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 influences 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 NO₃^--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.     

牧场土壤碳、氮和微生物动力学研究:放牧强度和种植方式的影响

Management intensity critically influences the productivity and sustainability of pasture systems through modifying soil microbes, and soil carbon(C) and nutrient dynamics; however, such effects are not well understood yet in the southeastern USA. We examined the effects of grazing intensity and grass planting system on soil C and nitrogen(N) dynamics, and microbial biomass and respiration in a long-term field experiment in Goldsboro, North Carolina, USA. A split-plot experiment was initiated in 2003 on a highly sandy soil under treatments of two grass planting systems(ryegrass rotation with sorghum-sudangrass hybrid and ryegrass seeding into a perennial bermudagrass stand) at low and high grazing densities. After 4 years of continuous treatments, soil total C and N contents across the 0–30 cm soil profile were 24.7% and 17.5% higher at the high than at the low grazing intensity, likely through promoting plant productivity and C allocation belowground as well as fecal and urinary inputs. Grass planting system effects were significant only at the low grazing intensity, with soil C, N, and microbial biomass and respiration in the top 10 cm being higher under the ryegrass/bermudagrass than under the ryegrass/sorghum-sudangrass hybrid planting systems. These results suggest that effective management could mitigate potential adverse effects of high grazing intensities on soil properties and facilitate sustainability of pastureland.     

温室菜园土壤氮矿化和微生物群落对水分的响应

Soil drying and wetting impose significant influences on soil nitrogen (N) dynamics and microbial communities. However, effects of drying-wetting cycles, while common in vegetable soils, especially under greenhouse conditions, have not been well studied. In this study, two greenhouse vegetable soils, which were collected from Xinji (XJ) and Hangzhou (HZ), China, were maintained at 30% and 75% water-holding capacity (WHC), or five cycles of 75% WHC followed by a 7-day dry-down to 30% WHC (DW). Soil inorganic N content increased during incubation. Net N mineralization (Nmin), microbial activity, and microbial biomass were significantly higher in the DW treatment than in the 30% and 75% WHC treatments. The higher water content (75% WHC) treatment had higher Nmin, microbial activity, and microbial biomass than the lower water content treatment (30% WHC). Multivariate analyses of community-level physiological profile (CLPP) and phospholipid fatty acid (PLFA) data indicated that soil moisture regime had a significant effect on soil microbial community substrate utilization pattern and microbial community composition. The significant positive correlation between Nmin and microbial substrate utilization or PLFAs suggested that soil N mineralization had a close relationship with microbial community.     

土壤微生物生物氮与植物氮吸收的关系

The contents of the soil microbial biomass nitrogen (SMBN) in the soils sampled from the Loess Plateau of China were determined using chloroform fumigation aerobic incubation method (CFAIM),chloroform fumigation anaerobic incubation method (CFANIM) and chloroform fumigation-extraction method (CFEM). The N taken up by ryegrass on the soils was determined after a galsshouse pot experiment. The flushes of nitrogen (FN) of the soils obtained by the CFAIM and CFANIM were higher than that by the CFEM, and there were significantly positive correlations between the FN obtained by the 3 methods. The N extracted from the fumigated soils by the CFAIM,CFANIM and CFEM were significantly positively correlated with the N uptake by ryegrass. The FN obtained by the 3 methods was also closely positively correlated with the N uptake by ryegrass. The FN obtained by the 3 methods was also closely positively correlated with the plant N uptake. The contributions of the SMBN and mineral N and mineralized N during the incubation period to plant N uptake were evaluated with the multiple regression method. The results showed that the N contained in the soil microbial biomass might play a noticeable role in the N supply of the soils to the plant.     

黄土高原半干旱地区撂荒地次生植被演替过程中土壤微生物活性研究

To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers (0--60 cm) were determined in six lands, i.e., 2-, 7-, 11-, 20-, 43-year-old abandoned lands and one native grassland, in a semiarid hilly area of the Loess Plateau. The results indicated that the successional time and soil depths affected soil microbiological parameters significantly. In 20-cm soil layer, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), MBC/MBN, MBC to soil organic carbon ratio (MBC/SOC), and soil basal respiration tended to increase with successional stages but decrease with soil depths. In contrast, metabolic quotient (qCO2) tended to decrease with successional stages but increase with soil depths. In addition, the activities of urease, catalase, neutral phosphatase, β-fructofuranosidase, and carboxymethyl cellulose (CMC) enzyme increased with successional stages and soil depths. They were significantly positively correlated with microbial biomass and SOC (P < 0.05), whereas no obvious trend was observed for the polyphenoloxidase activity. The results indicated that natural vegetation succession could improve soil quality and promote ecosystem restoration, but it needed a long time under local climate conditions.     

