Effects of liming on soil chemical characteristics and grass growth in laboratory and long-term field-amended soils

Summary The influence of liming on soil solution composition was compared in two laboratory amended soils and one field amended soil. In the laboratory study, soil solutions were sampled by miscible displacement at intervals of 1 and 10 weeks after liming. In addition to increases in pH and Ca, there were large reductions in the concentrations of Mg, K, Na, Si and Mn. Solution concentration of free Al decreased with liming; however, organically complexed Al increased, as did soluble organic matter. Liming also stimulated mineralization of N as indicated by increased solution NO₃ levels. The field amended soils were obtained from a long-term cutting trial investigating the effects of lime on pasture. Despite the passage of a 16-year interval since application, the effects of lime on soil solution characteristics were still clearly evident and generally consistent with those observed in the laboratory study. Estimated leaching losses of Ca from limed soil were relatively low, amounting to 12%, 27% and 44% of the 4.2, 8.4 and 12.5 t lime ha⁻¹ applied, respectively. The results suggest that, in Eastern Ireland, a lime treatment would maintain and elevated pH and would influence the avialability and mobility of plant nutrients for some decades following application.     

Woodchip and biochar amendments differentially influence microbial responses,but do not enhance plant recovery in disturbed semiarid soils

Restoration presents a global challenge in drylands (arid and semiarid ecosystems) where uses can range from exclusive conservation to open‐pit mining and restoration practices are constrained by scarce, unpredictable precipitation, and high ambient temperatures. Adding woodchip amendments to soils is a common strategy for mitigating soil degradation as amendments may enhance soil carbon and increase plant cover. We assessed the effect of surface or incorporated woodchip addition and incorporated wood‐derived biochar on soil carbon dynamics and microbial activities as well as plant cover in semiarid soils that had been removed and replaced. We found that woodchips at the soil surface increased soil organic carbon (SOC), and both surface and incorporated woodchips increased the dissolved organic carbon (DOC) content. The incorporation of woodchips inhibited plant cover yet increased soil CO₂ efflux and dissolved organic matter stoichiometry. Surface woodchips also significantly enhanced microbial activities but not plant cover. A significant amount of the soil efflux in response to incorporating woodchips was explained by plant cover and exoenzyme activities, but this was not the case for other amendment treatments. Biochar, thought to be more resistant to decomposition, neither stimulated nor reduced microbial activities or plant cover and did not influence SOC or DOC. Our findings demonstrate that the influence of woodchip amendments on microbial processes and soil carbon dynamics depends on the location of application and that coarse fast‐pyrolysis biochar has limited influence on soil processes over a 22‐month study in a water‐limited ecosystem.     

Heavy metals fractionation and organic matter mineralisation in contaminated calcareous soil amended with organic materials

Degradation of organic matter (OM) from organic amendments used in the remediation of metal contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of two differing organic amendments on OM mineralisation and fractionation of heavy metals in a contaminated soil were investigated in an incubation experiment. The treatments were: control unamended soil, soil amended with fresh cow manure, and soil amended with a compost having a high maturity degree. The soil used was characteristic of the mining area at La Unión (Murcia, Spain) with 28% CaCO(3) and sandy-loam texture (pH 7.7; 2602 mg kg(-1)Zn; 1572 mg kg(-1)Pb). Manure and compost C-mineralisation after 56 days (24% and 3.8%, respectively) were below values reported previously for uncontaminated soils. Both amendments favoured Zn and Pb fixation, particularly the manure. Mn solubility increased at the beginning of the experiment due to a pH effect, and only Cu solubility increased through organic matter chelation in both amended soils.     

Growth of Jatropha curcas on heavy metal contaminated soil amended with industrial wastes and Azotobacter. A greenhouse study

The aims of the study were to evaluate the effect of organic wastes (biosludge and dairy sludge) and biofertilizer (Azotobacter chroococcum) on the planting conditions of Jatropha curcas in metal contaminated soils. Results showed that the plants survival rate in heavy metal contaminated soil increased with addition of amendments. Treatment T6 (heavy metal contaminated soils+dairy sludge+biofertilizer) observed to be the best treatment for growth (height and biomass) as compared with the treatment T5 (heavy metal contaminated soils+biosludge+biofertilizer). In addition, organic amendments provided nutrients such as carbon, N, P and K to support plant growth and reduced the metal toxicity to plant. The present study showed that metal contaminated lands/soils could be suitably remediated by adapting appropriate measures.     

