Restoration of pasture after topsoil removal: Effects on soil carbon and nitrogen mineralization,microbial biomass and enzyme activities

The restoration of soil biochemical activities after topsoil removal to depths 0 (S₀), 10 (S₁₀) or 20 (S₂₀)cm, and re-establishment of a grass-clover pasture, was studied with Judgeford silt loam, a Typic Dystrochrept, in the Wellington area. Organic matter contents of the S₁₀ and S₂₀ samples were initially 58 and 40%, and biochemical activities, on average, 32 and 20%, respectively of S₀ values. Organic matter content increased only slowly in the stripped plots. Yields of pasture herbage, soil CO₂ and mineral-N production, three indices of microbial biomass, and invertase, amylase, cellulase, xylanase, urease, phosphatase, and sulphatase activities increased more rapidly, but had not reached S₀ levels after 3 yr. The ratios of biomass indices varied with depth of topsoil removed; over the trial, biomass-C to ATP ratios averaged 236, 205, and 168 in the S₀, S₁₀, and S₂₀ samples respectively. Biochemical activities were generally correlated significantly with herbage yields in the S₁₀ or S₂₀, but not in the S₀ plots; organic C or total N contents were not generally correlated significantly with yields over the first 2 yr. Overall, invertase, and then sulphatase, activity appeared to be the best indicators of soil fertility status in this stripped soil.     

A principal components analysis of some biochemical activities in a climosequence of soils

Ten biochemical properties, comprising oxygen uptakes with and without added glucose, dehydrogenase, invertase, amylase. protease, urease, phosphatase, and sulphatase activities, and the invertase/amylase ratio, were measured in a climosequence of nine soils in tussock grasslands in New Zealand. Generally, these properties had no consistent distribution pattern. Some activities, however, were greater in the more developed soils of the sequence while others were lower in the “alpine” soil.The influence of 10 environmental and soil factors on the activities was assessed by principal components analysis. Nearly 90% of the total variance could be accounted for by only three components. The amounts of variance in individual activities accounted for by these components differed, but were usually high. The percentage of organic C, soil moisture regime, and mean annual temperature accounted for much of the variance in all three components; total N was unimportant. As a result of the principal components analysis, the soils could be grouped biochemically into arrangements that were consistent with either the pedological classification of the soils or the influence of a dominant environmental factor. The usefulness of principal components analysis for other ecological studies of soil biochemical properties is indicated.     

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.     

蚯蚓活动对生态滤池土壤酶活性的影响

通过构建蚯蚓生态滤池和无蚯蚓对照生态滤池的实验,研究了蚯蚓活动对生态滤池土壤酶活性(蔗糖酶、脲酶、碱性磷酸酶)的影响以及酶活性的季节动态变化特征。研究结果表明,在0~20 cm的基质层,三种土壤酶活性随土壤深度的增加而减少;蚯蚓活动对生态滤池的基质酶活性有促进作,蔗糖酶和脲酶活性在蚯蚓作用下得到显著的提高,而碱性磷酸酶对蚯蚓活动的响应仅限于5~10 cm基质层;在试验期内,生态滤池内的蚯蚓数量及生物量受温度及土壤湿度的影响表现出较大的季节波动:夏季最高,春季冬季相对较高,秋季最低;三种土壤酶活性表现为相似的季节变化规律:秋季活性最高,而秋季和夏季的酶活性高于春季和冬季。蚯蚓活动对生态滤池基质土壤蔗糖酶活性和脲酶显著的促进作用,并间接影响了其对生活污水污染物去除效果。     

Spatial variability of biochemical properties in a taxonomically-uniform soil under grazed pasture

