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1.
The effect of crop residue incorporation date on soil inorganic nitrogen, nitrate leaching and nitrogen mineralization 总被引:7,自引:0,他引:7
R. D. J. Mitchell R. Harrison K. J. Russell J. Webb 《Biology and Fertility of Soils》2000,32(4):294-301
Delaying cultivation and incorporation of arable crop residues may delay the release of NO3
– and hence reduce leaching. The objective of this study was to investigate the effect of timing of cultivation on the mineralization
and leaching of NO3
– from an arable crop residue. Overwinter N leaching and periodic measurements of soil inorganic N were combined to estimate
net N mineralized after ploughing a crop residue into a free-draining loamy sand soil in central England on six dates from
June 1994 to January 1995. The crop residue was whole green barley with approximately 2% N. N leaching in the two following
winters was increased by the addition of crop residues. Early residue application also tended to increase N leached in the
first winter, largely as a consequence of relatively large losses early in the drainage period. Thus, early incorporation
of crop residues presents a greater leaching risk. The amount of N leached in the second (drier) winter was similar for all
dates of incorporation. At the end of the first winter, inorganic N derived from the crop residue was greatest for earlier
additions: June (40% N applied) > September (30% N applied) > August (20% N applied) > October (19% N applied) > November
(11% N applied) > January (3% N applied). However, at the end of the experiment, there was no evidence that the residues which
had mineralized least by the end of the first winter had, to any significant degree, caught up, and this was confirmed by
the parameters of the equation for first-order decomposition in thermal time. These results indicate that the effect of temperature,
particularly in the early stages of residue mineralization, is complex and interacts with other soil processes in terms of
the fate of the N mineralized.
Received: 19 July 1999 相似文献
2.
S. J. González-Prieto A. Cabaneiro M. C. Villar T. Carballas M. Carballas 《Biology and Fertility of Soils》1996,22(3):252-260
N mineralization capacity and its main controlling factors were studied in a large variety (n=112) of native (forest, bush) and agricultural (pasture, cultivated) soils from several climatic zones in Spain. The available inorganic N content, net N mineralization, and net N mineralization rate were determined after 6 weeks of aerobic incubation. NH
inf4
sup+
–N largely predominated over NO
inf3
sup-
-N (ratio near 10:1) except in some agricultural soils. Net N mineralization predominated (83% of soils) over net N immobilization, which was more frequent in agricultural soils (25%) than in native soils (9%). In forest soils, both net N mineralization and the net N mineralization rate were significantly higher than in the other soil groups. The net N mineralization rate of pasture and cultivated soils was similar to that of bush soils, but available inorganic N was lower. The net N mineralization rate decreased in the order: soils over acid rocks>soils over sediments>soils over basic rocks or limestone; moreover, the highest net N mineralization and available inorganic N were found in soils over acid rocks. The highest N mineralization was found in soils with low C and N contents, particularly in the native soils, in which N mineralization increased as the C:N ratio increased. N mineralization was higher in soils with a low pH and base saturation than in soils with high pH and base saturation values, which sometimes favoured N immobilization. Soils with an Al gel content of >1% showed lower net N mineralization rates than soils with Al gel contents of <1%, although net N mineralization and available inorganic N did not differ between these groups. The net N mineralization rate in silty soils was significantly lower than in sandy and clayey soils, although soil texture only explained a low proportion of the differences in N mineralization between soils. 相似文献
3.
A study was conducted to determine mineralization rates in the field and in different soil layers under three grassland managements
(viz. a reseeded sward, a permanent sward with a conventional N management, and a long-term grass sward with 0 N (0-N) input).
Potential mineralization rates of soil particles (sand, silt and clay) and macro-organic matter fractions of different sizes
(i.e. 0.2–0.5, 0.5–2.0 and >2 mm) were also determined in the laboratory. In the reseeded plots, net mineralization was unchanged
down to 40 cm depth. In the undisturbed conventional-N swards, mineralization rates were substantially higher in the top layer
(0–10 cm) than in the deeper layers. In plots which had received no fertilizer N, mineralization was consistently low in all
the layers. There was more macro-organic matter (MOM) in the 0-N plots (equivalent to 23 g kg–1 soil for 0–40 cm) than in the two fertilized plots (i.e. conventional-N and reseeded) which contained similar amounts (ca. 15 g kg–1 soil). C and N contents of separated soil particles did not differ amongst the treatments, but there were large differences
with depth. Potential mineralization in the bulk soil was greatest in the 0–10 cm layers and gradually decreased with depth
in all the treatments. Separated sand particles had negligible rates of potential mineralization and the clay component had
the highest rates in the subsurface layers (10–40 cm). MOMs had high potential rate of mineralization in the surface layer
and decreased with soil depth, but there was no clear pattern in the differences between different size fractions.