土壤乙烯产生和氧化的研究进展

乙烯作为植物生长调节素及挥发性有机气体影响着植物生长和大气环境质量。有关土壤源乙烯产生和氧化特征,已发表的文献偏重实验室过程研究,很少涉及野外观测实验;陆地生态系统中土壤源乙烯行为有可能影响到植物生长及区域大气环境,大气环境变化(如水热状况和氮/酸沉降等)势必引起陆地土壤理化和生物学特性发生改变,进而影响土壤源乙烯产生和氧化过程。根据以前出版的文献,就土壤理化性质及外源碳氮施加、土壤微生物和重金属行为等对影响土壤乙烯产生和氧化作了详细综述,并简要阐述根际土壤乙烯产生和氧化以及不同土地利用方式对土壤乙烯产生和氧化的影响。指出应加强大气氮/酸沉降对典型林地土壤乙烯产生和氧化的影响机制以及不同土地利用方式下土壤乙烯产生和氧化的原位观测等方面的研究;同时也应关注不同成熟林型及森林演替不同阶段土壤理化和生物学特性跟乙烯产生和氧化的关联,明确土壤微生物(如细菌和真菌等)对此的相对贡献程度,利于丰富陆地土壤乙烯产生和氧化等有关科学认识,寻求适宜措施减少陆地土壤源乙烯产生潜势。     

Phytostabilization of Amended Soils Polluted with Trace Elements Using the Mediterranean Shrub: Rosmarinus Officinalis

We evaluate the mid-term effects of two amendments and the establishment of R. officinalis on chemical and biochemical properties in a trace element contaminated soil by a mine spill and the possible use of this plant for stabilization purposes. The experiment was carried out using containers filled with trace element polluted soil, where four treatments were established: organic treatment (biosolid compost, OAR), inorganic treatment (sugar beet lime, IAR), control with plant (NAR) and control without plant (NA). Amendment addition and plant establishment contributed to restore soil chemical (pH, total organic carbon, and water soluble carbon) and biochemical properties (microbial biomass carbon and the enzymatic activities: aryl-sulphatase and protease). The presence of rosemary did not affect soluble (0.01 M CaCl₂) Cd and Zn and decreased trace element EDTA extractability in amended soils. There were no negative effects found on plant growth and nutrient content on polluted soils (NAR, OAR, and IAR). Trace element contents were within normal levels in plants. Therefore, rosemary might be a reliable option for successful phytostablization of moderate trace element contaminated soils.     

Effect of amendments on phytoavailability and fractionation of copper and zinc in a contaminated soil

The ability of amendments to modify the soil properties and influence plants to immobilise Cu and Zn was studied in a naturally contaminated, additionally spiked podzolic soil. Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue) and Poa pratensis L (Kentucky blue grass) were tested in a pot study in the presence of soil amendments (lime, phosphate, and compost, individually and in combination) to assess the effect of soil-plant-amendment interaction on phytostabilisation. The ability of treatments to stabilize metals was assessed on the basis of metal fractionation in soil, partitioning of metals in plants, and metal uptake by the plants. Significant partitioning of Cu into immobile forms occurred as a result of the growth of Festuca rubra, and of Zn by the growth of Poa pratensis. Application of lime significantly reduced the exchangeable fraction of Zn, whereas phosphate application had an accelerating effect on exchangeable Cu. With combined application of amendments, the plant metal concentration decreased by more than 40% for Cu and 70% for Zn, compared to soils receiving no amendments. Combined application of amendments, in conjunction with growth of Festuca and Poa, can be recommended for phytostabilising of Cu and Zn in moderately contaminated acid soils of southwest British Columbia.     

