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1.
Defining the validity of a biochemical index of soil quality 总被引:2,自引:0,他引:2
M. C. Leirós C. Trasar-Cepeda F. García-Fernández F. Gil-Sotres 《Biology and Fertility of Soils》1999,30(1-2):140-146
The native soils of Galicia (NW Spain) exhibit a biochemical equilibrium such that total soil N is a function of five biochemical
and microbiological parameters: microbial biomass C, mineralized N, phosphomonoesterase, β-glucosidase and urease activities.
To investigate whether the ratio of the total N calculated from biochemical soil properties (Nc) and the total N as measured
by the Kjeldahl method (Nk; Nc/Nk) can be used as an index of soil quality, we determined these variables and consequently
the ratio in three kinds of disturbed soils: an artificially Cu-contaminated soil, two lignite mine soils, and a number of
arable soils. In none of the studied soils did the individual biochemical parameters respond consistently to the factors influencing
soil quality, but in all cases soil degradation was reflected by the Nc/Nk value, which differed more or less markedly from
100%. Nc/Nk can therefore be used for the rapid evaluation of soil degradation, since it distinguishes among biochemically
balanced soils, soils in a transient state of high microbiological and biochemical activity and degraded soils. It can also
serve as a reliable basis for the rapid calculation of the "ecological dose" (ED50) of soil pollutants. The use of Nc/Nk as an objective index of the biochemical quality of soils is recommended.
Received: 20 December 1998 相似文献
2.
The composition of soil microbiota in four heated (350 °C, 1 h) soils (one Ortic Podsol over sandstone and three Humic Cambisol
over granite, schist or limestone) inoculated (1.5 μg chlorophyll a g–1 soil or 3.0 μg chlorophyll a g–1 soil) with cyanobacteria (Oscillatoria PCC9014, Nostoc PCC9025, Nostoc PCC9104, Scytonema CCC9801, and a mixture of the four) was studied by cultural methods. The aims of the work were to investigate the potential
value of cyanobacteria as biofertilizers for accelerating soil recolonization after fire as well as promoting microbiotic
crust formation and to determine the microbial composition of such a crust. The inoculated cyanobacteria proliferated by 5
logarithmic units in the heated soils which were colonized very quickly and, after 2 months of incubation, the cyanobacterial
filaments and associated fungal hyphae made up a matrix in which surface soil particles were gathered into crusts of up to
1.0 cm in thickness. These crusts were composed, on average, of 2.5×1010 cyanobacteria, 2.8×106 algae, 6.1×1010 heterotrophic bacteria (of which 1.2×108 were acidophilic, 1.3×106 were Bacillus spp. and 1.5×108 were actinomycetes) and 77.8 m fungal mycelium (1.4×106 were fungal propagules) g–1 crust. Counts of most microbial groups were positively correlated to cyanobacterial numbers. The efficacy of treatment depended
on both the class of inoculum and the type of soil. The best inoculum was the mixture of the four strains and, whatever the
inoculum used, the soil over lime showed the most developed crust followed by the soils over schist, granite and sandstone;
however, the latter was comparatively the most favoured by the amendment. In the medium term there were no significant differences
between the two inocula rates used. Biofertilization increased counts of cyanobacteria by 8 logarithmic units while heterotrophic
bacteria, actinomycetes, algae and fungal propagules rose by >4 logarithmic units, acidophilic bacteria and Bacillus spp. by around 3 logarithmic units and fungal mycelia showed an 80-fold increase. The results showed that inoculation of
burned soils with particle-binding diazotrophic cyanobacteria may be a means of both improving crust formation and restoring
microbial populations.
Received: 8 March 2000 相似文献
3.
