Removal of benzo (a) pyrene from soil using an endogeic earthworm Pontoscolex corethrurus ()

The endogeic earthworm Pontoscolex corethrurus (Müller, 1857) was the most abundant species (75%) in soil contaminated with hydrocarbons, mostly benzo(a)pyrene (BaP), in the state of Tabasco (Mexico). The earthworm P. corethrurus was tested for its capacity to remove 100 mg BaP kg⁻¹ from an Anthrosol soil (sterilized or not) and amended with legume Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker ex Burck (3%) or the grass Brachiaria humidicola (L.) DC (3%) (recently renamed as Urochloa humidicola (Rendle) Morrone & Zuloaga) in an aerobic incubation experiment. P. corethrurus removed 26.6 mg BaP kg⁻¹ from the sterilized soil and application of B. humidicola as feed increased this to 35.7 mg BaP kg⁻¹ and M. pruriens to 34.2 mg BaP kg⁻¹ after 112 days. The autochthonous microorganisms removed 9.1 mg BaP kg⁻¹ from the unsterilized soil and application of B. humidicola increased this to 18.0 mg BaP kg⁻¹ and M. pruriens to 11.2 mg BaP kg⁻¹. Adding P. corethrurus to the unsterilized soil accelerated the removal of BaP and 36.1 mg kg⁻¹ was dissipated from soil. It was found that the autochthonous microorganisms removed BaP from soil, but addition of P. corethrurus increased the dissipation 4-fold. The endogeic earthworm P. corethrurus can thus be used to remediate hydrocarbon-contaminated soils in tropical regions.     

Life cycle of Pontoscolex corethrurus () in tropical artificial soil

Pontoscolex corethrurus (Müller) is a widespread, peregrine earthworm species of the Glossoscolecidae family, native to the Neotropics. This endogeic earthworm shows wide tolerance to environmental variations, being found in many different habitats and soil types throughout the tropics and sub-tropics. To evaluate the life cycle of this species in tropical artificial soil (TAS), a substrate used in ecotoxicological tests, and the influence of food availability and humidity on its growth, earthworms were incubated individually under laboratory conditions. The life cycle was evaluated in four treatments with 24 earthworms (replicates) each: TAS (120 g) without additional food (TAS0), TAS with 5 g of horse manure (TAS5), TAS with 10 g of manure (TAS10) and TAS with 25% greater soil moisture with 5 g of manure (TAS5H). Food was provided every 14 d and the containers maintained at room temperature (20 ± 4 °C). Cocoons collected in the field were placed individually in the different treatments and the hatching date, growth, development, and reproduction followed for 50 weeks after hatching. New cocoons hatched at 34 d, adulthood was reached at 8 months, and cocoon deposition began 3 months later, so that its life cycle was completed in 12 months. By the 13th week all juveniles in TAS0 had died due to insufficient food resources, while in the other treatments, all the animals had matured by 44 weeks, with significantly higher biomass and length in TAS10 (0.72 g, 5.4 cm), compared with TAS5 and TAS5H (0.59–0.61 g, 5.1–5.4 cm). Growth and weight gain were positively related to food availability, and no negative effect of excess moisture was observed on their growth. With additional food TAS showed no limitations for the development of the species, and it can be used for ecotoxicological tests involving acute toxicity (mortality) and avoidance, although its potential use in chronic tests (reproduction) is more limited. The length of its life cycle and other biological characteristics associated with this parthenogenetic species create some challenges that must be dealt with before this species can be recommended for wider use as a standard ecotoxicological test species.     

Effect of organic manure and the endogeic earthworm Pontoscolex corethrurus (Oligochaeta: Glossoscolecidae) on soil fertility and bean production

A biofertilisation assay was conducted in Maripasoula (French Guiana), testing the effects of three different organic amendments (manioc peels, sawdust and wood charcoal) and the inoculation of the endogeic earthworm Pontoscolex corethrurus on pod production of Vigna unguiculata sesquipedalis and on soil chemical properties (pH, C, N, total and exchangeable P and K). Pod production was highest with manioc peels as available P increased in the soil. Wood charcoal also had a beneficial effect on pod production as it decreased acidity and increased the C:N ratio in the soil. In sawdust-amended soil, pod production did not differ from that in unamended soil. Inoculation of earthworms at a density of 80 sub-adults m^-2 did not significantly affect either pod production or soil nutrient content directly, although it increased the positive effect of manioc peels on pod production. Soil nutrient content, pod production and earthworm density at the end of the experiment were negatively correlated with soil moisture and positively with each other. Despite the strong effect of moisture, this assay demonstrated an interaction between the earthworm P. corethrurus and the legume V. unguiculata sesquipedalis mediated by soil nutrient content and organic matter inputs. We conclude that manioc peels improved soil P availability and were an interesting amendment for legume crops. We discuss also the effect of earthworm inoculation.     