Fertilization influences nitrogen dynamics in soils under Dalbergia sissoo

The influence of added ammonium, phosphorus, potassium, and gypsum on net nitrogen mineralization was studied in soil beneath a six-year-old plantation of the N₂-fixing tree Dalbergia sissoo in Pakistan. Soil with and without amendments was placed in polyethylene bags and incubated, buried in the soil, for 30 days. After that time the soil was analyzed and net ammonium and nitrate production and net nitrogen mineralization were calculated. The addition of ammonium stimulated nitrification indicating that the process was substrate limited. The inhibition of nitrification by Nitrapyrin showed that the process is autotrophic in these soils. Gypsum addition lowered soil pH from 8.0 to 7.2 and significantly stimulated ammonification, nitrification and net nitrogen mineralization. The addition of potassium more than tripled the soil K:Na ratio. Net ammonium and nitrate production and net nitrogen mineralization all increased in this treatment. The addition of phosphorus had no significant effect on soil nitrogen dynamics.     

Ethylene: potential key for biochar amendment impacts

Significant increases in root density, crop growth and productivity have been observed following soil additions of biochar, which is a solid product from the pyrolysis of biomass. In addition, alterations in the soil microbial dynamics have been observed following biochar amendments, with decreased carbon dioxide (CO₂) respiration, suppression of methane (CH₄) oxidation and reduction of nitrous oxide (N₂O) production. However, there has not been a full elucidation of the mechanisms behind these effects. Here we show data on ethylene production that was observed from biochar and biochar-amended soil. Ethylene is an important plant hormone as well as an inhibitor for soil microbial processes. Our current hypothesis is that the ethylene is biochar derived, with a majority of biochars exhibiting ethylene production even without soil or microbial inoculums. There was increased ethylene production from non-sterile compared to sterile soil (215%), indicating a role of soil microbes in the observed ethylene production. Production varied with different biomass sources and production conditions. These observations provide a tantalizing insight into a potential mechanism behind the biochar effects observed, particularly in light of the important role ethylene plays in plant and microbial processes.     

Controls on the distribution of productivity and organic resources in Antarctic Dry Valley soils

The Antarctic Dry Valleys are regarded as one of the harshest terrestrial habitats on Earth because of the extremely cold and dry conditions. Despite the extreme environment and scarcity of conspicuous primary producers, the soils contain organic carbon and heterotrophic micro-organisms and invertebrates. Potential sources of organic compounds to sustain soil organisms include in situ primary production by micro-organisms and mosses, spatial subsidies from lacustrine and marine-derived detritus, and temporal subsidies ('legacies') from ancient lake deposits. The contributions from these sources at different sites are likely to be influenced by local environmental conditions, especially soil moisture content, position in the landscape in relation to lake level oscillations and legacies from previous geomorphic processes. Here we review the abiotic factors that influence biological activity in Dry Valley soils and present a conceptual model that summarizes mechanisms leading to organic resources therein.     

Soil Carbon, Nitrogen and Phosphorus Dynamics as Affected by Solarization Alone or Combined with Organic Amendment

Soil solarization, alone or combined with organic amendment, is an increasingly attractive approach for managing soil-borne plant pathogens in agricultural soils. Even though it consists in a relatively mild heating treatment, the increased soil temperature may strongly affect soil microbial processes and nutrients dynamics. This study aimed to investigate the impact of solarization, either with or without addition of farmyard manure, in soil dynamics of various C, N and P pools. Changes in total C, N and P contents and in some functionally-related labile pools (soil microbial biomass C and N, K₂SO₄-extractable C and N, basal respiration, KCl-exchangeable ammonium and nitrate, and water-soluble P) were followed across a 72-day field soil solarization experiment carried out during a summer period on a clay loam soil in Southern Italy. Soil physico-chemical properties (temperature, moisture content and pH) were also monitored. The average soil temperature at 8-cm depth in solarized soils approached 55 °C as compared to 35 °C found in nonsolarized soil. Two-way ANOVA (solarization×organic amendment) showed that both factors significantly affected most of the above variables, being the highest influence exerted by the organic amendment. With no manure addition, solarization did not significantly affect soil total C, N and P pools. Whereas soil pH, microbial biomass and, at a greater extent, K₂SO₄-extractable N and KCl-exchangeable ammonium were greatly affected. An increased release of water-soluble P was also found in solarized soils. Yet, solarization altered the quality of soluble organic residues released in soil as it lowered the C-to-N ratio of both soil microbial biomass and K₂SO₄-extractable organic substrates. Additionally, in solarized soils the metabolic quotient (qCO₂) significantly increased while the microbial biomass C-to-total organic C ratio (microbial quotient) decreased over the whole time course. We argued that soil solarization promoted the mineralization of readily decomposable pools of the native soil organic matter (e.g. the microbial biomass) thus rendering larger, at least over a short-term, the available fraction of some soil mineral nutrients, namely N and P forms. However, over a longer prospective solarization may lead to an over-exploitation of labile organic resources in agricultural soils. Manure addition greatly increased the levels of both total and labile C, N and P pools. Thus, addition of organic amendments could represent an important strategy to protect agricultural lands from excessive soil resources exploitation and to maintain soil fertility while enhancing pest control.     