Spatial variability in levels of three chemical and twelve biochemical properties was measured in samples of a Typic Haplaquoll taken from a small, uniform site under grazed pasture. Three separate comparisons were made between: ten small samples to assess topsoil variability, two sets of adjacent cores to assess short-range variability, and six samples taken at different depths down the soil profile. A method for estimating xylopyranosidase activity is also given.Properties generally differed significantly among the topsoil samples, with biochemical variability being often significantly greater than chemical variability. The sample sizes required to estimate the site means, with a standard error of 5%, were calculated for each property; they ranged from 44 for urease activity to 3 for organic C content and invertase activity. Most biochemical activities were positively and significantly correlated with soil organic C and total N contents. Respiratory activity, however, was correlated significantly only with soil moisture. There were few highly-significant relationships between enzyme activities. Exceptions were the very significant relationship between urease and sulphatase activities, and the significant correlations of phosphatase activity with all other enzyme activities except xylanase.Values of chemical properties in adjacent cores were very similar within each set, but biochemical properties often varied considerably. One set of samples was generally more variable than the other.All properties showed the expected decline with soil depth. Biochemical activities declined more rapidly than organic C and total N contents, and were clearly influenced by factors additional to organic matter content.Recommended sampling procedures are given for seasonal or soil characterization studies.     

Plant availability of phosphorus in superphosphate and a phosphate rock as influenced by earthworms

The effect of earthworms on the plant availability of phosphorus (P) in superphosphate and Chatham Rise phosphorite (CRP) was evaluated in a glasshouse experiment using perennial ryegrass over seven harvests. A mixed earthworm population of Lumbricus rubellus (Hoff.) and Allolobophora caliginosa (Savigny) was used. Increases in the yield of ryegrass in the presence of earthworms varied from 2 to 32%, whereas increases in P uptake by ryegrass ranged from 0 to 40% over seven harvests. With superphosphate, the initial increases in both ryegrass yield and P uptake by ryegrass in the presence of earthworms ranged from 20 to 40% at first harvest to less than 10% by the seventh. In marked contrast, earthworms increased the agronomic performance of pelletized CRP by 15 to 30% throughout the trial period. An increase in plant-available soil N concentrations due to earthworm activity probably explains the initial difference in the performance of superphosphate. The increased agronomic effectiveness of CRP appears to result from the incorporation and intimate mixing of the PR with the soil by earthworms. The implications of the results obtained in the present study to the interpretation of glasshouse and field trials evaluating P fertilizers are also discussed.     

Effects of earthworms on soil enzyme activity in an organic residue amended rice–wheat rotation agro-ecosystem

The effect of earthworms on soil hydrolases (protease, urease, invertase, and alkaline phosphatase) and dehydrogenase activities was investigated in maize residue amended rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and an untreated control. The application of maize residues to soil without earthworms significantly enhanced the five soil enzyme activities compared with the control treatment during rice and wheat cultivation. The presence of earthworms further significantly enhanced protease activity in the soils with both incorporated and mulched maize residues during two cultivation seasons, but only significantly increased alkaline phosphatase activity in the soil with incorporated maize residue during the rice cultivation season. Invertase activity was significantly enhanced by the presence of earthworms in the soil with maize residue incorporation during two cultivation seasons. There were no changes in dehydrogenase activity when earthworms were present. Additionally, the five enzyme activities in earthworm casts were significant higher than those in the surrounding soil, especially dehydrogenase and invertase activities. Whatever the treatment, the values obtained for the enzyme activities in both soil and casts, except for dehydrogenase activity in earthworm casts, were significantly higher under wheat than those in rice-cultivated soil. These results indicate that the presence of earthworms strongly affected soil enzyme activities, depending on the method of organic residue application, and the enhanced enzyme activities of earthworm casts probably contributed to the surrounding soil enzyme activities.     

