Selenium concentrations in crops grown on low-selenium soils as affected by fly-ash amendment

Summary Studies were conducted under greenhouse and field conditions to evaluate the feasibility of using fly-ash amendments to produce selenium-adequate crops (0.10 to 0.30 ppm Se) on low-Se soils without adversely affecting either the crops or the soils. Two soils, a fine-loamy Alfisol belonging to the Honeoye series and a coarse-loamy Inceptisol belonging to the Mardin series were used to make 3 soil treatments thus: Honeoye, limed Mardin and unlimed Mardin. Fly-ash was mixed with the soils at rates of 0, 2500, 5000, 5000, 10000, 25000 and 50000 ppm. In the greenhouse studies the test crops were corn (Zea mays L.), alfalfa (Medicago sativa), birdsfoot trefoil (Loitus corniculatus) and dry beans (Phaseolus vulgaris L.). There were no yield differences due to fly-ash additions. The rates of 25,000 and 50,000 ppm fly-ash produced the desired Se levels in the utilizable parts of the crops. In the field studies, conducted on another fine-loamy Alfisol belonging to the Lima series and using fly-ash at the rates of 0, 11.2, 22.4 and 112.0 metric tons/ha, it was observed that the yields of corn and dry beans grown were also not influenced by the treatments. Increased levels of Se in corn grains (0.10 ppm) and stover (0.08 ppm) and dry bean seeds (0.14 ppm) were observed at the application rate of 112 metric tons per ha.The results indicate that fly-ash has a potential for producing forages and feed crops containing adequate amounts of Se to protect livestock from Se-responsive diseases.     

Amendment Placement Directs Soil Carbon and Nitrogen Cycling in Severely Disturbed Soils

The recovery of ecosystem processes in severely disturbed systems is often limited by biological resources in the soil. The objective of this study was to direct soil microbial biomass (SMB) size and activity with organic amendments. These amendments were applied to the soil at different amendment locations (incorporated versus surface‐applied) and amounts (none, light, and heavy) in a 2 × 3 factorial design. The size and activity of SMB, soil nutrients, and aboveground biomass were monitored over 3 years to determine the rate and direction of change. Contrary to expectations that SMB and carbon mineralization potential (C‐MIN) would be larger with amendment incorporation, SMB‐carbon was greatest in the surface‐heavy treatment and lowest in the incorporated‐control treatment. SMB‐nitrogen, C‐MIN, and organic carbon were greater in the surface than in the incorporated treatments and in amended plots compared to controls. This departure from expectations suggests that other factors, such as microclimate or vegetation, are interacting with the amendment to affect SMB. The degree of contribution, however, is unclear. The treatments only affected planted aboveground biomass early in the experiment, with greater total biomass in the surface‐light treatment in fall 2003. There was also a significant positive relationship between aboveground biomass and SMB in fall 2004. Inorganic nitrogen, total nitrogen, and the soil quality indicators qCO₂ and C_mic/C_org did not vary systematically with amendment treatment. In general, amendment addition did enhance soil biotic properties and supported increased vegetation, but the complication of incorporating the amendment was not necessary for promoting biological development in disturbed soils.     

Plant‐facilitated effects of exotic earthworm Pontoscolex corethrurus on the soil carbon and nitrogen dynamics and soil microbial community in a subtropical field ecosystem

Earthworms and plants greatly affect belowground properties; however, their combined effects are more attractive based on the ecosystem scale in the field condition. To address this point, we manipulated earthworms (exotic endogeic species Pontoscolex corethrurus) and plants (living plants [native tree species Evodia lepta] and artificial plants) to investigate their combined effects on soil microorganisms, soil nutrients, and soil respiration in a subtropical forest. The manipulation of artificial plants aimed to simulate the physical effects of plants (e.g., shading and interception of water) such that the biological effects of plants could be evaluated separately. We found that relative to the controls, living plants but not artificial plants significantly increased the ratio of fungal to bacterial phospholipid fatty acids (PLFAs) and fungal PLFAs. Furthermore, earthworms plus living plants significantly increased the soil respiration and decreased the soil NH₄⁺‐N, which indicates that the earthworm effects on the associated carbon, and nitrogen processes were greatly affected by living plants. The permutational multivariate analysis of variance results also indicated that living plants but not earthworms or artificial plants significantly changed the soil microbial community. Our results suggest that the effects of plants on soil microbes and associated soil properties in this study were largely explained by their biological rather than their physical effects.     

