共查询到20条相似文献,搜索用时 15 毫秒
1.
A sterilized, but undecomposed, organic by-product of municipal waste processing was incubated in sandy soils to compare C and N mineralization with mature municipal waste compost. Waste products were added to two soils at rates of 17.9, 35.8, 71.6, and dry weight and incubated at for 90 d. Every 30 d, nitrate and ammonium concentrations were analyzed and C mineralization was measured as total CO2-C evolved and added total organic C. Carbon mineralization of the undecomposed waste decreased over time, was directly related to application rate and soil nutrient status, and was significantly higher than C mineralization of the compost, in which C evolution was relatively unaffected across time, soils, and application rates. Carbon mineralization, measured as percentage C added by the wastes, also indicated no differences between composted waste treatments. However, mineralization as a percentage of C added in the undecomposed waste treatments was inversely related to application rate in the more productive soil, and no rate differences were observed in the highly degraded soil. Total inorganic N concentrations were much higher in the compost- and un-amended soils than in undecomposed waste treatments. Significant N immobilization occurred in all undecomposed waste treatments. Because C mineralization of the undecomposed waste was dependant on soil nutrient status and led to significant immobilization of N, this material appears to be best suited for highly degraded soils low in organic matter where restoration of vegetation adapted to nutrient poor soils is desired. 相似文献
2.
Influence of soil compaction on carbon and nitrogen mineralization of soil organic matter and crop residues 总被引:18,自引:0,他引:18
We studied the influence of soil compaction in a loamy sand soil on C and N mineralization and nitrification of soil organic
matter and added crop residues. Samples of unamended soil, and soil amended with leek residues, at six bulk densities ranging
from 1.2 to 1.6 Mg m–3 and 75% field capacity, were incubated. In the unamended soil, bulk density within the range studied did not influence any
measure of microbial activity significantly. A small (but insignificant) decrease in nitrification rate at the highest bulk
density was the only evidence for possible effects of compaction on microbial activity. In the amended soil the amounts of
mineralized N at the end of the incubation were equal at all bulk densities, but first-order N mineralization rates tended
to increase with increasing compaction, although the increase was not significant. Nitrification in the amended soils was
more affected by compaction, and NO3
–-N contents after 3 weeks of incubation at bulk densities of 1.5 and 1.6 Mg m–3 were significantly lower (by about 8% and 16% of total added N, respectively), than those of the less compacted treatments.
The C mineralization rate was strongly depressed at a bulk density of 1.6 Mg m–3, compared with the other treatments. The depression of C mineralization in compacted soils can lead to higher organic matter
accumulation. Since N mineralization was not affected by compaction (within the range used here) the accumulated organic matter
would have had higher C : N ratios than in the uncompacted soils, and hence would have been of a lower quality. In general,
increasing soil compaction in this soil, starting at a bulk density of 1.5 Mg m–3, will affect some microbially driven processes.
Received: 10 June 1999 相似文献
3.
Effects of a cadmium-contaminated sewage sludge compost on dynamics of organic matter and microbial activity in an arid soil 总被引:3,自引:0,他引:3
An incubation experiment lasting 120 days was carried out to ascertain the effect on the soil microbial activity and organic
matter mineralization of adding a sewage sludge compost contaminated with two different levels of Cd to an arid soil. Two
composts, with a low (2 mg kg–1) and high (815 mg kg–1) Cd content, respectively, were used in this experiment. Both composts increased the total organic C, humic substance and
water-soluble C contents, the beneficial effects still being noticeable after 120 days of incubation. The most labile C fraction
(water-soluble C) was the most sensitive to the high Cd content. The high Cd concentration decreased soil microbial biomass
C and stimulated the metabolic activity of the microbial biomass, the metabolic quotient (qCO2) revealing itself to be a very sensitive index of the stress that the incorporation of a Cd-contaminated sewage sludge compost
causes in a soil. The effect of Cd contamination on enzyme activities (urease, protease that hydrolyse N-α-benzoil-l-arginamide, phosphatase, and β-glucosidase) depended on the enzyme studied.
