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1.
The contents of phospholipids and carbon of the total microbial biomass were determined in the modern chestnut soil and in
the paleosols buried under mounds of the Bronze and Early Iron Ages (5000–1800 years ago) in the dry steppe of the Lower Volga
River basin. Judging from data on the ratio between the contents of phospholipids and organic carbon in the microbial cells,
the carbon content of the living microbial biomass was calculated and compared with the total microbial biomass and total
organic carbon in the studied soils. In the background chestnut soil, the content of phospholipids in the A1, B1, and B2 horizons
amounted to 452, 205, and 189 nmol/g, respectively; in the paleosols, it was 28–130% of the present-day level. The maximum
content was measured in the paleosols buried 5000 and 2000 years ago, in the periods with an increased humidity of the climate.
In the background chestnut soil, the total microbial biomass was estimated at 5680 (the A1 horizon), 3380 (B1), and 4250 (B2)
μg C/g; in the paleosols, it was by 2.5–7.0 times lower. In the upper horizons of the background soil, the portion of the
living microbial biomass in the total biomass was much less than that in the paleosols under the burial mounds; it varied
within 8.5–15.3% and 15–81%, respectively. The portion of living microbial biomass in the total organic carbon content of
the background chestnut soil was about 4–8%. In the paleosols buried in the Early Iron Age (2000 and 1800 years ago), this
value did not exceed 3–8%; in the paleosols of the Bronze Age (5000–4000 years ago), it reached 40% of the total organic carbon. 相似文献
2.
Conservation tillage, and especially no-tillage, induce changes in the distribution of organic pools in the soil profile.
In long-term field experiments, marked stratification of the total soil microbial biomass and its activity have been observed
as consequence of the application of no-tillage to previously tilled soils. Our objective was to study the evolution of the
total and active soil microbial biomass and mineralized C in vitro during the first crop after the introduction of no-tillage
to an agricultural soil. The experiment was performed on a Typic Hapludoll from the Argentinean Pampa. Remaining plant residues,
total and active microbial biomass and mineralized C were determined at 0–5 cm and 5–15 cm depths, at three sampling times:
wheat tilling, silking and maturity. The introduction of no-tillage produced an accumulation of plant residues in the soil
surface layer (0–5 cm), showing stratification with depth at all sampling dates. Active microbial biomass and C mineralization
were higher under no-tillage than under conventional tillage in the top 5 cm of the profile. The total soil microbial biomass
did not differ between treatments. The active soil biomass was highly and positive correlated with plant residues (r
2=0.617;P<0.01) and with mineralized C (r
2=0.732;P<0.01). Consequently, the active microbial biomass and mineralized C reflected immediately the changes in residue management,
whereas the total microbial biomass seemed not to be an early indicator of the introduction of a new form of soil management
in our experiment.
Received: 23 February 1999 相似文献
3.
Spatial changes of soil fungal and bacterial biomass from a sub-alpine coniferous forest to grassland in a humid, sub-tropical region 总被引:7,自引:0,他引:7
Fungal and bacterial biomass were determined across a gradient from a forest to grassland in a sub-alpine region in central
Taiwan. The respiration-inhibition and ergosterol methods for the evaluation of the microbial biomass were compared. Soil
fungal and bacterial biomass both significantly decreased (P<0.05) with the shift of vegetation from forest to grassland. Fungal and bacterial respiration rates (evolved CO2) were, respectively, 89.1 μl CO2 g–1 soil h–1 and 55.1 μl CO2 g–1 soil h–1 in the forest and 36.7 μl CO2 g–1 soil h–1 and 35.7 μl CO2 g–1 soil h–1 in the grassland surface soils (0–10 cm). The fungal ergosterol content in the surface soil decreased from the forest zone
(108 μg g–1) to the grassland zone (15.9 μg g–1). A good correlation (R
2=0.90) was exhibited between the soil fungal ergosterol content and soil fungal CO2 production (respiration) for all sampling sites. For the forest and grassland soil profiles, microbial biomass (respiration
and ergosterol) declined dramatically with depth, ten- to 100-fold from the surface organic horizon to the deepest mineral
horizon. With respect to fungal to bacterial ratios for the surface soil (0–10 cm), the forest zone had a significantly (P<0.05) higher ratio (1.65) than the grassland zone (1.05). However, there was no fungal to bacterial ratio trend from the surface
horizon to the deeper mineral horizons of the soil profiles.