稻田系统管理措施对微生物生物量C、N、P的长期影响

A 12-year field experiment was conducted to investigate the effect of different tillage methods and fertil-ization systems on microbial biomass C,N and P of a gray fluvo-aguic soil in rice-based cropping system .Five fertilization treatments were designed under conventional tillae(CT) or on tillage(NT) system:no fertilizer(CK) ; chemical fertilizer only(CF) ; combining chemical fertilizer with pig manure(PM); combining chemical fertilizer with crop straw (CS) and fallow (F). The results showed that biomass C,N and P were enriched in the surface layer of no-tilled soil,whereas they distributed relatively evenly in the tilled soil,which might result from enrichment of crop resdue,organic manure and mineral fertilzer,and surficial developent of root systems under NT.Under the cultivation system NT had slightly greater biomass C,N and P at 0-5 cm depth ,significantly less biomass C,N and P at 5-15 cm depth ,less microbial biomass C,N and equivalent biomass P at 15-30 cm depth as compared to CT,indicating hat tillage was beneficial for the multiplication of organims in the plowed layer of soil.Under the fallow system,biomass C,N and P in the surface layer were significantly greater for NT than CT while their differences between the two tillage methods were neligible in the deeper layers.In the surface layer,biomass C,N and P in the soils amended with oranic manure combined with mineral fertilizers were significantly greater than those of the treatments only with mineral fertilizers and the control.Soils without fertilzer had the least biomass nutrient contents among the five fertilization treatments.Obviously,the long-term application of organic manure could maintain the higher activity of microorganisms in soils.The amounts of biomass C,N and P in the fallowed soils varied with the tillage methods;they were much greater under NT than under CT,especially in the surface layer,suggesting that the frequent plowing could decrease the content of organic matter in the surface layer of the fallowed soil.     

Effect of indaziflam on microbial activity and nitrogen cycling processes in an orchard soil

Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan (Carya illinoinensis) orchards in the southwestern region of the United States. Given the paucity of data regarding the effect of indaziflam on the biochemical properties of soils supporting pecan production, this study was conducted to evaluate the effects of different application rates of indaziflam on soil microbial activity, diversity, and biochemical processes related to nitrogen (N) cycling. During two consecutive growing seasons (2015 and 2016), soil samples were obtained from experimental mesocosms consisting of soil-filled pots where pecan saplings were grown and treated with indaziflam applied at two different rates (25 and 50 g active ingredient (ai) ha^-1, with the higher rate being slightly lower than the recommended field application rate of 73.1 g ai ha^-1). Soil samples were collected approximately one week before and one week after herbicide application for determination of soil microbial biomass and diversity, N mineralization, and β-glucosaminidase activity. Soil samples collected from the control mesocosms without herbicide application were treated in the laboratory with two rates of indaziflam (75 and 150 g ai ha^-1) to determine the immediate effect on microbial activity. No significant effect of herbicide treatment on soil respiration and microbial biomass was detected. The results showed a slight to moderate decrease in microbial diversity (7% in 2015 and 44% in 2016). However, decreased β-glucosaminidase activity with herbicide treatment was observed in soils from the mesocosms (33%) and soils treated with indaziflam in the laboratory (45%). The mineral N pool was generally dominated by ammonium after indaziflam application, which was consistent with the drastic decrease (75%) in nitrification activity measured in the laboratory experiment. The results of this study indicate that indaziflam, even when applied at higher than recommended rates, has limited effects on soil microbial activity, but may affect N cycling processes.     

