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1.
Douglas L. Karlen Mark D. Tomer Jerry Neppel Cynthia A. Cambardella 《Soil & Tillage Research》2008,99(2):291-299
Soil quality assessment has been recognized as an important step toward understanding the long-term effects of conservation practices within agricultural watersheds. Our objective was to assess soil quality within the South Fork watershed of the Iowa River using various indicators and assessment approaches. Soil samples were collected during 2003 and 2004 from 29 areas of 32 ha (80 acres) each along two transects traversing the watershed. Soil pH, Mehlich III extractable P, K, Ca and Mg, electrical conductivity (EC), total organic carbon (TOC), and total N (TN) were measured. The Soil Management Assessment Framework (SMAF) was used to compute a soil quality index (SQI), while soil loss, the soil tillage intensity rating (STIR), N-leaching potential, and soil conditioning index (SCI) were determined for each sampling area using the 2003 version of the Revised Soil Loss Equation (RUSLE2). Overall, there were no soil fertility limitations within the watershed based on an average pH of 6.96 and extractable P and K levels of 36 and 162 mg kg−1, respectively. Soil loss, STIR, N-leaching, and SCI averaged 1.13 Mg ha−1, 68, 3, and 0.4, respectively. The SMAF analysis indicated soils within the watershed were functioning at 87% of their full potential. The lowest indicator score was associated with TOC (0.60) because the average value was only 28.4 g kg−1. The SCI and SQI indices were positively correlated although since it used measured data, the SMAF appears to provide more information about the effects of management practices within the watershed. Soils in upper landscape positions had lower TOC and C:N ratios indicating an increased risks for both erosion and for nitrate leaching. Management of soils on hilltops may be the most effective way to minimize N and P losses within the watershed. 相似文献
2.
To assess cultivation-induced changes followed during the Green Revolution on continuous rice–rice and rice–wheat cropping,
fence-line comparisons between cultivated and adjacent noncultivated soils were made to (a) quantify changes in selected soil
chemical and biological properties at two moisture conditions, (b) determine the N, P, and K uptake of rice and wheat as affected
by changes in soil properties, and (c) determine the relationship between N, P, and K uptake and soil properties. Two parallel
experiments were conducted: laboratory incubation and a greenhouse experiment with soils collected from seven rice–wheat and
two rice–rice soils. As an average, NH4OAc-extractable K, water soluble organic carbon, and hot water soluble organic carbon were all lower by 48%, total carbon
by 35%, total nitrogen by 33%, and microbial biomass carbon by 38% in the cultivated soils, whereas no significant change
was observed in the enzyme activities. Changes were mostly associated with the existing fertilizer practices and moisture
status of the soil during cultivation. In general, fertilizers were not sufficient to replenish crop removal. Soil type also
influenced cultivation changes especially soil carbon parameters. Lighter soil texture had higher decomposable organic C and
total C declined than heavy soils. Soils with higher declined in both decomposable organic C and total C had higher reduction
in functional diversity of culturable microorganisms. The declining C pools caused lower N uptake and there was a clear association
between organic matter parameters and N uptake. Olsen P was correlated with P uptake and extractable K with K uptake. As expected,
crop biomass correlated with N, P, and K uptake of plants. Comparison of cultivated and its corresponding uncultivated soil
provides possibility to determine management effect on soil status. 相似文献
3.
Aggregate stability and glomalin in alternative crop rotations for the central Great Plains 总被引:11,自引:0,他引:11
Land productivity, along with improvement or maintenance of soil health, must be evaluated together to achieve sustainable
agricultural practices. Winter wheat-fallow (W-F) has been the prevalent cropping system in the central Great Plains for 60 years
where moisture is a limitation to crop production. Alternative cropping systems show that producers can crop more frequently
if residue management and minimum tillage are used. The impact of different crops, crop rotations and tillage management practices
on soil quality was assessed by measuring aggregate stability and glomalin production by arbuscular mycorrhizal (AM) fungi
in soil from cropping trials established in 1990. Crops were wheat (W), corn (C), proso millet (M), and sunflower (S). Rotations
sampled were W-F, W-C-M, W-C-M-F, W-C-F, and W-S-F. In the same area as the cropping trials, soils were taken from a perennial
grass (crested wheatgrass) and from a buffer area that had been planted to Triticale for the past 2 years but prior to that
had been extensively plowed for weed control. We found that aggregate stability and glomalin were linearly correlated (r=0.73, n=54, P<0.001) across all treatments sampled. Highest and lowest aggregate stability and glomalin values were seen in perennial grass
and Triticale soils, respectively. Aggregate stability in W-S-F was significantly lower than in the other crop rotations (P≤0.03), while W-C-M had significantly higher glomalin than the other rotations (P<0.05). Differences between crop rotations and the perennial grass indicate that selected comparisons should be studied in
greater detail to determine ways to manage AM fungi to increase glomalin and aggregate stability in these soils.