Received: 30 March 2000 相似文献
4.
Giancarlo Renella Amar M. Chaudri Céline M. Falloon Loretta Landi Paolo Nannipieri Philip C. Brookes 《Biology and Fertility of Soils》2007,43(6):751-758
We investigated Cd, Zn, and Cd + Zn toxicity to soil microbial biomass and activity, and indigenous Rhizobium leguminosarum biovar trifolii, in two near neutral pH clay loam soils, under long-term arable and grassland management, in a 6-month laboratory incubation,
with a view to determining the causative metal. Both soils were amended with Cd- or Zn-enriched sewage sludge, to produce
soils with total Cd concentrations at four times (12 mg Cd g−1 soil), and total Zn concentrations (300 mg Zn kg−1 soil) at the EU upper permitted limit. The additive effects of Cd plus Zn at these soil concentrations were also investigated.
There were no significant differences in microbial biomass C (B
C), biomass ninhydrin N (B
N), ATP, or microbial respiration between the different treatments. Microbial metabolic quotient (defined as qCO2 = units of CO2–C evolved unit−1 biomass C unit−1 time) also did not differ significantly between treatments. However, the microbial maintenance energy (in this study defined
as qCO2-to-μ ratio value, where μ is the growth rate) indicated that more energy was required for microbial synthesis in metal-rich sludge-treated soils (especially
Zn) than in control sludge-treated soils. Indigenous R.
leguminosarum bv. trifolii numbers were not significantly different between untreated and sludge-treated grassland soils after 24 weeks regardless of
metal or metal concentrations. However, rhizobial numbers in the arable soils treated with metal-contaminated sludges decreased
significantly (P < 0.05) compared to the untreated control and uncontaminated sludge-treated soils after 24 weeks. The order of decreasing
toxicity to rhizobia in the arable soils was Zn > Cd > Cd + Zn. 相似文献
5.
Arylsulfatase activity of microbial biomass in soils as affected by cropping systems 总被引:5,自引:0,他引:5
The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and
extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial
biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow
(alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation;
microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected
by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular,
and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow,
and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly
correlated with Cmic (r>0.41, P<0.01) and Nmic (r>0.38, P<0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed
per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values >0.79 (P<0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial
biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
Received: 23 April 1998 相似文献
6.
This study examines the effects of atrazine on both microbial biomass C and C mineralization dynamics in two contrasting agricultural
soils (organic C, texture, and atrazine application history) located at Galicia (NW Spain). Atrazine was added to soils, a
Humic Cambisol (H) and a Gleyic Cambisol (G), at a recommended agronomic dose and C mineralization (CO2 evolved), and microbial biomass measurements were made in non-treated and atrazine-treated samples at different time intervals
during a 12-week aerobic incubation. The cumulative curves of CO2–C evolved over time fit the simple first-order kinetic model [Ct = Co (1 − e
−kt
)], whose kinetic parameters were quantified. Differences in these parameters were observed between the two soils studied;
the G soil, with a higher content in organic matter and microbial biomass C and lower atrazine application history, exhibited
higher values of the total C mineralization and the potentially mineralizable labile C pool than those for the H soil. The
addition of atrazine modified the kinetic parameters and increased notably the C mineralized; by the end of the incubation
the cumulative CO2–C values were 33–41% higher than those in the corresponding non-added soils. In contrast, a variable effect or even no effect
was observed on the soil microbial biomass following atrazine addition. The data clearly showed that atrazine application
at normal agricultural rates may have important implications in the C cycling of these two contrasting acid soils. 相似文献
7.
Microwave irradiation was evaluated as a non-toxic alternate to chloroform fumigation for routine measurement of soil microbial
biomass C. Microwave energy was applied to moist soil to disrupt microbial cells. The flush of C released was then measured
after extraction or incubation. Microwave irradiation at 800 J g–1 soil was optimal because this level resulted in an almost instantaneous rise in soil temperature (≥80 °C), an abrupt reduction
in microbial activity, maximal release of biomass C, and minimal solubilization of humic substances. Both incubation-CO2 titration and extraction-colorimetry methods were used on separate 20-g subsamples to compare the labile C in the microwave-treated
and untreated soil samples. The incubation-titration method was also used to measure C in chloroform-fumigated soil samples.
