硫对石灰性土壤化学性质的影响

通过连续两茬油菜盆栽试验,分析了硫对土壤pH、电导率、交换性阳离子和水溶性阴离子等指标的影响.结果表明：硫能显著降低土壤pH、增加土壤电导率;施硫会使土壤交换性Na⁺和交换性K⁺含量升高,并加剧土壤水溶性阴离子总量的累积;施硫对交换性Ca²⁺和Mg²⁺含量影响较小,也未能显著改变土壤阳离子交换量和土壤碱化度.与尿素相比,硫包膜尿素对土壤pH和电导率的影响不显著,但对交换性阳离子和水溶性阴离子影响较大;与尿素处理相比,施硫未表现出明显的增产效应;施硫较多时,油菜产量显著降低.     

The effects of soil moisture at the time potato tubers are forming on the incidence of common scab (Streptomyces scabies)

Two complementary field experiments at Rothamsted in 1965, with the potato variety Majestic, related the incidence of common scab (Streptomyces scabies) to rainfall, soil moisture and time of tuber formation. In plots where the soil was maintained at field capacity (less than 10 cm. Hg moisture tension) by watering, tubers had little or no scab; infection increased in amount on plots allowed to dry to 30 cm., 50 cm. or more Hg moisture tension during late June. The time tubers formed was varied by planting sprouted (chitted) and non-sprouted seed tubers, and tuber development and scab incidence were observed on sample plants lifted at frequent intervals from unwatered plots. Scab lesions were first seen on 12 July when the distribution of lesions on the surface of tubers was affected by size of tuber both within and between the different seed-tuber treatments. These differences were correlated with estimates of tuber size on 28 June, the beginning of the first dry period. Tubers 1.0 cm. or more in diameter on 28 June had few or no lesions at the stolon attachment (heel) end of tubers on 12 July, whereas tubers smaller than this on 28 June had many lesions in this region on 12 July. The larger the tuber was on 28 June, the greater was the area free from scab lesions on 12 July.     

Effect of exchangeable aluminium on the reduction of potato scab

The severity of the incidence of the fungal disease, potato scab, varies with different soil groups at the same soil pH. At a soil pH of 5.3, potato scab is easily controlled in soils of western Hokkaido (soil group A) by simply decreasing soil pH, but in soils from eastern Hokkaido (soil group B) it is not so easily controlled. The difference appears to be due to higher levels and exchangeable aluminium in Group A.Addition of sufficient aluminium or ferrous sulfate to a group B soil decreased the incidence of potato scab in a field experiment. Higher levels of aluminium sulfate depressed crop production. It is concluded that aluminium ions control the incidence of potato scab in acid soils. It is suggested that, in soils with low exchange acidity Y1, potato scab can be controlled by adding sufficient aluminium to increase their exchange acidity Y1 to above 7–8.     

Arsenic Pollution of a Loam Soil: Retention Form and Decontamination

A study was conducted to assess the retention form of arsenic in soil and to evaluate the use of phosphate for releasing it from the soil. In this study, a loam soil was artificially polluted with arsenate at pH 5.5, which is one of the pH values at which maximum arsenic adsorption occurred. The soil was kept for 2.5 months under wet conditions to allow for stabilization. The soil was maintained under aerobic condition and losses of arsenic by volatilization were determined to be minimal. The soil was then sequentially extracted with a series of chemicals to identify the soil fractions in which the arsenic was bound. The percentage of arsenic found in the Fe bound-exchangeable, reducible-residual, Al bound exchangeable, residual, calcium bound exchangeable, and easily exchangeable forms was 31.6, 27.3, 25.2, 5.5, 4.9, and 4.7%, respectively. A batch experiment showed that at 20°C, 80% of the bound arsenic was removed by phosphate in the pH range of 5 to 7. A power function model was found to fit the data with a desorption rate constant of 402?mg/kg As h^?1.     