Received: 10 September 1997 相似文献
4.
Carmine Crecchio Magda Curci Maria D.R. Pizzigallo Patrizia Ricciuti Pacifico Ruggiero 《Soil biology & biochemistry》2004,36(10):1595-1605
Municipal solid waste (MSW) composts have been used to maintain the long-term productivity of agroecosystems and to protect the soil environment from overcropping, changes in climatic conditions and inadequate management; they also have the additional benefit of reducing waste disposal costs. Since MSW may contain heavy metals and other toxic compounds, amendments cannot only influence soil fertility, but may also affect the composition and activity of soil microorganisms. The effects of MSW compost and mineral N amendments in a 6-year field trial on some physical-chemical properties, enzyme activities and bacterial genetic diversity of cropped plots (Beta vulgaris-Triticum turgidum rotation) and uncropped plots were investigated. The compost was added at the recommended and twice the recommended dosage (12, 24 t ha−1). Amendments of cropped plots with MSW compost increased the contents of organic C from 13.3 to 15.0 g kg−1 soil and total N from 1.55 to 1.65 g kg−1 soil. There were significant increases in dehydrogenase (9.6%), β-glucosidase (13.5%), urease (15.4%), nitrate reductase (21.4%) and phosphatase (9.7%) activities. A significant reduction in protease activity (from 3.6 to 2.8 U g−1 soil) was measured when a double dose of compost was added to the cropped plots. No dosage effect was detected for the other enzymes. Changes in the microbial community, as a consequence of MSW amendment, were minimal as determined using denaturing gradient gel electrophoresis, rDNA internal spacer analysis and amplified ribosomal DNA restriction analysis of bacteria, archaea, actinomycetes, and ammonia oxidizers. This indicates that there was no significant variation in the overall bacterial communities nor in selected taxonomic groups deemed to be essential for soil fertility. 相似文献
5.
Influence of inorganic fertilizers and organic amendments on soil organic matter and soil microbial properties under tropical conditions 总被引:33,自引:0,他引:33
Soil organic matter level, mineralizable C and N, microbial biomass C and dehydrogenase, urease and alkaline phosphatase
activities were studied in soils from a field experiment under a pearl millet-wheat cropping sequence receiving inorganic
fertilizers and a combination of inorganic fertilizers and organic amendments for the last 11 years. The amounts of soil organic
matter and mineralizable C and N increased with the application of inorganic fertilizers. However, there were greater increases
of these parameters when farmyard manure, wheat straw or Sesbania bispinosa green manure was applied along with inorganic fertilizers. Microbial biomass C increased from 147 mg kg–1 soil in unfertilized soil to 423 mg kg–1 soil in soil amended with wheat straw and inorganic fertilizers. The urease and alkaline phosphatase activities of soils
increased significantly with a combination of inorganic fertilizers and organic amendments. The results indicate that soil
organic matter level and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil,
are enhanced by use of organic amendments along with inorganic fertilizers.
Received: 6 May 1998 相似文献
6.
