首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Ferralsols under native vegetation have a weak to moderate macrostructure and a well-developed microstructure corresponding to subrounded microaggregates that are usually 80 to 300 μm in size. The aim of this study was to analyze how the hydraulic properties of a clay Ferralsol were affected by a change of structure when the native vegetation is cleared for pasture. We studied the macrostructure in the field and microstructure in scanning electron microscopy. The water retention properties were determined by using pressure cell equipment. We determined the saturated hydraulic conductivity, Ks, by applying a constant hydraulic head to saturated core samples, and the unsaturated hydraulic conductivity, K(Ψ), by applying the evaporation method to undisturbed core samples. Results showed a significant decrease in the water retained at −1 and −10 hPa from 0- to 40-cm-depth when the native vegetation is cleared for pasture. That decrease in the water retained was related to a smaller development of microaggregation and greater proportion of microaggregates in close packing. For smaller water potential, there was no difference of water retained at every depth between native vegetation and pasture. Pedotransfer functions established earlier for Brazilian Ferralsols and using clay content as single predictor gave pretty good results but the precision of the estimation decreased when the water potential increased. This decrease in the precision was related to the lack of predictor taking structure into account. Ks and K(Ψ) showed an upward trend with depth under native vegetation and pasture. Except at 0–7-cm depth between the Brachiaria clumps in the pasture where smaller Ks and K(Ψ) than at the other depth was recorded whatever land use, we did not record any significant difference of Ks and K(Ψ) at every depth between native vegetation and pasture. The upward trend shown by the hydraulic conductivity with depth was related to the increase in the development of microaggregation with depth.  相似文献   

2.
Soil compaction affects hydraulic properties, and thus can lead to soil degradation and other adverse effects on environmental quality. This study evaluates the effects of three levels of compaction on the hydraulic properties of two silty loam soils from the Loess Plateau, China. Undisturbed soil cores were collected from the surface (0–5 cm) and subsurface (10–15 cm) layers at sites in Mizhi and Heyang in Shaanxi Province. The three levels of soil compaction were set by increasing soil bulk density by 0% (C0), 10% (C1) and 20% (C2) through compression and hammering in the laboratory. Soil water retention curves were then determined, and both saturated hydraulic conductivity (Ks) and unsaturated hydraulic conductivity were estimated for all of the samples using standard suction apparatus, a constant head method and the hot-air method, respectively. The high level of compaction (C2) significantly changed the water retention curves of both the surface and subsurface layers of the Heyang soil, and both levels of compaction (C1 and C2) changed the curves of the two layers from the Mizhi site. However, the effects of compaction on the two soils were only pronounced below water tensions of 100 kPa. Saturated hydraulic conductivities (Ks) were significantly reduced by the highest compaction level for both sampled layers of the Heyang soil, but no difference was observed in this respect between the C0 and C1 treatments. Ks values decreased with increasing soil compaction for both layers of the Mizhi soil. Unsaturated hydraulic conductivities were not affected by soil compaction levels in the measured water volume ratio range, and the values obtained were two to five orders of magnitude higher for the Mizhi soil than for the Heyang soil. The results indicate that soil compaction could strongly influence, in different ways, the hydraulic properties of the two soils.  相似文献   

3.
Field experiments were conducted at the Alameda del Obispo Experiment Station of the Andalusian Autonomous Government, Córdoba, Spain, to compare the field-saturated hydraulic conductivity (Kfs) measured by four different techniques: constant-head well permeameter (CP), falling-head lined borehole permeameter (FP), twin-rings (TR) and disk infiltrometer (DI). For each technique, measurements under and outside the olive-canopy were compared in order to detect differences in Kfs. All techniques gave higher Kfs values under the canopy, but significantly higher only for FP and TR. Outside the canopy Kfs values obtained with CP and TR were significantly higher than those obtained with the FP and the DI methods, but the FP and the DI as well as the CP and the TR Kfs values were statistically the same. Under the canopy, Kfs values obtained with the TR method were significantly higher than those obtained with the other three techniques. Estimates of Kfs, however, are most comparable for DI and FP.  相似文献   