The combined effects of earthworms and arbuscular mycorrhizal fungi on microbial biomass and enzyme activities in a calcareous soil spiked with cadmium

Earthworms and arbuscular mycorrhizal fungi (AMF) are known to independently affect soil microbial and biochemical properties, in particular soil microbial biomass (SMB) and enzymes. However, less information is available about their interactive effects, particularly in soils contaminated with heavy metals such as cadmium (Cd). The amount of soil microbial biomass C (MBC), the rate of soil respiration (SRR) and the activities of urease and alkaline phosphatase (ALP) were measured in a calcareous soil artificially spiked with Cd (10 and 20 mg Cd kg⁻¹), inoculated with earthworm (Lumbricus rubellus L.), and AMF (Glomus intraradices and Glomus mosseae species) under maize (Zea mays L.) crop for 60 days. Results showed that the quantity of MBC, SRR and enzyme activities decreased with increasing Cd levels as a result of the elevated exchangeable Cd concentration. Earthworm addition increased soil exchangeable Cd levels, while AMF and their interaction with earthworms had no influence on this fraction of Cd. Earthworm activity resulted in no change in soil MBC, while inoculation with both AMF species significantly enhanced soil MBC contents. However, the presence of earthworms lowered soil MBC when inoculated with G. mosseae fungi, showing an interaction between the two organisms. Soil enzyme activities and SRR values tended to increase considerably with the inoculation of both earthworms and AMF. Nevertheless, earthworm activity did not affect ALP activity when inoculated with G. mosseae fungi, while the presence of earthworm enhanced urease activity only with G. intraradices species. The increases in enzyme activities and SRR were better ascribed to changes in soil organic carbon (OC), MBC and dissolved organic carbon (DOC) contents. In summary, results demonstrated that the influence of earthworms alone on Cd availability is more important than that of AMF in Cd-polluted soils; and that the interaction effects between these organisms on soil microorganism are much more important than on Cd availability. Thus, the presence of both earthworms and AMF could alleviate Cd effects on soil microbial life.     

城市生活污泥蚯蚓处理过程中相关酶活性的动态变化特征

利用大平2号蚯蚓处理城市生活污泥,分析了其对污泥磷酸酶、脲酶、蛋白酶、蔗糖酶活性的影响。结果表明,污泥经蚯蚓处理后,相关酶的活性发生了较大的变化,污泥酸性和碱性磷酸酶活性先升高而后下降,中性磷酸酶的活性则持续下降;污泥脲酶的活性先升高后下降;蛋白酶和蔗糖酶的活性则持续下降。总体来说,所研究的4种酶的活性随着时间延长有下降的趋势,其中污泥蛋白酶的活性下降最为显著,其他相对较小。污泥蚯蚓处理过程中有机质等的降低可能是酶活性下降的主要原因。     

不同机械改土方式对白浆土物理特性及酶活性的影响

白浆土是我国东北地区主要低产土壤之一,土体中白浆层通气透水能力极差,生物酶活性很低,导致土壤表旱表涝严重,旱田作物根系有效土层一般只有20 cm左右。自20世纪80年代开始,包括深松在内的机械改土逐渐演变为白浆土的主要改良方式。为了探讨不同机械改土方式的改土效果,研究采用3种机械改土方式,依次为普通深松犁、秸秆心土混合犁、心土间隔混拌犁,并以普通深松犁为对照,在典型白浆土上开展改土试验。机械作业后,分别测定土壤物理性质及土壤酶活性。结果表明:秸秆心土混合犁、心土间隔混拌犁处理后,白浆层的硬度降低至7~9 kg cm-2,远低于对照白浆层硬度10~14 kg cm-2;固相分别为47.74%、50.13%,均低于对照53.16%;容重与对照相比分别降低了14.01%、10.19%。与对照相比,秸秆心土混合犁、心土间隔混拌犁降低了白浆层过氧化氢酶活性,秸秆心土混合犁处理降低了白浆层脲酶和蔗糖酶活性、增加了淀积层脲酶和蔗糖酶活性;两个处理与对照相比大豆分别增产21.34%、4.94%。秸秆心土混合犁、心土间隔混拌犁改善了土壤不良的理化性质,同时对土壤酶活性有很大的影响。研究为机械改良白浆土的评价方法探索了新途径。     