Received: 16 March 1999 相似文献
4.
Soil organic matter quantity and quality in mountain soils of the Alay Range, Kyrgyzia, affected by land use change 总被引:4,自引:0,他引:4
Changes in soil management practices influence the amount, quality and turnover of soil organic matter (SOM). Our objective
was to study the effects of deforestation followed by pasture establishment on SOM quantity, quality and turnover in mountain
soils of the Sui Checti valley in the Alay Range, Kyrgyzia. This objective was approached by analysis of total organic C (TOC),
N, lignin-derived phenols, and neutral sugars in soil samples and primary particle-size soil fractions. Pasture installation
led to a loss of about 30% TOC compared with the native Juniperus turkestanica forests. The pasture soils accumulated about 20% N, due to inputs via animal excrement. A change in land use from forest
to pasture mainly affected the SOM bound to the silt fraction; there was more microbial decomposition in the pasture than
in the forest silt fraction, as indicated by lower yields of lignin and carbohydrates, and also by a more advanced oxidative
lignin side-chain oxidation and higher values of plant : microbial sugar ratios. The ratio of arabinose : xylose was indicative
of the removal of carbohydrates when the original forest was replaced by pasture, and we conclude that this can be used as
an indicator of deforestation. The accumulation of lignin and its low humification within the forest floor could be due to
the extremely cold winter and dry summer climate.
Received: 10 March 1999 相似文献
5.
W. De Boer S. Gerards P. J. A. Klein Gunnewiek R. Modderman 《Biology and Fertility of Soils》1999,29(2):170-177
The dynamics of culturable chitin-degrading microorganisms were studied during a 16-week incubation of chitin-amended coastal
dune soils that differed in acidity. Soil samples were incubated at normal (5% w/w) and high (15% w/w) moisture levels. More
than half of the added chitin was decomposed within 4 weeks of incubation in most soils. This rapid degradation was most likely
due to fast-growing chitinolytic fungi (mainly Mortierella spp. and Fusarium spp.) at both moisture levels, as dense hyphal networks of these fungi were observed during the first 4 weeks of incubation.
Chitin N mineralization was inhibited by cycloheximide, and fast-growing fungal isolates were capable of rapid chitin decomposition
in sterile sand, further suggesting that these fungi play an important role in initial chitin degradation. The strong increase
in fast-growing fungi in chitin-amended dune soils was only detected by direct observation. Plate counts and microscopic quantification
of stained hyphae failed to reveal such an increase. During the first part of the incubation, numbers of unicellular chitinolytic
bacteria also increased, but their contribution to chitin degradation was indicated to be of minor importance. During prolonged
incubation, colony forming units (CFU) of chitinolytic streptomycetes and/or slow-growing fungi increased strongly in several
soils, especially at the 5% moisture level. Hence, the general trend observed was a succession from fast-growing fungi and
unicellular bacteria to actinomycetes and slow-growing fungi. Yet, the composition of chitinolytic CFU over time differed
strongly between chitin-amended dune soils, and also between the two moisture levels. These differences could not be attributed
to pH, organic matter or initial microbial composition. The possible consequence of such unpredictable variation in microbial
community composition for the use of chitin-amendments as a biocontrol measure is discussed.
Received: 10 March 1998 相似文献
6.
Microbiological and chemical changes in two arable soils after long-term sludge amendments 总被引:7,自引:0,他引:7
Sludge amendments increase the input of carbon and nutrients to the soil. However, the soil concentrations of heavy metals
and xenobiotica can also increase due to sludge amendments, with possible effects on soil microorganisms and soil fertility.