4.
It is widely recognized that saturated hydraulic conductivity is dominated by the micromorphology of soil pores rather than by the merely total porosity or dry bulk density. Nevertheless, some researchers are reporting that the decrease in saturated hydraulic conductivity of subsoil is simply associated with the decrease in soil porosity or increase in dry bulk density. Based on these understandings in published papers and on our preliminary field investigation, we assumed that micromorphology of soil pores in topsoils is subjected to be destroyed with continuous disturbance by frequent tillage while subsoils tend to be compacted without serious changes of micromorphology of soil pores. Thus, we focused on finding the dependence of saturated hydraulic conductivity on dry bulk density by separating the soils into tilled layer and compacted layer. The objective of this study was to describe the relationship between saturated hydraulic conductivity and dry bulk density using a theoretical model, the non-similar media concept (NSMC) model, capable of predicting saturated hydraulic conductivities of soils with different values of dry bulk densities. The study area was located near the Tone River in Saitama Prefecture, Japan, where the soils were classified into Haplic Brown Lowland Soils according to the Classification of Cultivated Soils in Japan (Eutric Fluvisol according to FAO/UNESCO). Two sites, where the topsoils were seasonally tilled while the subsoils were sustained as it is, and another site where the topsoil was seasonally tilled, too, but extra deep tillage (1 m tillage depth) had been done, were chosen for the measurements. The saturated hydraulic conductivities and dry bulk densities of undisturbed soil cores from different depths were measured in the laboratory. The NSMC model was carefully applied only when the soil textures were the same among samples. The well-known conventional equations formulated by Kozeny–Carman and by Campbell, were used to compare the applicabilities with the NSMC model. The NSMC model succeeded in predicting the saturated hydraulic conductivities in the compacted subsoils. On the other hand, the NSMC model was not applicable to the tilled topsoils and to the deeply tilled subsoil. The saturated hydraulic conductivity of tilled topsoils and deeply tilled subsoil was always lower than that of compacted subsoils at the same dry bulk densities. The Kozeny–Carman and Campbell equations both failed in the prediction of saturated hydraulic conductivity in subsoil. It was concluded that the saturated hydraulic conductivity of subsoils under compaction without extreme disturbance is well related with its dry bulk density by the NSMC model.  相似文献   

5.
Abstract. Soil hydraulic conductivities are frequently required for process-based modelling of the soil water regime. Field-saturated hydraulic conductivity was measured with the Guelph permeameter in 10 soil series with a range of structures and textures. The permeameter offers a range of options for calculating conductivities depending on soil conditions, particularly homogeneity of pore distribution within each horizon. However, even horizons described as massive or apedal were not sufficiently homogeneous to satisfy the boundary conditions entirely.
Hydraulic conductivities were calculated by the one head, fixed α* procedure; α* is an index of capillarity. No direct correlations were found between hydraulic conductivity and land use. However, the average hydraulic conductivity of coarse textured topsoils which were mainly under arable agriculture was less than that of the finer textured topsoils largely under grassland. Even limited structural development increased the hydraulic conductivities of fine textured, compact subsurface horizons. It is important to match the adopted procedure to the soil conditions both during the determination of flow rates in the field and in the subsequent analyses.  相似文献   

6.
Deep mouldboard ploughing to a depth of 0.45 m, gypsum (5 t ha−1) and double cropping wheat (Triticum aestivum) with a summer forage crop were applied individually, and in combination, to modify a hardsetting red-brown earth (Alfisol) used for flood-irrigated wheat production. The effects of these treatments upon water infiltration, storage and intake during irrigations, application efficiency, and depletion between irrigations were measured. Gypsum markedly increased saturated hydraulic conductivity (Ks) immediately after being applied in June 1984 but not in 1985. Mouldboard ploughing and double cropping had little effect on Ks. All Ks values were less than 0.5 m day−1. Plant available water content (PAWC) was increased by gypsum application and mouldboard ploughing after the initial irrigation in 1984, and by the three main treatments in 1985. The order in which the main treatments increased PAWC was: gypsum>mouldboard ploughing>double cropping. Water applied and water intake during irrigations were increased by mouldboard ploughing and gypsum during the first irrigation in 1984 by as much as 60 mm. Thereafter mouldboard ploughing, gypsum and double cropping had little effect on water intake, and only gypsum increased the amount of water applied in 1985. The ratio of water intake to water applied during irrigations (application efficiency) was increased by mouldboard ploughing to 59% in 1984; no treatment had values greater than 40% during 1985. Water depletion was significantly increased by mouldboard ploughing in 1984 and by gypsum and double cropping in 1985. Few significant interactions were found between the three main treatments, each of which would improve soil-water relations for crop growth, although the effect of mouldboard ploughing on soil-water relations declined after the first year. Despite substantial improvements after 2 years in some treatments, soil hydraulic properties were inadequate for optimal irrigated cropping.  相似文献   

7.
A no-tillage system was imposed on a structurally degraded fine-textured soil (Humic Gleysol) that had been under continuous corn with moldboard tillage for more than 20 years. After 3 years of no-tillage, several soil structural properties were compared with the conventional tillage treatment to assess whether the soil structure had improved.