土壤紧实程度对其某些相关理化性状和土壤酶活性的影响

利用外力夯实、向土壤中加入蛭石等方法造成土壤容重不同,以研究土壤紧实程度对其理化性状的影响。结果表明,紧实土壤水分的散失较快,晴天地温高,且变化幅度大,阴天和夜间紧实土壤地温低,变化幅度小。紧实土壤可降低植株对土壤养分的吸收,致使土壤余留的有效态养分较多。土壤的转化酶、脲酶、过氧化氢酶、多酚氧化酶、磷酸酶活性的变化也受土壤紧实度的影响。总之,土壤疏松有助于保水、蓄热和提高多种土壤酶活性。     

Effects of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal fungus (Glomus intraradices) on enzyme activities of a sterilized soil–sand mixture and nutrient uptake by maize

A pot experiment was conducted to investigate the effect of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal (AM) fungi (Glomus intraradices) on soil enzyme activities and nutrient uptake by maize, which was grown on a mixture of sterilized soil and sand. Maize plants were grown in pots inoculated or not inoculated with AMF, treated or not treated with earthworms. Wheat straw was added as a feed source for earthworms. Mycorrhizal colonization of maize was markedly increased in AM fungi inoculated pots and further increased by addition of epigeic earthworms. AM fungi and epigeic earthworms increased maize shoot and root biomass, respectively. Soil acid phosphatase activity was increased by both earthworms and mycorrhiza, while urease and cellulase activities were only affected by earthworms. Inoculation with AM fungi significantly (p?<?0.001) increased the activity of soil acid phosphatase but decreased soil available phosphorus (P) and potassium (K) concentrations at harvest. Addition of earthworms alone significantly (p?<?0.05) increased soil ammonium-N content, but decreased soil available P and K contents. AM fungi increased maize shoot weight and root P content, while earthworms improved N, P, and K contents in shoots. AM fungi and earthworm interactively increased maize shoot and root biomass through their regulation of soil enzyme activities and on the content of available soil N, P, and K.     

A comparison of sulphatase,urease and protease activities in planted and in fallow soils

Sulphatase, urease and protease activities were studied in 12 New Zealand topsoils over 5 months during which the soils were held at 10, 18 and 25°C in pots sown with perennial ryegrass and in pots left fallow.Sulphatase activity in the planted soils showed little significant change over the period of examination. In contrast, sulphatase activity in the fallow soils decreased significantly in almost every instance, the extent of the decrease becoming larger with increasing temperature. Urease behaved similarly to sulphatase, except that in the planted soils several significant increases in activity occurred. Protease activities proved to be very variable. Because of this few significant differences in protease activity were recorded, although it showed the same trends as the other two enzymes.It is suggested that temperature-dependent denaturation could have caused the decrease in enzyme activity in the fallow soils. Replacement of activity lost in this manner by enzymes liberated from plants and microorganisms, and by intracellular enzymes, may have been responsible for the maintenance or increase of activity in the planted soils.     

铅对两个红壤中酶活性的影响

Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate（FDA） hydrolysis were measured in two red soils spiked with Pb^2＋ ranging from 0 to 2 400 mg kg^-1 to relate the enzyme activity values to both plant growth and the levels of available and total Pb^2＋ concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month’s incubation and then after planting of celery（Apium graveolens L.） and Chinese cabbage（Brassica chinensis L.）. Enzyme activities in the red soil derived from arenaceous rock（RAR） were generally lower than those in the red soil developed on Quaternary red earths（REQ）. At high Pb^2＋ loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb^2＋ loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb^2＋ than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.     