V. Acosta-Martínez Z. Reicher M. Bischoff R. F. Turco 《Biology and Fertility of Soils》1999,29(1):55-61
The influence of tree leaf amendment and N fertilization on soil quality in turfgrass environments was evaluated. Our objective
was to assess changes in soil quality after additions of leaf materials and N fertilization by monitoring soil chemical and
physical parameters, microbial biomass and soil enzymes. Established perennial ryegrass (Lolium perenne) plots were amended annually with maple (Acer spp.) leaves at three different rates (0, 2240, and 4480 kg ha–1 year–1) and treated with three nitrogen rates (0, 63, and 126 kg N ha–1 year–1). Tree leaf mulching did not significantly affect water infiltration or bulk density. However, trends in the data suggest
increased infiltration with increasing leaf application rate. Tree leaf mulching increased total soil C and N at 0–1.3 cm
depth but not at 1.3–9.0 cm. Extracted microbial phospholipid, an indicator of microbial biomass size, ranged from 28 to 68
nmol phospholipid g–1 soil at the 1.3–9.0 cm depth. The activity of β-glucosidase estimated on samples from 0–1.3 cm and 1.3–9.0 cm depths, and
dehydrogenase activity estimated on samples from 1.3–9.0 cm were significantly increased by leaf mulching and N fertilizer
application. Changes in microbial community composition, as indicated by phospholipid fatty acid methyl ester analysis, appear
to be due to seasonal variations and did not reflect changes due to N or leaf amendment treatments. There were no negative
effects of tree leaf mulching into turfgrass and early data suggest this practice will improve soil chemical, physical, and
biological structure.
Received: 10 December 1997 相似文献
4.
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
5.
Zhihong Xu Sally Ward Chengrong Chen Tim Blumfield Nina Prasolova Juxiu Liu 《Journal of Soils and Sediments》2008,8(2):99-105
Background, Aims, and Scope An improved understanding of important soil carbon (C) and nutrient pools as well as microbial activities in forest ecosystems
is required for developing effective forest management regimes underpinning forest productivity and sustainability. Forest
types and management practices can have significant impacts on soil C and nutrient pools as well as biological properties
in forest ecosystems. Soil C and nutrient pools were assessed for adjacent natural forest (NF), first rotation (1R) (50-year-old),
and second rotation (2R) (1-year-old) hoop pine (Araucaria cunninghamii Ait. ex D. Don) plantations in southeast Queensland of subtropical Australia.
Materials and Methods Five transects spaced 3 m apart with 9 sampling points along each transect were selected (9.6 m × 12.0 m each site), with
45 soil cores (7.5 cm in diameter) collected and separated into 0–10 and 10–20 cm depths. These soils were analysed for total
C, total nitrogen (N), C (δ13C) and N (δ15N) isotope composition. The 0–10 cm soils were analysed for pH, CEC, exchangeable cations, total P and total K, and assayed
for microbial biomass C and N, respiration, metabolic quotient, potential mineralizable N (PMN), gross N mineralization (M) and immobilization (I).
Results Total C and N in 0–10 cm soils were higher under NF and 1R plantation than under 2R plantation, while they were highest in
10–20 cm soils under NF, followed by the 1R and then 2R plantation. δ13C was lower under NF than under the plantations, while δ15N was higher under NF than under the plantations. Total P was the highest under NF, followed by the 1R and then 2R plantation,
while total K was higher under the 2R plantation. No significant differences were detected for pH, CEC, exchangeable cations,
microbial C and N, respiration and metabolic quotient among the 3 sites. PMN and M were higher under NF, while I was the highest under the 2R plantation, followed by the NF and then 1R plantation.
Discussion Soil total C and N in 0–10 cm depth were significantly lower under 2R hoop pine plantation than those under NF and 1R hoop
pine plantation. There were significant reductions in soil total C and N from NF to 1R and from 1R to 2R hoop pine plantations
in 10–20 cm depth. This highlights potential N deficiency in the 2R hoop pine plantations, and application of N fertilizers
may be required to improve the productivity of 2R hoop pine plantations.
There were no significant differences in other soil chemical and physical properties in 0–10 cm depth among the 3 sites under
NF, 1R and 2R hoop pine plantations, except for soil total P and K.
Soil microbial biomass C, CO2 respiration and metabolic quotient did not differ among the 3 sites assessed, perhaps mainly due to these biological variables
being too sensitive to variations in soil chemical and physical properties and thereby being associated with a larger variability
in the soil biological properties. However, soil potential mineralizable N, gross N mineralization and immobilization were
rather sensitive to the conversion of NF to hoop pine plantation and forest management practices.
Conclusions Total C and N in the top 20 cm soil were highest under NF, followed by 1R and then 2R hoop pine plantations, indicating that
N deficiency may become a growth-limiting factor in the 2R hoop pine plantations and subsequent rotations of hoop pine plantation.
