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81.
湖北省几种土壤的重金属镉、铜形态 总被引:17,自引:1,他引:17
研究了湖北省棕红壤、黄棕壤和和黄褐土中重金属镉、铜的形态差异,分析了重金属负荷水平对土壤重金属形态的影响,结果表明:未污染土壤中重金属镉、铜主要为氧化铁结合态和残渣态,占土壤重金属全量的75%以上;交换态镉含量与土壤pH呈负相关,从未污染土、污染土到镉质土,随土壤Cd负荷提高,土壤中交换态、碳酸盐结合态镉的比例增大,有效地提高,残渣态、氧化铁结合态镉的比例降低,土壤中铜有相似的变化趋势。 相似文献
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砂土供磷特性及磷肥效应的研究结果表明,砂土磷的活度在0.64~1.39之间,土壤磷素活性高低的顺序为轻砂潮土>细砂潮土>粗砂潮土。砂土磷素形态以无机磷为主,有机磷甚少,仅占全磷含量的8.84%,无机磷占91.15%。无机磷形态组成以磷酸钙为主,Ca-P 平均为无机磷总量的86.1%,O-P 占9.6%,Al-P 占3%,Fe-P 占1.3%,各种形态无机磷与速效磷的关系为:y(速效磷)=49.30x_1(Al-P)+21.854 7x_4(Ca-P)-3.420 9。Al-P 和 Ca-P 对砂土速效磷的贡献具有一定的意义。磷酸铁铝和磷酸钙盐均可以作为砂土磷素的给源。砂土全磷和有效磷的消长决定于磷素收支平衡。施入土壤中磷的形态转化主要受土壤本身性质的制约。磷肥的作用主要在作物生育前期,而在中、后期则更多地吸收利用土壤中的磷素。磷肥肥效随土壤供磷水平和速效磷含量的增高而降低,粗、细砂潮土中磷肥对小麦的肥效分别比轻砂潮土高41.1%和17.7%。 相似文献
85.
Agroforestry systems have the potential to increase sequestration of atmospheric carbon dioxide (CO2) as soil organic carbon (SOC) because of the increased rates of organic matter addition and retention. However, few studies have characterized the relative stability of sequestered SOC in soil. We characterized SOC storage in aggregate size and chemical stability classes to estimate the relative stability of SOC pools after the addition of Leucaena-KX2 pruning residues (mulch) from 2006 to 2008 in a shaded coffee agroforestry system in Hawaii. Soil samples were separated by microaggregate isolation, density flotation and dispersion, and acid hydrolysis, resulting in five distinct fractions that differed in relative stability: coarse particulate organic matter (POM), fine POM, microaggregate-protected POM, silt + clay hydrolyzable soil organic matter (SOM), and silt + clay non-hydrolyzable SOM. With mulch addition, the fine POM fraction increased. There was also a shift in the proportion of SOC to more stable silt + clay fractions. In the absence of mulch there was no significant change in SOC fractions. Given that the turnover time of SOC in silt + clay fractions is on the order of decades to centuries, the potential benefits of active shade management and mulching compensate for the loss of C sequestration in tree biomass from pollarding. 相似文献
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陕北不同土地利用类型下土壤无机磷形态分布及有效性研究 总被引:2,自引:0,他引:2
采用蒋柏藩-顾益初无机磷分级方法,对黄土高原两种农田土壤剖面(0~100 cm)中无机磷形态分布特征进行了研究.结果表明:两种农田土壤剖面(0~100 cm)中无机磷形态占全磷的90.95%;无机磷又以Ca-P为主,所占比例在87.86%~92.55%之间;糜子地土壤剖面中无机磷总量、Ca2-P、Ca8-P、Al-P和... 相似文献
88.
花岗岩地区坡耕地径流泥沙观测试验研究 总被引:1,自引:0,他引:1
本文总结分析了三年来对花岗岩地区坡耕地径流泥沙的观测试验资料, 得出以下结论: 1.荒坡地的泥沙流失量大于作物地; 2.作物地覆盖度低于30%以下则比荒坡地的泥沙流失量要大; 3.大于25°的坡耕地, 头两年产量虽然较好, 但第3年以后产量大幅度下降, 并造成大量的泥沙流失, 故种多年生植物为佳。 同时通过试验研究表明: 在花岗岩地区, 泥沙流失量多数来源于坡耕地。 因此搞好坡耕地的综合治理, 是防治水土流失提高单位面积产量的关键措施。 相似文献
89.
Runoff and sediment losses from rough and smooth soil surfaces in a laboratory experiment 总被引:5,自引:0,他引:5
Soil surface roughness may significantly impact runoff and erosion under rainfall. A common perception is that runoff and erosion are decreased as a function of roughness because of surface ponding and increased hydraulic roughness that reduces effective flow shear stress. The objective of this study was to measure the effects of initial surface roughness on runoff and erosion under controlled laboratory conditions. Initially, rough and smooth surfaces were exposed to five simulated rainfall applications at 5% and 20% slopes. In all cases, runoff was delayed for the case of the initially rough surface; however, this effect was temporary. Overall, no statistical differences in either total runoff or erosion were measured on the 20% slope. At 5% slope, runoff was less on the rough surface for the first rainfall application but greater on the final three, probably due to the formation of a depositional seal in that case. This resulted in an overall insignificant difference in runoff for the sum of the five rainfall applications. Erosion was greater on the rougher slope at 5% steepness, probably due to concentration of flow as it moved around the roughness elements on the rougher slope. These results indicate that commonly held perceptions of the impact of soil surface roughness on runoff and erosion may not be entirely correct in all cases. 相似文献
90.
Rice fields are an important source for atmospheric CH4, but the effects of fertilization are not well known. We studied the turnover of CH4 in rice soil microcosms without and with addition of potassium phosphate. Height and tiller number of rice plants were higher in the fertilized than in the unfertilized microcosms. Emission rates of CH4 were also higher, but porewater concentrations of CH4 were lower. The δ13C values of the emitted CH4 and of the CH4 in the porewater were both 2-6% higher in the fertilized microcosms than in the control. Potassium phosphate did not affect rate and isotopic signature of CH4 production in anoxic soil slurries. On the other hand, roots retrieved from fertilized microcosms at the end of incubation exhibited slightly higher CH4 production rates and slightly higher CH4-δ13C values compared to roots from unfertilized plants. Addition of potassium phosphate to excised rice roots generally inhibited CH4 production and resulted in increasingly lower δ13C values of the produced CH4. Fractionation of 13C during plant ventilation (i.e. δ13C in pore water CH4 versus CH4 emitted) was larger in the fertilized microcosms than in the control. Besides plant ventilation, this difference may also have been caused by CH4 oxidation in the rhizosphere. However, calculation from the isotopic data showed that less than 27% of the produced CH4 was oxidized. Collectively, our results indicate that potassium phosphate fertilization stimulated CH4 emission by enhancing root methanogenesis, plant ventilation and/or CH4 oxidation, resulting in residence times of CH4 in the porewater in the order of hours. 相似文献