Repair of a compacted Oxisol by the earthworm Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta)

The potential of Pontoscolex corethrurus to repair the physical degradation of a compacted Oxisol was studied. The Oxisol from Kingaroy, Queensland, Australia was uniformly packed to four treatments of different bulk densities (0.95, 1.15, 1.25, 1.35 Mg m^–3) in pots of 0.24 m diameter and 0.22 m deep. Each pot was inoculated with 12 earthworms (equivalent to 300 m^–2) and maintained close to field capacity water content for 3 months, after which selected soil physical (dry bulk density, penetration resistance, water infiltration), worm activity (cast production, worm weight) measurements and image analysis were carried out. Results showed that worm numbers were maintained at the initial levels in all the treatments except in the 1.35 Mg m^–3 treatment, where there was a 33% decrease. The weight of surface casts per surviving worm was the greatest in the 1.35 Mg m^–3 treatment compared to the lower density treatments. Final soil density was lessened in all treatments to a depth of 0.2 m. Surface cast production was positively correlated with the percentage reduction in bulk density. The greatest percentage reduction in bulk density was in the 1.35 Mg m^–3 treatment and was equivalent to a doubling of soil aeration (to 18.4%). Penetration resistance to the 0.2-m layer was also reduced and values were less than 2 MPa. Slumping of the surface soil was evident in both the lowest and the highest bulk densities resulting in low rates of water infiltration. Image analysis supported the soil physical properties showing an abundance of both fine pores and worm channels in the three lowest bulk densities, and lesser activity (concentrated in the immediate soil surface) in the 1.35 Mg m^–3 treatment. Received: 6 November 1996     

Nitrogen mineralization and reorganization in casts of the geophagous tropical earthworm Pontoscolex corethrurus (Glossoscolecidae)

Summary Mineral N concentrations ranged from 133.1 to 167.8 g g^-1 dry soil in fresh casts of the endogeic earthworm Pontoscolex corethrurus fed on an Amazonian Ultisol; this was approximately five times the concentration in non-ingested soil. Most of this N was in the form of NH _inf4 ^sup+ . N also accumulated in microbial biomass, which increased from a control value of 10.5–11.3 to 67.5–74.1 g g^-1 in fresh casts. During a 16-day incubation, part of the NH _inf4 ^sup+ -N was nitrified and/or transferred to the microbial biomass. Total labile N (i.e., mineral+biomas N) decreased sharply at first (ca. 50% in the first 12 h), and then more slowly. The exact fate of this N (microbial metabolites, denitrification, or volatilization) is not known. After 16 days, the overall N content of the casts was still 28% higher than that of the control soil. Incubation of the soil before ingestion by the earthworms significantly increased the production of NH _inf4 ^sup+ in casts. We calculate that in a humid tropical pasture, 50–100 kg mineral N may be produced annually in earthworm casts. Part of this N may be conserved in the compact structure of the cast where the cast is not in close contact with plant roots.     

Soil structure changes induced by the tropical earthworm Pontoscolex corethrurus and organic inputs in a Peruvian ultisol

Inoculation of Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) in a Peruvian ultisol under several treatments (without or with organic input) has been previously shown to increase macroaggregation and bulk density and to decrease water infiltration and soil moisture. In the present study, we used image analysis of thin sections of soil to understand the impact of earthworm on the structure of the upper layer of the soil. Morphological analysis allowed to quantify the abundance of casts, soil compactness, pore morphology and connections between different pore classes. This approach was applied to experiments carried out at Yurimaguas (Peru), in four plots. Two of them had been inoculated with Pontoscolex corethrurus. In each case, one control plot was conducted without organic input, the other with crop residues and legume green manure. Morphological parameters were measured in fourteen horizontal sections within the first 3 cm. They showed compaction of soil surface due to cast coalescence in plots with earthworms but without organic input and illustrated the typical crumb structure induced by earthworms in plots with organic input.     

