Survival of Aporrectodea caliginosa and its effects on nutrient availability in biosolids amended soil

Few earthworms are present in production agricultural fields in the semi-arid plains of Colorado, where earthworm populations may be constrained by limited water and/or organic matter resources. We conducted a 12-week laboratory incubation study to determine the potential of a non-native endogeic earthworm (Aporrectodea caliginosa) to survive in a low-organic matter Colorado soil (1.4% organic C content), supplemented with or without biosolids, and to determine the effects of A. caliginosa on soil microbial biomass and soil nutrient availability. A factorial design with three main effects of A. caliginosa, biosolids addition, and time was used. Data was collected through destructively sampling at one, two, four, eight, and twelve weeks. During the 12-week study, 97.5% of the worms in the soil survived, and the survival of the earthworms was not significantly affected by the addition of biosolids. The addition of biosolids, however, did significantly reduce the gain in mass of the earthworms (8% mass gain compared to 18% in soil without biosolids). The presence of A. caliginosa significantly increased soil NH₄-N, and NO₃-N concentrations by 31% and 4%, respectively, which was less than the six fold increases in both soil NH₄-N, and NO₃-N concentrations supplied from biosolids. Microbial biomass carbon was not affected by A. caliginosa, but microbial biomass N was affected by an earthworm × biosolids interaction at week 1 and 12. We concluded that A. caliginosa can survive in a low-organic matter Colorado soil under optimal moisture content and that once established, A. caliginosa can provide modest increases in inorganic N availability to crops Colorado agroecosystems.     

The earthworm (Aporrectodea caliginosa) primes the release of mobile and available micronutrients in soil

The objectives of our study were to quantify the impact of endogeic earthworms Aporrectodea caliginosa (Savigny) on iron (Fe), manganese (Mn) and zinc (Zn) mobility and availability in soil. Dried rye straw (Cecale cereale L.), clover aboveground parts (Trifolium pratense L.) or calcium carbonate were added to determine the effects on soil micronutrient mobility. To test the importance of soil–water saturation mediated by earthworms, soil samples were modified to 60% (control) and 100% (as in casts) water holding capacity (WHC). To assess availability of micronutrients, a cucumber plant (Cucumis sativus L.) bioassay were used. Earthworm casts had generally higher amounts of water-soluble micronutrients compared with bulk soils regardless of their moisture contents. The increased micronutrient mobility was more pronounced in casts from soil samples amended with plant residues (especially with straw) and was significantly higher than mobility in control soil for at least 1 week after the casts were deposited. Pre-incubation of soils amended with clover or straw with living earthworms for 4 weeks produced an increase in both shoot biomass and translocation rate of micronutrients (Mn, Zn) into xylem sap of cucumber compared to soils not worked by earthworms. The earthworm-mediated plant performances were determined 4 weeks after the earthworms were removed. The results demonstrated that earthworms can significantly impact the formation of mobile and available micronutrients in a soil. The relationship between micronutrient availability to cucumber plants and earthworm contribution to nitrogen (N) mineralization and micronutrient mobility are discussed.     

C and N turnover of fermented residues from biogas plants in soil in the presence of three different earthworm species (Lumbricus terrestris,Aporrectodea longa,Aporrectodea caliginosa)

A soil microcosm experiment was performed to assess (1) the C- and N- turnover of residues from biogas plants in soils in the presence of three earthworm species (Lumbricus terrestris, Aporrectodea longa and Aporrectodea caliginosa) and (2) the resulting changes in soil chemical and microbiological properties when using these residues as fertilizer in comparison to conventional slurry. Earthworms were exposed in soils, fertilized with an equivalent amount of 120 kg of NH₄-N ha^?1 from: (1) conventional cattle slurry and (2) a fermented residue derived from cattle slurry, grass (silage) and maize. Additional treatments without slurry and earthworms were used as controls.There was considerable evidence that soils fertilized by fermented slurry comprised fewer amounts of readily available nutrients for microbial C and N turnover. We observed significant stimulation of microbial biomass, basal respiration and nitrification in treatments with conventional slurry, especially in the presence of earthworms. However, the stimulation of microbial activity by manure and earthworms were significantly lower in treatments with fermented slurry. Moreover, the results showed clear interactions between different earthworm species and manures. While the biomass of the anecic species (L. terrestris and A. longa) increased in both slurry treatments, the biomass of A. caliginosa (endogeic) decreased, with a significantly stronger biomass decline in treatments with fermented slurry. The metabolic quotients revealed microbial stress metabolism in fermented slurry treatments, predominantly in treatments with A. caliginosa. We conclude that particularly A. caliginosa and soil microorganisms competed for labile C sources in treatments with fermented slurry. An application of these residues as fertilizer might result in a reduction of microbial activity in agricultural soils and in a decline of endogeic earthworms.     

