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1.
《国际水土保持研究(英文)》2022,10(3):457-469
Soil structure plays an important role in edaphic conditions and the environment. In this study, we investigated the effects of organic amendment on soil structure and hydraulic properties. A corn field in a semiarid land was separately amended with sheep manure compost at five different rates (2, 4, 6, 8 and 10 t/ha) and corn stover (6 t/ha) in combination with two decomposing agents. The soil structure of different amended soils was analyzed from the aggregate and pore domain perspectives. The internal pore structure of the soil was visualized through X-ray computed tomography and quantified using a pore-network model. Soil aggregate-size distribution and stability, saturated hydraulic conductivity, and water-retention curves were measured by sampling or in situ. The gas permeability and diffusivity of different amended soils were simulated based on the extracted pore networks. The aggregate stability of the amended soils was improved compared with the control, that is, the mean weight diameter increased and the percentage of aggregate destruction decreased. The stability of soil aggregates varied non-monotonically with the application rate of compost and decreased after treatment with corn stover and decomposing agents. The pore-network parameters including air-filled porosity, pore radius, throat length, and coordinate number increased for the amended soils compared with the control. The mean pore size increased with increasing compost incorporation rate. The saturated hydraulic conductivity of the compost-amended soils was higher than that of the control but varied quadratically with the application rate. The saturated hydraulic conductivity of soil treated with corn stover and decomposing agents was clearly higher than that without the agent and the control. The greater gas diffusivity and air permeability indicate that soil aeration improved following the incorporation of organic amendments. The air permeability versus air-filled porosity relationship followed a power law, and the gas diffusivity versus air-filled porosity relationship was characterized by a generalized density-corrected model regardless of amendment. The findings of this study can help improve the understanding of soil structure and hydrological function to organic fertilizer incorporation and further monitor the quality of soil structure through the pore space perspective. 相似文献
2.
耕作与覆盖措施对黄土塬区春玉米田土壤水气传输的影响 总被引：2，自引：1，他引：1
3.
PORE CHARACTERISTICS OF SOILS FROM TWO CULTIVATION EXPERIMENTS AS SHOWN BY GAS DIFFUSIVITIES AND PERMEABILITIES AND AIR-FILLED POROSITIES 总被引：1，自引：0，他引：1
B. C. BALL 《European Journal of Soil Science》1981,32(4):483-498
Gas diffusivity and permeability, and air-filled porosity, were measured in undisturbed soil cores at six water potentials between -2 kPa and oven dryness. All increased as water potential fell. In silt loam at 30 to 80 mm depth, relative diffusivity and air permeability at -2 kPa were 0.0013 and 5 × 10?8cm2 after direct drilling, and were 6 and 15 times greater respectively after ploughing, presumably because of the larger volume of air-filled large pores in the ploughed soil. These pores may also have been more continuous or less tortuous than in the direct drilled soil. However, at equal air-filled porosities up to 0.18 v/v, the pores were apparently more continuous and less tortuous in the direct drilled than in the ploughed soil. In the direct drilled silt loam at any given matric potential, air-filled porosity, gas diffusivity and permeability within and below the previously ploughed layer were isotropic. In clay loam at 30 to 80 mm depth gas diffusivity and permeability at -2 kPa were greater than in the silt loam irrespective of tillage but increased less on oven drying. 相似文献
4.