The sample size for soil δ13C seems to be much smaller than those for soil total C and N as well as δ15N. The significant reductions in soil total P from NF to 1R and then from 1R to 2R hoop pine plantations highlight that P
deficiency might become another growth-limiting factor in the second and subsequent rotations of hoop pine plantations. Soil
microbial properties may be associated with large spatial variations due to these biological properties being too sensitive
to the variations in soil chemical and physical properties in these forest ecosystems.
Recommendations and Perspectives Soil potential mineralizable N, gross N mineralization and immobilization were useful indices of soil N availability in response
to forest types and management practices. The sampling size for soil δ13C was much smaller than the other soil chemical and biological properties due to the different patterns of spatial variation
in these soil properties. 相似文献
6.
Effects of increasing periods under intensive arable vegetable production on biological, chemical and physical indices of soil quality 总被引:6,自引:0,他引:6
The effects on soil condition of increasing periods under intensive cultivation for vegetable production on a Typic Haplohumult
were compared with those of pastoral management using soil biological, physical and chemical indices of soil quality. The
majority of the soils studied had reasonably high pH, exchangeable cation and extractable P levels reflecting the high fertilizer
rates applied to dairy pasture and more particularly vegetable-producing soils. Soil organic C (Corg) content under long-term pasture (>60 years) was in the range of 55 g C kg–1 to 65 g C kg–1. With increasing periods under vegetable production soil organic matter declined until a new equilibrium level was attained
at about 15–20 g C kg–1 after 60–80 years. The loss of soil organic matter resulted in a linear decline in microbial biomass C (Cmic) and basal respiratory rate. The microbial quotient (Cmic/Corg) decreased from 2.3% to 1.1% as soil organic matter content declined from 65 g C kg–1 to 15 g C kg–1 but the microbial metabolic quotient (basal respiration/Cmic ratio) remained unaffected. With decreasing soil organic matter content, the decline in arginine ammonification rate, fluorescein
diacetate hydrolytic activity, earthworm numbers, soil aggregate stability and total clod porosity was curvilinear and little
affected until soil organic C content fell below about 45 g C kg–1. Soils with an organic C content above 45 g C kg–1 had been under pasture for at least 30 years. At the same Corg content, soil biological activity and soil physical conditions were markedly improved when soils were under grass rather
than vegetables. It was concluded that for soils under continuous vegetable production, practices that add organic residues
to the soil should be promoted and that extending routine soil testing procedures to include key physical and biological properties
will be an important future step in promoting sustainable management practices in the area.
Received: 18 November 1997 相似文献
7.
Microbiological and biochemical investigations of chestnut soils and solonetzes were conducted in the dry steppe of the southern
Privolzhskaya and northern Ergeni uplands. The living biomass of the microbial communities in the soils was estimated based
on the content of phospholipids in the soils. Significant correlations were revealed between the contents of phospholipids
and the main soil properties (the contents of humus, r = 0.66, P = 0.999; clay, r = −0.41, P = 0.95; physical clay, r = −0.57, P = 0.99; and pH, r = −0.59, P = 0.99). The content of phospholipids varied from 69 to 192 nmol/g of soil in the A1 horizons; with depth it decreased down
to 36–135 in the B1 horizon and to 26–79 nmol/g of soil in the B2 horizon. The microbial biomass in the solonetzes was lower
by 5 to 38% than that in the chestnut soils. A trend of the decreasing of the microbial biomass in the soils from the north
to the south was revealed. Based on the content of phospholipids, the number of living microbial cells was assessed; the weighed
averages of their number varied from 0.7–3.2 × 1010 to 7.5–13.6 × 1010. 相似文献
8.