Effects of Aporrectodea caliginosa (Savigny) on nitrogen mobilization and decomposition of elevated‐CO2 Charlock mustard litter

This study was conducted to improve our understanding of how earthworms and microorganisms interact in the decomposition of litter of low quality (high C : N ratio) grown under elevated atmospheric [CO₂]. A microcosm approach was used to investigate the influence of endogeic earthworm (Aporrectodea caliginosa Savigny) activity on the decomposition of senescent Charlock mustard (Sinapis arvensis L.) litter produced under ambient and elevated [CO₂]. Earthworms and microorganisms were exposed to litter which had changed in quality (C : N ratio) while growing under elevated [CO₂]. After 50 d of incubation in microcosms, C mineralization (CO₂ production) in the treatment with elevated‐[CO₂] litter was significantly lower in comparison to the ambient‐[CO₂] litter treatment. The input of Charlock mustard litter into the soil generally induced N immobilization and reduced N₂O‐emission rates from soil. Earthworm activity enhanced CO₂ production, but there was no relationship to litter quality. Although earthworm biomass was not affected by the lower quality of the elevated‐[CO₂] litter, soil microbial biomass (C_mic, N_mic) was significantly decreased. Earthworms reduced C_mic and fungal biomass, the latter only in treatments without litter. Our study clearly showed that A. caliginosa used the litter grown under different [CO₂] independent of its quality and that their effect on the litter‐decomposition process was also independent of litter quality. Soil microorganisms were shown to negatively react to small changes in Charlock mustard litter quality; therefore we expect that microbially mediated C and N cycling may change under future atmospheric [CO₂].     

烤烟不同生育期土壤酶及微生物活性的变化

在盆栽条件下研究了烤烟不同生长发育阶段土壤酶和微生物的变化规律.结果发现:随着烤烟的生长,过氧化氢酶活性、碱性磷酸酶活性、细菌数量以及砂壤土条件下的硝化细菌和解磷细菌都表现为先降后升再降的规律;硝酸还原酶活性、砂壤土条件下的氨化细菌和壤土下的解钾细菌数量表现为先升后降后期有所回升的规律;淀粉酶活性、真菌、放线菌、壤土条件下的解磷细菌和砂壤土下的解钾细菌数量表现先降后升.除碱性磷酸酶外,所测的土壤酶和微生物在烤烟不同生育阶段差异极显著.这说明在烤烟-土壤-土壤酶及微生物相互作用的系统中,土壤酶活性和微生物数量明显受到烤烟生长发育的影响.     

不同土壤背景下秸秆还田量对水稻产量构成及氮吸收利用的影响

以辽宁省新审定的北方粳稻(辽粳2501)为材料,在总施氮量为N200kg/hm2、基-蘖-穗氮肥比例50-30-20条件下,采用盆栽试验,研究不同土壤类型(砂质荒漠土、壤质滨海盐土、粘质棕壤土)及秸秆还田量(0、30％、50％、70％)对水稻产量构成及氮吸收利用的影响.结果表明,荒漠土和滨海盐土稻田均以50％秸秆还田产...     