Soil enzyme activities in dependence on tree litter and season of a social forest,Burdwan, India

The study was done to evaluate enzyme activities (amylase, cellulase and invertase) from the soils of different vegetation sites, with seasonal variation, of social forest, Burdwan, India. Study results showed significant lower enzymatic activities in the subsoil compared to those of the topsoil. The seasonal variations indicated that amylase, cellulase and invertase enzyme activities had reached peaks during the rainy seasons in different soil depths. Amylase activity was highest in Tectona litter containing soil in all seasons in both the soil layers. All the three enzyme activities have shown significant positive correlation with available nitrogen (p < 0.05) and available phosphorous (p < 0.05) during rainy season in both the soil depths. Correlation study revealed that soil organic carbon was positively correlated with cellulase and invertase activities except in the Anacardium vegetation site in the topsoil during rainy season. Irrespective of the seasons and the depths of soil, control site without vegetation showed much lower levels of organic carbon and enzyme activity compared to those of the experimental sites. Therefore, it is concluded that carbon transformation will be higher during rainy season in the vegetation sites of forest soil under such agroclimatic conditions.     

Interactive effects of biochar and the earthworm Pontoscolex corethrurus on plant productivity and soil enzyme activities

Purpose

There is a growing interest in the use of soil enzymes as early indicators of soil quality change under contrasting agricultural management practices. In recent years, there has been increasing interest in the use of biochar to improve soil properties and thus soil quality. In addition, earthworms can also be used to ameliorate soil properties. However, there is no literature available on how biochar and earthworms interact and affect soil enzymes. The general objective of the present study was to test the suitability of adding biochar and earthworms in two tropical soils with low fertility status in order to improve their characteristics and productivity.

Materials and methods

Biochars were prepared from four different materials [sewage sludge (B1), deinking sewage sludge (B2), Miscanthus (B3) and pine wood (B4)] on two tropical soils (an Acrisol and a Ferralsol) planted with proso millet (Panicum milliaceum L.). In addition, in order to investigate the interaction between earthworms and biochar, earthworm Pontoscolex corethrurus was added to half of the mesocosms, while excluded in the remaining half. The activities of invertase, β-glucosidase, β-glucosaminidase, urease, phosphomonoesterase and arylsulphatase were determined. The geometric mean of the assayed enzymes (GMea) was used as an integrative soil quality index.

Results and discussion

Overall, earthworms and especially biochar had a positive effect on soil quality. GMea showed B1, B2 and B3 performing better than B4; however, results were soil specific. Plant productivity increased under both biochar and earthworm addition. Fruit productivity and plant growth was enhanced by B1 and B2 but not by B3 or B4.

Conclusions

Enhancements of productivity and soil enzymatic activities are possible in the presence of earthworms and the combination of the practices earthworm and biochar addition can be suggested in low fertility tropical soils. However, scientists should proceed carefully in the selection of biochars as the results of this study show a high specificity in the biochar–soil interaction.     

土霉素及镉污染对土壤呼吸及酶活性的影响

随着饲料工业以及畜禽养殖业的规模化发展,抗生素和重金属在土壤环境中同时存在的几率不断增大。为了分析抗生素和重金属对土壤微生物生态系统的影响,以土霉素(OTC)与镉(Cd)为污染物,采用室内培养法,研究了土霉素(OTC)与镉(Cd)单一处理及复合污染对土壤呼吸和酶活性的影响。结果表明,10mg/kg重金属镉单独污染对土壤微生物呼吸表现为先抑制后激活作用,且显著抑制了土壤蔗糖酶、脲酶、磷酸酶活性,对3种酶活性平均抑制率从大到小依次为:蔗糖酶磷酸酶脲酶;1mg/kg土霉素显著激活土壤微生物呼吸,50和200mg/kg土霉素对土壤微生物呼吸的影响呈现出先抑制后激活的规律。各处理浓度下的土霉素对蔗糖酶和脲酶活性均主要表现为抑制作用,对磷酸酶活性的影响呈现出一定的波动性;当土霉素的浓度为1和200mg/kg时,其与10mg/kg镉的复合污染对土壤微生物呼吸及3种酶活性的影响主要为拮抗作用,但当土霉素的浓度为50mg/kg时,与10mg/kg镉的复合污染对土壤微生物呼吸及3种酶活性的影响则主要为协同作用。微生物呼吸对土霉素与镉胁迫更为敏感,最高抑制率和激活率分别可达98.98%和300.82%,土壤酶活性受土霉素和镉污染的影响要弱于它们对土壤微生物呼吸的影响。     

