbed by earthworms than ryegrass. However, the total amounts of fluoranthene accumulated in both the ryegrass and earthworms were small, only accounting for 0.01%-1.20% of the lost fluoranthene. Therefore, we assumed that microbial degradation would play a dominant functional role in fluoranthene removal from soil. We found that earthworms significantly increased microbial biomass C and polyphenol oxidase activity （P 〈 0.01） in the presence of ryegrass at the end of the experiment. Furthermore, microbial biomass C and polyphenol oxidase activity were significantly （P 〈 0.05） and negatively related to the residual fluoranthene concentration. This implied that earthworms might promote the removal of fluoranthene from soil via stimulating microbial biomass C and polyphenol oxidase activity.

Prediction of Polycyclic Aromatic Hydrocarbon Bioaccessibility to Earthworms in Spiked Soils by Composite Extraction with Hydroxypropyl-β-Cyclodextrin and Organic Acids

Traditional exhaustive extraction methods often overestimate the risk of polycyclic aromatic hydrocarbon(PAH) bioaccessibility to biota. Therefore, reliable assessment methods need to be established. In this study, a composite extraction with hydroxypropyl-β-cyclodextrin(HPCD) and three low-molecular-weight organic acids, oxalic acid(OA), malic acid(MA), and citric acid(CA), was used to predict the PAH bioaccessibility to earthworms, subjecting to two soils(red soil and yellow soil) spiked with selected PAHs,phenanthrene, pyrene, chrysene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene. For both soils,concentrations of PAHs by composite extraction using HPCD-OA(R^2= 0.89–0.92, slope = 1.89–2.03; n = 35), HPCD-MA(R^2=0.92–0.96, slope = 1.43–1.67; n = 35), and HPCD-CA(R^2= 0.92–0.96, slope = 1.26–1.56; n = 35) were significantly correlated with PAH accumulation in the Eisenia fetida earthworms. Moreover, the HPCD-CA-and HPCD-MA-extracted PAH concentrations were closer to the earthworm-accumulated PAH concentration than the extraction using just HPCD. The results indicated that the composite extraction could improve the prediction of PAH bioaccessibility, and therefore can serve as a reliable chemical method to predict PAH bioaccessibility to earthworms in contaminated soils.

Functional attributes： Compacting vs decompacting earth- worms and influence on soil structure

A short term field mesocosm experiment was performed in semi-deciduous forest areas of Ivory Coast to assess the impact of a decompacting （Hyperiodrilus africanus, Eudrilidae） and two compacting （Millsonia omodeoi and Dichogaster terrae nigrae, Acanthodrilidae） earthworm species on soil properties. These species have been selected for their predominance in the re- gion and their contrasting impact on soil structure. The experimental design consisted of a treatment without worms （control）, and treatments with one, two or three species of earthworms. Both compacting and decompacting earthworms increased water infil- tration rate in all treatments, with marked impact in H. africanus and M. omodeoi＋D, terraenigrae treatments. Interactions be- tween compacting and decompacting species resulted in more large aggregates in comparison to when the compacting species D. terraenigrae was alone. This may be accounted for by their compacting attribute as compacting earthworms are responsible for producing the highest number of large aggregates. The low values of mean weight diameter in treatments combining decompact-ing and compacting earthworms compared with compacting ＂M. omodeoi＂ one also confirmed the trend of decline in soil com-paction in the presence of the decompacting species. These results showed positive impact of species richness on soil structure regulation, which is crucial in ecosystem productivity and support consequently the insurance hypothesis. In fact, this study showed that the preservation of earthworm species belonging to these two contrasting functional groups is essential for the main-tenance of stable soil structure regulation in agro-tropical ecosystems.