Determination of total soil organic C and hot water‐extractable C from VIS‐NIR soil reflectance with partial least squares regression and spectral feature selection techniques

The calibration of soil organic C (SOC) and hot water‐extractable C (HWE‐C) from visible and near‐infrared soil reflectance spectra is hindered by the complex spectral interaction of soil chromophores that usually varies from one soil or soil type to another. The exploitation of spectral variables from spectroradiometer data is further affected by multicollinearity and noise. In this study, a set of soil samples (Fluvisols, Podzols, Cambisols and Chernozems; n = 48) representing a wide range of properties was analysed. Spectral readings with a fibre‐optics visible to near‐infrared instrument were used to estimate SOC and HWE‐C contents by partial least squares regression (PLS). In addition to full‐spectrum PLS, spectral feature selection techniques were applied with PLS (uninformative variable elimination, UVE‐PLS, and a genetic algorithm, GA‐PLS). On the basis of normalized spectra (mean centring + vector normalization), the order of prediction accuracy was GA‐PLS ? UVE‐PLS > PLS for SOC; for HWE‐C, it was GA‐PLS > UVE‐PLS, PLS. With GA‐PLS, acceptable cross‐validated (cv) prediction accuracies were obtained for the complete dataset (SOC, , RPD_cv = 2.42; HWE‐C_cv, , RPD_cv = 2.13). Splitting the soil data into two groups with different basic properties (Podzols compared with Fluvisols/Cambisols; n = 21 and n = 23, respectively) improved SOC predictions with GA‐PLS distinctly (Podzols, , RPD_cv = 3.14; Fluvisols/Cambisols, , RPD_cv = 3.64). This demonstrates the importance of using stratified models for successful quantitative approaches after an initial rough screening. GA selection frequencies suggest that the spectral region over 1900 nm, and in particular the hydroxyl band at 2200 nm are of great importance for the spectral prediction of both SOC and HWE‐C.     

不同微咸水灌水量条件下覆砂措施对土壤水盐运移的影响

采用室内土柱模拟试验,对比研究了不同微咸水灌水量条件下覆砂与不覆砂对土壤水盐分布和运移的影响,以期为压砂地合理利用微咸水提供理论支持。结果表明,与不覆砂相比,覆砂增加了土壤水分下渗深度,最大增加深度可达8 cm;减少了试验期间土壤水分累计蒸发量,低、中、高3个灌水量分别减少了74%、54%和21%,减少幅度随灌水量增加有降低的趋势。在土壤水分再分布过程中,土壤剖面出现明显分界点,覆砂提高了分界点处土壤水分含量,增加量为2%~5%;保蓄了上层土壤水分含量,尤其是低灌水量时,不覆砂处理0~20 cm土壤水分含量在试验期间减少幅度达到34%,而覆砂处理仅减少了16.9%;增加了下层土壤水分含量。同时,覆砂明显抑制了表层土壤盐分累积,抑制幅度达到92.4%~95.2%;提高了土壤剖面盐分峰值处盐分含量,提高幅度在11.02%~37.55%;盐分峰值的位置随着试验时间延长不断向下运移。表明,微咸水灌溉条件下,覆砂措施通过减少土壤水分蒸发和增加土壤水分入渗而抑制表层土壤盐分累积,促进土壤盐分向下层运动。     

不同氮磷施肥量对玉米生育期土壤微生物量的影响

通过田间小区试验研究了不同N、P施肥量对玉米生育期土壤微生物量C、N、P的影响。结果表明，不同N、P施肥量对微生物量C无明显影响；施N肥量高(225kg/hm²)时降低微生物量N；当施P肥达225kg/hm²时则对微生物量P产生明显的抑制作用。     

城市林木枯落物与河道底泥不同配比的堆肥效果

为利用城市林木枯落物与河道底泥堆肥生产有机肥,设计城市林木枯落物和经加粉煤灰钝化处理的河道底泥5种不同比例(1∶1、1∶2、1∶3、2∶1和3∶1)的高温堆肥试验,测定堆肥过程中堆温、p H值、有机质和C/N的动态变化,以及这5种配方堆肥产物的种子发芽指数。结果显示,堆温和p H值均呈先升高后下降的趋势,3∶1的配比升温迅速、高温期维持时间(5 d)最长;堆肥结束时,各处理均达到腐熟,p H值在7.47~8.87,有机质分别下降了36%、38%、42%、33%和29%,城市林木枯落物比例增加有利于减少有机质损失;由于底泥的C/N较低,增加枯落物有助于提高堆肥效率;处理1、4和5的种子发芽率分别在26、18和19 d达80%以上,而处理2和3直至堆肥结束其种子发芽率仍小于80%。综合考虑堆肥质量和效率,底泥和城市林木枯落物3∶1的处理为规模化生产有机肥的适宜原料比例。     