Manure Application and Cannabis Cultivation Influence on Speciation of Lead and Cadmium by Selective Sequential Extraction

The contamination of agricultural soils by heavy metals is a worldwide problem. Degradation of organic matter (OM) from organic amendments used in the remediation of metal-contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of four differing organic amendments on chemical forms of Pb and Cd in a contaminated soil were investigated in a pot experiment of control unamended soil and soils amended with dry cow and poultry manures (20 g CM or PM kg^?1 soil), and cow and poultry manure extracts (2 g CME or PME kg^?1 soil) cultured with cannabis sativa. After eight weeks, a sequential extraction scheme was used to fractionate soil Pb and Cd into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), and carbonates associated (ACar) forms. The addition of animal manures and their extracts increased the DTPA-extractable Pb and Cd in soil significantly. Soil Pb and Cd in Sol-Exch fraction were increased by manure applications. Both Pb and Cd in AOM fraction were increased by application of manures and their extracts. This increase was more obvious for Pb in application of cow and poultry manure extracts. The ACar chemical forms of Pb and Cd were also increased by application of manures and their extracts. The increases of Pb and Cd in Acar fraction was noticeable in soils treated with cow manure. Soil cultivation with cannabis sativa increased available, Sol-Exch, and AOM chemical forms of Pb in soil significantly compared to control soil. However, soil Pb and Cd in ACar fraction were decreased significantly by cannabis cultivation. The effect of cannabis cultivation on all of the Cd chemical forms (except on Sol-Exch) was similar to the results of Pb chemical forms. Plant cultivation had no significant effect on Cd in Sol-Exch chemical form.     

Phytostabilization of Acidic Soils with Heavy Metal Contamination Using Three Forage Grasses in Combination with Organic and Inorganic Amendments

Two experiments were conducted to investigate the effects of organic and inorganic amendments on metal stabilization and the potential of three forage grasses, i.e., Pennisetum americanum × Pennisetum, Euchlaena mexicana, and Sorghum dochna, for phytostabilization of acidic heavy metal-contaminated soils. The three grasses died 5 days after transplanting into the contaminated soils. Organic fertilizer (pig slurry and plant ash) only or combined with lime, NPK fertilizer, and sewage sludge resulted in adequate grass growth in the contaminated soils through a significant increase in the soil pH, N, P, K, and organic matter contents, and a decrease in the metal concentrations. The shoot biomass of P. americanum×P. purpureum and S. dochna was 1.92 and 2.00 times higher than that of E. Mexicana. The solubility of Cd, Pb, and Zn strongly depends on organic matter, while the solubility of Cu strongly depends on both soil organic matter and pH. The concentrations of Cd, Pb, and Zn in plant shoots growing in soil with a mixed amendment were significantly lower than plants growing in soil amended with an organic fertilizer only, whereas the Cu concentrations in plant shoots exhibited the opposite trend. The results indicated that 5% organic fertilizer only or combined with 5% sewage sludge were appropriate amendments and S. dochna and P. americanum × Pennisetum are suitable plants for phytostabilization of acidic heavy metal-polluted soils.     