No significant difference (P<0.05) was found between tillage treatments for the saturated hydraulic conductivity, porosity and penetration resistance in the surface 5 cm. Measurements of soil penetration resistance and in situ saturated hydraulic conductivity (Kwp) using the well permeameter method were sensitive to structural changes that had occurred at 5–20 cm depth. The Kwp at this depth was significantly greater in the moldboard treatment than in the no-tillage treatment. Resistance measurements indicated significantly greater soil strengths at 10–20 cm under no-tillage. Aggregate stabilities were assessed by wet sieving twice during the growing season. No-tillage resulted in larger soil aggregates, especially at the surface, compared with the moldboard tillage.

These data suggest that degraded soils with low structural stability may initially suffer further deterioration with the elimination of tillage, owing to the loss or reduction of mechanically formed pores.  相似文献   


8.
Soil structure and the saturated hydraulic conductivity of subsoils   总被引：1，自引：0，他引：1  
The saturated hydraulic conductivity, Ksat, was measured on soil samples collected from the plough layer and the subsoil. A range of naturally occurring soil bulk densities was obtained by sampling in different years, with different crops and within and without wheel-tracks, etc. It was found that, for the plough layer, quite good linear relationships exist between the logarithm of Ksat and the bulk density. However, for the subsoils, the value of Ksat usually lies above the regression line for found for the corresponding plough layer. This “excess” hydraulic conductivity of subsoils is attributed to the presence of biopores, especially root channels. The lower hydraulic conductivity of the plough layer, relative to the subsoil, is attributed to the destruction of these biopores by tillage. A simple model for the separate contributions of soil texture and root channels to the overall value of Ksat is presented. It is concluded that subsoil tillage could cause significant reductions in Ksat with potentially serious environmental consequences unless it is repeated periodically.  相似文献   

9.
Determining temporal changes in field-saturated hydraulic conductivity (Kfs) is important for understanding and modeling hydrological phenomena at the field scale. Little is known about temporal variability of Kfs values measured at permanent sampling points. In this investigation, the simplified falling head (SFH) technique was used for an approximately 2-year period to determine temporal changes in Kfs at 11 permanent sampling points established at the surface of a sandy loam soil. Additional Kfs measurements were obtained by the single-ring pressure infiltrometer (PI) technique to also compare the SFH and PI techniques. The lowest mean values of Kfs, M(Kfs), were detected in December and January (20.5 ≤ M(Kfs) ≤ 146.2 mm h−1), whereas higher results (190.5 ≤ M(Kfs) ≤ 951.9 mm h−1) were obtained in the other months of the year. The Kfs values were higher and less variable in the dry soil (θi ≤ 0.21 m3 m−3, M(Kfs) = 340.6 mm h−1, CV(Kfs) = 106%) than in the wet one (θi > 0.21 m3 m−3, M(Kfs) = 78.4 mm h−1, CV(Kfs) = 185%). Both wet and dry soil were less conductive at the end of the study period than at the beginning one but a more appreciable change was detected for the dry soil (Kfs decreasing by 83.4%) than for the wet one (Kfs decreasing by 63.0%). The simple SFH technique yielded Kfs results similar to the more laborious and time-consuming PI technique (i.e., mean values differing at the most by a factor of two). It was concluded that (i) the soil water content was an important factor affecting the Kfs results obtained in a relatively coarse-textured soil, (ii) the impact of time from the beginning of the experiment on the saturated hydraulic conductivity was larger for a repeated sampling of dry soil than of wet soil and (iii) the SFH technique yielded reliable Kfs results in a relatively short period of time without the need for extensive instrumentation or analytical methodology.  相似文献   