Prediction of soil organic matter using a spatially constrained local partial least squares regression and the Chinese vis–NIR spectral library

We need to determine the best use of soil vis–NIR spectral libraries that are being developed at regional, national and global scales to predict soil properties from new spectral readings. To reduce the complexity of a calibration dataset derived from the Chinese vis–NIR soil spectral library (CSSL), we tested a local regression method that combined geographical sub‐setting with a local partial least squares regression (local‐PLSR) that uses a limited number of similar vis–NIR spectra (k‐nearest neighbours). The central idea of the local regression, and of other local statistical approaches, is to derive a local prediction model by identifying samples in the calibration dataset that are similar, in spectral variable space, to the samples used for prediction. Here, to derive our local regressions we used Euclidean distance in spectral space between the calibration dataset and prediction samples, and we also used soil geographical zoning to account for similarities in soil‐forming conditions. We tested this approach with the CSSL, which comprised 2732 soil samples collected from 20 provinces in the People's Republic of China to predict soil organic matter (SOM). Results showed that the prediction accuracy of our spatially constrained local‐PLSR method (R² = 0.74, RPIQ = 2.6) was better than that from local‐PLSR (R² = 0.69, RPIQ = 2.3) and PLSR alone (R² = 0.50, RPIQ = 1.5). The coupling of a local‐PLSR regression with soil geographical zoning can improve the accuracy of local SOM predictions using large, complex soil spectral libraries. The approach might be embedded into vis–NIR sensors for laboratory analysis or field estimation.     

Maps of averaged spectral deviations from soil lines and their comparison with traditional soil maps

The analysis of 34 cloudless fragments of Landsat 5, 7, and 8 images (1985–2014) on the territory of Plavsk, Arsen’evsk, and Chern districts of Tula oblast has been performed. It is shown that bare soil surface on the RED–NIR plots derived from the images cannot be described in the form of a sector of spectral plane as it can be done for the NDVI values. The notion of spectral neighborhood of soil line (SNSL) is suggested. It is defined as the sum of points of the RED–NIR spectral space, which are characterized by spectral characteristics of the bare soil applied for constructing soil lines. The way of the SNSL separation along the line of the lowest concentration density of points on the RED–NIR spectral space is suggested. This line separates bare soil surface from vegetating plants. The SNSL has been applied to construct soil line (SL) for each of the 34 images and to delineate bare soil surface on them. Distances from the points with averaged RED–NIR coordinates to the SL have been calculated using the method of moving window. These distances can be referred to as averaged spectral deviations (ASDs). The calculations have been performed strictly for the SNSL areas. As a result, 34 maps of ASDs have been created. These maps contain ASD values for 6036 points of a grid used in the study. Then, the integral map of normalized ASD values has been built with due account for the number of points participating in the calculation (i.e., lying in the SNSL) within the moving window. The integral map of ASD values has been compared with four traditional soil maps on the studied territory. It is shown that this integral map can be interpreted in terms of soil taxa: the areas of seven soil subtypes (soddy moderately podzolic, soddy slightly podzolic, light gray forest. gray forest, dark gray forest, podzolized chernozems, and leached chernozems) belonging to three soil types (soddy-podzolic, gray forest, and chernozemic soils) can be delineated on it.     

间伐和去除凋落物对马尾松林细根生产力和土壤有机碳含量的影响

Soils play a critical role in the global carbon cycle, and can be major source or sink of CO₂ depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine (Pinus resinosa) plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature (T_soil) and soil moisture (M_soil) were higher in the thinning plots than those in the controls. Litter fall removal had significant effiects on T_soil and M_soil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.     