Effect of soil K, Ca and Mg saturation and endomycorrhization on growth and nutrient uptake of sugar maple seedlings

Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated with high exchangeable Mg levels in soils relative to soil K and Ca. A greenhouse experiment was set up to test the hypothesis that the equilibrium between soil exchangeable K, Ca, and Mg ions influences the growth and nutrient status of sugar maple seedlings. Also tested was whether endomycorrhization can alter nutrient acquisition under various soil exchangeable basic cations ratios. Treatments consisted of seven ratios of soil exchangeable K, Ca, and Mg making up a total base saturation of 58%, and a soil inoculation treatment with the endomycorrhizal fungus Glomus versiforme (control and inoculated), in a complete factorial design. Sugar maple seedlings were grown for 3 months in the treated soils. Plant shoot elongation rate, dry biomass and nutrient concentrations in foliage were influenced by the various ratios of soil cations. The predicted plant biomass and foliar K concentration were highest at a soil Ca saturation of 38%, a soil K saturation of 12%, and a soil Mg saturation of 8%. Potassium concentration in foliage was dependent on the level of Ca and Mg saturation in the soil when soil K saturation was close to 12%. Foliar Ca and Mg levels were more dependent on their corresponding levels in soil than foliar K. Colonization by G. versiforme did not influence seedling growth and macronutrient uptake. The results confirm that growth and nutrition of sugar maple are negatively affected by imbalances in exchangeable basic cations in soils.     

鼎湖山主要森林类型土壤交换性阳离子含量及其季节动态特征

研究鼎湖山自然保护区马尾松林、马尾松荷木混交林和季风常绿阔叶林三种代表性森林类型表层土壤(0~20cm)交换性阳离子含量及其季节动态。结果表明:土壤交换性阳离子含量因元素种类、森林类型和季节不同而异。三种森林土壤交换性阳离子含量都表现为:Al3+>H+>K+>Ca2+、Mg2+、Na+。几乎所有调查的阳离子含量在阔叶林显著高于马尾松林和混交林,但后两者之间大多数阳离子含量差异不显著。鼎湖山森林土壤可交换性阳离子含量虽然较高,但盐基饱和度却很低。马尾松林、混交林和阔叶林土壤可交换性阳离子含量在1997年6月份分别为:58.3、84.5和118.7mmolc/kg,盐基饱和度分别为:5.5%、3.2%和4.5%。三种森林土壤交换性Ca2+、Mg2+、K+和H+含量季节差异极显著(P<0.001),但交换性Al3+含量只在马尾松林土壤存在极显著的季节性差异(P<0.001)。同一元素季节变化大小程度趋向马尾松林>混交林>阔叶林。森林土壤交换性Ca2+、Na+和H+含量与土壤pH值相关关系不明显,但交换性Mg2+、K+和Al3+与土壤pH值间呈极显著负相关。     

Removal of Cadmium from Contaminated Soils by Multiple Washing with Iron (III) Chloride

In the present study, three concentrations of FeCl₃ were applied to the Cd-contaminated soils at two solid-to-solution ratios, and 1–3 washes were applied. The Cd removal percentages increased with the number of washes. An optimal treatment for removing Cd from the soil was a solid-to-solution ratio of 1/2 using 45 mM FeCl₃ and three washes. However, the application of FeCl₃ decreased the soil pH values, increased the soil electrical conductivity, and also changed the exchangeable concentrations of cations. These changes negatively influenced the germination percentage of pak choi (Brassica campestris L. ssp. chinensis) compared with control soils.     

Development of a genotyping method for potato scab pathogens based on multiplex PCR

Scab disease significantly damages potato and other root crops. Streptomyces scabiei, S. acidiscabiei, and S. turgidiscabiei are the best-known causal agents of this disease. We have developed a novel genotyping method for these potato scab pathogens using multiplex PCR, whose benefits include rapid and easy detection of multiple species. We designed a species-specific primer set (6 primers, 3 pairs) for the 16S rRNA genes and 16S-23S ITS regions of these potato scab pathogens. The specificity of the primer set was confirmed by testing 18 strains containing potato scab pathogens, other Streptomyces species, and strains of other genera. The application of the developed method to potato field soil and potato tissue samples resulted in the clear detection and identification of pathogens. Since this method is applicable to a large number of environmental samples, it is expected to be useful for a high-throughput analysis of soil and plant tissues of scab disease.     