Adaptive strategies of Pontoscolex corethrurus (Glossoscolecidae,Oligochaeta), a peregrine geophagous earthworm of the humid tropics

Summary Pontoscolex corethrurus is a medium-sized geophagous earthworm species which has invaded most cultivated land in the humid tropics. It is generally found in gardens, cropland and fallowland, where it has been introduced accidentally by man. The species has quite narrow microclimatic requirements. Reproduction only occurs at 23°–27°C, and the worms are fully active only where soil moisture is well above field capacity (pF 2.5). This limitation is balanced by the ability to live in a great Variety of soils differing in pH, organic matter content and texture. The demographic profile is typically of the r type, which gives populations a colonization capacity greater than that of comparable native species. This can be explained by the limited size of individuals and the great efficiency of their mutualist digestion system, in association with the free soil microflora. As a result, growth is fast and a great amount of energy may be invested in reproduction, which is made even more efficient by parthenogenesis.     

Reconciling apparent variability in effects of biochar amendment on soil enzyme activities by assay optimization

We studied the effects of a biochar made from fast pyrolysis of switchgrass on four soil enzymes (β-glucosidase, β-N-acetylglucosaminidase, lipase, and leucine aminopeptidase) to determine if biochar would consistently modify soil biological activities. Thus, we conducted a series of enzyme assays on biochar-amended soils. Inconsistent results from enzyme assays of char-amended soils suggested that biochar had variable effects on soil enzyme activities, thus we conducted a second experiment to determine if biochar reacts predictably with either enzyme or substrate in in vitro reactions. Both colorimetric and fluorescent assays were used for β-glucosidase and β-N-acetylglucosaminidase. Seven days after biochar was added to microcosms of 3 different soils, fluorescence-based assays revealed some increased enzyme activities (up to 7-fold for one measure of β-glucosidase in a shrub-steppe soil) and some decreased activities (one-fifth of the unamended control for lipase measured in the same shrub-steppe soil), compared to non-amended soil. In an effort understand the varied effects, purified enzymes or substrates were briefly exposed to biochar and then assayed. In contrast to the soil assays, except for β-N-acetylglucosaminidase, the exposure of substrate to biochar reduced the apparent activity of the enzymes, suggesting that sorption reactions between substrate and biochar impeded enzyme function. Our findings indicate that fluorometric assays are more robust to, or account for, this sorption better than the colorimetric assays used herein. The activity of purified β-N-acetylglucosaminidase increased 50-75% following biochar exposure, suggesting a chemical enhancement of enzyme function. In some cases, biochar stimulates soil enzyme activities, to a much greater degree than soil assays would indicate, given that substrate reactivity can be impeded by biochar exposure. We conclude that the effects of biochar on enzyme activities in soils are highly variable; these effects are likely associated with reactions between biochar and the target substrate.     

Alteration of soil labile organic carbon by invasive earthworms (Pontoscolex corethrurus) in tropical rubber plantations

The invasive earthworm (Pontoscolex corethrurus) is commonly found in rubber plantations of Xishuangbanna, southwestern China. To understand the long-term impact of this invasive earthworm on soil labile organic carbon (LOC), we examined changes in LOC that was protected and unprotected by soil aggregates during a worm-exclusion experiment in rubber plantations of Xishuangbanna. We found that the presence of this invasive earthworm for 20 months increased LOC (up to 35%) protected by aggregates in surface soil layer (0–5 cm). In contrast, the presence of this earthworm increased LOC unprotected by the aggregates and the turnover rate of LOC protected by the aggregates in subsurface soil layer (5–15 cm). Soil total LOC did not differ between the control and worm-exclusion treatments. These findings suggest that the invasion of P. corethrurus can redistribute LOC along soil vertical profiles with accumulation of protected LOC on surface soil layer and unprotected LOC on subsurface soil layer. Earthworms' redistribution of LOC between the protected and unprotected forms and along soil profile may affect long-term soil carbon cycling.     

生物耕作对蔬菜田土壤养分及酶活性的影响

通过在上海市崇明岛西部设置的长期定位试验,探讨生物耕作对菜田土壤养分及酶活性的影响。3年结果表明,与免耕处理相比,生物耕作有助于土壤养分含量增加,其中土壤有机质、 全氮、 全磷最高增幅分别为1822%、 1745%和1332%,速效氮、 速效磷和速效钾最高增幅分别为125.0%、 432.5%和21.3%,最高值多出现在生物耕作两年和三年时,差异显著（P0.05）。同时,随生物耕作年限的增加,05 cm土层过氧化氢酶、 脲酶、 蔗糖酶和蛋白酶活性均呈增加趋势,最高增幅分别为27.78%、 951.11%、 16.11%和420.00%,分别出现在生物耕作的第三年和第二年,且差异显著（P0.05）。此系统中过氧化氢酶活性与有机质、 全磷、 速效氮、 速效磷、 速效钾和含水量等呈显著正相关,与土壤pH值呈显著负相关（P0.05）, 有机质等是土壤酶活性主要影响因子,它们单独或是综合影响酶活性; 生物耕作时间对酶活性直接影响力大小顺序为过氧化氢酶活性蔗糖酶活性脲酶活性蛋白酶活性,直接通径系数为分别为1.353、 1.070、 0.421和0.110,其主要通过有机质和速效氮正向影响酶活性。     