C and N mineralization data for 17 different added organic materials (AOM) in a sandy soil were collected from an incubation experiment conducted under controlled laboratory conditions. The AOM originated from plants, animal wastes, manures, composts, and organic fertilizers. The C-to-NAOM ratios (ηAOM) ranged from 1.1 to 27.1. Sequential fibre analyses gave C-to-N ratios of soluble (ηSol), holocellulosic (ηHol) and ligneous compounds (ηLig) ranging from 1.1 to 57.2, 0.8 to 65.2, and 3.5 to 25.3, respectively. Very different patterns of net AOM-N mineralization were observed: (i) immobilization for four plant AOM; (ii) moderate mineralization (4-15% AOM-N) for composts; (iii) marked mineralization (11-27% AOM-N) for 1 animal AOM, 1 manure and 2 organic fertilizers; and (iv) high rates of transformations with possible gaseous losses for some N-rich AOM.The Transformation of Added Organics (TAO) model proposed here, described AOM-C mineralization (28 °C, 75% WHC) from three labile (L′), resistant (R) and stable (S) compartments with the sole parameters P′L and PS=fractions of very labile and stable compounds of AOM, respectively. Dividing the C-compartments by their C-to-N estimates supplied the remaining NAOM fraction (RAONF). A Pim parameter split the TAO nitrogen fraction (TAONF=added N-RAONF) into two compartments, immobilized (imN) and inorganic (inorgN) N. A Pim>0 value meant that all the TAONF plus a fraction (Pim−1) of native soil inorganic N was immobilized. Additional N mineralization was predicted when necessary from imN by first order kinetics (constant kremin). The TAO version with two parameters Pim and kremin allowed us to predict very different patterns of N mineralization and N immobilization. In a few cases, a further first order kinetic law (constant kv) was added to predict N volatilization from inorgN. Two hypotheses were tested: (i) ηL′, ηR, ηS (C-to-N of L′, R and S)=ηSol, ηHol, ηLig, respectively, (ii) ηL′=ηR=ηS=ηAOM. The first hypothesis was validated by these data, and the second was a good approximation of the former one. In all the cases, predictions were in good agreement with measured values. 相似文献
7.
Invertebrate control of soil organic matter stability 总被引:17,自引:0,他引:17
V. Wolters 《Biology and Fertility of Soils》2000,31(1):1-19
The control of soil organic matter (SOM) stability by soil invertebrates is evaluated in terms of their impact on the inherent
recalcitrance, accessibility to microorganisms, and interaction with stabilizing substances of organic compounds. Present
knowledge on internal (ingestion and associated transformations) and external (defecation, constructions) control mechanisms
of soil invertebrates is also reviewed. Soil animals contribute to the stabilization and destabilization of SOM by simultaneously
affecting chemical, physical, and microbial processes over several orders of magnitude. A very important aspect of this is
that invertebrates at higher trophic levels create feedback mechanisms that modify the spatio-temporal framework in which
the micro-food web affects SOM stability. Quantification of non-trophic and indirect effects is thus essential in order to
understand the long-term effects of soil biota on SOM turnover. It is hypothesized that the activities of invertebrates which
lead to an increase in SOM stability partly evolved as an adaptation to the need for increasing the suitability of their soil
habitat. Several gaps in knowledge are identified: food selection and associated changes in C pools, differential effects
on SOM turnover, specific associations with microorganisms, effects on dissolution and desorption reactions, humus-forming
and humus-degrading processes in gut and faeces, and the modification of invertebrate effects by environmental variables.
Future studies must not be confined merely to a mechanistic analysis of invertebrate control of SOM stability, but also pay
considerable attention to the functional and evolutionary aspects of animal diversity in soil. This alone will allow an integration
of biological expertise in order to develop new strategies of soil management which can be applied under a variety of environmental
conditions.
Received: 6 April 1999 相似文献
8.
An incubation experiment with composted sewage sludge (CSS) just added to the soil was conducted to determine its initial
effects on C decomposition, N nitrification and the transformation of organic matter. CSS was mixed with a sandy loam soil
from uncultivated ochric epipedon of a Typic Haploxeralf at rates of 0, 40 and 80 t ha–1 (dry weight). The data obtained showed that with regard to the unamended soil, both the 40 and the 80 t ha–1 treatments produced the same result in decreasing respiratory activity, but the addition of increasing amounts of CSS progressively
delayed C decomposition. The nitrification index (NI), defined as the relation between nitrate-N and nitrate-N + ammonium-N,
increased in correlation with the C mineralization coefficient. Total organic matter decreased after incubation whereas the
humic substances increased in relation to the total C mineralized.
Received: 28 October 1999 相似文献
9.