P. Schjønning B.V. Iversen L.J. Munkholrn R. Labouriau O.H. Jacobsen 《Soil Use and Management》2005,21(3):265-275
Abstract Application of organic residues to soil is generally assumed to improve soil tilth. Only few studies have reported the long‐term effects on the more subtle aspects of soil porosity, and no reports have considered the potential effects of organic amendments on the pore system in the subsoil. We sampled undisturbed soil cores (100 cm3 and 6280 cm3) using metal cylinders in differently fertilized plots in the long‐term field experiment at Askov Experimental Station, Denmark. We selected the 0–60 cm soil layer of plots dressed for a century with either mineral fertilizers (labelled NPK) or animal manure (labelled AM) and unfertilized plots (UNF) as a reference. Both fertilization treatments were studied at two levels of nutrient application: ‘normal’ (labelled ‘1’) and 1.5 times ‘normal’ (labelled ‘1½’). Water retention, air permeability and air diffusivity were measured on the small cores, and we used the large cores for measuring near‐saturated and saturated hydraulic conductivity. In the plough layer, the AM and NPK soils displayed identical pore volumes in size fractions that were larger as well as smaller than 30 μm, while the UNF soil had a significantly smaller volume of pores < 30 μm. No clear trends were found in treatment effects on pore organization as calculated from air diffusivity and air permeability measurements. No significant differences in hydraulic conductivity were found in the plough layer. For the subsoil below ploughing depth, significantly larger macropore volumes and near‐saturated hydraulic conductivities were found for soil of plots receiving the larger (‘1½’) amount of nutrients compared with the ‘normally’ dressed soil. This effect was independent of fertilization system (AM or NPK). We attribute the larger volume of macropores to the improved root growth conditions in the soil with the higher nutrient level. We conclude that addition of animal manure at rates realistic in agriculture has only a modest effect on soil pore characteristics of the plough layer soil compared with the use of mineral fertilizers. For the subsoil below ploughing depth, a high level of nutrient application may increase soil macroporosity and near‐saturated hydraulic conductivity, but the origin of nutrients is of no significance. 相似文献
5.
MODELLING OF SOIL PORES AS TUBES USING GAS PERMEABILITIES, GAS DIFFUSIVITIES AND WATER RELEASE 总被引：1，自引：0，他引：1
B. C. BALL 《European Journal of Soil Science》1981,32(4):465-481
Two models are presented describing the air-filled continuous pores in soil and how they change with soil water potential. In the first model (A), the pores are represented by tortuous tubes of uniform radius. The radius, length and number are calculated from air permeability, relative diffusivity and air-filled porosity measured at each soil water potential. In the second model (B), the pores are represented by tortuous tubes of three radii joined at random in series. The radii and total lengths of the tube sections are estimated by comparison of air permeability, diffusion coefficient and air-filled porosity at each water potential with values calculated for a large number of theoretical systems. The models were applied to the results from undisturbed cores of a silt loam taken from 30 to 80 mm depth. For both models, the sequences of continuous pores were estimated to be 2 to 7 times as long as the sample but shortened as the sample dried. From the second model the average pore radius in direct drilled soil, 0.3 mm, was half that in ploughed soil and the minimum radius, 0.1 mm, was one-quarter that in ploughed soil. 相似文献
6.
7.
Soil compaction caused by traffic of heavy vehicles and machinery has become a problem of world-wide concern. The aims of this study were to evaluate and compare the changes in bulk density, soil strength, porosity, saturated hydraulic conductivity and air permeability during sugar beet (Beta vulgaris L.) harvesting on a typical Bavarian soil (Regosol) as well as to assess the most appropriate variable factors that fit with the effective controlling of subsequent compaction. The field experiments, measurements and laboratory testing were carried out in Freising, Germany. Two tillage systems (conventional plough tillage and reduced chisel tillage) were used in the experiments. The soil water contents were adjusted to 0.17 g g−1 (w1), 0.27 g g−1 (w2) and 0.35 g g−1 (w3).Taking the increase in bulk density, the decrease in air permeability and reduction of wide coarse pore size porosity (−6 kPa) into account, it seems that CT (ploughing to a depth of 0.25 m followed by two passes of rotary harrow to a depth 0.05 m) of plots were compacted to a depth of at least 0.25 m and at most 0.40 m in high soil water (w3) conditions. The trends were similar for “CT w1” (low soil water content) plots. However, it seems that “CT w1” plots were less affected than “CT w3” plots with regard to bulk density increases under partial load. In contrast, diminishments of wide coarse pores (−6 kPa) and narrow (tight) coarse pores (−30 kPa) were significantly higher in “CT w1” plots down to 0.4 m. Among CT plots, the best physical properties were obtained at medium soil water (w2) content. No significant increase in bulk density and no significant decrease in coarse pore size porosity and total porosity below 0.2 m were observed at medium soil water content. The soil water content seemed to be the most decisive factor.It is likely that, CS (chiselling to a depth of 0.13 m followed by two passes of rotary harrow to a depth 0.05 m) plots were less affected by traffic treatments than CT plots. Considering the proportion of coarse pore size porosity (structural porosity) and total porosity, no compaction effects below 0.3 m were found. Medium soil water content (w2) provides better soil conditions after traffic with regard to wide coarse pore size porosity (−6 kPa), air permeability (at 6 and 30 kPa water suction), total porosity and bulk density. Proportion of wide coarse pores, air permeability and bulk density seems to be suitable parameters to detect soil compaction under the conditions tested. 相似文献
8.