Effects of soil acidification and subsequent leaching on levels of extractable nutrients in a soil

Summary The effects of soil acidification (pH values from 6.5 to 3.8), and subsequent leaching, on levels of extractable nutrients in a soil were studied in a laboratory experiment. Below pH 5.5, acidification resulted in large increases in the amounts of exchangeable Al in the soil. Simultaneously, exchangeable cations were displayed from exchange sites and Ca, Mg, K and Na in soil solution increased markedly. With increasing soil acidification, increasing amounts of cations were leached; the magnitude of leaching loss was in the same order as the cations were present in the soil: Ca²⁺>Mg²⁺>K⁺>Na⁺. Soil acidification appeared to inhibit nitrification since in the unleached soils, levels of NO ₃ ⁻ clearly declined below pH 5.5 and at the same time levels of NH ₄ ⁺ increased greatly. Significant amounts of NH ₄ ⁺ and larger amounts of NO ₃ ⁻ , were removed from the soil during leaching. Concentrations of NaHCO₃-extractable phosphate remained unchanged between pH 4.3 and 6.0 but were raised at higher and lower pH values. No leaching losses of phosphate were detected. For the unleached soils, levels of EDTA-extractable Mn and Zn increased as the soil was acidified whilst levels of extractable Fe were first decreased and then increased greatly and those for Cu were decreased slightly between pH 6.5 and 6.0 and then unaffected by further acidification. Significant leaching losses of Mn and Zn were observed at pH values below 5.5 but losses of Fe were very small and those of Cu were not detectable.     

Development of a Genotyping Method for Potato Scab Pathogens Based on Multiplex PCR

Scab disease significantly damages potato and other root crops. Streptomyces scabiei, S. acidiscabiei, and S. turgidiscabiei are the best-known causal agents of this disease. We have developed a novel genotyping method for these potato scab pathogens using multiplex PCR, whose benefits include rapid and easy detection of multiple species. We designed a species-specific primer set (6 primers, 3 pairs) for the 16S rRNA genes and 16S–23S ITS regions of these potato scab pathogens. The specificity of the primer set was confirmed by testing 18 strains containing potato scab pathogens, other Streptomyces species, and strains of other genera. The application of the developed method to potato field soil and potato tissue samples resulted in the clear detection and identification of pathogens. Since this method is applicable to a large number of environmental samples, it is expected to be useful for a high-throughput analysis of soil and plant tissues of scab disease.     

Root biomass distribution in a moist tropical montane forest

Effects of N sources (ammonium, nitrate and ammonitrate) and VA mycorrhizae (Glomus intraradices) on rhizosphere soil characteristics (pH, exchangeable acidity, exchangeable cations, inorganic N concentrations) growth and nutrient acquisition of coffee seedlings (Coffea arabica L. cv guatemala) were investigated in a pot study with an acid soil (Red Bluff Loam) sterilized by autoclaving. Ammonium addition decreased rhizosphere pH while nitrate and ammonitrate additions both increased rhizosphere pH. Mycorrhizae induced a higher pH, a lower exchangeable acidity and higher values of exchangeable cations in the rhizosphere. Ammonium addition resulted in a lower mycorrhizal infection than the two other N sources. Mycorrhizal plants grew better and accumulated more N, Ca and Mg than non-mycorrhizal plants.     

Impact of grazing around a watering point on soil status of a semi-arid rangeland in Ethiopia

The influence of long‐term livestock grazing on the soil status of a semi‐arid rangeland was studied along a grazing gradient from a watering point in southern Afar Region of Ethiopia for two seasons. The soil samples were analysed for organic carbon (OC), total nitrogen (N), available phosphorus (P), exchangeable cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺), acidity (pH), cation exchange capacity, and particle size distribution (clay, silt and sand). No significant differences (P > 0.05) were observed for particle size distribution, OC, N, P and K contents along the grazing gradient further than 1500 m from the watering point. Ca²⁺ and Mg²⁺ were found to be dominant cations particularly in the severely degraded area contributing about 74% to the exchangeable cations. The study has also recognized high concentrations of Na⁺ and more than 11% exchangeable sodium percentage. Total exchangeable bases significantly declined (P < 0.05) along the grazing gradient and were indicative of the exchange complex of the soil being saturated with Ca²⁺ and Mg²⁺ ions. Thus this study concluded that there are soil differences in the grazing gradient caused by impact of grazing, particularly in the severely degraded area.     