Received: 17 November 1997 相似文献
4.
P. M. Groffman 《Biology and Fertility of Soils》1999,29(4):430-433
The effects of acetate additions to northern hardwood forest soils on microbial biomass carbon (C) and nitrogen (N) content,
soil inorganic N levels, respirable C and potential net N mineralization and nitrification were evaluated. The experiment
was relevant to a potential watershed-scale calcium (Ca) addition that aims to replace Ca depleted by long-term exposure to
acid rain. One option for this addition is to use calcium-magnesium (Mg) acetate, a compound that is inexpensive and much
more readily soluble than the Ca carbonate that is generally used for large-scale liming. Field plots were treated with sodium
(NA) acetate, Na bicarbonate or water (control) and were sampled (forest floor – Oe and Oa combined) 2, 10 and 58 days following
application. It was expected that the addition of C would lead to an increase in biomass C and N and a decrease in inorganic
N. Instead, we observed no effect on biomass C, a decline in biomass N and an increase in N availability. One possible explanation
for our surprising results is that the C addition stimulated microbial activity but not growth. A second, and more likely,
explanation for our results is that the C addition did stimulate microbial growth and activity, but there was no increase
in microbial biomass due to predation of the new biomass by soil fauna. The results confirm the emerging realization that
the effects of increases in the flow of C to soils, either by deliberate addition or from changes in atmospheric CO2, are more complex than would be expected from a simple C : N ratio analysis. Evaluations of large-scale manipulations of
forest soils to ameliorate effects of atmospheric deposition or to dispose of wastes should consider microbial and faunal
dynamics in considerable detail.
Received: 13 March 1998 相似文献
5.
Influence of soil phosphorus status and nitrogen addition on carbon mineralization from 14C-labelled glucose in pasture soils 总被引:2,自引:0,他引:2
This study examines the effect of soil P status and N addition on the decomposition of 14C-labelled glucose to assess the consequences of reduced fertilizer inputs on the functioning of pastoral systems. A contrast
in soil P fertility was obtained by selecting two hill pasture soils with different fertilizer history. At the two selected
sites, representing low (LF) and high (HF) fertility status, total P concentrations were 640 and 820 mg kg–1 and annual pasture production was 4,868 and 14,120 kg DM ha–1 respectively. Soils were amended with 14C-labelled glucose (2,076 mg C kg–1 soil), with and without the addition of N (207 mg kg–1 soil), and incubated for 168 days. During incubation, the amounts of 14CO2 respired, microbial biomass C and 14C, microbial biomass P, extractable inorganic P (Pi) and net N mineralization were determined periodically. Carbon turnover was greatly influenced by nutrient P availability.
The amount of glucose-derived 14CO2 production was high (72%) in the HF and low (67%) in the LF soil, as were microbial biomass C and P concentrations. The 14C that remained in the microbial biomass at the end of the 6-month incubation was higher in the LF soil (15%) than in the
HF soil (11%). Fluctuations in Pi in the LF soil during incubation were small compared with those in HF soil, suggesting that P was cycling through microbial
biomass. The concentrations of Pi were significantly greater in the HF samples throughout the incubation than in the LF samples. Net N mineralization and nitrification
rates were also low in the LF soils, indicating a slow turnover of microorganisms under limited nutrient supply. Addition
of N had little effect on biomass 14C and glucose utilization. This suggests that, at limiting P fertility, C turnover is retarded because microbial biomass becomes
less efficient in the utilization of substrates.
Received: 18 October 1999 相似文献
6.