Recent studies have suggested that the organic matter contents of undisturbed soils (under natural vegetation) are in equilibrium with biological and biochemical properties. Accordingly, we hypothesised that such equilibria should be disrupted when soils are subjected to disturbance or stress, and that measurement of this disruption can be expressed mathematically and used as a soil quality index. In this study, we evaluated these hypotheses in soils from the H.J. Andrews Experimental Forest in Oregon. Both O and A horizons were sampled from nine sites in Spring 2005 and Fall 2006. Soil samples were analyzed for enzyme activities (phosphatase, β-glucosidase, laccase, N-acetyl-glucosaminidase, protease and urease), and other biological and chemical properties including N-mineralization, respiration, microbial biomass C (MBC), soil organic carbon (SOC) and total nitrogen content. In addition, soil samples from one old-growth site were manipulated in the laboratory to either simulate chemical stresses (Cu addition or pH alteration) or physical disturbances (wet-dry or freeze-thaw cycles). The results showed variation in biological and biochemical soil properties that were closely correlated with SOC. Multiple regression analysis of SOC levels against all soil properties showed that a model containing only MBC and phosphatase activity could account for 97% of the SOC variation among the sites. The model fit was independent of spatial and temporal variations because covariates such as site, stand age, sampling date, and soil horizon were found to be not statistically significant. Although the application of stress/disturbance treatments inconsistently affected most of the individual biochemical properties, in contrast, the ratio of soil C predicted by the model (Cp), and soil C measured (Cm) was consistently reduced in soils submitted to at least one level of stress and disturbance treatments. In addition, Cp/Cm was more affected in soils submitted to wet-dry cycles and Cu contamination than to freeze-thaw cycles or shifts in soil pH. Our results confirm previous evidence of a biochemical balance in high quality undisturbed soils, and that this balance is disrupted when the soil is submitted to disturbances or placed under stress conditions. The Cp/Cm ratio provides a simple reference value against which the degrading effects of pollutants or management practices on soil quality can be assessed. 相似文献
9.
S. Luna-Suárez J. T. Frias-Hernández V. Olalde-Portugal L. Dendooven 《Biology and Fertility of Soils》2000,32(2):109-113
In the central highlands of Mexico, heavily eroded soils are often colonized by catclaw (Mimosa buincifiera): an N2-fixing shrub. An experiment was carried out to investigate how this shrub affected characteristics of the soil and its biological
functioning. Soil was sampled from outside and under the canopy of catclaw at three sites characterized by different degrees
of erosion and an increase in plant density. The soil microbial biomass C, total amounts of bacteria, fungi, actinomycetes
and free-living N2-fixing micro-organisms were measured, while production of CO2 and dynamics of nitrate (NO3
–), nitrite (NO2
–) and ammonium (NH4
+) were monitored in an aerobic incubation at 22±1 °C for 35 days. The C content was 1.6 times greater in the area with the
largest density of plants and the least erosion (RECUP) compared with the site with the lowest density and greatest erosion
(DEGR), while it was 1.2 times greater under the canopy of the catclaw than outside it (average of the three sites). The incorporation
of N into the soil organic matter was greater under the canopy of the catclaw than outside it as the C:N ratio was on average
8.4 and 9. 1, respectively. The microbial biomass C, as a percentage of soil organic matter, was 1.5 times greater in the
RECUP than in the DEGR site. Greatest total number of colony-forming bacteria and fungi (mean of organisms found under and
outside the canopy) were found in the RECUP treatment and lowest in the DEGR treatment. Free-living N2-fixing organisms and actinomycetes showed opposite trends. Greater total numbers of colony-forming bacteria, fungi, actinomycetes
and free-living N2-fixing organisms (mean of the three treatments) were found under the canopy of catclaw than outside of it, Production of
CO2 was 1.8 times greater in the RECUP than in the DEGR and 1.6 times greater under the canopy of catclaw than outside. Production
of NO3
– was 1.3 times greater in the RECUP than in the DEGR and 3.5 times greater under the canopy of catclaw than outside. There
was no significant effect of location or canopy on NO2
– and NH4
+ concentrations. It is concluded that the natural vegetation of catclaw increased microbial biomass and soil organic matter
content under, but also outside its canopy, and preserved N better, releasing greater amounts of inorganic N upon mineralization.
Catclaw can serve as a first colonizer of heavily eroded soil and be replaced by other vegetation, natural or crops, when
fertility is restored.
Received: 4 November 1999 相似文献
10.
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
11.
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
12.
Soil respiration, nitrogen mineralization and uptake in barley following cultivation of grazed grasslands 总被引:3,自引:0,他引:3
Soil tillage was studied as a strategy to synchronize N mineralization with plant demand following ploughing of two types
of grazed pastures [ryegrass/white clover (Lolium perenne/Trifolium repens) and pure ryegrass]. The swards were either rotovated and ploughed or ploughed only. Soil respiration, as determined by a
dynamic chamber method, was related to net N mineralization and to plant N uptake in a subsequent spring barley crop (Hordeum vulgare). Diurnal variations in temperature were important for the CO2 flux and care must be taken that temperatures during measuring periods are representative of the daily mean. Soil tillage
increased the CO2 flux considerably compared with untilled soil with total emissions of 2.6 and 1.4 t C ha–1, respectively, from start of April to end of June. Sward type or rotovation did not markedly influence accumulated emissions.