Isotopomer signatures of soil-emitted N2O under different moisture conditions—A microcosm study with arable loess soil

Soils represent the major source of the atmospheric greenhouse gas nitrous oxide (N₂O) and there is a need to better constrain the total global flux and the relative contribution of the microbial source processes. The aim of our study was to evaluate isotopomer analysis of N₂O (intramolecular distribution of ¹⁵N) as well as conventional nitrogen and oxygen isotope ratios (i) as a tool to identify N₂O production processes in soils and (ii) to constrain the isotopic fingerprint of soil-derived N₂O. We conducted a microcosm study with arable loess soil fertilized with 20 mg N kg⁻¹ of ¹⁵NO₃⁻-labeled or non-labeled ammonium nitrate. Soils were incubated for 16 d at varying moisture (55%, 75% and 85% water-filled pore space (WFPS)) in order to establish different levels of nitrification and denitrification. Dual isotope and isotopomer ratios of emitted N₂O were determined by mass spectrometric analysis of δ¹⁸O, average δ¹⁵N (δ¹⁵N^bulk) and ¹⁵N site preference (SP=difference in δ¹⁵N between the central and peripheral N-positions of the asymmetric N₂O molecule). Total rates and N₂O emission of denitrification and nitrification were determined by ¹⁵N analysis of headspace gases and soil extracts of the ¹⁵NO₃⁻ treatment. N₂O emission and denitrification increased with moisture whereas gross nitrification was almost constant. In the 55% WFPS treatment, more than half of the N₂O flux was derived from nitrification, whereas denitrification was the dominant N₂O source in the 75% WFPS and 85% WFPS treatments. Moisture conditions were reflected by the isotopic signatures since highly significant differences were observed for average δ¹⁵N^bulk, SP and δ¹⁸O. Experiment means of the 75% WFPS and 85% WFPS treatments gave negative δ¹⁵N^bulk (−18.0‰ and −34.8‰, respectively) and positive SP (8.6‰ and 15.3‰, respectively), which we explained by the fractionation during N₂O production and partial reduction to N₂. In the 55% WFPS treatment, mean SP was relatively low (1.9‰), which suggests that nitrification produced N₂O with low or negative SP. The observed influence of process condition on isotopomer signatures suggests that the isotopomer approach might be suitable for identifying N₂O source processes. However, more research is needed to determine the impact from process rates and microbial community structure. Isotopomer signatures were within the range reported from previous soil studies which supports the assumption that SP of soil-derived N₂O is lower than SP of tropospheric N₂O.     

Effect of N addition,moisture, and temperature on soil microbial respiration and microbial biomass in forest soil at different stages of litter decomposition

Purpose

The objective of the present study was to investigate the interactive effects of nitrogen (N) addition, temperature, and moisture on soil microbial respiration, microbial biomass, and metabolic quotient (qCO₂) at different decomposition stages of different tree leaf litters.

Materials and methods

A laboratory incubation experiment with and without litter addition was conducted for 80 days at two temperatures (15 and 25 °C), two wetting intensities (35 and 50 % water-filled porosity space (WFPS)) and two doses of N addition (0 and 4.5 g N m^?2, as NH₄NO₃). The tree leaf litters included three types of broadleaf litters, a needle litter, and a mixed litter of them. Soil microbial respiration, microbial biomass, and qCO₂ along with other soil properties were measured at two decomposition stages of tree leaf litters.

Results and discussion

The increase in soil cumulative carbon dioxide (CO₂) flux and microbial biomass during the incubation depended on types of tree leaf litters, N addition, and hydrothermal conditions. Soil microbial biomass carbon (C) and N and qCO₂ were significantly greater in all litter-amended than in non-amended soils. However, the difference in the qCO₂ became smaller during the late period of incubation, especially at 25 °C. The interactive effect of temperature with soil moisture and N addition was significant for affecting the cumulative litter-derived CO₂-C flux at the early and late stages of litter decomposition. Furthermore, the interactive effect of soil moisture and N addition was significant for affecting the cumulative CO₂ flux at the late stage of litter decomposition but not early in the experiment.

Conclusions

This present study indicated that the effects of addition of N and hydrothermal conditions on soil microbial respiration, qCO₂, and concentrations of labile C and N depended on types of tree leaf litters and the development of litter decomposition. The results highlight the importance of N availability and hydrothermal conditions in interactively regulating soil microbial respiration and microbial C utilization during litter decomposition under forest ecosystems.