Therefore, we studied the effects on soil microorganisms and soil chemistry in two arable soils after 12 and 16 years of sewage
sludge amendment (0, 1 and 3 dry matter ha–1 year–1). The sludge amendments were combined with nitrogen addition at three rates according to crop requirements, and all combinations
were replicated 4 times, giving a total number of 36 parcels at each experimental site in a non-randomised block design. Univariate
data evaluation as well as principal component analysis and discriminant function analysis (DFA) were used to identify differences
between treatments in microbial and chemical parameters. The DFA showed that acid and alkaline phosphatase, potential ammonium
oxidation and total nitrogen were the most important parameters to discriminate between a priori defined groups of sludge
treatments. Among the heavy metals, copper showed the highest increase in soil concentration with sludge amendments, but this
increase was still not high enough to have a significant influence on the measured parameters. None of the xenobiotica investigated
was found in high soil concentrations. In conclusion, the present study showed that the sewage sludge affected several of
the biological and chemical parameters investigated. However, no severe negative effects on soil microorganisms were detected
at these moderate levels of sludge amendment.
Received: 3 December 1998 相似文献
7.
Short-term effects of different tillage in a sustainable farming system on nematode community structure 总被引:7,自引:0,他引:7
This study investigated the effects of different tillage practices on the nematode community structure. The different tillage systems were: untilled control, conventional deep plough, two-layer plough and cultivator. Sampling was carried out in a field experiment at Wörrstadt-Rommersheim (Rhineland-Palatinate, Germany) in order to study the effects of these tillage systems in a sustainable farming system. Soil samples were taken every 3?months from June 1994 to March 1995 and divided into two depths of 0–10 and 10–20?cm in order to study the vertical distribution of nematode density and community structure. Nematode density was significantly reduced after the first tillage. The second tillage had no effect on the nematode density, whereas the nematode community structure was strongly influenced on both structural (taxonomic) and functional (trophic group, life strategy) level. After tillage, the density of plant parasitic nematodes decreased and the density and dominance of bacterivorous nematodes increased. In the tilled plots, and especially in the cultivator and the two-layer plough plot, the nematode community was dominated by bacterial feeders, whereas, in the untilled control, plant feeders were more dominant. Our results showed that the nematode Maturity Index and Plant Parasite Index are suitable for indicating immediate tillage effects on the nematode community. 相似文献
8.
Long-term monitoring of microbial biomass, N mineralisation and enzyme activities of a Chernozem under different tillage management 总被引:13,自引:0,他引:13
We investigated the influence of tillage (conventional, minimum and reduced) on selected soil microbial properties of a fine-sandy
loamy Haplic Chernozem over a period of 8 years. The microbial biomass and soil microbial processes were affected mostly by
type of tillage and to a lesser extent by the date of soil sampling. Whereas xylanase activity was significantly higher in
the 0 to 10-cm soil layer of the reduced and minimum tillage systems within the first year of the experiment (protease and
phosphatase activities were significantly higher in the second year), significant treatment effects on microbial biomass,
N mineralisation and potential nitrification were observed after a 4-year period. The slow response of substrate-induced respiration
to the change in type of tillage may have been due to the differences in the biomass C turnover rates. After a 4-year period,
the stratification of the soil microbial biomass within the profile of reduced and minimum tillage systems was probably responsible
for the more intensive soil microbial processes near the soil surface compared with conventional tillage. In the 20 to 30-cm
layer, N mineralisation, potential nitrification and xylanase activity in the conventional treatment were significantly higher
than in the minimum and reduced tillage plots due to buried organic materials. Discriminant analysis underlined the similarity
of the enzyme activity patterns in the top layer of the reduced and minimum tillage treatments, and in both layers of the
conventional tillage system. The trend towards a significant increase in functional diversity caused by reduced tillage became
obvious within the first year of the experiment, and this effect was still manifest after 8 years. All relationships suggested
that there were differences in available resources (e.g. organic matter) along the sequence of different tillage systems;
this was reflected in part by enhanced enzymatic and microbial activities in the soil layers. In conclusion, this study showed
that soils affected by tillage may be classified on the basis of their functional diversity. Therefore, the soil microbial
properties chosen for microbiological soil monitoring (microbial biomass, N mineralisation and enzyme activities involved
in C, N and P cycling) provide a reliable tool with which to estimate early changes in the dynamics and distribution of soil
microbial processes within soil profiles.