Long-term winter cover cropping effects on corn (Zea mays L.) production and soil nitrogen availability 总被引:1,自引:0,他引:1
This study was conducted to determine effects of long-term winter cover cropping with hairy vetch, cereal rye and annual
ryegrass on soil N availability and corn productivity. From 1987 to 1995, with the exception of the first year of the study,
the cover crops were seeded each year in late September or early October after the corn harvest and incorporated into the
soil in late April or early May. Corn was seeded 10 days to 2 weeks after the cover crop residues had been incorporated, and
N fertilizer was applied as a side-dressing at rates of 0, 67, 134, or 201 kg N ha–1 each year. While the average annual total N input from the above-ground biomass of the cover crops was highest for hairy
vetch (72.4 kg N ha–1), the average annual total C input was highest for cereal rye (1043 kg C ha–1) compared with the other cover crops. Hairy vetch was the only cover crop that significantly increased pre-side-dressed NO3
–-N (Ni) corn biomass and N uptake at 0 N. At an N fertilizer rate of 134 kg N ha–1 or higher, the cover crops had a minimal effect on corn biomass. This indicated that even after 9 years of winter cover cropping,
the effect of the cover crops on corn growth resulted primarily from their influence on soil N availability. The amount of
available N estimated from the cover crops (Nac) was significantly correlated with relative corn biomass production (r
2=0.707, P<0.001). The total amount of available N, comprising Nac and N added from fertilizer (Nf), was strongly correlated (r
2=0.820, P<0.001)) with relative corn biomass production. The correlation was also high for the available N comprising Ni and Nf (r
2=0.775, P<0.001). Although cereal rye and annual ryegrass did not improve corn biomass production in the short term, they benefited
soil organic N accumulation and gradually improved corn biomass production compared with the control over the long term.
Received: 10 August 1999 相似文献
7.
Effect of cropping systems on nitrogen mineralization in soils 总被引:3,自引:0,他引:3
Understanding the effect of cropping systems on N mineralization in soils is crucial for a better assessment of N fertilizer
requirements of crops in order to minimize nitrate contamination of surface and groundwater resources. The effects of crop
rotations and N fertilization on N mineralization were studied in soils from two long-term field experiments at the Northeast
Research Center and the Clarion-Webster Research Center in Iowa that were initiated in 1979 and 1954, respectively. Surface
soil samples were taken in 1996 from plots of corn (Zea mays L.), soybean (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) that had received 0 or 180 kg N ha–1 before corn and an annual application of 20 kg P and 56 kg K ha–1. N mineralization was studied in leaching columns under aerobic conditions at 30 °C for 24 weeks. The results showed that
N mineralization was affected by cover crop at the time of sampling. Continuous soybean decreased, whereas inclusion of meadow
increased, the amount of cumulative N mineralized. The mineralizable N pool (N
o) varied considerably among the soil samples studied, ranging from 137 mg N kg–1 soil under continuous soybean to >500 mg N kg–1 soil under meadow-based rotations, sampled in meadow. The results suggest that the N
o and/or organic N in soils under meadow-based cropping systems contained a higher proportion of active N fractions.
Received: 10 February 1999 相似文献
8.
Soil texture is an important influence on nutrient cycling in upland soils, with documented relationships between mineral particle size distribution and organic matter retention, nitrogen (N) mineralization, microbial biomass and other soil properties. However, little is known of the role of mineral particle size in riparian soils, where fluvial sorting creates strong spatial contrasts in the size distribution of sediments in sedimentary landforms. We studied total organic carbon (TOC) and total N (TN) storage and net N mineralization relative to soil texture and landform in soils of a riparian toposequence along the Phugwane River in Kruger National Park, South Africa. TOC, TN and potential N mineralization related strongly to particle size distribution in all soils along the toposequence. TOC and TN were positively correlated with silt and clay concentration (r2 =0.78). In long-term laboratory incubations, N mineralization was greatest in fine-textured, N-rich soils, although the proportions of soil N mineralized were inversely related to fine particle concentrations (r2=0.61). There were differences in TOC, TN and potential N mineralization among landform types, but none of these soil properties were statistically significant after accounting for the effect of particle size. These results demonstrate the influence of particle size in mediating N retention and mineralization in these soils. Predictable differences in soil texture across alluvial landforms contribute to corresponding contrasts in soil conditions, and may play an important role in structuring riparian soil and plant communities. 相似文献
9.