《Soil & Tillage Research》1988,11(1):1-18
With the increasing use of conservation tillage, many questions about the long-term effects of tillage system on soil physical properties have been raised. Studies were conducted to evaluate saturated hydraulic conductivity (KSAT), macropore characteristics and air permeability of two silty soils as affected by long-term conservation tillage systems in the state of Indiana. Measurements were taken during the tenth year of a tillage study on a Chalmers silty clay loam (Typic Haplaquoll) and the fifth year of a study on a Clermont silt loam (Typic Ochraqualf). Tillage systems were moldboard plow, chisel, ridge till-plant, and no-till in a rotation of corn (Zea mays L.) and soya beans (Glycine max L.). Saturated hydraulic conductivity was measured on large soil columns (25 × 25 × 40 cm) before spring tillage, and macropore size and continuity were assessed with staining techniques. Intact soil cores (8 cm diam × 10 cm) were collected in early July in the row and non-trafficked interrow at three depths (10–20, 20–30, and 30–40 cm) and were analyzed for air permeability (Kair), air-filled porosity and bulk density. Saturated hydraulic conductivity values were in the order plow > chisel > ridge till > no-till for the Chalmers soil and were significantly greater in the plow treatment than in the other 3 tillage systems on the Clermont soil. Differences in KSAT between the 2 soils were generally greater than differences among tillage systems, and coefficients of variation were lower for treatments that did not include may fall tillage operations. At the 10-cm depth on the Chalmers soil, the chisel treatment had the greatest number of stained cylindrical channels, whereas for the Clermont soil the ridge till had the greatest number at this depth. Although the no-till treatment had similar or fewer total channels, it had the most continuous channels from the 10-cm depth to the 20- and 30-cm depths on both soils. Tillage system, row position and depth all affected Kair. On the Chalmers soil, plow, chisel and ridge systems had lower Kair between rows than in the row at the 10–20-cm depth, whereas no-till had constant Kair in the row and between the row. On the Clermont soil, ridge till had the highest Kair of all treatments at the 10–20-cm depth, and no-till had the highest Kair of all treatments at the 20–30-cm depth. 相似文献
9.
Soil macropore dynamics affected by tillage and irrigation for a silty loam alluvial soil in southern Portugal 总被引：5，自引：0，他引：5
Soil tillage can have a significant effect on soil porosity and water infiltration. This study reports field measurements of near saturated hydraulic conductivity in an undisturbed soil under two tillage treatments, conventional tillage (CT) and minimum tillage (MT). The objective was to determine effective macro and mesoporosities, porosity dynamics during the irrigation season, and their contribution to water flow. Field observations were performed during the 1998 maize (Zea mays L.) cropping season in an Eutric Fluvisol with a silty loam texture, located in the Sorraia River Watershed in the south of Portugal. Infiltration measurements were done with a tension infiltrometer. At each location an infiltration sequence was performed corresponding to water tensions (φ) of 0, 3, 6 and 15 cm. Five sets of infiltration measurements were taken in both treatments in the top soil layer between May and September. One set of measurements was done at the depth of 30 cm at the bottom of the plowed layer in the CT plot. After 5 years of continuous tillage treatments the results show that regardless of the tillage treatment, saturated conductivity values K(φ0) were several times larger than near saturation conductivity K(φ3). This indicates that subsurface networks of water conducting soil pores can exist in both CT and MT maize production systems. In CT, the moldboard plow created macro and mesoporosity in the top soil layer while breaking pore continuity at 30 cm depth. This porosity was partially disrupted by the first irrigation, resulting in a significant decrease of 45% in the macropore contribution to flow. Later in the season, the irrigation effect was overlaid by the root development effect creating new channels or continuity between existing pores. In MT macroporosity contribution to flow did not show significant differences in time, representing 85% of the total flow. In both the treatments, macropores were the main contributing pores to the total flow, in spite of the very low macroporosity volumes. 相似文献
10.