城市固体废弃物堆肥与化肥对不同土壤植物生长的影响研究 总被引:2,自引:0,他引:2
温室盆栽试验研究城市固体废弃物堆肥与化肥对不同土壤黑麦草生长的影响,结果表明,堆肥和化肥可明显增加黑麦草干物质产量,阳春和大安2种土壤处理C50干物质产量分别比对照增加39.53%和109.38%,而NPK处理则分别增产267.44%和406.25%。堆肥与化肥配施处理(NPK C25对阳春和NPK C50对大安)产量最高。堆肥处理明显增加土壤pH、有机碳、土壤有效态磷、钾、铁、锰、锌和铜含量。 相似文献
10.
Soil properties may affect the decomposition of added organic materials and inorganic nitrogen (N) production in agricultural soils. Three soils, Potu (Pu), Sankengtzu (Sk) and Erhlin (Eh) soils, mixed with sewage sludge compost (SSC) at application rates of 0 (control), 25, 75 and 150 Mg ha−1 were selected from Taiwan for incubation for 112 days. The aim of the present study was to examine the effects of SSC application rates on the carbon decomposition rate, N transformation and pH changes in three soils with different initial soil pH values (4.8–7.7). The results indicated that the highest peaks of the CO2 evolution rate occurred after 3 days of incubation, for all treatments. The Pu soil (pH 4.8) had a relatively low rate of CO2 evolution, total amounts of CO2 evolution and percentage of added organic C loss, all of which resulted from inhibition of microbial activity under low pH. For the Pu and Sk soils, the concentration of NH4 + -N reached its peak after 7–14 days of incubation, which indicated that ammonification might have occurred in the two soils with low initial pH values. NO3 − -N rapidly accumulated in the first 7 days of incubation in the Eh soil (pH 7.7). The direction and extent of the soil pH changes were influenced by the N in the SSC and the initial soil pH. Ammonification of organic N in the SSC caused the soil pH to increase, whereas nitrification of mineralized N caused the soil pH to decline. Consequently, the initial soil pH greatly affected the rate of carbon decomposition, ammonification and nitrification of SSC. 相似文献
11.
生物质炭与有机物料配施的土壤培肥效果及对玉米生长的影响 总被引:7,自引:0,他引:7
生物质炭作为一种多功能的土壤培肥材料被广泛应用,但其与传统有机物料的对比及配施研究还比较少。通过盆栽试验,研究了生物质炭与秸秆、发酵鸡粪单施及配施对壤质潮土和砂土养分含量、酶活性及玉米生长的影响,并采用主成分分析方法对3种有机物料的培肥效果进行综合评价。试验设6个处理,分别为不添加有机物料(CK)、添加生物质炭(BC)、小麦秸秆(WS)、发酵鸡粪(CM)、秸秆和生物质炭(WS+BC)、鸡粪和生物质炭(CM+BC)。研究结果表明,各处理均增加了砂土玉米生物量和株高,3种有机物料的提升幅度排序为:鸡粪生物质炭秸秆,鸡粪还可增加壤质潮土玉米生物量和株高。添加生物质炭和有机物料还可提高土壤有机质含量,其中生物质炭的提升幅度最大。此外,3种有机物料对土壤养分和酶活性的影响各异,单施鸡粪分别增加壤质潮土和砂土的碱解氮22.08%和26.67%,速效磷91.92%和53.65%,脲酶活性40.54%和36.94%;单施生物质炭分别增加壤质潮土和砂土速效磷83.52%和89.91%,速效钾79.38%和127.02%,过氧化氢酶活性3.41%和11.22%,却降低了土壤碱解氮含量,且与鸡粪配施后会抑制鸡粪中氮的有效性;单施秸秆分别增加壤质潮土和砂土速效钾49.48%和63.02%,β-葡糖苷酶活性51.86%和59.09%;生物质炭与鸡粪或秸秆配施可以更均衡地提升土壤肥力。通过主成分分析和相关分析发现,玉米生物量和株高与土壤氮、磷供应正变化的第2主成分(PC2)得分呈极显著正相关关系。因此,3种有机物料中,鸡粪对土壤氮、磷含量及相关酶活性影响最大;秸秆对土壤钾以及纤维素分解相关酶影响较大,而生物质炭对土壤肥力的提升作用更均衡,且土壤肥力综合得分最高。秸秆或鸡粪配施生物质炭可以更全面地提高土壤肥力。 相似文献
12.