Daniel Geisseler William R. Horwath Timothy A. Doane 《Soil biology & biochemistry》2009,41(6):1281-12
Soil microorganisms can use a wide range of nitrogen (N) compounds. When organic N sources are degraded, microorganisms can either take up simple organic molecules directly (direct route), or organic N may be mineralized first and taken up in the form of mineral N (mineralization-immobilization-turnover [MIT] route). To determine the importance of the direct route, a microcosm experiment was carried out. Two types of wheat residue were added to soil samples, including younger residue with a carbon (C) to N ratio of 12 and older residue with a C to N ratio of 29. Between days 1 and 4, the gross N mineralization rate reached 8.4 and 4.0 mg N kg−1 dry soil day−1 in the treatment with younger and older residue, respectively. During the same period, there was no difference in protease activity between the two residue amended treatments. The fact that protease activity was not related to gross N mineralization, even though the products of protease activity are the substrates for N mineralization, suggests that not all organic molecules released from residue or soil N passed through the soil mineral N pool. In fact, when leucine and glycine were added, only 10 and 53% of the amino acid-N, respectively, was mineralized. The fraction of N taken up via the direct route was estimated to be 55 and 62% for the young and older residue, respectively. After 28 days of incubation, the proportion of amino acid-N mineralized had increased especially in the soil amended with older residue, suggesting that the MIT route became increasingly important. This result is supported by an increase in the activities of enzymes responsible for the intracellular assimilation of ammonium (NH4+). Our results suggest that in contrast to what is proposed by many models of soil N cycling, both the direct and MIT routes were operative, with the direct route being the preferred route of residue N uptake. The direct route became less important over time and was more important in soil amended with older residue, suggesting that the direct route is favored by lower mineral N availabilities. An important implication of these findings is that when the direct route is dominant, gross N mineralization underestimates the amount of N made available from the residue. 相似文献
10.
Dynamics of soil microbial biomass and nitrogen availability in a flooded rice soil amended with different C and N sources 总被引:4,自引:0,他引:4
A greenhouse experiment was conducted to compare effects of different C and N sources applied to a flooded soil on soil microbial
biomass (SMB) C and N, extractable soil organic N (NORG), and NH4
+-N in relation to plant N accumulation of rice (Oryza sativa L.). In addition to a control without inputs (CON), four treatments were imposed receiving: prilled urea (PU), rice straw
(RS), RS and PU (RS+PU), or Sesbania rostrata as green manure (SES). Treatments were arranged according to a completely randomized design with four replicates and further
consisted of pots with and without transplanted rice. While plant effects on the SMB were relatively small, the application
of organic N sources resulted in a rapid increase in SMB until 10 days after transplanting (DAT) followed by a gradual decline
until 73 DAT. Plant N accumulation data in these treatments clearly indicated that the SMB underwent a transition from a sink
to a source of plant-available soil N during the period of crop growth. Seasonal variation of the SMB was small in treatments
without amendment of organic material (CON, PU) presumably due to a lack of available C as energy source. Extractable NORG was significantly affected by soil planting status and organic N source amendment, but represented only a small N pool with
little temporal variation despite an assumed rapid turnover. Among the three treatments receiving the same amount of N from
different sources, the recovery efficiency of applied N was 58% for PU and 28% for both RS+PU and SES treatments at 73 DAT.
The N uptake of rice, however, was not driven by N availability alone, as most evident in the RS+PU treatment. We assume that
root physiological functions were impeded after application of organic N sources.
Received: 1 June 1999 相似文献
11.
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
12.
A field study was conducted to investigate the effect of abandonment of management on net N mineralization (NNM) in subalpine
meadows. NNM, soil microbial biomass N (SMBN), fungal biomass and physicochemical characteristics (total C, total N, dissolved
organic carbon (DOC) and pH) were determined in surface (0–10 cm) soil from May to October 1997 in an intensively managed
and an abandoned meadow at 1770 m a.s.l.. The cumulative NNM was lower in the abandoned area and ranged from 150 to 373 and
from 25 to 85 μg N g–1 soil in the intensively managed and the abandoned areas, respectively. The total organic C increased in the abandoned area,
while total N showed no difference between abandoned and managed meadow. SMBN showed no difference between the investigated
sites, whereas ergosterol, a measure of fungal biomass, increased significantly at the abandoned site. The cumulative NNM
was negatively correlated with total organic C, C : N ratio, DOC and ergosterol content, and positively correlated with the
NH4
+-N content of soil. The decrease in NNM at the abandoned site may be explained by the lower availability of N in substrates
characterized by a high C : N ratio which, together with a decrease in pH in the litter layer, may have increased fungal biomass.