Averaged across soils, the chloroform fumigation yielded 123.3±5.1 mg CO2-C kg–1. Microwave irradiation yielded 93.6±3.9 mg CO2-C kg–1 soil determined by incubation and 52.4±2.4 mg C kg–1 soil determined by extraction, accounting for 76% and 42% of the net flush of C measured by the chloroform fumigation. Microwave-stimulated
net flushes of C were correlated closely (r
2=0.974 for incubation or 0.908 for extraction) with microbial biomass C measured by the chloroform fumigation. Little correlation
was found with the total soil organic C (r
2=0.241 for incubation or for 0.166 extraction). Mean efficiency factors for incubation (K
MI) or extraction (K
ME) were used to calculate microbial biomass C from net flushes of C between microwaved and unmicrowaved soils. Values of K
MI and K
ME were not affected by soil pH, bulk density or clay contents. Extraction of microwaved soil by 0.5M K2SO4 proved to be a simple, fast, precise, reliable, and safe method to measure soil microbial biomass C.
Received: 12 September 1997 相似文献
8.
Christophe Dambreville Catherine Hénault Florian Bizouard Thierry Morvan Rémi Chaussod Jean-Claude Germon 《Biology and Fertility of Soils》2006,42(6):490-500
The long-term (9 years) effect of pig slurry applications vs mineral fertilization on denitrifying activity, N2O production and soil organic carbon (C) (extractable C, microbial biomass C and total organic C) was compared at three soil depths of adjacent plots. The denitrifying activities were measured on undisturbed soil cores and on sieved soil samples with acetylene method to estimate denitrification rates under field or potential conditions. Pig slurry applications had a moderate impact on the C pools. Total organic C was increased by +6.5% and microbial biomass C by ≥25%. The potential denitrifying activity on soil suspension was stimulated (×1.8, P<0.05) 12 days after the last slurry application. This stimulation was still apparent, but not significant, 10 months later and, according to both methods of denitrifying activity measurement (r
2=0.916, P<0.01 on sieved soil; r
2=0.845, P<0.001 on soil cores), was associated with an increase in microbial biomass C above a threshold of about 105 mg kg−1. The effect of pig slurry on denitrification and N2O reduction rates was detected on the surface layer (0–20 cm) only. However, no pig slurry effect could be detected on soil cores at field conditions or after NO3
− enrichments at 20°C. Although the potential denitrifying activity in sieved soil samples was stimulated, the N2O production was lower (P<0.03) in the plot fertilized with pig slurry, indicating a lower N2O/(N2O + N2) ratio of the released gases. The pig-slurry-fertilized plot also showed a higher N2O reduction activity, which is coherent with the lower N2O production in anaerobiosis. 相似文献
9.
G. Sparling L. A. Schipper G. W. Yeates J. Aislabie M. Vojvodic-Vukovic J. Ryburn H. J. Di A. E. Hewitt 《Biology and Fertility of Soils》2008,44(4):633-640
The chemical, physical and biological conditions of a New Zealand Gley Soil was examined on matched sites under long-term
permanent pasture or used to grow blackcurrants (Ribes nigrum) for 2, 8, 10 or 20 years. The chemical and physical conditions of topsoils (0–10 cm) were assessed by soil pH, Olsen P,
total C, total N, mineralisable N, cation exchange, bulk density, porosity and moisture release characteristics. The biological
conditions were assessed from the microbial biomass, soil respiration, catabolic evenness and numbers and diversity of the
soil nematode populations. The ability of the soil populations to degrade the triazine herbicide simazine was tested. The
particle size distribution confirmed all the sites were very well matched, within 2%, in terms of percentage clay, silt and
sand contents, which were 36.5–40.5% clay and 59.5–62.5% silt. Compared with the soil under pasture, that under horticultural
use for 2, 8, 10 and 20 years had lower total C and N, lower mineralisable N, lower cation exchange and lower porosity but
higher bulk density and particle density. The differences were greater the longer the plots had been under blackcurrant production.
Olsen P content was greatest (58 μg P cm−3) under the 20-year blackcurrant plots. Changes in biological characteristics were greater than in physical or chemical characteristics.
