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101.
102.
Soil catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles. We quantified differences in these redistribution processes along granitic catenas across an arid to sub-humid climate gradient in Kruger National Park, South Africa. We measured soil properties in nine catenas sampled from three areas receiving annual rainfall of 470 mm (arid zone), 550 mm (semi-arid zone) and 730 mm (sub-humid zone). As rainfall increased, kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the catenas. Toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid catenas but complete prevalence of kaolinite in toeslopes of sub-humid catenas. The concentration and distribution of clay along the catenas were dependent on landscape position as well — soil profiles at and near the crests were clay depleted (as low as 1%) while those at the toeslopes had much more clay (up to 60%). Clay redistribution along catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites. As a consequence, the sub-humid catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils. In contrast, arid zone catenas showed little clay redistribution and semi-arid sites displayed the greatest within-catena clay redistribution and preservation. Clay movement and storage conditioned other soil properties such as CEC, base cation distribution, base saturation and pH. 相似文献
103.
104.
乌拉盖水库工程天然建筑材料调查与评价 总被引:1,自引:0,他引:1
水利水电工程一般多因地制宜、就地取材,有的当地天然建筑材料甚至成为决定建筑物类型和工程造价的决定性因素。本文分析了区域地形、地貌、地层、岩性等,通过地质调查、钻探、坑探等勘察手段,在前人工作程度很低的地区寻找到了设计需要的建造土坝的各种材料。同时,使用野外和室内土工实验方法,研究了这些建材的物理、力学性质。在此基础上根据平均厚度法和设计、规范标准对各料场建材进行了计算和评价,其质量和数量均满足要求,为本工程设计和施工提供了可靠的建材依据。 相似文献
105.
M. I. Bajwa 《Journal of Agronomy and Crop Science》1987,158(1):65-68
Comparative fixation of NH4 and K by wetland rice soils in relation to clay mineral composition and treatment sequence is of agronomic interest, but information on the subject is scanty. An attempt has been made to clarify this relationship by employing the normally recommended doses of fertilizers, 3 application sequences, and 5 soil clays of divergent mineralogies. The results show that montmorillonitic clay is the greatest fixer of NH4 , but least of K. X-ray amorphous clay also prefers NH4 over K. Vermiculitic and beidellitic clays strongly fix both NH4 and K. Soil clay consisting of hydrous mica, chlorite, and halloysite fixes low proportions of applied NH4 and K. The sequence in which NH4 and K are applied does not appear to affect the relative amounts that are fixed. 相似文献
106.
Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double-ring infiltrometers and tensiometers, respectively, on two sandy loams in north-east Scotland. The time to ponding for constant-rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (-2 to - 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation. 相似文献
107.
泥浆的排水固结变化对水坠坝筑坝过程中坝体排水系统的合理布设具有重要的指导作用。将中粉质壤土以1∶1,1.5∶1和2∶1的土水比制成泥浆,并将制得泥浆分别填充在高度为50,100,150和200cm的聚乙烯波纹管中,对其排水量、上析水量、下渗水量和固结沉陷量等指标进行测定。结果表明,同一土水比的泥浆,上述指标随着泥浆填充高度的增加而增大;同一泥浆填充高度,上述指标随着土水比的增大而减小。泥浆的排水量、固结沉陷量主要集中于前24h,排水量最大可占总排水量的89.48%,固结沉陷量最大可占总固结沉陷量的93.24%。因此,在实际筑坝过程中土水比较小时,应注重坝体泥浆的前期排水,并加强表层排水;土水比较大,充填高度较小时,可考虑不布设坝体泥浆表层排水措施,而要加强下渗水的排水措施。 相似文献
108.