Received: 8 January 1999 相似文献
13.
Estimation of the capacity of soils to supply N for crop growth requires estimates of the complex interactions among organic
and inorganic N components as a function of soil properties. Identification and measurement of active soil N forms could help
to quantify estimates of N supply to crops. Isotopic dilution during incubation of soils with added 15NH4
+ compounds could identify active N components. Dilution of 15N in KCl extracts of mineral and total N, non-exchangeable NH44
+, and N in K2SO4 extracts of fumigated and non-fumigated soil was measured during 7-week incubation. Samples from four soils varying in clay
content from 60 to 710 g kg–1 were used. A constant level of 15N enrichment within KCl and K2SO4 extracted components was found at the end of the incubation period. Total N, microbial biomass C and non-exchangeable NH4
+ contents of the soils were positively related to the clay contents. The mineralized N was positively related to the silt
plus clay contents. The active soil N (ASN) contained 28–36% mineral N, 29–44% microbial biomass N, 0.3–5% non-exchangeable
NH4
+ with approximately one third of the ASN unidentified. Assuming that absolute amounts of active N are related to N availability,
increasing clay content was related to increased N reserve for crop production but a slower turnover.
Received: 7 July 1998 相似文献
14.
Effects of storage time and straw content of cattle slurry on the mineralization of nitrogen and carbon in soil 总被引:2,自引:0,他引:2
P. Sørensen 《Biology and Fertility of Soils》1998,27(1):85-91
Animal slurries are stored for a variable period of time before application in the field. The effect of cattle slurry storage
time and temperature on the subsequent mineralization of C and N in soil was studied under laboratory conditions. Urine and
faeces from a dairy cow were sampled separately and mixed to a slurry. After 4 weeks of storage under anaerobic conditions
at 15 °C, the NH4
+ N content exceeded the original urinary N content of the slurry; the NH4
+ content increased only slightly during the following 16 weeks of storage. After 4 weeks of storage, the proportion of slurry
C in volatile fatty acids (VFA) amounted to 10% and increased to 15% after 20 weeks. Straw addition to the slurry caused an
increase of VFA-C in stored slurry, but had a negligible influence on the proportion of slurry N in the form of NH4
+. Slurries subjected to different storage conditions were added to a sandy and a sandy loam soil. After 1 week, the preceding
storage period (0–20 weeks) and temperature (5 °C or 15 °C) had no significant effect on the net release of inorganic N
from the slurry in soil. Thus, the increased NH4
+ content in the slurry after storage was followed by increased net N immobilization in soil. Additional straw in the slurry
caused increased net N immobilization only in the sandy loam soil. Following anaerobic storage, 8–14% of slurry C was released
in gaseous form, and the net mineralization of slurry C after 12 weeks in soil amounted to 54–63%. The extra net mineralization
of C in soil due to straw in slurry was equivalent to 76% of straw C, suggesting that the straw accelerated the mineralization
of C derived from faeces, urine and/or soil.
Received: 25 August 1997 相似文献
15.
Climate and litter quality have been identified as major drivers of litter decomposition, but our knowledge of how soil characteristics (e.g. microbial community and chemical properties) determine carbon (C) and nitrogen (N) availability derived from the decomposition of litter of different qualities is still scarce. We conducted a microcosm experiment to evaluate how soils with contrasting microbial communities and soil properties (denoted Soils A and B hereafter, where Soil B has higher bacterial and fungal abundance, fungal:bacterial ratio, and organic C than Soil A) determine the availability of soil C (carbohydrates, proteins, amino acids and phenols) and N (dissolved organic and inorganic N, microbial biomass N and available N) during the decomposition of litter of contrasting quality (C:N ratios ranging from 20 to 102). We also evaluated the relative importance of soil characteristics and litter quality as drivers of C and N inputs to the soil during this process. Overall, higher soil C and N availability after litter decomposition was found in Soil B than in Soil A. Soil characteristics had a higher positive effect on soil C and N contents than litter quality during litter decomposition. We also found that changes in N availability and organic matter quality registered after litter decomposition, linked to different soil characteristics, were able to promote dissimilarities in the potential mineralization rates. In conclusion, our study provides evidence that soil characteristics (e.g. microbial communities and chemical properties) can be more important than litter quality in determining soil C and equally important for N availability during the decomposition of leaf litter. 相似文献
16.