Microbial biomass was 1.73 mg C cm−3 under pasture and decreased to 0.87 mg C cm−3 after 20 years of blackcurrants. Total nematode populations deceased from 3.89 million m−2 under pasture to 0.36 million m−2 after 2 years of blackcurrant production and to 108 000 m−2 after 20 years. There were similar proportional decreases in bacterial-feeding, fungal-feeding, plant-feeding and omnivore
nematodes; however, there was comparatively little change in nematode diversity (Shannon–Weiner) or in microbial catabolic
diversity or soil respiration. Despite the decreased microbial biomass, the microbial community under blackcurrant production
had enhanced capacity to degrade simazine, as compared with the pasture soil. That capacity to degrade simazine was similar
in soils that had grown blackcurrants for 2, 8, 10 or 20 years. Yield of blackcurrants had been maintained in the longer-term
sites, despite the marked changes in soil chemical, physical and biological conditions. 相似文献
10.
A study was conducted to investigate the effects of cow manure and sewage sludge application on the activity and kinetics
of soil l-glutaminase. Soil samples were collected from a farm experiment in which 0, 25, and 100 Mg ha−1 of either cow manure or sewage sludge had been applied annually for 4 consecutive years to a clay loam soil (Typic Haplargid).
A chemical fertilizer treatment had also been applied. Results indicated that the effects of chemical fertilizer and the solid
waste application on pH in the 18 surface soil (0–15 cm) samples were not significant. The organic C content, however, was
affected significantly by the different treatments, being the greatest in soils treated with 100 Mg ha−1 cow manure, and the least in the control treatment. l-Glutaminase activity was generally greater in solid-waste applied soils and was significantly correlated (r = 0.939, P < 0.001) with organic C content of soils. The values of l-glutaminase maximum velocity (Vmax) ranged from 331 to 1,389 mg NH4
+–N kg−1 2 h−1. Values of the Michaelis constant (K
m) ranged from 35.1 to 71.7 mM. Organic C content of the soils were significantly correlated with V
max (r = 0.919, P < 0.001) and K
m (r = 0.763, P < 0.001) values. These results demonstrate the considerable influence that solid waste application has on this enzymatic
reaction involved in N mineralization in soil. 相似文献
11.
Soil-released carbon dioxide from microbial biomass carbon in the cultivated soils of karst areas of southwest China 总被引:1,自引:0,他引:1
Soil microbial biomass and the emission of CO2 from the soil surface were measured in yellow soils (Ultisols) of the karst areas of southwest China. The soils are relatively
weathered, leached and impoverished, and have a low input of plant residues. The measurements were made for a 1-year period
and show a reciprocal relationship between microbial biomass and surface CO2 efflux. The highest (42.6±2.8 mg CO2-C m–2 h–1) and lowest (15.6±0.6 mg CO2-C m–2 h–1) CO2 effluxes are found in the summer and winter, respectively. The cumulative CO2 efflux is 0.24 kg CO2-C m–2 year–1. There is also a marked seasonal variation in the amount of soil microbial biomass carbon, but with the highest (644±71 μg
C g–1 soil) and lowest (270±24 μg C g–1 soil) values occurring in the winter and summer, respectively. The cumulative loss of soil microbial biomass carbon in the
top 10 cm of the soil was 608 μg C g–1 year–1 soil over 17 sampling times. The mean residence time of microbial biomass is estimated at 105 days, suggesting that the carbon
in soil microbial biomass may act as a source of the CO2 released from soils.
Received: 13 July 1999 相似文献
12.
Thermal diffusivity of the upper horizons of leached meadow-chernozemic soils varies in dependence on the soil water content
within the following limits: 1.20–4.11 × 10−7 m2/s for the Ap horizon, 1.21–3.85 ×10−7 m2/s for the A1 horizon, and 1.35–3.73 × 10−7 m2/s for the A1B horizon. The relationships between the thermal diffusivity and the soil water content are described by S-shape
curves with a long gently inclined segment within the range of water contents of <0.20 cm3/cm3, a distinct rise in thermal diffusivity within the water contents from 0.20 to 0.30–0.35 cm3/cm3, and a flattened or somewhat declining segment in the area with the high (>0.30–0.35 cm3/cm3) water contents. The thermal diffusivity of air-dried soil samples correlates with the physical clay (<0.01 mm) content.
The Pearson correlation coefficient for these two variables equals −0.67 and is statistically significant at the significance
level of 0.05. Regression equations allowing one to calculate the thermal diffusivity of the investigated soil horizons on
the basis of data on the soil water content have been obtained. 相似文献
13.
Shixue Yin Yuanhua Dong Yangchun Xu Qiwei Huang Qirong Shen 《Biology and Fertility of Soils》2011,47(3):303-313
Rice seedling wilt frequently occurs in upland nurseries under well-aerated conditions and causes considerable economic loss.