Earthworm-mycorrhiza interaction on Cd uptake and growth of ryegrass

The effects of inoculation of earthworms and arbuscular mycorrhiza separately, and in combination, on Cd uptake and growth of ryegrass were studied in soils contaminated with 0, 5, 10, 20 mg of Cd kg⁻¹ soil. Both earthworms and mycorrhiza were able to survive in all the treatments with added Cd. Earthworm activity significantly increased mycorrhizal infection rate of root and ryegrass shoot biomass. Earthworm activity decreased soil pH by about 0.2 units, and enhanced root Cd concentration and ryegrass Cd uptake. Mycorrhiza inoculation increased shoot and root Cd concentration substantially, and at the highest dosage of 20 mg Cd kg⁻¹ decreased biomass of ryegrass. Inoculation of both earthworms and mycorrhiza increased ryegrass shoot Cd uptake at low Cd concentrations (5 and 10 mg Cd kg⁻¹ soil), when compared with inoculation of earthworms or mycorrhiza alone. In conclusion, earthworm, mycorrhiza and their interaction may have a potential role in elevating phytoextraction efficiency in low to medium level metal contaminated soil.     

Meta-analysis of experimental warming on soil invertase and urease activities

Soil enzymes are regulate terrestrial carbon (C) and nitrogen (N) cycles, and how the activity of these enzymes are affected by soil warming duration is unclear. In the study, the effect of experimental soil warming duration (<2 years and >2 years) on invertase and urease activities were examined by meta-analysis. Soil warming increased invertase activity by 22% (<2 years) and 16% (>2 years), respectively, while they increased urease by 29% and 9%. Meta-analysis of soil warming experiments found that warming by less than 1.5°C increased invertase by 22%, while warming it by more than 1.5°C increased invertase by 29%; the corresponding increases in urease were 16% and 8%. These effects of experiment warming differed among ecosystem types, with warming-induced increases being greatest in forest ecosystem. The results of this meta-analysis suggest that invertase and urease become less responsive to warming over longer periods and invertase with greater warming-responsiveness than urease activity.     

Recovery of topsoil characteristics after landslip erosion in dry hill country of New Zealand, and a test of the space-for-time hypothesis

The rate of development of topsoil is an important characteristic for soil resilience and sustainable use. We located a chronosequence (1-59 yr) of recovering landslip scars in erodible siltstone hill country under permanent pasture for sheep farming in New Zealand. We measured the rates of recovery in microbial C, respiration, catabolic diversity, phosphatase, sulphatase and invertase activities, pH, total C, total N, C/N ratio, potentially mineralizable N, total P, Olsen P, cation-exchange capacity, bulk density, particle density, porosity, available water and aggregate stability (0-10 cm depth). A subset of the same sites was sampled again after a 14-yr interval, enabling us to test whether rates of change estimated by resampling the same sites were the same as those estimated from a single time sample from the chronosequence (the space-for-time hypothesis).Most topsoil characteristics had recovered to 71-85% of those in the non-slipped sites after 59 yr. Exceptions were soil respiration, invertase and sulphatase activities, and bulk density, which recovered to 94-110% of the values of the non-slipped sites. There was little change in soil pH, total P, Olsen P, exchangeable cations and water storage along the chronosequence. An asymptote model fitted the patterns of recovery in biochemical characteristics, organic matter, bulk density and particle density. Recovery (to 90% of the asymptote value) was most rapid for the C/N ratio (5 yr) and longest for particle density (79 yr); most other characteristics fell in an 18-50 yr range. Overall, a single sampling of a chronosequence of matched landslip scars was as reliable to estimate rates of recovery as was resampling individual sites through time. Total C and N were as effective as more complicated biochemical measures to monitor the recovery of topsoil.