Dr Erasmus Otabbong Katarina Börling Thomas Kätterer Lennart Mattsson 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(4):373-378
Abstract Plant-available P was first extracted in soils 114 years ago and a number of different analytical methods have since been developed, but for good reasons none of these methods has been adopted as a standard for all soils. With increasing cooperation within research, there is a need to harmonise the interpretation of analytical data for fertiliser recommendations, research, and environmental control. This paper evaluates the compatibility of the Swedish standard ammonium lactate (PAL) method and the widely used Olson's sodium bicarbonate (POls) method in 82 topsoil samples taken from Swedish long-term soil fertility field trials. The PAL-values were usually larger than POls, with a mean PAL/POls quotient of 2.30±1.04 (0.67–6.58). The PAL and POls means and ranges were 126±89 (5–360) and 55.1±33 (3.1–122.8) mg P kg?1 dry soil, respectively. Stepwise multiple linear regression analysis was used to evaluate the relationship between PAL and POls and how this relationship was affected by clay content, pH, and soil organic carbon content (SOC). After statistical transformation, it emerged that the square root of clay content (17.4%±13.82, range 1–54.4) and pH (6.45±0.54, range 5.5–7.7) significantly affected the relationship at partial R 2-values of 2 and 12%, respectively, while ln(SOC) (2.54%±1.21, range 1–6.03) did not, apparently due the narrow range. The regressions of predicted vs. measured values explained 95 and 94% of the variation in PAL and POls, respectively. The mean deviation of predicted compared with measured values was 21.3 and 8.3 mg P kg?1 dry soil for PAL and POls, respectively, corresponding to 20 or 19% of the measured values. We conclude that a data set consisting of PAL-values can be converted into POls-values and vice versa with reasonably high accuracy when accounting for clay content and pH. 相似文献
109.
Tetsuya Eguchi 《Soil Science and Plant Nutrition》2013,59(1):52-64
We examined soils derived from volcanic ash of Kikai-Akahoya tephra on Yakushima Island, Japan, and classified them according to the Unified Soil Classification System of Japan, 2nd Approximation (USCSJ 2nd) and the World Reference Base for Soil Resources (WRB). Five pedons with horizons showing high (>20%) volcanic glass content were investigated. Soils developed under evergreen broad-leaved forests had high acid oxalate-extractable aluminum (Alo) and acid oxalate-extractable silicon (Sio) concentrations, and low acid oxalate-extractable iron (Fe)/dithionite-citrate-extractable Fe ratio. This indicates a warmer climate and less severe leaching conditions compared with soils developed under coniferous forests dominated by Cryptomeria japonica and grasslands dominated by Pseudosasa owatarii. All soils contained considerable amount of hydroxyl-Al-interlayered 2:1 clay minerals. The surface horizons of the pedons developed under the cool-temperate C. japonica forests contained smectite as a result of podzolization. However, the surface horizon of the pedon developed under cool-temperate P. owatarii grasslands did not contain smectite. All pedons belonged to the Kuroboku soils great group (USCSJ 2nd) and Andosols (WRB). Pedons in mountainous areas did not contain horizons with more than 6?g?kg?1 of Sio and hence were classified as non-allophanic Andosols. In mountainous areas, it was observed that allophane formation was inhibited by Al leaching due to intense rainfall (>10,000?mm year?1); Al consumption due to the formation of the Al-humus complex; and Al incorporation into the interlayers of vermiculite. The low soil water pH [pH(H2O)] and leaching of silicon (Si) in mountainous areas would support these anti-allophanic effects. 相似文献
110.
[目的]获得适合测定甘肃景泰灌区砂壤土pH的浸提液、水土比及静置时间。[方法]通过设定不同浸提液、水土比及静置时间,研究它们对甘肃景泰砂壤土pH的影响。[结果]2种浸提液测定结果间存在0.05水平显著差异;不同水土比2.5∶1.0与1.0∶1.0、5.0∶1.0与2.5∶1.0间无显著性差异,5.0∶1.0与1.0∶1.0存在0.01水平显著差异;土壤pH随静置时间的延长而增大,样品pH在静置0.5~5.0 min后变化相对较大,5.0~60.0 min时间内有所增大,但增大幅度不大,基本达到稳定。[结论]在测定该地区土壤pH时,可以在持续搅拌3 min后静置5 min时测定。 相似文献