10.
Tillage action associated with liquid slurry application systems/management practices can modify soil infiltration properties. The degree or nature of such modification will depend largely on the type of tillage implement used, and the soil conditions at time of tillage activity. The specific objective of this study is to evaluate differences in soil infiltration properties, as measured using pressure infiltrometers and Guelph permeameters, resulting from the immediate tine action of two commonly used slurry application tillage implements (Kongskilde Vibro-Flex (S-tine) and the AerWay SSD (rolling aerator-type tine)) over a variety of silt–clay loam soil water content conditions. The results indicated that there were consistent negative correlations between field saturated hydraulic conductivity and soil water content for all tine-disturbed and undisturbed soil treatments. For Kongskilde, field-saturated hydraulic conductivity was, on average, lower in tine-influenced furrow bottoms, relative to those measured in undisturbed conditions at similar depths for most water content conditions. Generally, the Kongskilde tine-action reduced macropore-based infiltration in the bottom of the furrow for most soil conditions, albeit, this effect was most pronounced at the higher soil water contents. For AerWay, the tine-disturbed soils had generally higher field saturated hydraulic conductivities than undisturbed soil treatments over the observed water content range. This effect was manifested to a greater degree at higher, relative to lower observed water contents.  相似文献   

11.
A new field method of obtaining, with minimal disturbance, the unsaturated hydraulic conductivity ( K0 ) and sorptivity ( S0 ) from unconfined disc permeameter measurements is introduced. Conventionally, the sorptivity is obtained from the initial square-root-of-time behaviour of discharge from the disc permeameter. In some cases this can be difficult to measure, in part because multi-dimensional flows approach quasi-steady state very rapidly. As an alternative we extend the ponded twin-ring method to unsaturated discs of several radii. This method has the advantage that only long-time, quasi-steady discharges are needed to obtain K0 and S0. In the present study, the two methods are tested using data obtained for a fine sandy loam at a supply potential ( Ψ0 ) of – 35 mm and agreement is good.  相似文献   

12.
Knowledge of hydraulic properties is essential for understanding water movement in soil. However, very few data on these properties are available from the Loess Plateau of China. We determined the hydraulic properties of two silty loam soils on agricultural land at sites in Mizhi and Heyang in the region. Undisturbed soil cores were collected from seven layers to one meter depth to determine saturated hydraulic conductivity, soil water retention curves and unsaturated hydraulic conductivity (by the hot-air method). Additional field methods (internal drainage and Guelph permeameter) were applied at the Heyang site to compare differences between methods. Soil water retention curves were flatter at Mizhi than at Heyang. Water contents at saturation and wilting point (1500 kPa) were higher at Heyang than at Mizhi. However, unsaturated hydraulic conductivity was lower at Heyang than at Mizhi, with maximum differences of more than six orders of magnitude. Nevertheless, the two soils had similar saturated hydraulic conductivities of about 60 cm day− 1. Comparison between the methods showed that soil water retention curves obtained in the laboratory generally agreed well with the field data. Field-saturated conductivities had similar values to those obtained using the soil core method. Unsaturated hydraulic conductivities predicted by the Brooks–Corey model were closer to field data than corresponding values predicted by the van Genuchten model.  相似文献   

13.
Despite our best efforts to reduce the waste stream, there will always remain some residues which cannot be further treated and must be disposed in landfills. One critical aspect of landfill construction is the integrity of the landfill liner. Current landfill liner technology includes a composite liner which consists of a FML component and a compacted soil component. The primary characteristic for selecting a soil for use in composite liner construction is that the soil have a saturated hydraulic conductivity of 1 × 10?7 cm s?1 or less. In the present study the effects of desiccation cracks on the hydraulic conductivity of the compacted soil were measured. Two soils of diverse mineralogy and typical of soils used for clay liner construction were selected for use. Each was tested in its native state plus after the addition of 30% sand. Laboratory measurements were made of the volumetric shrinkage of each soil. In addition, the hydraulic conductivity was determined using 10 cm diameter fixed wall permeameters. Additional conductivity measurements were made using 60 cm diameter fixed wall double ring permeameters which had been exposed to 0, 1, and 2 periods of desiccation prior to hydraulic conductivity determinations. The data show that laboratory measurements using 10- cm diameter fixed wall permeameters underestimate the hydraulic conductivity of the same soils when packed in large diameter permeameters. It was also found that exposure to two cycles of desiccation resulted in large increases in hydraulic conductivity. The time required to reach a steady outflow volume decreased as the amount of desiccation increased. The hydraulic conductivities of soils which had been allowed to dry were greater than those which were not allowed to dry prior to measurement. The relationship between volumetric shrinkage and the increase in hydraulic conductivity after desiccation indicates that soils which exhibit less than 11% shrinkage in the laboratory, exhibit increases in K of less than a factor of 2 upon desiccation. Clay soils with greater than 11% shrinkage can potentially be amended with sand to decrease the volumetric shrinkage and their response to desiccation.  相似文献   