Received: 3 February 1998 相似文献
9.
Changing role of cultivated land in the global carbon cycle 总被引:3,自引:0,他引:3
The carbon balance is ill defined for agricultural lands so that their role in global C balance cannot be accurately estimated.
Changes in agriculture in the last 50 years have resulted in a general increase in grain yields, total net annual production
(TNAP), and C input to the soil. Amounts of C returned annually with crop residues on Sanborn Field, one of the oldest experimental
fields in the United States, increased after 1950, and this was accompanied by C accumulation in soils. Under wheat monocrop
(with mineral fertilizer), C accumulated at a rate of 50 g m–2 year–1. A 3-year rotation (corn/wheat/clover) with manure and nitrogen applications sequestered 150 g m–2 year–1 of C. Total C balance for the wheat and corn production area in the United States, approximated on the basis of these rates,
indicates that at least 32 Tg C was sequestered annually during the last 40–50 years.
Received: 1 December 1997 相似文献
10.
Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides 总被引:1,自引:0,他引:1
Jeanine L. Kay-Shoemake M. E. Watwood Robert E. Sojka Roderick D. Lentz 《Biology and Fertility of Soils》2000,31(2):183-186
Polyacrylamide (PAM) is currently used as an irrigation water additive to significantly reduce the amount of soil erosion
that occurs during furrow irrigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been
reported in PAM-treated field soils; the substrate specificity of the induced amidase is uncertain. PAM-treated and untreated
soils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene
acetamide. Based on results obtained with a soil amidase assay, there was no difference between PAM-treated and untreated
soils with respect to the rate of amide bond hydrolysis of any of the agrochemicals tested. It appears that under these assay
conditions the PAM-induced soil amidase is not active toward the amide bonds within these molecules. However, carbaryl was
hydrolyzed by a different soil amidase. To our knowledge, this is the first soil enzyme assay-based demonstration of the hydrolysis
of carbaryl by a soil amidase.
Received: 23 June 1999 相似文献
11.
N. D. Ananyeva T. S. Demkina W. J. Jones M. L. Cabrera W. C. Steen 《Biology and Fertility of Soils》1999,29(3):291-299
Non-tilled and tilled plots on a spodosol (Corg 0.65–1.70%; pH 4.1–4.5) and a mollisol (Corg 3.02–3.13%, pH 4.9–5.3), located in the European region of Russia, were investigated to determine variances in soil microbial
biomass and microbial community composition. Continuous, long-term management practices, including tillage and treatment with
inorganic fertilizers or manure, were used on the spodosol (39 years) and mollisol (22 years). Total microbial biomass (Cmic), estimated by the substrate-induced respiration (SIR) method, and total fungal hyphae length (membrane filter technique)
were determined seasonally over a 3-year period. Long-term soil management practices (primarily tillage and fertilizer application)
led to decreases in total microbial biomass (80–85% lower in spodosol and 20–55% lower in mollisol), decreases in the contribution
of Cmic to Corg (2.3- to 3.5-fold lower in spodosol and 1.2- to 2.3-fold lower in mollisol), and 50–87% decreases in total fungal hyphae
length compared to non-tilled control plots. The contribution of fungi to total SIR in virgin mollisol and fallow spodosol
plots was approximately 30%. However, the contribution of fungi to SIR was approximately two times greater in tilled spodosol
plots compared to a fallow plot. In contrast, the contribution of fungi to SIR in tilled plots of mollisol was less (1.4–4.7
times) than for a virgin plot. In summary, long-term soil management practices such as tillage and treatment with organic
or inorganic fertilizers are important determinants of soil microbial biomass and the contribution of fungi to total SIR.
Received: 28 April 1998 相似文献
12.