Contrasting effects of wheat straw and its biochar on greenhouse gas emissions and enzyme activities in a Chernozemic soil

Biochar produced from plant biomass through pyrolysis has been shown to be much more resistant to biodegradation in the soil as compared with the raw biomass, such as cereal straw that is routinely shredded and discharged on to farm fields in large amounts. Biochar application to soil has also been reported to decrease greenhouse gas (GHG) emissions, although the mechanisms are not fully understood. In this study, the emissions of three main GHGs (CO₂, CH₄, and N₂O) and enzyme activities (urease, β-glycosidase, and dehydrogenase) were measured during a 100-day laboratory incubation of a Chernozemic soil amended with either straw or its biochar at rates of 0.67 and 1.68 % (based on the amount of C added) for the low and high rates, respectively. The biochar application dramatically reduced N₂O emissions, but CO₂ or CH₄ emissions were not different, as compared with the un-amended soil. At the same C equivalent application rate, CO₂ and N₂O emission rates were greater while CH₄ emission rates were lower in straw than in biochar application treatments. The activities of both the dehydrogenase and β-glycosidase significantly declined while that of urease significantly increased with the biochar as compared with the straw treatment. We conclude that pyrolysis of cereal straw prior to land application would significantly reduce CO₂ and N₂O emissions, in association with changed enzyme activities, while increasing the soil C pool through the addition of stable C in the form of biochar.     

生物质炭及过氧化钙对旱地红壤酶活性和微生物群落结构的影响

明确生物质炭等改良剂对土壤酶活性及土壤微生物群落结构的影响,对南方红壤旱地改良剂的合理施用及评价不同改良剂对旱地红壤肥力的影响具有重要意义。针对江西旱地红壤进行室内培养试验,试验设置4个处理,即CK、Ca(过氧化钙,1.72 g/kg)、C(生物质炭,21.46 g/kg)、C+Ca(过氧化钙,1.72 g/kg;生物质炭,21.46 g/kg),利用磷脂脂肪酸方法(PLFA),研究改良剂对土壤微生物量和组成以及土壤酶活性、土壤活性有机碳的影响。结果表明:旱地红壤中添加生物质炭和过氧化钙土壤提高可溶性有机碳(DOC)和微生物量碳(MBC)含量;增加蔗糖酶(INV)、淀粉酶(AMY)及脲酶(URE)活性,特别是配施(C+Ca)显著提高土壤活性碳含量及酶活性。PLFA分析表明,土壤微生物总PLFAs量的大小顺序为:C+CaCCaCK;各处理土壤细菌的相对丰度最大,大约占微生物总含量的80%,放线菌次之,大约占微生物总含量的13%～15%,而真菌和丛枝菌根真菌的相对丰度较低。生物质炭和过氧化钙增加了革兰氏阴性菌(GN)/革兰氏阳性菌(GP)值,尤以C+Ca处理增加幅度最大。主成分分析(PCA)表明,添加生物质炭和过氧化钙能够改善土壤微生物群落结构;计算主成分的综合得分,配施(C+Ca)处理的综合得分最高,对土壤微生物群落结构的影响最大。冗余分析(RDA)表明,土壤MBC、DOC和土壤INV酶活性是影响土壤微生物数量和结构的主要因子。因此,施用生物质炭和过氧化钙能够明显提高旱地红壤微生物生物量,改变红壤微生物群落结构以及激发红壤酶活性,且配施效果最显著。     