Rotovation significantly increased the content of nitrate in the soil until 43 days after rotovation, showing that net N mineralization
occurred rapidly during this period, in spite of low soil temperatures (5–10 °C). Rotovation increased barley grain yield
by 10–12% and N-uptake by 14%. For both sward types, rotovation caused an extra N-uptake in harvested plant material of about
12 kg ha–1. The availability of soil inorganic N at the early stages of barley was important for the final yield and N-uptake. The results
indicated that soil biological activity was not enhanced by rotovation and that the yield effect of rotovation was mainly
caused by quicker availability and better synchrony between N mineralization and plant uptake due to earlier start of decomposition.
Received: 3 May 2000 相似文献
13.
Michele Freppaz Berwyn L. Williams Anthony C. Edwards Riccardo Scalenghe Ermanno Zanini 《Biology and Fertility of Soils》2007,43(5):519-529
Surface mineral horizons from four ecosystems sampled in the northwestern Italian Alps were incubated at −3 and +3°C to simulate
subnivial and early thaw period temperatures for a seasonally snow-covered area. The soil profiles at these sites represent
extreme examples of management, grazed meadow (site M) and extensive grazing beneath larch (site L) or naturally disturbed
by avalanche and colonized by alder (site A) and the expected forest climax vegetation beneath fir (site F). Changes in labile
pools of nitrogen (N) and phosphorus (P) were active at all sites at both temperatures during 14 days of laboratory incubation.
Ammonium was the dominant inorganic form of total dissolved N (TDN), being equivalent to 1.8–9.8 g N m−2 within the mineral horizon. Gross rates of ammonification were similar at the two temperatures but significantly (p<0.05) greater in soil from beneath fir than in the other three. Nitrification occurred in all soils and displayed a wide
range in rates, from 2 to 85 mg N m−2 day−1, and was least in the two most acid soils, A and F. Immobilization of NH4
+ as microbial N was greater in the fir soil than in the other three. Also, the fir soil showed greatest gross ammonification
and least accumulation of NO3
− and greatest tendency to retain N. This high N retention capacity in the climax ecosystem contrasted with the managed systems
characterized by higher nitrification rates and greater potential spring NO3
− loss. Dissolved organic N ranged between 30 and 50% of the TDN, while dissolved organic P was greater than 70% of total dissolved
P (TDP). The dissolved organic compounds were important components of the labile pool, in equilibrium with a large reserve
of organic N, and may significantly contribute to the soil N availability at low temperatures. 相似文献
14.
A. A. Larionova I. N. Kurganova V. O. Lopes de Gerenyu B. N. Zolotareva I. V. Yevdokimov V. N. Kudeyarov 《Eurasian Soil Science》2010,43(2):168-176
The effect of droughts and drying-wetting cycles on the respiration activity of agrogray soils was studied in field and laboratory
experiments. The alternation of drought periods and rains during the vegetation season did not increase the annual emission
of CO2 from the soils under a sown meadow and an agrocenosis. In laboratory experiments, the wetting of dried soil released 1–1.5%
of Corg with a high decomposition constant n × 10−1 day−1 and a very short renewal time (2.1–2.4 days); therefore, an abrupt change in the wetting conditions did not intensify the
loss of soil carbon under field conditions. 相似文献
15.
Transformations and recovery of residue and fertilizer nitrogen-15 in a sandy Lixisol of West Africa
The fate of 15N-labeled plant residues from different cover-cropping systems and labeled inorganic N fertilizer in the organic, soil mineral,
microbial biomass and soil organic matter (SOM) particle-size fractions was investigated in a sandy Lixisol. Plant residues
were from mucuna (legume), lablab (legume), imperata (grass), maize (cereal) and mixtures of mucuna or lablab with imperata
or maize, applied as a surface mulch. Inorganic N fertilizer was applied as 15N-(NH4)2SO4 at two rates (21 and 42 mg N kg–1 soil). Total N release from mucuna or lablab residues was 2–3 times higher than from the other residues, whereas imperata
immobilized N throughout the study period. In contrast, 15N was mineralized from all the plant residues irrespective of the mineralization–immobilization pattern observed for total
N. After 168 days, 69% of soil mineral N in mucuna- or lablab-mulched soils was derived from the added residues, representing
4–8% of residue N, whereas 9–30% of inorganic N was derived from imperata, maize and the mixed residues. At the end of the
study, 4–19% of microbial biomass N was derived from the added residue/fertilizer-N, accounting for 1–3% of added residue-N.