The impact of a low humus level in arable soils on microbial properties, soil organic matter quality and crop yield 总被引:7,自引:0,他引:7
In arable soils in Schleswig-Holstein (Northwest Germany) nearly 30% of the total organic C (TOC) stored in former times
in the soil has been mineralized in the last 20 years. Microbial biomass, enzyme activities and the soil organic matter (SOM)
composition were investigated in order to elucidate if a low TOC level affects microbial parameters, SOM quality and crop
yield. Microbial biomass C (Cmic) and enzyme activities decreased in soils with a low TOC level compared to soils with a typical TOC level. The decrease in
the Cmic/TOC ratio suggested low-level, steady-state microbial activity. The SOM quality changed with respect to an enrichment of
initial litter compounds in the top soil layers with a low TOC level. Recent management of the soils had not maintained a
desirable level of humic compounds. However, we found no significant decrease in crop yield. We suggest that microbial biomass
and dehydrogenase and alkaline phosphatase activities are not necessarily indicators of soil fertility in soils with a high
fertilization level without forage production and manure application.
Received: 12 December 1997 相似文献
13.
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
14.
The NO turnover in soils was measured in two different experimental set-ups, a flow-through system, which is very time-consuming
and needs rather sophisticated equipment, and a closed system using serum bottles. We compared the NO turnover parameters
(NO consumption rate constant, NO production rate, NO compensation concentration) that were measured with both systems in
different soils, under different conditions and in the presence of 10 Pa acetylene to inhibit nitrification. The values of
the NO turnover parameters that were measured with the two systems under oxic conditions were usually comparable. The addition
of acetylene did not affect the NO consumption rate constants of the soils with the exception of soil G1. However, the NO
production rates and the NO compensation concentrations decreased significantly in the presence of acetylene, indicating that
nitrification was the main source of NO in these soils. Only one soil (Bol) showed no nitrifying activity. Increasing soil
moisture content resulted in decreasing NO consumption rate constants and NO production rates. Even at a high soil moisture
content of 80% water holding capacity, nitrification was the main source of NO. The values of the NO turnover parameters that
were measured with the two systems were not comparable under anoxic conditions. The NO consumption rate constants and the
NO production rates were much lower in the closed than in the flow-through system, indicating that the NO consumption activity
became saturated by the high NO concentrations accumulating in the closed system. Under oxic conditions, however, closed serum
bottles were a cheap, easy and reliable tool with which to determine NO turnover parameters and to distinguish between nitrification
and denitrification as sources of NO.
Received: 21 April 1998 相似文献
15.
Timothy A. Quine Gerard Govers Jean Poesen Des Walling Bas van Wesemael Jose Martinez-Fernandez 《Soil & Tillage Research》1999,51(3-4):279-301
Tillage erosion is increasingly recognised as an important soil erosion process on agricultural land. In view of its potential significance, there is a clear need to broaden the experimental database for the magnitude of tillage erosion to include a range of tillage implements and agricultural environments. The study discussed in this paper sought to address the need for such data by examining tillage erosion by a duckfoot chisel plough in stony soils on steep slopes in a semi-arid environment. Results of the investigation of coarse fraction (rock fragment) translocation by tillage in this environment have been presented elsewhere and the paper focuses on tillage translocation and erosion of the fine earth. Tillage translocation was measured at 10 sites, representing both upslope and downslope tillage by a duckfoot chisel plough on five different slopes, with tangents ranging from 0.02 to 0.41. A fine-earth tracer, comprising fine earth labelled with 134Cs, was introduced into the plough layer before tillage. After a single pass of the plough, incremental samples of plough soil were excavated and sieved to separate the fine earth from the rock fragments. Translocation of the fine-earth tracer was established by analysing the 134Cs content of the samples of fine earth. These data were used to establish translocation distances for each combination of slope and tillage direction. Translocation distances of the fine earth were not significantly different from translocation distances of the coarse fraction. For all sites, except uphill on the 0.41 slope, translocation distances were found to be linearly related to slope tangent. The soil flux due to tillage for each site was calculated using the translocation distance and the mass per unit area of the plough layer. For slopes with tangents <0.25, the relationship between soil flux and tangent was linear and the soil flux coefficient derived was 520–660 kg m−1 per pass. This is much larger than the coefficients found in other studies and this high magnitude is attributed to the non-cohesive nature and high rock fragment content of the soil in this investigation. A second contrast with previous studies was found in non-linearity in the relationship between soil flux and tangent when steeper slopes were included. This was a product of variation in plough depth between the steepest slopes and the remainder of the study area. On the basis of the study it is suggested that an improved understanding of tillage erosion may be obtained by considering the dual processes of tillage detachment (mass per unit area of soil subject to tillage) and tillage displacement (equivalent to translocation distance per pass) in assessing, comparing and modelling tillage translocation. An improved model is proposed that recognises the complexity of soil redistribution by tillage, provides a framework for process-based investigation of the controls on tillage fluxes, and allows identification of potential self-limiting conditions for tillage erosion. 相似文献
16.