Experimental snowpack reduction alters organic matter and net N mineralization potential of soil macroaggregates in a northern hardwood forest 总被引:1,自引:0,他引:1
J. Megan Steinweg Melany C. Fisk Benjamin McAlexander Peter M. Groffman Janet P. Hardy 《Biology and Fertility of Soils》2008,45(1):1-10
Climate change is predicted to reduce or delay annual wintertime snow pack formation in the forests of the northeastern US.
Any delay in snowpack formation could increase soil freezing in winter and, thereby, alter soil characteristics and processes.
We examined the hypothesis that delayed snowpack would disrupt soil structure and change organic matter bioavailability in
an experimental snow removal study at the Hubbard Brook Experimental Forest (HBEF), NH, USA. Pairs of reference and snow removal
treatment plots were studied in four different sites at HBEF. Snow was removed from November–January of two winters, inducing
soil freezing throughout both winters. Size class distribution and organic matter concentration and content of aggregates,
and carbon and nitrogen mineralization potential of size fractions were quantified for surface mineral soils in the spring
of both years immediately after snowmelt. In the first year of sampling, the only significant effect of snow removal was an
increase in the smallest (<53 μm) size fraction of mineral soil. In the second year, snow removal increased organic matter
concentrations of macroaggregate (250–2,000 μm) and microaggregate (53–250 μm) size fractions. This change corresponded to
an increase in net N mineralization potential and the ratio of N to C mineralized in the macroaggregate fraction, but there
were no effects of snow removal on C mineralization. We propose that soil freezing increases the movement of organic matter
from organic to mineral soil horizons and increases the N content of mineralizable substrates in mineral soil following years
with delayed snowpack formation. 相似文献
13.
Summary The effect of fly ash on N mineralization in sewage sludge was studied during a 5-week aerobic incubation of soil-waste mixtures at different loading rates under controlled conditions. Periodically, the mixtures were leached with distilled water and the inorganic N released was determined in the percolates. The data were tested by an analysis of variance with repeated measures. Significant differences were found among different incubation periods and also between different treatments. The net N mineralization, expressed as a percentage of organic N added in the sludge, was drastically reduced when higher rates (500 Mg ha-1) of fly ash were added. 相似文献
14.
Saline water and municipal solid waste compost application on tomato crop: Effects on plant and soil
Rita Leogrande Ornella Lopedota Carolina Vitti Francesco Montemurro 《Journal of plant nutrition》2016,39(4):491-501
A field experiment was conducted in Southern Italy to evaluate the effects of different water quality and fertilizers on yield performance of tomato crop. In mineral nitrogen (N) fertilizer and irrigation with fresh water (Electrical Conductivity, EC, = 0.9 dS m?1) (FWF); mineral N fertilizer and irrigation with saline water (EC = 6.0 dS m?1) (SWF); municipal solid waste (MSW) compost and irrigation with fresh water (EC = 0.9 dS m?1) (FWC); MSW compost and irrigation with saline water (EC = 6.0 dS m?1) (SWC). At harvest, weight and number of fruits and refractometric index (°Brix) were measured, total and marketable yield and dry matter of fruit were calculated. The results indicated that MSW compost, applied as amendment, could substitute the mineral fertilizer. In fact, in the treatments based on compost application, the tomato average marketable yield increased by 9% compared with treatments with mineral fertilizer. The marketable yield in the SWF and SWC treatments (with an average soil EC in two years to about 3.5 dS m?1) decreased respectively of 20 and 10%, in respect to fresh water treatments. At the end of the experiment, application of compost significantly decreased the sodium absorption rate (SAR) of SWC treatment in respect of SWF (?29.9%). Significant differences were observed among the four treatments both on soil solution cations either exchangeable cations. In particular compost application increased the calcium (Ca) and potassium (K) contents in saturated soil paste respect to the SWF ones (31.4% and 59.5%, respectively). At the same time saturated soil paste sodium (Na) in SWC treatment recorded a decrease of 17.4% compared to SWF. 相似文献
15.