D.T. PRITCHARD 《European Journal of Soil Science》1985,36(2):153-162
Gas diffusivity was measured in duplicate soil cores (10 cm long and 6 cm diameter) from depths of 0–10, 10–20 and 20–30 cm, and in beds of 1–2 mm aggregates taken from the same site at the same depths. A steady state method was used, with ethane as the diffusing gas. As the samples dried, the fractional air-filled pore space increased, from 0. 1 to 0.45 for the cores and from 0.35 to 0.65 for the aggregates. The maximum relative diffusivity of the aggregate samples (0.38) was approximately twice that of the core samples, reflecting the difference in pore space. Equations are presented for calculating the solid, air and water fractions of the samples and for calculating the diffusivity within peds and aggregates. These calculations allowed a comparison of the diffusion/porosity relationship within aggregates and peds. 相似文献
11.
An apparatus was constructed to measure diffusivity of krypton-85 and gas permeability in an enclosed core of soil of field structure or in other porous material. Sample enclosure decreased water loss by evaporation, reduced mass flow caused by changes in ambient temperature and pressure during diffusion measurement, and allowed subsequent measurement of gas permeability without further sample disturbance. When a bundle of tubes was used as a test sample to calibrate the apparatus, the resistances to diffusion and viscous flow agreed approximately with those calculated from the tube size and number. Gas movement was measured in dry sieved soil and in undisturbed cores of silty loam soil to illustrate the practical value of the method. In the dry cores, diffusivity relative to free air (DA/Do) was greater in ploughed soil, 0.18, than in direct drilled soil, 0.14, nearly in proportion to the greater air porosity in the ploughed soil, but air permeability in ploughed soil was four times greater than in direct drilled soil and was about 1 000 times greater than in compacted sieved soil. 相似文献
12.
A. P. HAMBLIN 《European Journal of Soil Science》1982,33(3):375-386
Surface horizons of two Australian alfisols which had been cropped for 3 years to wheat by zero, minimum and ploughed tillage were compared for differences in structure. Total porosities and pore size distributions differed between treatments, but values for water and air permeability, sorptivity, diffusivity and evaporation rate were not necessarily ranked in the same order. The stability of soil structure was usefully described by the ratio of water to air permeability (kw/ka), which indicated the relatively fragile nature of the ploughed structures, despite their initially greater proportion of coarse porosity. Time of sampling after seeding also influenced hydraulic properties which were found to vary significantly over a 10-week period. Variations in vertical distribution of organic matter between tillage treatments is postulated as influencing the differences in structural stability. 相似文献
13.
Abstract. There is a lack of information about the influence of tillage and time of sowing on N2 O and NO emission in cereal production. Both factors influence crop growth and soil conditions and thereby can affect trace gas emissions from soils. We measured fluxes of NO and N2 O in a tillage experiment where grassland on clay loam soil was converted to arable by either direct drilling or ploughing to 30 cm depth. We made measurements in spring for 20 days after fertilizer application to spring-sown and to winter-sown barley. Both were the second barley crop after grass. Direct drilling enhanced N2 O emission primarily as a result of restricted gas diffusivity causing poor aeration after rainfall. Deep ploughing enhanced NO emission, because of the large air-filled porosity in the topsoil. NO and N2 O emissions were smaller from winter sown crops than from spring sown crops. The three rates of N fertilizer application (40, 80 or 120 kg N ha–1 ) did not produce the expected linear response in either soil available N concentrations or in NO and N2 O fluxes. We attributed this to the lack of rainfall in the ten-day period after fertilizer application and therefore very slow incorporation and movement of fertilizer into and through the soil. 相似文献
14.
Despite the current global attention on biochar (BC) as a soil amendment, knowledge is limited on how BC impacts the physical properties of coarse-textured soils (sand > 95%), particularly in tropical regions. A two-season field-study was conducted to investigate the effect of rice straw BC (3% w/w) on water retention, gas transport and structure of a sand-textured tropical soil. We sampled 3 months and 15 months after BC application and measured wet- and dry-region soil water retention, air permeability and gas diffusivity at selected matric potentials. At all measured potentials and for both sampling times, soil water retention was significantly higher (20–150%) for the BC treatment due to increased fraction of smaller pores (< 30 µm) at the expense of macropores (< 100 µm). Although there was no consistent effect of BC on air-filled porosity, BC significantly reduced air permeability and gas diffusivity (~20%) at ?30 kPa matric potential. After 15-months, air permeability decreased by ~15% after BC amendment, but analyses of the pore structure revealed a more tortuous and complex soil structure. Thus, application of rice straw BC to similar coarse-textured soils will improve soil-water relations and over time provide better structure for agricultural purposes. 相似文献
15.