大气CO2浓度升高对温带森林土壤微生物活性的影响

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide (CO2) as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 (2006) and 9 (2007) of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon (C), nitrogen (N) and phosphorus (P) cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly (P < 0.01) increased in the August 2006 samples that received the elevated CO2 treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly (P < 0.04) decreased by elevated CO2 treatments in the August 2006 and June 2007 (P < 0.09) samples. β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.     

中国东北黑土上长期施用化肥对土壤微生物生物量和功能多样性的影响

An experiment with seven N, P, K-fertilizer treatments, i.e., control （no fertilizer）, NP, NK, PK, NPK, NP2K, and NPK2 where P2 and K2 indicate double amounts of P and K fertilizers respectively, was conducted to examine the effect of long-term continuous application of chemical fertilizers on microbial biomass and functional diversity of a black soil （Udoll in the USDA Soil Taxonomy） in Northeast China. The soil microbial biomass C ranged between 94 and 145 mg kg^-1, with the NK treatment showing a lower biomass; the functional diversity of soil microbial community ranged from 4.13 to 4.25, with an increasing tendency from control to double-fertilizer treatments, and to triple-fertilizer treatments. The soil microbial biomass, and the microbial functional diversity and evenness did not show any significant differences among the different fertilizer treatments including control, suggesting that the long-term application of chemical fertilization would not result in significant changes in the microbial characteristics of the black soil.     

Pb-Zn交互作用对红壤微生物生物量的影响

A laboratory incubation experiment was conducted to evaluate the effects of lead and zinc applied alone or in various combinations on the size of microbial biomass in a red soil. Treatments included the application of lead at six different levels i. e., 0 (background), 100, 200, 300, 450 and 600 g g^-1 soil along with each of the four levels of zinc (0, 50, 150 or 250 g g^-1 soil). Application of lead or zinc alone to soil significantly (P < 0. 001) affected the soil microbial biomass. The microbial biomass carbon (C_mic), biomass nitrogen (N_mic) and biomass phosphorus (P_mic) decreased sharply in soils contaminated with lead or zinc. Combined application of lead and zinc resulted in a greater biocidal effect on soil microbial biomass, which was significantly higher (P < 0. 001) than that when either lead or zinc was applied alone. Consistent increase in the biomass C: N and decline in the biomass C:P ratios were also observed with the increased metal (Pb and Zn) toxicity in the soil.     

不同恢复方式下盐渍化弃耕地土壤生物学活性的变化

以干旱区新疆玛纳斯河流域冲积扇缘定点定位试验地为研究对象, 研究灌溉处理、人工草地处理和补植处理对盐渍化弃耕地土壤微生物量、酶活性及土壤呼吸速率的影响。结果表明, 不同恢复方式均明显增加了土壤微生物数量和土壤微生物量碳、氮及土壤酶活性。不同处理土壤微生物量碳、氮分别比原始弃耕地高17.80%、26.38%、5.33%和7.89%、12.75%、21.93%; 不同处理土壤微生物数量分别是原始弃耕地的4.72倍、6.04倍和4.56倍; 不同处理土壤蔗糖酶活性分别比原始弃耕地高3.4倍、3.2倍和7.7倍, 多酚氧化酶活性比原始弃耕地高1.7倍、1.2倍和1.5倍, 脲酶活性比原始弃耕地高11.1%、52.3%和37.1%; 灌溉处理土壤过氧化氢酶活性最高, 是原始弃耕地的1.53倍, 土壤呼吸速率变化表现为人工草地处理>灌溉处理>补植处理>原始弃耕地, 其中, 人工草地处理土壤呼吸速率比弃耕地高52.25%。相关分析表明, 微生物量碳与微生物C/N和微生物数量之间均呈显著正相关关系(P<0.05); 土壤呼吸速率与土壤脲酶、微生物数量和微生物量碳的相关性达到显著水平(P<0.05), 与土壤微生物量氮呈负相关关系, 但相关性不显著; 土壤蔗糖酶与其他3种酶以及微生物量氮呈显著正相关关系, 土壤脲酶与微生物数量呈显著正相关关系, 多酚氧化酶与过氧化氢酶相关性达到显著水平(P<0.05)。本研究表明干旱区盐渍化弃耕地采用灌溉与人工草地处理有利于土壤养分积累, 可在一定程度上改善土壤质量。     

Influence of lanthanum on microbial biomass C,P and C- and P-cycling enzyme activities in tea garden soil