施用尿素引起红壤pH及铝活性的短期变化

酸性红壤在我国南方广泛分布,其酸性是限制大多数作物生长的一个主要环境胁迫因子,主要原因是低pH条件下土壤中Al的溶解所导致的毒性.对3种红壤施用不同浓度的尿素,其pH值在短期内都随着施入尿素浓度的增大而急剧上升,交换性Al随着施用尿素浓度的增大而急剧下降.交换性Al含量与土壤pH值变化呈显著负相关.动态试验表明,pH值上升的现象是短期的,pH值在达最大值后缓慢下降,下降幅度最大的阶段在第2～4周.短期内,施用尿素能显著降低酸性土壤对玉米的铝毒效应.     

The effect of level of CaCO3, inoculation and lime pelleting on the nodulation and growth of beans in five acid soils

Summary The effect of level of CaCO₃, inoculation and lime pelleting on the nodulation, dry matter yield and % N content of common bean plants (Phaseolus vulgaris) grown in five acid soils was investigated in a greenhouse study. The soils represented a range in pH from 3.9 to 5.1, in exchangeable Al from 0.0 to 4 meq/100 gm, in exchangeable Mn from 0.35 to 2.32 me/100 gm, and in %C from 0.69 to 5.60.Nodule weight decreased with increasing %C and for the soil with highest %C (5.60) no nodules were observed. In soils with low organic matter and low exchangeable Al and Mn, inoculation increased nodule weight, dry matter yield and %N especially at the lowest pH level. Where the seeds were not inoculated, nodule weight and dry matter yield increased with soil pH. No such increases were observed where the seeds were inoculated. There was no apparent advantage in lime pelleting in such soils.In soils with low organic matter content and with substantial amounts of Al and/or Mn, liming increased nodule weight and dry matter yield, and decreased exchangeable Al and/or Mn. Lime pelleting was superior to mere inoculation in increasing nodule weight particularly at low lime rates.In soils with relatively high organic matter content, nodulation was very low or none at all. Low lime rates had little effect on exchangeable Al and Ca and dry matter yield. Higher lime rates, however, decreased exchangeable Al and dry matter yield but increased exchangeable Ca.     

Effect of brewery sludge amendments on some chemical properties of acid soil in pot experiments

A laboratory experiment was performed for an incubation period of 120 days in order to evaluate the changes in chemical properties of an acid soil amended with 0, 15, 30, 60 and 120 t ha-' of brewery sludge (BS). Increasing BS rates and incubation time reduced pH of the soil by 0.3-0.5 unit with respect to the control while soluble salts increased from 0.11 to 0.80 dS m(-1). Organic C, exchangeable cations, soluble cations and anions, NH4+-N and NO3--N contents of the amended soil increased as BS rates increased. In addition, BS application caused a slight increase in cation exchange capacity (CEC) and a slight decrease in exchangeable acidity.     

土壤中铁锰的形态分布及其有效性研究

以乌鲁木齐雅马里克山的土壤为研究对象,采用Tessier连续提取法对土壤铁、锰各种化学形态进行浸提.研究了土壤中有效铁、锰和土壤的理化性质与土壤铁、锰形态之间的关系,及对铁、锰在土壤中存在形态的影响;并通过盆栽试验对铁、锰的植物有效性进行了分析.结果表明,土壤铁主要以残渣态为主,占全铁的92.3%,其它形态含量均小于全量的8%.土壤锰主要是以铁锰氧化态和残渣态为主,分别占全锰的49%和41.6%,其它形态含量均小于全量的10%.用二级出水灌溉处理可增加铁、锰的有效性,原污水灌溉不利于铁、锰的供应,土壤缺铁、锰的现象可通过施加一定量的铁盐和锰盐而得以改善.相关分析还表明,土壤的理化性质与铁锰形态之间有一定的相关性.供试土壤的pH值、CaCO3含量、有机质及阳离子交换态等对土壤铁、锰的有效性影响较大.逐步回归分析表明,铁的氧化物结合态对植物最为有效,锰的有机结合态对植物有效性贡献最大.     