Many studies have reported impeded root growth in topsoil under reduced tillage or direct drilling, but few have quantified the effects on the least limiting water range for root growth. This study explored the effects of tillage intensity on critical soil physical conditions for root growth in the topsoil. Samples were taken from a 7-year tillage experiment on a Danish sandy loam at Foulum, Denmark (56°30′ N, 9°35′ E) in 2008. The main crop was spring barley followed by either dyer's woad (Isatis tinctoria L.) or fodder radish (Raphanus sativus L.) cover crops as subtreatment. The tillage treatments were direct drilling (D), harrowing 8-10 cm (H), and ploughing (P) to 20 cm depth. A chisel coulter drill was used in the H and D treatments and a traditional seed drill in the P treatment. Undisturbed soil cores were collected in November 2008 at soil field moisture capacity from the 4-8 and 12-16 cm depths.We estimated the critical aeration limit from either 10% air-filled porosity (εa) or relative gas diffusivity (D/D0) of 0.005 or 0.02 and found a difference between the two methods. The critical limit of soil aeration was best assessed by measuring gas diffusivity directly. Root growth was limited by a high penetration resistance in the D and H soils (below tillage depth). Poor soil aeration did not appear to be a significant limiting factor for root growth for this sandy loam soil, irrespective of tillage treatment. The soil had a high macroporosity and D/D0 exceeded 0.02 at field capacity. Fodder radish resulted in more macropores, higher gas diffusivity and lower pore tortuosity compared to dyer's woad. This was especially important for the H treatment where compaction was a significant problem at the lower depths of the arable layer (10-20 cm depth). Our results suggest that fodder radish could be a promising tool in the amelioration of soil compaction. 相似文献
16.
A silage corn crop was grown on field plots entering their 2nd-year cycle of zero tillage, and on control plots representing traditional tillage practices. Concurrent measurements of soil matric suction and water content were made under transient conditions of a draining profile without evaporation. The results indicated some similarity in the soil moisture characteristics of the untilled soils which produced high crop yields. The time rate of change of soil water content, the root extraction rate and the unsaturated hydraulic conductivity were always smaller in the zero-tilled plots than in the conventionally tilled plots. 相似文献
17.
Soil structural quality, compaction and land management 总被引：3，自引：0，他引：3
B. C. BALL D. J. CAMPBELL J. T. DOUGLAS J. K. HENSHALL M. F. O'SULLIVAN 《European Journal of Soil Science》1997,48(4):593-601
Soil compaction is a concern worldwide, particularly where compactible soils are used for intensive agriculture in a wet climate. We have investigated the impact of compaction and the associated changes in soil structural qualities on crop production and environmental pollution. The overall objective was to develop soil management systems that provide suitable conditions for crop growth and minimize environmental damage. We ran large-scale field experiments studying the preservation of structural quality in arable and permanent grassland, using management systems such as the control or elimination of field traffic and the application of conservation tillage and zero tillage. We measured bulk density, shear strength, cone resistance, macroporosity, relative diffusivity, air permeability and water infiltrability to identify soil qualities that could be used for selecting suitable soil management. Along with crop yield, we measured environmental impacts, such as the emissions of nitrous oxide from the soil, which require the interaction of soil structure and water content near the soil surface. Soil structure influenced wetness, which affected trafficability, compaction and nitrogen retention. Measurement of properties that affect fluid storage and transport, such as macroporosity, provided soil quality indices that helped in recommending suitable soil management systems. Spatial variation of structure associated with wheel-track locations could be estimated rapidly using a cone penetrometer. Variation was particularly important in determining crop yield consistency. Crop productivity and soil structural qualities were preserved best when field traffic was eliminated. A reduced ground-pressure system successfully minimized compaction in grassland but was less effective in an arable rotation. Unless traffic is eliminated, good timing of operations is the most effective way to preserve soil structural quality. 相似文献
18.