     

Soil aggregation and water holding capacity of soil amended with agro-industrial byproducts and poultry litter

Journal of Soils and Sediments - Soil organic matter (SOM) addition has been shown to be effective for improving physicochemical and hydrological properties, but its effectiveness may be improved...     

Peat amendment and production of different crop plants affect earthworm populations in field soil

A field experiment was conducted to study the effects of peat amendment and crop production system on earthworms. The experiment was established on a field previously cultivated with oats and with silt as the main soil type. Perennial crops strawberry, timothy and caraway, and annual crops rye, turnip rape, buckwheat, onion and fiddleneck were cultivated with conventional methods. All the crops were grown with and without soil amendment with peat. Earthworms were sampled twice: 4 and 28 months after establishment of the experiment. In the former case part of the experimental plots were soil sampled and hand sorted for estimation of earthworms. In the latter case all experimental plots were sampled and both soil sampling and mustard extraction was carried out. Soil organic carbon and microbial biomass was measured at 14 and 28 months. Peat increased the abundance of juvenile Aporrectodea caliginosa by 74% in three growing seasons, but had no effect on adult numbers. Lumbricus terrestris numbers were not increased by peat treatment. Three season cultivation of caraway favoured both A. caliginosa and L. terrestris. An equal abundance of A. caliginosa was also found in plots cultivated with turnip rape and fiddleneck. Total earthworm and especially A. caliginosa numbers were very small in plastic-mulched strawberry beds. This was mainly attributed to repeated use of the insecticide endosulfan. With the strawberry plots omitted there was a significant correlation between soil microbial N measured at 14 months and juvenile Aporrectodea spp. and Lumbricus spp. numbers measured at 28 months. Adult earthworm numbers were not associated with either soil organic C or microbial biomass.     

土壤团聚体氧化亚氮排放潜势与微生物学机制

氧化亚氮（N2O）是主要温室气体之一,土壤是N2O的重要排放源,其排放主要受N2O产生和还原的功能微生物影响。土壤团聚体是由原生颗粒（砂、粉、黏粒）、胶结物质和孔隙组成的土壤基本结构单元。土壤不同粒径团聚体之间因基质和孔隙差异形成特殊独立的微生境被视为N2O的生物化学反应器。在不同的微生境中,N2O产生和还原的功能微生物分布不同,因而土壤不同粒径团聚体N2O排放可能存在差异。目前在不同生态系统土壤全土N2O排放特征的报道较多,而对于不同粒径土壤团聚体N2O排放相对贡献尚不清楚、功能微生物分布还未知、N2O产生和还原热区尚未明确。本文综述了近年来国内外关于土壤团聚体对N2O产生和排放机制的研究,总结了土壤团聚体性状特征对N2O产生和还原的影响,阐述了不同粒径土壤团聚体对N2O排放影响的微生物学机制,进一步明确了今后需加强土壤团聚体N2O产生和还原的热区、环境因子阈值范围的确定、系列功能基因（酶）整体性的研究,以期为N2O模拟排放模型优化提供参考,为土壤N2O减排提供理论依据。     

Differential responses of litter decomposition to nutrient addition and soil water availability with long-term vegetation recovery

The litter decomposition, nutrient patterns, as well as nutrient release and soil nutrient contents were determined in response to nitrogen (N) and phosphorus (P) addition and drought treatments following long-term vegetation recovery. The litter decomposition rate decreased with vegetation recovery, due to changes in litter quality, soil nutrient availability, and soil enzyme activity. Nitrogen addition promoted litter decomposition in the early recovery stages but inhibited decomposition in the later stages, indicating a shift in the nutrient limitations to litter decomposition with succession. Neither N nor P addition had any effect on the release of litter carbon (C), whereas N addition inhibited litter N release. In addition, drought decreased litter decomposition and nutrient release during the vegetation recovery process. Our findings suggest that litter quality, soil nutrient availability, and moisture at different vegetation recovery stages should be considered when modeling the C cycle and nutrient dynamics in these ecosystems.