土壤快速强烈还原对于尖孢镰刀菌的抑制作用

香蕉枯萎病是由尖孢镰刀菌古巴专化型(Fusarium oxysporum f.sp.cubense,FOC)引起的一种世界性的土传病害,每年造成大量的经济损失,目前尚未找到有效的防治办法。实验采取土壤淹水及添加有机物料的方法,抑制土壤中FOC的数量。结果表明:土壤淹水处理在第5天显著增加了土壤的pH值,但随着处理时间的增加,淹水的处理中土壤pH值逐渐下降;土壤淹水及添加有机物料显著降低了土壤中SO2-4和NO-3的浓度;土壤中添加秸秆、猪粪和石灰的处理显著增加了土壤中NH+4的浓度。土壤淹水及添加有机物料对于土壤中可培养细菌数量无显著影响;但显著降低了土壤中可培养放线菌和真菌的数量;土壤淹水及添加秸秆、甘蔗渣和石灰的处理显著降低了土壤中FOC的数量,其中添加高量秸秆处理中FOC的数量下降最多,仅为处理前土壤中FOC数量的2.88%。添加有机物料但未加石灰的处理土壤中总微生物量较处理前相比显著增加。研究表明土壤淹水及添加有机物料是一种可以防控香蕉枯萎病的高效和环保的方法。     

Heavy metal bioavailability in a soil affected by mineral sulphides contamination following the mine spillage at Aznalcóllar (Spain)

A field experiment, lasting 14 months, was carried out in order to assess the effect of organic amendment and lime addition on the bioavailability of heavy metals in contaminated soils. The experiment took place in a soil affected by acid, highly toxic pyritic waste from the Aznalcóllar mine (Seville, Spain) in April 1998. The following treatments were applied (3 plots per treatment): cow manure, a mature compost, lime (to plots having pH < 4), and control without amendment. During the study two crops of Brassica juncea were grown, with two additions of each organic amendment. Throughout the study, the evolution of soil pH, total and available (DTPA-extractable) heavy metals content (Zn, Cu, Mn, Fe, Pb and Cd), electrical conductivity (EC), soluble sulphates and plant growth and heavy metal uptake were followed. The study indicates that: (1) soil acidification, due to the oxidation of metallic sulphides in the soil, increased heavy metal bioavailability; (2) liming succeeded in controlling the soil acidification; and (3) the organic materials generally promoted fixation of heavy metals in non-available soil fractions, with Cu bioavailability being particularly affected by the organic treatments.     

Enhancing the mineralization of [U-14C]dibenzo-p-dioxin in three different soils by addition of organic substrate or inoculation with white-rot fungi

The potential for aerobic mineralization of [U-¹⁴C]dibenzo-p-dioxin (DD) was investigated in samples of three different agricultural soils already contaminated with polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) by industrial activities. The influence of amendments, i.e. wheat straw and compost, and of soil treatment by inoculation with lignolytic fungi, grown on wheat straw substrate, was tested. All the soils tested contained an indigenous DD-mineralizing microflora. The soil characterized by the highest organic matter content and the highest content of soil microbial biomass displayed the best DD mineralization of 36.6% within 70 days, compared with the two organic-matter-poor soils with an endogenous DD mineralization of 19.5% and 23.3% respectively. Amendments with compost increased DD mineralization up to 28% in both soils with low organic matter and microbial biomass content, but did not affect mineralization in the organic-matter-rich soil. Addition of wheat straw had no constant influence on DD mineralization in the soils tested. The best DD mineralization resulted from inoculation with lignolytic white-rot fungi (Phanerochaete chrysosporium, Pleurotus sp. Florida, Dichomitus squalens) and with an unidentified lignolytic fungus, which was isolated originally from a long-term PCDD/F-contaminated soil. A mineralization of up to 50% within 70 days was reached by this treatment. The influence of inoculated fungi on mineralization differed between the soils investigated. Received: 14 April 1997 / Received revision: 24 June 1997 / Accepted: 29 June 1997     

Microbiological aspects of soil structure

Summary A simple experimental model has been devised to study the effects of organic amendments on aggregate stability and microbial activity in the soil. In the two soils investigated the different organic materials used all produced increases in aggregate stability but significant differences were observed both in the magnitude and time of the increase attributable to individual treatments. Microbial activity, as assessed by visual techniques, was broadly correlated with the changes in aggregate stability though the different treatments tended to produce their own characteristic patterns of colonization. It was generally difficult to relate changes in aggregate stability with the activity of specific micro-organisms but in the case of samples treated with glucose and cellulose, yeasts were the dominant organisms. These have subsequently been shown to produce substantial quantities of an extracellular polysaccharide which is effective in bringing about aggregation.     