14.
Alfisols exhibit a high degree of spatial variability in their physical properties. As a result, it is difficult to use information on physical parameters measured at one location to model larger-scale hydrologic processes. In this study, the saturated hydraulic conductivity, KS , of an Alfisol was determined on 109 undisturbed monoliths using the falling-head permeameter method. The model developed by Arya & Paris (1981) was used to calculate the pore volume from sand and clay fractions. Scaling factors were calculated from the measured Ks , sand pore-volume, clay pore-volume, clay content and effective porosity, using the similar media concept. Prediction of Ks of gravelly Alfisol using clay pore-volume is confounded by high gravel content which, when discounted, improves the prediction remarkably. The scaled mean saturated hydraulic conductivity K* for all horizons of the Alfisol was approximately l.0x 10−5ms−1.  相似文献   

15.
The purpose of the present study was to compare two methods for estimating the hydraulic conductivity near saturation with disc permeameters, and to identify their merits when studying runoff on sloping land. The soil's hydraulic conductivity (K) was measured with disc permeameters at a sequence of nominal pressures (ψ) in three blocks with average slope gradients of 11.0% (two occasions), 21.5% (two occasions) and 29.3% (one occasion), respectively, within a sloping area, 40 m wide and 100 m long. Two different methods were used. In the first, the split‐location method, the permeameter was moved to an adjacent spot after measurement at each applied ψ. The estimate of K(ψ) was based on measured sorptivity, steady‐state volumetric flow, initial volumetric water content and the volumetric water content at the applied ψ. In the second method, the one‐location method, the permeameter was not moved during the measurements at each sequence of applied ψ and the estimate of K(ψ) was based only on steady‐state volumetric flow and piece‐wise application of the exponential relation between K and ψ. The latter method generally gave smaller estimates of K than the former on the gentle slopes. These differences were smaller or negligible on steeper slopes. The slope gradient and the conditions in the uppermost soil layers had a definite influence on the values of K obtained. The one‐location method is recommended in studies in which disturbance of the soil surface must be kept to a minimum, as is the case in experimental plots.  相似文献   

16.
The main objective of this study is to determine if bottom ashes of dried sludge cakes (SCbash) could be used as landfill cover or liner, a function which is normally performed with clay. Laboratory tests were performed to determine its particle size distribution, Atterberg limits, compaction characteristics, hydraulic conductivity, and shear strength parameters. The effects of desiccation and freeze–thaw on the hydraulic conductivity of SCbash were also examined. The results of this investigation proved that properly compacted and stabilized SCbash has the required properties to be used in landfill covers or liners. The SCbash can be compacted into a dense mass with a low hydraulic conductivity of the order of 1.15×10−7 m/s. The compacted SCbash showed also a good resistance to the increase in hydraulic conductivity caused by desiccation and freeze–thaw as compared to other compacted clays. The results also indicated that the compacted SCbash has greater shear strength as typically expected for compacted clay, and therefore is likely to remain stable on a typical landfill slope designed and based on clay shear strength.  相似文献   

17.
塔里木沙漠公路防护林带土壤入渗研究   总被引：1，自引：0，他引：1  
为了探明塔里木沙漠公路防护林带咸水灌溉土壤入渗特性,在塔里木沙漠公路防护林带内选取5种不同种植年限的土壤,并取3种不同矿化度水,应用Guelph入渗仪测定土壤水分入渗过程,并进行模型拟合与分析。结果表明:不同种植年限对土壤初始入渗速率、饱和导水率有显著影响,尤其是0-10cm,10-15cm层土壤,随着种植年限增加土壤初始入渗速率、饱和导水率呈减小趋势。咸水灌溉条件下,土壤饱和导水率较淡水大。不同深度土壤入渗特性有差异,表现为25-40cm,40-60cm层土壤饱和导水率较其他层大。用常用的入渗模型对入渗过程进行模拟,可以发现通用经验模型对研究该区域土壤入渗有最好的适用性,Kostiakov模型也较适用,Horton模型在该区域土壤入渗研究中适用性相对较差。  相似文献   

18.
The effects of conservation tillage (CT) systems on crop production and erosion control have been well documented, but limited information is available concerning the effects of different CT systems on the hydraulic properties of layered soils. The effects of three CT treatments: chisel (CH), no-tillage (NT) and till-plant (TP) as compared with conventional modlboard plowing (CN) were investigated on a Griswold silt loam soil (Typic Argiudoll), formed in loess overlaying glacial till. Hydraulic properties were determined in situ. In addition, hydraulic conductivity was determined in the laboratory where more detailed hydraulic conductivity changes were monitored for the lower soil moisture tension range near soil saturation.