Conservation tillage: Short- and long-term effects on soil carbon fractions and enzymatic activities under Mediterranean conditions 总被引:2,自引:0,他引:2
Sebastiana Melero Rosa Lpez-Garrido Jos Manuel Murillo Flix Moreno 《Soil & Tillage Research》2009,104(2):292-298
Short- and long-term field experiments are necessary to provide important information about how soil carbon sequestration is affected by soil tillage system; such systems can also be useful for developing sustainable crop production systems. In this study, we evaluated the short- and long-term effects of conservation tillage (CT) on soil organic carbon fractions and biological properties in a sandy clay loam soil. Both trials consisted of rainfed crop rotation systems (cereal–sunflower–legumes) located in semi-arid SW Spain. In both trials, results were compared to those obtained using traditional tillage (TT). Soil samples were taken in flowering and after harvesting of a pea crop and collected at three depths (0–5, 5–10 and 10–20 cm). The soil organic carbon fractions were measured by the determination of total organic carbon (TOC), active carbon (AC) and water soluble carbon (WSC). Biological status was evaluated by the measurement of soil microbial biomass carbon (MBC) and enzymatic activities [dehydrogenase activity (DHA), o-diphenol oxidase activity (DphOx), and β-glucosidase activity (β-glu)].The contents of AC and MBC in the long-term trial and contents of AC in the short-term trial were higher for CT than TT at 0–5 cm depth for both sampling periods. Furthermore, DHA and β-glucosidase values in the July sampling were higher in the topsoil under conservation management in both trials (short- and long-term). The parameters studied tended to decrease as depth increased for both tillage system (TT and CT) and in both trials with the exception of the DphOx values, which tended to be higher at deeper layers.Values of DHA and β-glu presented high correlation coefficients (r from 0.338 to 0.751, p ≤ 0.01) with AC, WSC and TOC values in the long-term trial. However, there was no correlation between either TOC or MBC and the other parameters in the short-term trial. In general, only stratification ratios of AC were higher in CT than in TT in both trials. The results of this study showed that AC content was the most sensitive and reliable indicator for assessing the impact of different soil management on soil quality in the two experiments (short- and long-term).Conservation management in dryland farming systems improved the quality of soil under our conditions, especially at the surface layers, by enhancing its storage of organic matter and its biological properties, mainly to long-term. 相似文献
17.
18.
J. A. Montgomery D. K. McCool A. J. Busacca B. E. Frazier 《Soil & Tillage Research》1999,51(3-4):175-187
Most of the erosion research in the Palouse region of eastern Washington State, USA has focused on quantifying the rates and patterns of water erosion for purposes of conservation planing. Tillage translocation, however, has largely been overlooked as a significant geomorphic process on Palouse hillslopes. Tillage translocation and tillage deposition together have resulted in severe soil degradation in many steep croplands of the Palouse region. Few controlled experiments have heretofore been conducted to model these important geomorphic processes on Palouse hillslopes. The overarching purpose of this investigation, therefore, was to model tillage translocation and deposition due to moldboard plowing in the Palouse region. Soil movement by moldboard plowing was measured using 480-steel flat washers. Washers were buried in silt loam soils on convex–convex shoulder, linear-convex backslope, and linear-concave footslope landform components, and then displaced from their original burial locations by a moldboard plow pulled by a wheel tractor traveling parallel to the contour at ca. 1.0 m s−1. Displaced washers were located using a metal detector, and the distance and azimuth of the resultant displacement of each washer from its original burial location was measured using compass and tape. Resultant displacement distances were then resolved into their component vectors of displacement parallel and perpendicular to the contour. A linear regression equation was developed expressing mean soil displacement distance as a function of slope gradient. Tillage translocation and deposition were modeled as diffusion-type geomorphic processes, and their rates were described in terms of the diffusion constant (k). A multivariate statistical model was developed expressing mean soil displacement distance as a function of gravimetric moisture content, soil bulk density, slope gradient, and direction of furrow slice displacement. Analysis of variance (ANOVA) revealed a weak correlation between soil displacement and both bulk density and moisture content. Soil displacement was, however, significantly correlated with direction of furrow slice displacement. Tillage translocation rates were expressed in terms of the diffusion constant (k) and ranged from 105 to 113 kg m−1 per tillage operation. Tillage deposition rates ranged from 54 to 148 kg m−1 per tillage operation. With respect to tillage deposition, the diffusion constant calculated from volumetric measurements of tillage deposits equals ca. 150 kg/m. The rates of tillage translocation and deposition are not completely in balance; however, these rates do suggest that soil tillage is a significant geomorphic process on Palouse hillslopes and could account for the some of the variations in soil physical properties and crop yield potential at the hillslope and farm-field scale in the Palouse region. 相似文献
19.