At present, reports of the effect of lanthanum on nitrogen cycling in the soil are very detailed, but information on carbon (C) and phosphorus (P) cycling is less reported. We present an investigation into the effects of lanthanum on the pH, microbial biomass C and P and enzyme activities (such as that of β-glucosidase, peroxidase, polyphenol oxidase, acid phosphomonoesterase, phosphodiesterase and phosphotriesterase) in soil in an indoor culture experiment. The results show that the application of lanthanum decreased the pH and had an inhibitory effect on microbial biomass C and P throughout the experiment. The application of lanthanum significantly inhibited most of enzyme activities at the 14th day of the experiment. However, soil samples treated with 100 mg kg^?1 of lanthanum significantly stimulated the activity of polyphenol oxidase at the 14th day, and the range 100–300 mg kg^?1 stimulated the activities during the 28th day to the 56th day. From the 42nd to the 56th day, the pH and all enzyme activities gradually increased. We inferred that the lanthanum had different effects on microbial biomass C and P and enzymes. We recommended that the amount of the rare earth element applied in a tea garden should be lower than 100 mg kg^?1.     

氮素和水分对贝加尔针茅草原土壤酶活性和微生物量碳氮的影响

在内蒙古贝加尔针茅草原,分别设对照(N0)、1.5 g·m-2(N15)、3.0 g·m-2(N30)、5.0 g·m-2(N50)、10.0 g·m-2(N100)、15.0 g·m-2(N150)、20.0 g·m-2(N200)和30g·m-2(N300)(不包括大气沉降的氮量)8个氮素(NH4NO3)梯度和模拟夏季增加降水100 mm的水分添加交互试验,研究氮素和水分添加对草原土壤养分、酶活性及微生物量碳氮的影响。结果表明:氮素和水分添加对草原土壤理化性质和生物学特性有显著影响。随施氮量的增加土壤总有机碳、全氮、硝态氮、铵态氮含量呈增加的趋势,相反,土壤pH值呈降低的趋势。土壤脲酶和过氧化氢酶的活性随施氮量的增加而升高,多酚氧化酶则随施氮量的增加呈下降的趋势。氮素和水分添加对草原土壤微生物量碳氮含量有显著影响,高氮处理(N150、N200和N300)显著降低了微生物碳含量,微生物氮含量随施氮量的增加呈上升趋势。水分添加能够减缓氮素添加对微生物的抑制作用,提高微生物量碳、微生物量氮含量。草原土壤养分、土壤酶活性及土壤微生物量碳氮含量间关系密切,过氧化氢酶与全氮、总有机碳、硝态氮呈显著正相关,多酚氧化酶与铵态氮、硝态氮、全氮呈显著负相关。微生物量氮含量与土壤全氮、铵态氮、硝态氮含量以及过氧化氢酶和磷酸酶活性呈显著正相关,与多酚氧化酶呈负相关;微生物量碳与过氧化氢酶呈负相关,与多酚氧化酶活性呈正相关。     

菲在黑麦草种植土壤中的降解及其对土壤酶的影响

研究了种植黑麦草对土壤中3环多环芳烃菲的动态降解作用。结果表明,黑麦草可以促进土壤中菲的降解,在75 d的盆栽试验里,种植黑麦草土壤中菲的可提取浓度明显低于不种植土壤（p<0.05）。在菲浓度为5 mg kg^-1、50 mg kg^-1、200 mg kg^-1的3种处理中,种植黑麦草壤中菲的降解率分别为81.07%、90.35%、84.94%,而不种植土壤中菲的降解率分别为75.34%、86.62%、67.60%。种植黑麦草增强了土壤中多酚氧化酶、脱氢酶和过氧化氢酶的活性以及增加土壤中微生物生物量碳的含量,即提高了土壤中生物活性,从而促进了土壤中菲的降解率。不同浓度菲处理,土壤中生物活性存在明显差异,高浓度菲(200 mg kg^-1)对土壤中生物活性产生较强的抑制作用,影响土壤中生物对菲的降解作用,从而揭示了植物促进菲降解的生物学及酶学机理。黑麦草对土壤中多环芳烃有较强的忍耐性,但过高的菲浓度对黑麦草的生长有影响。     