Comparative Mesocosm Study of Biostimulation Efficiency in Two Different Oil-Amended Sub-Antarctic Soils

Biological treatment has become increasingly popular as a remediation method for soils and groundwater contaminated with petroleum hydrocarbon, chlorinated solvents, and pesticides. Bioremediation has been considered for application in cold regions such as Arctic and sub-Arctic climates and Antarctica. Studies to date suggest that indigenous microbes suitable for bioremediation exist in soils in these regions. This paper reports on two case studies at the sub-Antarctic Kerguelen Island in which indigenous bacteria were found that were capable of mineralizing petroleum hydrocarbons in soil contaminated with crude oil and diesel fuel. All results demonstrate a serious influence of the soil properties on the biostimulation efficiency. Both temperature elevation and fertilizer addition have a more significant impact on the microbial assemblages in the mineral soil than in the organic one. Analysis of the hydrocarbons remaining at the end of the experiments confirmed the bacterial observations. Optimum temperature seems to be around 10 degrees C in organic soil, whereas it was higher in mineral soil. The benefit of adding nutrients was much stronger in mineral than in the organic soil. Overall, this study suggests that biostimulation treatments were driven by soil properties and that ex situ bioremediation for treatment of cold contaminated soils will allow greater control over soil temperature, a limiting factor in cold climates.     

Long-term availability of nutients in forest soil derived from fast- and slow-release fertilizers

The availability of P, K and Mg was studied in boreal forest soil treated 10 years earlier with slow- and fast-release fertilizers. Fast release superphosphate, potassium chloride and magnesium sulphate and slow-release apatite (P) and biotite (K, Mg) were applied alone or together with urea or urea+limestone. The concentrations of total and exchangeable nutrients in the organic horizon and the concentration of exchangeable nutrients in the uppermost mineral horizon were measured. CO₂ production during aerobic laboratory incubation was used to estimate the microbial activity and substrate-induced respiration to determine the microbial biomass C in soil. Biotite caused a moderate but persistent increase in pH in the organic horizon, but this increase was smaller than with lime. The fast-release fertilizers had no effects on the nutrient status of the soil 10 years after the fertilization. However, apatite and biotite still increased the total content of Mg, K and P and the concentrations of exchangeable Mg and soluble P in soil. On the other hand, simultaneous addition of lime and biotite reduced the release of soluble P from apatite. The reduction in soil microbial activity found with urea and the fast-release salts soon after application was no longer evident 10 years later. There was no increase in nitrification in the fertilized soils, not even with the urea+lime treatment. The previous results right after the application and the results presented here do not indicate major leaching of nutrients from the slow-release fertilizers to the deeper soil profiles.     

Soil physical strength rather than excess ethylene reduces root elongation of Eucalyptus seedlings in mechanically impeded sandy soils

Seedling establishment in heavily compact soils is hampered by poor root growth caused by soil chemical or physical factors. This study aims to determine the role of ethylene in regulating root elongation through mechanically impeded sandy soils using Eucalyptus todtiana F. Muell seedlings. Concentrations of ethephon (1, 10, and 100???M) were added to non-compact soils, and endogenous ethylene production from seedling roots was compared to ethylene production of roots grown in physically compacted field soils (98.6?% sand). The ethylene-inhibitor 3,5-diiodo-4-hydroxybenzoic acid (DIHB) (0.1???M) was included for each treatment to counteract the negative effects of excess ethylene or compact soils on root elongation. Root elongation was reduced in high ethylene soils by 49?% and high bulk density soils by 44?%. Root ethylene production increased ninefold in roots grown in the high ethylene environment (100???M), but decreased 80?% in compact soils. The use of DIHB did not alter root length and produced varying results with respect to ethylene production, suggesting an interaction effect involving high amounts of soil ethylene. While ethylene regulates root growth, the physical strength of sandy soils is the major factor limiting root elongation in mechanically impeded soils.