Mechanically loosened subsoil has been shown to be prone to recompaction. We addressed a sandy loam that had been mechanically loosened by a subsoiler to a depth of 35 cm in 1997 and again in 1998. Perennial grass/clover was grown with limited traffic intensity in 1999 and 2000. A recompaction experiment was conducted in 2001 and 2002 when the soil was grown with oat and winter wheat, respectively. Using the formerly loosened plots, on-land ploughing was compared with traditional mouldboard ploughing with the tractor wheels in the furrow. In addition, the loosened plots were either light-trafficked (<6 Mg axle load and <100 kPa inflation pressure) or heavy-trafficked (10–18 Mg axle load and 200 kPa inflation pressure), respectively. Finally, the soil loosened by non-inversion deep tillage was referenced with a conventional ploughing–harrowing tillage system that never received the subsoil treatment. The conventional treatment was also grown with the grass/clover in 1999 and 2000. On-land ploughing and light traffic was applied in 2001 and 2002 instead of traditional ploughing and traffic for the conventional treatment. Penetration resistance and bulk density was recorded in the field. Undisturbed soil cores were taken in 1998, 1999 and 2002 from the 7–14, 18–27 and 25–30 cm layer and used for measuring total porosity, pores >30 μm and air permeability at −100 hPa matric potential. The results showed that on-land ploughing mitigated recompaction of the upper part of the formerly loosened subsoil. In contrast, only small differences in recompaction between heavy and light traffic were observed. The mitigation of subsoil recompaction was needed for the loosened soil to provide an upper subsoil with similar—not better—pore characteristics than the non-loosened soil in the conventional treatment. The structural conditions in the plough pan improved for the conventional treatment from 1998 to 2002 as indicated by an almost doubling in air permeability. This was interpreted as being related to the growing of grass/clover ley in 1999 and 2000 combined with a shift from traditional tillage and traffic to on-land ploughing and light traffic when growing cereals in 2001 and 2002. Results on root growth and crop yield are reported in an adjoining paper. 相似文献
19.
The high input of mechanical energy in common agricultural practice can negatively affect soil structure. The impact of compaction (P) and rotovation (R) on soil pore characteristics was compared with those in soil from untreated reference (U) plots of a loamy sand soil receiving for 14 yr, either only mineral fertilizer (MF) or, in addition, animal manure (OF). Undisturbed soil cores were taken from two separate fields in consecutive years at an identical stage in the crop rotation. We measured soil organic carbon (OC), soil microbial biomass carbon (BC), and hot‐water extractable carbon (Chot). Water retention, air permeability and gas diffusivity were determined at ?100 hPa in both years and for a range of water potentials in one of the years. The continued addition of animal manure had increased OC, BC, and Chot compared with the soil receiving only mineral fertilizer. Soil under treatment OF had larger porosity than that from treatment MF. Treatment P eliminated this difference and significantly reduced the volume of macropores. This interaction between soil organic matter content and mechanical impact was also reflected in the gas diffusion data. Specific air permeability was mainly influenced by mechanical treatment. Modelling the diffusion data normalized to the inter‐aggregate pore space showed no significant treatment effects on pore‐connectivity, although there was a tendency of more water blockage in soil under treatment MF. More studies are needed to confirm this interpretation. Our studies indicate that organic manure increases soil porosity, but compaction reduces the related gas exchange effects to the level of compacted soils receiving mineral fertilizer. 相似文献
20.
In order to determine if soil hydraulic properties present a direction‐dependent behavior, undisturbed samples were collected at different horizons and orientations (vertical, diagonal [45°], and horizontal) in structured soils in the Weichselian moraine region in northern Germany. The water‐retention curve (WRC), the saturated hydraulic conductivity (kf), and the air permeability (ka) were measured. The air‐filled porosity (?a) was determined, and pore‐continuity indices (ka/?a, ka/?a2, N) and blocked porosities (?b) were derived from the relationship between ka and ?a. The development of soil structures with defined forms and dimensions (e.g., platy by soil compaction or prismatic up to subangular‐blocky by swelling–shrinkage processes) and the presence of biopores can induce a direction‐dependent behavior of pore functions. Although the pore volume as a scalar is isotropic, the saturated hydraulic conductivity and air permeability (as a function of air‐filled porosity) can be anisotropic. This behavior was observed in pore‐continuity indices showing that the identification of soil structure can be used as a first parameter to estimate if hydraulic properties present a direction‐dependent behavior at the scale of the soil horizon. 相似文献