EFFECTS OF GREEN MANURE CONTINUOUS APPLICATION ON SOIL MICROBIAL BIOMASS AND ENZYME ACTIVITY

A three-year field experiment was carried out to study the effects of green manure application on the soil microbial biomass carbon, nitrogen and soil enzyme activities in order to provide a theoretical basis on low-carbon agriculture, environment-friendly agriculture and promote the sustainable development of tobacco production. Six treatments were set and were: check (CK) (contrast, no application of green manure), T1 (application of ryegrass only 1 year), T2 (application of ryegrass 2 years), T3 (application of oats 2 years), T4 (application of ryegrass 3 years), and T5 (application of oats 3 years), which was based on continuous planting oats and ryegrass (Lolium multiflorum L.) in our experiment. The results showed that soil microbial biomass carbon, nitrogen, and the activity of soil urease, acid phosphatase (ACP), sucrase, and catalase increased with each year and with the application of green manure. Compared with the control, after the application of green manure the content of soil microbial biomass carbon and nitrogen increased 1.94%–93.07% and 2.30%–145.07%, respectively, and the activity of soil urease, ACP, sucrase, and catalase increased 1.45%–56.52%, 2.34%–33.17%, 0.96%–172.66%, and 3.33%–85.71%, respectively. Correlation analysis indicated that soil microbial biomass carbon and soil enzymes activity had certain relevance that showed the dynamic process of soil microbial biomass and enzyme activity were coordinate with the decomposition process of green manure and the absorption of mine nutritional to tobacco plant. The results demonstrate that continuous application of green manure could increase soil biological fertility level.     

Effects of earthworms on nitrogen mineralization

The influence of earthworms (Lumbricus terrestris and Aporrectodea tuberculata) on the rate of net N mineralization was studied, both in soil columns with intact soil structure (partly influenced by past earthworm activity) and in columns with sieved soil. Soil columns were collected from a well drained silt loam soil, and before the experiment all earthworms present were removed. Next, either new earthworms (at the rate of five earthworms per 1200 cm³, which was only slightly higher than field numbers and biomass) were added or they were left out. At five points in time, the columns were analyzed for NH ₄ ⁺ , NO ₃ ^– , and microbial biomass in separate samples from the upper and lower layers of the columns. N mineralization was estimated from these measurements. The total C and N content and the microbial biomass in the upper 5 cm of the intact soil columns was higher than in the lower layer. In the homogenized columns, the C and N content and the microbial biomass were equally divided over both layers. In all columns, the concentration of NH ₄ ⁺ was small at the start of the experiment and decreased over time. No earthworm effects on extractable NH ₄ ⁺ were observed. However, when earthworms were present, the concentration of NO ₃ ^– increased in both intact and homogenized cores. The microbial biomass content did not change significantly with time in any of the treatments. In both intact and homogenized soil, N mineralization increased when earthworms were present. Without earthworms, both type of cores mineralized comparable amounts of N, which indicates that mainly direct and indirect biological effects are responsible for the increase in mineralization in the presence of earthworms. The results of this study indicate that earthworm activity can result in considerable amounts of N being mineralized, up to 90 kg N ha^–1 year^–1, at the density used in this experiment.     

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.     

秸秆施用下接种蚯蚓对农田土壤微生物特性的影响

在连续6年稻麦轮作系统中，研究不同秸秆施用方式下接种蚯蚓对土壤微生物生物量、活性（基础呼吸）及群落功能多样性（BIOLOG单一碳源利用指纹方法）的影响，试验设5个处理：对照（CK）、秸秆表施（M）、秸秆混施（I）、秸秆表施且接种蚯蚓（ME）、秸秆混施且接种蚯蚓（IE）。不同秸秆施用下接种蚯蚓均对土壤微生物生物量、微生物生物活性和群落碳源利用能力产生显著影响：两种秸秆施用方式下接种蚯蚓均增加微生物生物量；秸秆表施并接种蚯蚓导致微生物活性、碳源利用丰富度和多样性指数均降低，而在秸秆混施下则均升高；BIOLOG碳源利用分析结果表明在秸秆施用下接种蚯蚓后土壤的微生物群落组成发生明显变化。