At or near saturation, there was no difference in hydraulic properties for all four tillage treatments. For example, mean saturated hydraulic conductivities (from laboratory determination) were 25.5, 25.1, 24.2 and 22.8 cm day−1 for CN, CH, TP and NT, respectively. However under unsaturated conditions, tillage treatments and soil layering (discontinuity between surface loess and glacial till beneath) affected hydraulic properties. In situ hydraulic conductivity (K) ranked CH>CN = NT = TP for the 0.32–0.33 m3 m−3 moisture content range. There were no differences in K for all treatments at other moisture ranges considered and at moisture contents 0.31 m3 m−3, in situ specific moisture capacity was, however, significantly lower in NT than in the other three treatments. Throughout the 20-day free drainage period for in situ K determination, the effect of layering is exhibited by the mean K values at the 50-cm depth being higher than those at 25 cm. There were negligible treatment-block interaction effects on the hydraulic properties as the soil became drier. Spatial variability in hydraulic properties was also noted for all treatments and soil depths considered.  相似文献   


19.
Compacted clay liners are commonly used as components of the lower portion of composite double liner systems for hazardous waste containment. Because the overlying leachate collection and removal systems and the FMLs are not perfect leachate still comes into contact with the lower liner and thus makes it critical that the clay liner component be constructed to achieve the lowest possible hydraulic conductivity. This research was conducted to evaluate the effects of clod size on the hydraulic conductivity of compacted soils and the uniformity of conductivity with depth within a lift of compacted soil. Two subsoils, one from the Beaumont series (smectitic) and one from the Kosse series (kaolinitic), were evaluated in the laboratory and then compacted in large fixed wall permeameters using maximum clod sizes of <2.5, <5.0, and <7.5 cm to a compacted lift thickness of 23 cm. Measurements were made of the hydraulic conductivity of the entire lift, the lower two thirds of the lift, and the lower one third of the lift. The results show that the conductivity of the lower one third of the lift can be as great as 8.7 times that measured for the entire lift and indicates that liners need to be constructed using thin lifts to achieve more uniform low conductivity throughout the liner. The data also indicated that under the carefully controlled conditions of this study and with the clod sizes used, the clod size did not have a significant effect on the hydraulic conductivity of the soils tested. Soil bulk density was poorly correlated with hydraulic conductivity and indicates that measuring the bulk density of a compacted soil is an inadequate method for assuring low hydraulic conductivity. Measurements of the time to the first appearance of leachate indicated that 8 to 17 d are required for water to penetrate a 23 cm thick compacted liner with an average conductivity of 1 × 10?7 cm s?1.  相似文献   

20.
For many centuries manure application to the soil has been common practice. Organic amendments and fertiliser applications can increase crop yields and soil organic matter (SOM). However, the long-term impacts on soil physical fertility are often neglected. This study was carried out on the Broadbalk Wheat Experiment at Rothamsted, UK, established in 1843 on an Aquic/Typic Paleudalf soil. Application of farmyard manure (FYM), N fertiliser and wheat straw on total organic C (CT), labile C (CL) and non-labile C (CNL), total N (NT), mean weight diameter (MWD) and unsaturated hydraulic conductivity (Kunsat) were studied on wheat (Triticum aestivum) and adjacent woodland and pasture areas. Manure additions, N fertiliser and straw incorporation increased all C fractions, particularly the CL fraction. The addition of 35 t ha−1 year−1 of FYM increased CT to 2.5 times that of the control (no fertiliser) treatment and CL to 5 times that of the control. With highest N application and straw returned, CT increased by 1.3 times and CL by 1.5 times that of the control treatment. There were linear relationships between rate of N fertiliser applied and all C fractions, with the rate of increase almost double with straw than straw removed. Manure application improved MWD, as did high N fertiliser additions with straw returned. Application of N fertiliser only increased MWD and Kunsat (at 10 mm tension) if straw was returned, while the addition of manure resulted in decreased Kunsat. The highest Kunsat rate was on the high N fertiliser, straw returned treatments. The uncropped areas all had high soil structural stability. Similar relationships occurred between all C fractions and NT and MWD for the high C soils, but relationships were much stronger with CL than the other C fractions in the low C soils. These results showed that soils with low C concentration are more reliant on CL for structural stability.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号