Whether the wilt is pathogenic or edaphic is not known. We hypothesize the use of composts to alleviate seedling wilt. The
severity level of upland rice seedling wilt was significantly (p < 0.05) positively correlated with soil pH (r = 0.499; n = 19), but negatively correlated with soil organic matter (r = −0.745), microbial biomass C (r = −0.669), activities of dehydrogenase (r = −0.589), arylsulfatase (r = −0.272), fluorescein diacetate hydrolysis (r = −0.466), and β-glucosidase (r = −0.280). Correlations between severity level and soil inorganic N and exchangeable potassium K were not significant. Contents
of Fe, Zn, Cu, and Mn in healthy seedlings were not significantly (p < 0.05) different from those in infected seedlings. These data suggest that seedling wilts are not associated with nutrient
constraints. Compost amendment at the rate of 3% or above in pot experiments significantly improved seedling growth and reduced
the wilt symptoms. Field trials further showed that aboveground weight of seedlings in compost-amended treatment ranged from
11.5 to 14.9 mg per plant, significantly higher than the range from 6.38 to 12.1 mg per plant in the control treatment; in
addition to rice growth compost significantly increased microbial biomass and enzyme activities of soils. Soil fumigation
significantly increased rice growth and alleviation symptoms in 11 out of 19 soils, suggesting the involvement of pathogens.
It is concluded that upland seedling wilt is a pathogen-associated disease. Probably high soil pH and low soil biochemical
activities may favor pathogen activities. 相似文献
14.
Long-term effects of mineral fertilization on microbial biomass C (MBC), basal respiration (R
B), substrate-induced respiration (R
S), β-glucosidase activity, and the r–K-growth strategy of soil microflora were investigated using a field trial on grassland established in 1969. The experimental
plots were fertilized at three rates of mineral N (0, 80, and 160 kg ha−1 year−1) with 32 kg P ha−1 year−1 and 100 kg K ha−1 year−1. No fertilizer was applied on the control plots (C). The application of a mineral fertilizer led to lower values of the MBC
and R
B, probably as a result of fast mineralization of available substrate after an input of the mineral fertilizer. The application
of mineral N decreased the content of C extracted by 0.5 M K2SO4 (C
ex). A positive correlation was found between pH and the proportion of active microflora (R
S/MBC). The specific growth rate (μ) of soil heterotrophs was higher in the fertilized than in unfertilized soils, suggesting the stimulation of r-strategists, probably as the result of the presence of available P and rhizodepositions. The cessation of fertilization with
320 kg N ha−1 year−1 (NF) in 1989 also stimulated r-strategists compared to C soil, probably as the result of the higher content of available P in the NF soil than in the C
soil. 相似文献
15.
Influence of soil properties on microbial populations, activity and biomass in humid subtropical mountainous ecosystems of India 总被引:1,自引:0,他引:1
Microbial populations, biomass, soil respiration and enzyme activities were determined in slightly acid organic soils of
major mountainous humid subtropical terrestrial ecosystems, along a soil fertility gradient, in order to evaluate the influence
of soil properties on microbial populations, activity and biomass and to understand the dynamics of the microbial biomass
in degraded ecosystems and mature forest. Although the population of fungi was highest in the undisturbed forest (Sacred Grove),
soil respiration was lowest in the 7-year-old regrowth and in natural grassland (approximately 373 μg g–1 h–1). Dehydrogenase and urease activities were high in "jhum" fallow, and among the forest stands they were highest in the 7-year-old
regrowth. Microbial biomass C (MBC) depended mainly on the organic C status of the soil. The MBC values were generally higher
in mature forest than in natural grassland, 1-year-old jhum fallow and the 4-year-old alder plantation. The MBC values obtained
by the chloroform-fumigation-incubation technique (330–1656 μg g–1) did not vary significantly from those obtained by the chloroform-fumigation-extraction technique (408–1684 μg g–1), however, the values correlated positively (P<0.001). The enzyme activities, soil respiration, bacterial and fungal populations and microbial biomass was greatly influenced
by several soil properties, particularly the levels of nutrients. The soil nutrient status, microbial populations, soil respiration
and dehydrogenase activity were greater in Sacred Grove, while urease activity was greater in grassland.
Received: 14 October 1998 相似文献
16.