有机质对土壤光谱特性的影响研究 总被引:19,自引:2,他引:19
为了探明土壤有机质的光谱特征及其影响作用,从而为有机质土壤铁氧化物的定量反演提供理论依据。利用去有机质前后土壤的光谱数据,研究了有机质对土壤反射率、土壤线参数、土壤铁氧化物定量反演的影响。研究结果表明,去除有机质后,能明显提高土壤反射率,变化最明显的为可见光橙黄光波段,即570~630 nm。相关性分析也显示橙黄光波段反射率的相对变化量或差值与有机质去除量之间的相关系数要比其他波段高,相关系数最大值在600 nm。因此,建议采用570~630 nm的光谱数据进行有机质的反演;土壤线斜率在去有机质后明显降低,截距显著增大,二者变化量与有机质去除量呈极显著相关关系,可用土壤线参数预测有机质含量。有机质对铁氧化物的反演具有明显影响,特别是有机质大于20 g kg-1的土壤,在进行反演时应考虑有机质对反演精度的影响,需采取有效地技术手段消减其影响作用,才能达到较好的效果。 相似文献
16.
Summary A method of assessing the enzymatic hydrolysis of ester sulphate in soil organic matter was developed. Soil organic matter extracted using a mild, chelating resin extraction procedure was incubated with a sulphatase from Helix pomatia in 0.05 M sodium acetate buffer (pH 4–8) at 37°C for 2h and the sulphate released was determined by a high performance liquid chromatography-conductivity detector system. The effect of some soil factors on the enzymatic hydrolysis of ester sulphate was examined. The study showed that part of the ester sulphate in soil organic matter was biochemically reactive. In the three Podzols studied, the ester sulphate hydrolysed accounted for 2%–12% of the hydriodic acid-reducible organic sulphate extracted. The largest amount of hydrolysable ester sulphate was found in the soil with a low pH, high inorganic sulphate and high hydriodic acid-reducible organic sulphate. 相似文献
17.
Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha−1 y−1, and urban sewage sludge at two different rates, 10 t ha−1 y−1 and 100 t ha−1 every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg−1 in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last application, the organic C content and the microbial biomass content remained higher in sludge-treated soils than in the control. In contrast, the proportion of labile organic matter was significantly lower in sludge-treated soils than in manure-treated and control soils. The labile organic matter of sludge extracts appeared less humified than that of manure-treated and control soils. 相似文献
18.
Role of organic fractions on C decomposition and N mineralization of animal wastes in soil 总被引:1,自引:0,他引:1
The relative contributions of water-soluble, water-non-soluble, Van Soest-soluble, and neutral detergent fiber (NDF) fractions
of pig slurry (PS), cattle slurry (CS), cattle farmyard manure (FYM), and composted cattle farmyard manure (CFYM) to the overall
C and N mineralization of the raw wastes were studied by incubating treated soil for 107 days at 15°C under non-limiting N
conditions. The C or N mineralization of soluble fractions was calculated from the difference between C or N mineralization
of the raw and non-soluble fractions. The organic N content of raw wastes ranged from 15 to 32 mg N g−1 dry matter and organic C to organic N ratio from 13 to 29. The water-soluble fraction (SOLW) was close to 100 mg C g−1 raw waste C for CS, FYM, and CFYM but reached 200 mg C g−1 for PS. The Van Soest-soluble fraction (SOLVS) was the main fraction for PS, CS, and CFYM (>500 mg C g−1 raw waste C) but only 303 mg C g−1 raw waste C for FYM. Both soluble and non-soluble fractions contributed to C decomposition of slurries, with half to more
than half of the decomposed C derived from the degradation of soluble compounds. Most of the C decomposed from FYM was derived
from the large NDF fraction, but the contribution from the water-soluble C to the decomposition was also significant. Carbon
mineralization of CFYM was due to the degradation of the NDF fraction, whereas soluble C did not contribute. Amounts of N
mineralized or immobilized by raw wastes and non-soluble fractions at the end of incubation were significantly correlated
(P < 0.01) with their organic C to organic N ratio. The contribution of the Van Soest-soluble fraction to N mineralization varied
greatly between the four wastes. Finally, large differences in the C degradability and N availability of the water and Van
Soest-soluble fractions were demonstrated. 相似文献
19.