生物质炭对黄瓜连作土壤理化性状、酶活性及土壤质量的持续效应

【目的】 探讨不同生物质炭施用量对连作黄瓜根区土壤环境的作用效果,为用生物质炭修复黄瓜连作土壤以及在农业中的推广应用提供科学依据。 【方法】 以如皋市农业科学研究所大棚示范区为试验基地,一次性向设施农田土壤中添加0 (CK)、5 (C1)、10 (C2)、20 (C3)、30 (C4)、40 (C5) t/hm2的生物质炭,通过连续两年温室定位试验,测定生物质炭施用后黄瓜连作根区土壤的物理性状、养分含量及酶活性的变化状况,采用土壤质量指数 (SQI) 评价不同生物质炭施用量对黄瓜连作两季后土壤质量的影响。 【结果】 随着生物质炭施用量的增加,第一季与第二季黄瓜根区土壤的理化性状变化趋势一致,具体表现为容重不断降低,土壤孔隙度、饱和含水量、田间持水量、饱和导水率、有效磷及有机质含量不断升高,且当生物质炭施用量为30 t/hm2(C4处理) 时,土壤中全氮、硝态氮和铵态氮含量最高。与CK相比,生物质炭的施用可以减少黄瓜根区土壤 < 0.25 mm粒径的微团聚体含量,而增加 > 0.25 mm粒径的大团聚体含量,土壤中0.25～0.5 mm和0.5～1 mm粒径的团聚体含量都在高施用量 (40 t/hm 2) 处理中达到最大值。生物质炭施用后的连续两季,黄瓜根区土壤中脲酶与过氧化氢酶活性均随生物质炭施用量的增加呈先增加后降低的趋势,其活性分别在生物质炭施用量为30 t/hm2和20 t/hm2时最大。当生物质炭施用量为30 t/hm2时,两季黄瓜产量都达到最高,分别为3.24 × 104 kg/hm2和6.18 × 104 kg/hm2。通过土壤质量指数 (SQI) 对生物质炭施用后两季黄瓜土壤质量进行评价可知,不同生物质炭施用水平下土壤质量指数依次为C4 > C5 > C3 > C2 > C1 > CK,相应的土壤质量指数分别为0.774、0.740、0.728、0.650、0.635、0.583。 【结论】 施用生物质炭对黄瓜连作田土壤的理化性状和酶活性均有显著影响,高施用量 (40 t/hm2) 条件下对土壤物理性状改善效果最好,当生物质炭施用量为30 t/hm2 (C4处理) 时对黄瓜连作根区土壤的养分含量提升效果最佳。SQI可以客观定量地评价生物质炭施用对连作黄瓜根区土壤质量的影响,其分析结果表明改善黄瓜连作土壤环境的最佳生物质炭施用量为30 t/hm2。      

Invasion of Pontoscolex corethrurus (Glossoscolecidae,Oligochaeta) in landscapes of the Amazonian deforestation arc

Pontoscolex corethrurus (Glossoscolecidae, Oligochaeta) is an invasive endogeic earthworm that has colonized most land transformed by human activities in the humid tropics. When installed, populations can change soil physical properties, biogeochemical processes and microbial communities. The aim of this study was to determine whether P. corethrurus establishment is a result of (1) a competitive exclusion of native earthworm species or (2) the exploitation of a new niche created by anthropogenic disturbance that native earthworm species cannot use. We tested these hypotheses by doing a survey of earthworm communities in 270 sites that represented the diversity of land use systems encountered in two contrasted regions of the Amazonian arc of deforestation located in Brazil and Colombia respectively. When present in forests, P. corethrurus had no negative effect on the native species communities that had similar (epigeic species) or even higher densities (endogeic species) in the presence of the invasive species. These results suggest the absence of competitive exclusion.The first two axes of a PCA multivariate analysis of communities represented the densities of native species (axis 1) and P. corethrurus (axis 2) respectively. This suggests that respective densities of the two groups respond to different conditions and that their variations are independent. The density of P. corethrurus co-varied with soil N content and pH in Colombian sites while the densities of other species did not. Our results thus suggest that this invasive species, unlike native species, is able to feed and develop in environments where litter resources are decreased while soils have been enriched in C and nutrients by deforestation and burning. We discuss the reasons why some primary forests in Central America have large populations of P. corethrurus.     