Averaged across treatments, particulate SOM fractions accounted for less than 1% of the total soil by weight but contained
20% of total soil C and 8% of soil N. Soils amended with mucuna or lablab incorporated more N in the 250–2000 μm SOM pool,
whereas soil amended with imperata or the mixed residues incorporated similar proportions of labeled N in the 250–2000 μm
and 53–250 μm fractions. In contrast, in soils receiving the maize or inorganic fertilizer-N treatments, higher proportions
of labeled N were incorporated into the 53–250 μm than the 250–2000 μm fractions. The relationship between these differences
in residue/fertilizer-N partitioning into different SOM particle-size fractions and soil productivity is discussed.
Received: 12 March 1999 相似文献
16.
Tillage systems influence soil properties and may influence the availability of applied and mineralized soil N. This laboratory study (20°C) compared N cycling in two soils, a Wooster (fine, loamy Typic Fragiudalf) and a Hoytville (fine, illitic Mollic Epiaqualf) under continuous corn (Zea mays) production since at least 1963 with no-tillage (NT), minimum (CT) and plow tillage (PT) management. Fertilizer was added at the rate of 100 mg 15N kg–1–1 soil as 99.9% 15N as NH4Cl or Ca(NO3)2 and the soils were incubated in leaching columns for 1 week at 34 kPa before being leached periodically with 0.05 M CaCl2 for 26 weeks. As expected, the majority of the 15NO3– additions were removed from both soils with the first leaching. The majority of applied 15NH4+ additions were recovered as 15NO3– by week 5, with the NT soils demonstrating faster nitrification rates compared with soils under other tillage practices. For the remaining 22 weeks, only low levels of 15NO3– were leached from the soils regardless of tillage management. In the coarser textured Wooster soils (150 g clay kg–1), mineralization of native soil N in the fertilized soils was related to the total N content (r2 0.99) and amino acid N (r2 0.99), but N mineralization in the finer textured Hoytville (400 g clay kg–1) was constant across tillage treatments and not significantly related to soil total N or amino acid N content. The release of native soil N was enhanced by NH4+ or NO3– addition compared to the values released by the unfertilized control and exceeded possible pool substitution. The results question the use of incubation N mineralization tests conducted with unfertilized soils as a means for predicting soil N availability for crop N needs. 相似文献
17.
Svetlana Bykova Pascal Boeckx Irina Kravchenko Valery Galchenko Oswald Van Cleemput 《Biology and Fertility of Soils》2007,43(3):341-348
Methane oxidising activity and community structure of 11, specifically targeted, methanotrophic species have been examined
in an arable soil. Soils were sampled from three different field plots, receiving no fertilisation (C), compost (G) and mineral
fertiliser (M), respectively. Incubation experiments were carried out with and without pre-incubation at elevated CH4 mixing ratios (100 ml CH4 l−1) and with and without ammonium (100 mg N kg−1) pre-incubation. Four months after fertilisation, plots C, G and M did not show significant differences in physicochemical
properties and CH4 oxidising activity. The total number of methanotrophs (determined as the sum the 11 specifically targeted methanotrophs)
in the fresh soils was 17.0×106, 13.7×106 and 15.5×106 cells g−1 for treatment C, G and M, respectively. This corresponded to 0.11 to 0.32% of the total bacterial number. The CH4 oxidising activity increased 105-fold (20–26 mg CH4 g−1 h−1), the total number of methanotrophs doubled (28–76×106 cells g−1) and the methanotrophic diversity markedly increased in treatments with a pre-incubation at elevated CH4 concentrations. In all soils and treatments, type II methanotrophs (62–91%) outnumbered type I methanotrophs (9–38%). Methylocystis and Methylosinus species were always most abundant. After pre-incubation with ammonium, CH4 oxidation was completely inhibited; however, no change in the methanotrophic community structure could be detected. 相似文献
18.