N. N. Kashirskaya T. E. Khomutova V. V. Dmitriev V. I. Duda N. E. Suzina V. A. Demkin 《Eurasian Soil Science》2010,43(10):1140-1149
The morphology of microbial cells was studied, and the biomass of microorganisms was estimated in the modern steppe soils
and paleosols buried under kurgans in the Lower Volga region with the methods of electron microscopy. The shape and ultrastructure
of the cells in the modern soils and paleosols were similar, though their average volumes differed (0.37 and 0.28 μm3, respectively). The portion of cells with a volume above 1 μm3 in the surface soils and paleosols reached 10.9 and 9.2%, respectively, and the portion of cells with a volume less than
0.01 μm3 in the surface soils was 10% lower than that in the buried paleosols. It was found that the cells of the microorganisms have
an external organomineral layer, which increases the cell volume by 4.9 times, and this fact was taken into account in the
calculation of the microbial biomass. In the chestnut and light chestnut paleosols, the latter comprised 1500 and 230 μg of
C/g soil, respectively. 相似文献
17.
Quantifying microbial biomass phosphorus in acid soils 总被引:10,自引:0,他引:10
J. Wu Z.-L. He W.-X. Wei A. G. O'Donnell J. K. Syers 《Biology and Fertility of Soils》2000,32(6):500-507
This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions
with the Olsen (0.5 M NaHCO3, pH 8.5) and Bray-1 (0.03 M NH4F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9).
The data indicated that the flushes (increases following CHCl3-fumigation) of total P (Pt) and inorganic P (Pi) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the
soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing Pi instead of Pt, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied,
the Pi flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore,
the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4
was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with
soil pH, indicating that it behaved differently from added Pi (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using
added Pi is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the Pi flush and a conversion factor (k
P) of 0.4, more reliable estimates require that k
P values are best determined independently for each soil.
Received: 3 February 2000 相似文献
18.
Haiyan Chu Jianguo Zhu Xiangui Lin Rui Yin Zubin Xie Zhihong Cao Takeshi Fujii 《Biology and Fertility of Soils》2007,43(6):811-814
In this study, we investigated the effects of lanthanum (La), one of the rare earth elements (REEs), on microbial biomass
C as well as the decomposition of 14C-labelled glucose in a fluvo-aquic soil in 28 days. The soil was collected from the field plots under maize/wheat rotation
in Fengqiu Ecological Experimental Station of Chinese Academy of Sciences, Henan Province, China. Application of La decreased
soil microbial biomass C during the experimental period, and there was a negative correlation (P < 0.01) between microbial biomass and application rate of La. La increased microbial biomass 14C after 14C glucose addition, and the increase was significant (P < 0.05) at the rates of more than 160 mg kg−1 soil. La slightly increased 14CO2 evolution at lower rates of application but decreased it at higher rates 1 day after 14C glucose addition, while there was no significant effect from days 2 to 28. For the cumulative 14CO2 evolution during the incubation of 28 days, La slightly increased it at the rates of less than 120 mg kg−1 soil, while significantly decreased (P < 0.05) it at the rate of 200 mg kg−1 soil. The results indicated that agricultural use of REEs such as La in soil could decrease the amount of soil microbial
biomass and change the pattern of microbial utilization on glucose C source in a short period. 相似文献
19.
Organic matter, microbial biomass and enzyme activity of soils under different crop rotations in the tropics 总被引:8,自引:0,他引:8
Soil organic matter level, soil microbial biomass C, ninhydrin-N, C mineralization, and dehydrogenase and alkaline phosphatase
activity were studied in soils under different crop rotations for 6 years. Inclusion of a green manure crop of Sesbania aculeata in the rotation improved soil organic matter status and led to an increase in soil microbial biomass, soil enzyme activity
and soil respiratory activity. Microbial biomass C increased from 192 mg kg–1 soil in a pearl millet-wheat-fallow rotation to 256 mg kg–1 soil in a pearl millet-wheat-green manure rotation. Inclusion of an oilseed crop such as sunflower or mustard led to a decrease
in soil microbial biomass, C mineralization and soil enzyme activity. There was a good correlation between microbial biomass
C, ninhydrin-N and dehydrogenase activity. The alkaline phosphatase activity of the soil under different crop rotations was
little affected. The results indicate the green manuring improved the organic matter status of the soil and soil microbial
activity vital for the nutrient turnover and long-term productivity of the soil.
Received: 7 January 1996 相似文献
20.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献