Microbial and soil parameters in relation to N mineralization in soils of diverse genesis under differing management systems 总被引:4,自引:1,他引:3
Oregon soils from various management and genetic histories were used in a greenhouse study to determine the relationships
between soil chemical and biological parameters and the uptake of soil mineralized nitrogen (N) by ryegrass (Lolium perenne L.). The soils were tested for asparaginase, amidase, urease, β-glucosidase, and dipeptidase activities and fluorescein diacetate
hydrolysis. Microbial biomass carbon (C) and N as well as metabolic diversity using Biolog GN plates were measured, as were
total soil N and C, pH, and absorbance of soil extracts at 270 nm and 210 nm. Potentially mineralizable N (N0) and the mineralization rate constant (k) were calculated using a first order nonlinear regression model and these coefficients were used to calculate the initial
potential rate of N mineralization (N0
k). Except for Biolog GN plates, the other parameters were highly correlated to mineralized N uptake and each other. A model
using total soil N and β-glucosidase as parameters provided the best predictor of mineralized N uptake by ryegrass (R
2
=0.83). Chemical and biological parameters of soils with the same history of formation but under different management systems
differed significantly from each other in most cases. The calculated values of the initial potential rate of mineralization
in some cases revealed management differences within the same soil types. The results showed that management of soils is readily
reflected in certain soil chemical and biological indicators and that some biological tests may be useful in predicting N
mineralization in soils.
Received: 31 January 1997 相似文献
17.
Effects of salts and moisture content on N2O emission and nitrogen dynamics in Yellow soil and Andosol in model experiments 总被引:2,自引:0,他引:2
The effects of salt type and its concentration on nitrification, N mineralization and N2O emission were examined under two levels of moisture content in Yellow soil and Andosol samples as simulated to agriculture
under arid/semi-arid conditions and under heavy application of fertilizer in a glass-house, respectively. The salt mixtures
were composed of chlorides (NaCl and NH4Cl) or sulphates [Na2SO4 and (NH4)2SO4] and were added at various concentrations (0, 0.1, 0.2, 0.4 and 0.6 M as in the soil solution). These salts were added to
non-saline Yellow soil at different moisture contents (45 or 40 and 65% of maximum water-holding capacity; WHC) and their
effects on the changes in mineral N (NH4
+-N and NO3
–-N) concentration as well as N2O emission were examined periodically during laboratory incubation. We also measured urease activities to know the effect
of salts on N mineralization. Furthermore, Ca(NO3)2 solution was added at various concentrations (0, 0.1, 0.3, 0.5 and 0.8 M as in the soil solution) to a non-saline Andosol
taken from the subsurface layer in a glass-house and incubated at different moisture contents (50% and 70% of WHC) to examine
their effects on changes in mineral N. Nitrification was inhibited by high, but remained unaffected by low, salt concentrations.
These phenomena were shown in both the model experiments. It was considered that the salinity level for inhibition of nitrification
was an electric conductivity (1 : 5) of 1 dS m–1. This level was independent of the type of salts or soil, and was not affected by soil moisture content. The critical level
of salts for urease activities was about 2 dS m–1. The emission rate of N2O was maximum at the beginning of the incubation period and stabilized at a low level after an initial peak. There was no
significant difference in N2O emission among the treatments at different salt concentrations, while higher moisture level enhanced N2O emission remarkably.
Received: 29 July 1998 相似文献
18.