The aim of this study was to investigate the effects of increased N deposition on new and old pools of soil organic matter (SOM). We made use of a 4-yr experiment, where spruce and beech growing on an acidic loam and a calcareous sand were exposed to increased N deposition (7 vs. 70 kg N ha−1 yr−1) and to elevated atmospheric CO2. The added CO2 was depleted in 13C, which enabled us to distinguish between old and new C in SOM-pools fractionated into particle sizes. Elevated N deposition for 4 yr increased significantly the contents of total SOM in 0-10 cm depth of the acidic loam (+9%), but not in the calcareous sand. Down to 25 cm soil depth, C storage in the acidic loam was between 100 and 300 g C m−2 larger under high than under low N additions. However, this increase was small as compared with the SOM losses of 600-700 g C g C 0.25 m−1 m−2 from the calcareous sand resulting from the disturbance of soils during setting up of the experiment. The amounts of new, less than 4 yr old SOM in the sand fractions of both soils were greater under high N deposition, showing that C inputs from trees into soils increased. Root biomass in the acidic loam was larger under N additions (+25%). Contents of old, more than 4 yr old C in the clay and silt fractions of both soils were significantly greater under high than under low N deposition. Since clay- and silt-bound SOM consists of humified compounds, this indicates that N additions retarded mineralization of old and humified SOM. The retardation of C mineralization in the clay and silt fraction accounted for 60-80 g C m−2 4 yr−1, which corresponds to about 40% of the old SOM mineralized in these fraction. As a consequence, preservation of old and humified SOM under elevated N deposition might be a process that could lead to an increased soil C storage in the long-term. 相似文献
20.
Claire Serra-Wittling Sabine Houot Enrique Barriuso 《Biology and Fertility of Soils》1995,20(4):226-236
Modifications of soil microbiological activity by the addition of municipal solid-waste compost were studied in laboratory incubations. Three composts were compared, one lumbricompost and two classical composts with different maturation times. Organic C mineralization and nine enzyme activities (dehydrogenase, peroxidase, cellulase, -glucosidase, -galactosidase, N-acetyl--glucosaminidase, protease, amidase, and urease) were determined in the composts and the amended soil. Initial enzyme activities varied in the soil according to the sampling date (winter or summer) and were greater in the composts than in the soil, except for urease. Generally, the youngest compost exhibited greater activity than the oldest one. In the amended soil, the composts did not increase enzyme activity in an additive way. Dehydrogenase, the only strictly endocellular enzyme, was the only one for which the activity in the amended soil increased significantly in proportion to the addition of compost. During the incubations, C mineralization and dehydrogenase activity were significantly correlated, indicating that dehydrogenase was a reliable indicator of global microbial activity. Peroxidase activity in the soil remained constant, but increased in the composts and amended soil. Addition of the oldest compost had no effect on the activity of the C cycle enzymes, but the youngest compost increased creased soil activity at the higher application rate. Enzymes of the N cycle were stimulated by all compost amendments, but the increase was only transient for amidase and urease. Lumbricomposting had no marked effect on compost enzyme activity, either before or during the incubation. 相似文献