Cover crop and tillage effects on soil enzyme activities following tomato

Increasing numbers of vegetable growers are adopting conservation tillage practices and including cover crops into crop rotations. The practice helps to increase or maintain an adequate level of soil organic matter and improves vegetable yields. The effects of the practices, however, on enzyme activities in southeastern soils of the United States have not been well documented. Thus, the objectives of the study were to investigate the effects of cover crops and two tillage systems on soil enzyme activity profiles following tomato and to establish relationships between enzyme activities and soil organic carbon (C) and nitrogen (N). The cover crops planted late in fall 2005 included black oat (Avena strigosa), crimson clover (Trifolium incarnatum L.), or crimson clover–black oat mixed. A weed control (no cover crop) was also included. Early in spring 2006, the plots were disk plowed and incorporated into soil (conventional tillage) or mowed and left on the soil surface (no-till). Broiler litter as source of N fertilizer was applied at a rate of 4.6 Mg ha⁻¹, triple super phosphate at 79.0 kg P ha⁻¹, and potassium chloride at 100 kg K ha⁻¹ were also applied according to soil testing recommendations. Tomato seedlings were transplanted and grown for 60 days on a Marvyn sandy loam soil (fine-loamy, kaolinitic, thermic Typic Kanhapludults). Ninety-six core soil samples were collected at incremental depths (0–5, 5–10, and 10–15 cm) and passed through a 2-mm sieve and kept moist to study arylamidase (EC 3.4.11.2), l-asparaginase (EC 3.5.1.1), l-glutaminase (EC 3.5.1.2), and urease (EC 3.5.1.5) activities. Tillage systems affected only l-glutaminase activity in soil while cover crops affected activities of all the enzymes studied with the exception of urease. The research clearly demonstrated that in till and no-till systems, l-asparaginase activity is greater (P ≤ 0.05) in plots preceded by crimson clover than in those preceded by black oat or their mixture. Activity of the enzyme decreased from 11.7 mg NH₄⁺–N kg⁻¹ 2 h⁻¹ at 0–5 cm depth to 8.73 mg NH₄⁺–N kg⁻¹ 2 h⁻¹ at 5–10 cm and 10–15 cm depths in the no-till crimson clover plots. Arylamidase activity significantly correlated with soil organic C (r = 0.699**) and soil organic N (r = 0.764***). Amidohydrolases activities significantly correlated with soil organic N but only urease significantly correlated with soil organic C (r = 0.481*). These results indicated that incorporation of cover crops into rotations may increase enzyme activities in soils.     

Soil biochemical activities and the geometric mean of enzyme activities after application of sewage sludge and sewage sludge biochar to soil

There is a need to improve the way in which wastes, such as sewage sludges, are managed and a potential way to proceed would be to transform them into biochar. On the other hand, there is a growing interest in the use of soil biochemical properties as indicators of soil quality because they are sensitive to alterations in soil management. Thus, we have studied the effect of a biochar obtained from sewage sludge on soil biochemical properties in an organic soil using two doses of biochar and comparing these results with the control soil and with soils amended with the same two doses of unpyrolyzed sewage sludge. Microbial biomass C, soil respiration, net N mineralization and several enzyme activities (dehydrogenase, β-glucosidase, phosphomoesterase and arylsulphatase) were monitored. The geometric mean of enzyme activities (GMea) was used as a soil quality index. Individual biochemical properties showed a different response to the treatments, while GMea showed an increase in the quality of soils amended with the high biochar dose and a decrease in those amended with a high sewage sludge dose. The geometric mean of enzyme activities was a suitable index to condense the whole set of soil enzyme values in a single numerical value, which was sensitive to management practices.     

生物炭施用下潮土团聚体微生物量碳氮和酶活性的分布特征

[目的]探究生物炭配施化肥对不同粒级团聚体中微生物量碳、氮(MBC、MBN)含量和胞外酶活性的影响,分析影响团聚体胞外酶活性变化的主控因素,为提升土壤质量提供科学依据.[方法]田间微区试验在河南现代农业研究基地进行,供试土壤为石灰性潮土.设置4个处理:不施肥(CK)、单施化肥(NPK)、单施生物炭(BC)和生物炭配施化...     

A comparison of the effects of air-drying and acetone dehydration on soil enzyme activities

The effects of air-drying or acetone dehydration on the activities of invertase, amylase, cellulase, xylanase, urease, protease, phosphatase and sulphatase in nine New Zealand soils from pastures were determined. Generally, air-drying of the soils reduced activities, with losses ranging from slight for sulphatase to very large for protease. For most of the enzymes, acetone dehydration generally resulted in smaller losses of activity than did air-drying; exceptions were invertase and all but two enzymes in the two sandy soils with lowest clay contents. In contrast to the other activities, the activity of urease was generally increased by both drying treatments and that of sulphatase by acetone dehydration. The effects of 6 weeks' storage at 4°C on the enzyme activities of field-moist, air-dried and acetone-dehydrated soils were also assessed. Generally, field-moist storage was best for preserving the original activity, primarily because of the initial losses caused by both drying processes.