Effect of fires on soil nutrient availability in an open savanna in Central Brazil

Fire is common in savannas but its effects on soil are poorly understood. We analyzed long-term effects of fire on surface soil of an open Brazilian savanna (campo sujo) in plots submitted to different fire regimes during 18 years. The five fire regimes were: unburned, quadrennial fires in middle dry season, and biennial fires in early, middle or late dry season. Soil was collected during the wet and the middle dry season of 2008, and analyzed for pH, organic matter, total N, potential acidity, exchangeable cations and available P, S, Mn, Cu, Zn and Fe. We applied multivariate analysis to search for patterns related to fire regimes, and to local climate, fuel, and fire behavior. Spearman test was used to establish correlations between soil variables and the multivariate analysis gradient structure. Seasonal differences were tested using t-test. We found evidence of long-term fire effects: the unburned plot was segregated mainly by lower soil pH; the quadrennial plot was also segregated by lower soil pH and higher amount of exchangeable cations; the time of burning during the dry season in biennial plots did not significantly affect soil availability of nutrients. Differences in elements amounts due to the season of soil sampling (wet or dry) were higher than due to the effect of fires. Higher availability of nutrients in the soil during the wet season was probably related to higher nutrient inputs via rainfall and higher microbial activity.     

Determination of Factors Associated with Natural Soil Suppressivity to Potato Common Scab

Common scab of potatoes is a disease, which is difficult to manage due to complex interactions of the pathogenic bacteria (Streptomyces spp.) with soil, microbial community and potato plants. In Bohemian-Moravian Highlands in the Czech Republic two sites (Vyklantice and Zdirec) were selected for a study of common scab disease suppressivity. At both sites, a field with low disease severity occurs next to one with high severity and the situation was regularly observed over four decades although all four fields undergo a crop rotation. In the four fields, quantities of bacteria, actinobacteria and the gene txtB from the biosynthetic gene cluster of thaxtomin, the main pathogenicity factor of common scab, were analyzed by real-time PCR. Microbial community structure was compared by terminal fragment length polymorphism analysis. Soil and potato periderm were characterized by contents of carbon, nitrogen, phosporus, sulphur, calcium, magnesium, and iron. Quality of organic matter was assessed by high performance liquid chromatography of soil extracts. The study demonstrated that the suppressive character of the fields is locally specific. At Zdirec, the suppressivity was associated with low txtB gene copies in bulk soil, while at Vyklantice site it was associated with low txtB gene copies in the tuberosphere. The differences were discussed with respect to the effect of abiotic conditions at Zdirec and interaction between potato plant and soil microbial community at Vyklantice. Soil pH, Ca soil content or cation concentrations, although different were not in the range to predict the disease severity. Low severity of common scab was associated with low content of soil C, N, C/N, Ca and Fe suggesting that oligotrophic conditions may be favorable to common scab suppression.     

Behaviour of phenoloxidases in the presence of clays and other soil-related adsorbents

Summary The tyrosinases from Agaricus bisporus and Streptomyces eurythermus, laccases from Polyporus versicolor and Pleurotus ostreatus, and peroxidase from horseradish were strongly adsorbed on different bentonites and a clay-humus complex but less to on kaolinite and quartz. The adsorption was significantly dependent on the pH, reaching maxima in the range of the specific isoelectric points; it was less influenced by the valency and type of exchangeable cations. Most of the enzymes lost their activity when adsorbed on bentonite. The activity of desorbed enzymes was distinctly diminished when compared with free enzyme preparations. Conclusions from this behaviour were drawn as to the possible use of phenoloxidases as agents to transform phenolics in soil.     

云南保山西庄山地流域土地利用方式与土壤肥力关系研究

以云南省保山地区西庄流域为例,研究了自然因素及人为活动对土壤性质的影响。该流域的土壤通常pH较低,缺乏有效磷和交换性阳离子。仅发育于石灰岩的土壤具适宜的pH和交换性阳离子量。海拔对土壤有机碳含量具显著影响。文中详细讨论了海拔、母质和土地利用方式等对土壤肥力及土壤侵蚀的影响。