红壤水稻土微生物生物量氮与总氮矿化的关系 总被引:1,自引:1,他引:0
通过田间采样并布置室内培育试验,研究了红壤水稻土微生物生物量N和总N的矿化动态及其相互关系。结果表明,红壤水稻土微生物生物量N矿化速率和矿化量随培养时间延长而降低,随水稻土肥力水平提高而增加。12周培养期内,红壤水稻土微生物生物量N的一半以上被矿化,其中约1/2的矿化量出现在前4周;不同熟化程度红壤水稻土的累积矿化N量为73.0~127.8mg/kg,平均矿化速率为6.09~10.7mg/(kg·wk)。用双指数方程和一级动力学方程可以很好地模拟红壤水稻土微生物生物量N和总N的矿化过程。微生物生物量N和总N的矿化过程均可分为快速和缓慢2个阶段,培养的前8周是快速矿化阶段。2个模拟方程参数的比较表明,微生物生物量N矿化量占总N矿化量的比例为10.8%~49.5%,其矿化潜力大,持续矿化时间长,对保证土壤N素的持续供应有积极作用。 相似文献
19.
Organic residues affect phosphorus availability and maize yields in a Nitisol of western Kenya 总被引:3,自引:0,他引:3
The effects of organic residues and inorganic fertilizers on P availability and maize yield were compared in a Nitisol of
western Kenya. Leaf biomass of Calliandra calothyrsus, Senna spectabilis, Croton megalocarpus, Lantana camara, Sesbania sesban, and Tithonia diversifolia were incorporated into the soil at 5 Mg ha–1 for six consecutive seasons in 3 years and responses compared with those following the application of 120 kg N ha–1, 0 kg P ha–1 (0P); 120 kg N ha–1, 10 kg P ha–1; and 120 kg N ha–1 25 kg P ha–1 as urea and triple superphosphate (TSP); K was supplied in all treatments. Addition of Tithonia, Lantana and Croton increased soil resin-extractable P over that of fertilizer-amended soil throughout the first crop, but the amounts in the
former treatments became similar to those for soils amended with inorganic fertilizers for subsequent crops. Addition of Sesbania, Calliandra and Senna had a similar effect on resin P as inorganic fertilizers. Total maize yields after six seasons were tripled by the application
of Tithonia compared to 0P, and were higher than those of the Calliandra, Senna, Sesbania and Lantana treatments, and similar only to that of the Croton treatment. P recovered in the above-ground biomass and resin P, immediately after the implementation of the treatments, was
higher in the Senna, Sesbania, Croton, Lantana and Tithonia (35–77%) treatments than in the inorganic fertilizer treatments (21–27%). The P content of organic residues, and the soluble
C:total P ratio, were the main residue parameters predicting soil P availability and maize yield. All organic residues used
in this study can replace inorganic fertilizers for the enhancement of P availability and maize production, while an additional
benefit could be obtained from the use of Croton, Lantana and Tithonia.
Received: 19 January 2000 相似文献
20.
Comparison of different methodologies for field measurement of net nitrogen mineralization in pasture soils under different soil conditions 总被引:3,自引:0,他引:3
D. J. Hatch A. Bhogal R. D. Lovell M. A. Shepherd S. C. Jarvis 《Biology and Fertility of Soils》2000,32(4):287-293
Net mineralization was measured in free-draining and poorly drained pasture soils using three different field incubation
methodologies. Two involved the use of enclosed incubation vessels (jar or box) containing C2H2 as a nitrification inhibitor. The third method confined soil cores in situ in an open tube in the ground, with an anion-exchange
resin at the base to retain leached NO3
– (resin-core technique, RCT). Measurements were made on three occasions on three free-draining pastures of different ages
and contrasting organic matter contents. In general, rates of net mineralization increased with pasture age and organic matter
content (range: 0.5–1.5 kg N ha–1 day–1) and similar rates were obtained between the three techniques for a particular pasture. Coefficients of variation (CVs) were
generally high (range: 10.4–98.5%), but the enclosed incubation methods were rather less variable than the RCT and were considered
overall to be the more reliable. The RCT did not include C2H2 and, therefore, newly formed NO3
– may have been lost through denitrification. In a poorly drained pasture soil, there were discrepancies between the two enclosed
methods, especially when the soil water content approached field capacity. The interpretation of the incubation measurements
in relation to the flux of N through the soil inorganic N pool is discussed and the drawbacks of the various methodologies
are evaluated.
Received: 18 November 1999 相似文献