The efficacy of three abundant organic wastes: poultry manure (PM), cattle slurry (CS) and sewage sludge (SS) for the reclamation
of burnt soils was evaluated. A forest soil, previously furnace-heated in order to simulate exposure to a high-intensity wildfire,
was labelled with nitrogen-15 (15N) to evaluate the contribution of N derived from the organic waste to the burnt soil and vegetation. Four treatments were
performed with the heated 15N-labelled soil: an unamended control soil (S) and three waste amended soils (S+PM, S+CS and S+SS) at a dose waste of 167mg
total N kg–1 soil. Lolium perenne was grown in all the pots for 3 months. In each treatment the phytomass produced and its N content decreased significantly
in the following order of treatments: S+PM S+CS > S+SS S. The percentage of plant N derived from the waste was similar in the S+PM (22.8%) and S+CS (24.0%) treatments, but significantly
lower in the S+SS treatment (16.5%). At the end of the 3 month experimental period, the available N reserves (phytomass N+soil
inorganic N) in the control soil accounted for 51.5–71.5% of those in the S+PM, S+CS and S+SS treatments, whereas the yield
of the plants was only 13.4–29.8% of that in the manured soils. These results demonstrated the importance of the addition
of organic wastes, particularly PM, for the recovery of the vegetation cover and for the stabilization of the soil ash layer.
They also showed that the level of N was not the main controlling factor of plant growth in the control soil, which, moreover,
did not show evidence of a shortage of macronutrients, i.e. phosphorus, potassium, calcium or magnesium. It is hypothesized
that, as occurs in heat-sterilized soils, phytomass production in the control-heated soil could have been inhibited by the
heat-induced production of phytotoxic compounds, their negative effects being microbially or chemically suppressed by the
addition of organic wastes.
Received: 3 March 1997 相似文献
19.
Improving the precision in estimating the nitrogen (N) requirement for citrus trees on sandy soils is important for increasing
N efficiency by the trees and minimizing potential losses of N in commercial citrus production areas. In this study, representative
Florida soils were sampled from major citrus production areas and the electro-ultrafiltration (EUF) technique was used to
measure the concentrations of total EUF-extractable nitrogen (EUF-Nt), ammonium-N (EUF-NH4
+–N) and nitrate-N (EUF-NO3
––N). Available organic N (Norg) was calculated as: EUF-Nt–(NH4
+–N+NO3
––N). The N concentrations in the EUF extraction were greater than those by the KCl or CaCl2 method. The Norg fraction, estimated by the EUF method, varied from 4.4 to 40.8 mg kg–1 soil, equivalent to 10 to 91 kg N ha–1 (for the top 15 cm depth soil) and was positively correlated with the total soil N determined by the Kjeldahl method. The
presence of appreciable amounts of Norg in these soils indicates that these soils contain high proportions of the total soil N in easily mineralizable Norg forms. This study demonstrates that the EUF-extractable organic bound N must be considered in developing N fertilizer recommendations
for citrus.
Received: 13 January 1999 相似文献
20.
Several studies have focused on the formation and losses of dissolved organic matter in forest systems, whereas a limited number have dealt with this aspect in agricultural soils. The purpose of this study was to estimate the leaching of dissolved organic carbon (DOC) and nitrogen (DON), with focus on the period after cultivating grass-clover swards. Grass-clovers were ploughed in the spring prior to sowing cereals followed by either catch crops or bare soil. The concentrations of DOC and DON decreased with soil depth and ranged at 90-cm soil depth between 7 and 21 mg C L−1 and between 1 and 3 mg N L−1, respectively, in a sandy loam soil, and between 16 and 63 mg C L−1 and between 1 and 10 mg N L−1, respectively, in a coarse sandy soil. The resulting DOC/DON ratios were in the range between 2 and 42, with higher values in the coarse sandy soil than in the sandy loam soil. The total percolation was 218 mm in the sandy loam soil and 596–645 mm in the coarse sandy soil, which resulted in an annual leaching of 22–40 kg DOC ha−1 year−1 and 3–4 kg DON ha−1 year−1 in the sandy loam soil, and 174–310 kg DOC ha−1 year−1 and 10–31 kg DON ha−1 year−1 in the coarse sandy soil. It was shown that higher amounts of DOC were lost by leaching under the catch crops than from bare soil, that losses of DON were higher from bare soil than from soils with catch crops and that DON contributed significantly to the total N loss. Thus, DON needs to be taken into account in N-balance calculations. 相似文献