Soil CH4 production potentials were investigated by incubating air-dried soils under anaerobic conditions in the laboratory. Twenty-eight
soils from different fields and locations were collected for this study. Soil CH4 production during a 100-day incubation differed greatly and were significantly correlated with soil organic content (r=0.61, P<0.01). The statistical significance increased when soils were grouped according to soil reduction rates. A significant correlation
was also found between CH4 production and total N content (r=0.64, P<0.01) and between CH4 production and soil particle sizes of 0.25–0.05 mm (r=0.48, P<0.05). A negative exponential correlation was found between CH4 production and aerobic soil pH (r=–0.74, P<0.01). The 28 soils were stratified into four groups on the basis of variation in CH4 production rates which were associated with the soil reduction rate and soil organic content. The faster the Eh of soil fell,
the more CH4 was formed. Adding rice straw to Hangzhou and Beijing soils increased CH4 production. The increase in CH4 production was more pronounced in the soil with the lowest organic matter content and slowest reduction rate than in the
soil with highest organic matter and fastest reduction rate. Inorganic fertilizer had no significant influence on CH4 production potentials of either type of soil.
Received: 26 November 1997 相似文献
20.
C. Bayer L. Martin-Neto J. Mielniczuk A. Pavinato J. Dieckow 《Soil & Tillage Research》2006,86(2):237-245
A considerable proportion of the 200 million hectares of the Brazilian Cerrado is suitable for annual crops but little is known about the effects of tillage on the C dynamics of Cerrado soils. We evaluated the role of two representative Cerrado Oxisols (350 and 650 g clay kg−1) as sources or sinks of atmospheric C when managed under three tillage systems (conventional tillage (CT), reduced tillage (RT), and no-till (NT)) in 8- and 5-year long-term experiments. A literature review was also carried out and the mean C sequestration rates in no-till soils of tropical and subtropical regions of Brazil were calculated and compared with values for soils from temperate regions of the world. The original C stocks in 0–20 cm layer of soils under native Cerrado were higher in the clayey (54.0 Mg ha−1) than in the sandy clay loam soil (35.4 Mg ha−1), suggesting a higher physical stability of organic matter associated with variable clay minerals in the clayey Oxisol. The original C stocks of the native Cerrado soils appear not to have decreased after 23 years of conventional tillage in the sandy clay loam Oxisol, except when the soil had been subjected to erosion (15% loss of C), or after 25 years in the clayey Oxisol. Compared to conventionally tilled soil, the C stocks in no-till sandy clay loam Oxisol increased by 2.4 Mg ha−1 (C sequestration rate = 0.30 Mg ha−1 year−1) and in the clayey Oxisol by 3.0 Mg ha−1 (C sequestration rate = 0.60 Mg ha−1 year−1). The mean rate of C sequestration in the no-till Brazilian tropical soils was estimated to be 0.35 Mg ha−1 year−1, similar to the 0.34 Mg ha−1 year−1 reported for soils from temperate regions but lower than the 0.48 Mg ha−1 year−1 estimated for southern Brazilian subtropical soils. Considering the large area (about 70 million hectares) of the Cerrado which is currently used and potentially available for cropland, the adoption of no-till systems could turn the Cerrado soils into a significant sink for atmospheric C and contribute to the mitigation of global climate change. 相似文献