Assessment of the Efficiency of a Metal Phytoextraction Process with Biological Indicators of Soil Health

The ultimate goal of any soil remediation process should be not only to remove the contaminant(s) from the polluted site but to restore soil health as well. In consequence, reliable indicators of soil health are needed if we are to properly evaluate the efficiency of a soil remediation process. The aim of the current work was to determine the effect of metal phytoextraction, through the utilization of the Zn hyperaccumulator T. caerulescens, on biological parameters of soil health, on the assumption that biological indicators of soil health might be valid monitoring tools to assess the efficiency of a metal phytoextraction process. To this end, a short-term microcosm phytoextraction study was carried out, with two heavy metal polluted soils collected from an abandoned mine, to determine the effect of metal phytoextraction on soil biological parameters. Higher values of biomass C, basal respiration, substrate induced respiration, and β-glucosidase activity were observed in the presence of T. caerulescens plants, as compared to unplanted pots. Our data confirm the great capacity of T. caerulescens to phytoextract Zn from polluted soils and, interestingly, suggest that metal phytoextraction has indeed a beneficial effect on soil biological activity. It was concluded that the revegetation of these metal polluted soils with T. caerulescens could help activate their biochemical and microbial functionality.     

Effect of Arsenic on Nodulation and Nitrogen Fixation of Blackgram (<Emphasis Type="Italic">Vigna mungo</Emphasis>)

Rhizobium–legume symbiotic interaction is an efficient model system for soil remediation and reclamation. We earlier isolated an arsenic (As) (2.8 mM arsenate) tolerant and symbiotically effective Rhizobium strain, VMA301 from Vigna mungo and in this study we further characterized its efficacy for arsenic removal from the soil and its nitrogen fixation capacity. Although nodule formation is delayed in plants with As-treated composite when the inoculum was prepared without arsenic in culture medium, whereas it attains the significant number of nodules compare to plant grown in As-free soil when the inoculum was prepared with arsenic supplemented medium. Arsenic accumulation was higher in roots than root nodules. Nitrogenase activity is reduced to almost 2 fold in plants with As-treated soil but not abolished. These results suggest that this strain, VMA301, has been able to establish an effective symbiotic interaction in V. mungo in As-contaminated soil and can perform dual role of arsenic bioremediation as well as soil nitrogen improvement.     

Nodulation and nitrogen fixation in Purshia: inoculation responses and species comparisons

Summary Nitrogen fixing trees and shrubs may be useful in revegetation efforts. Speculation that insufficient endophyte populations in surface soils may limit non-leguminous symbiotic nitrogen fixation in marginal land was explored.Purshia tridentata andP. glandulosa seedlings were grown in greenhouse trials using ten soils from nativePurshia sites. Treatments include a control, an inoculated treatment, and six mmole nitrogen amendment. When inoculated with aP.tridentata crushed nodule inoculum, two of five non-nodulating soils and three sparsely nodulating soils produced well nodulated plants. Inoculation also increased nodule mass, total nitrogen, nitrogen content and shoot dry mass in plants from some of the soils. Of the three soils failing to produce nodulated plants when inoculated, one produced plants that responded well to nitrogen additions but failed to nodulate under low nitrogen conditions; another produced severely stunted plants indicating nutritional limitations on the host; and the third produced plants that were not nitrogen deficient. An application of nitrogen completely suppressed nodulation in all but one soil. The twoPurshia species were similar in nodulation, nitrogen fixation and growth, although important exceptions exist that indicate species may differ in adaptability to certain soil conditions.     

Heavy-metal uptake and distribution in Silene vulgaris and Minuartia verna growing on mining-dump material containing lead and zinc

Plant and soil samples from a mining area in Carinthia (Austria) were investigated for their heavy metal content. In the soil surrounding roots of plants (Minuartia verna and Silene vulgaris) growing on the mining dumps, high concentrations of lead and zinc are to be expected. The two species (Minuartia and Silene) show very different heavy metal concentrations in their above- and belowground organs. From these observations it can be concluded that the divergent distribution of heavy metals within the plants is an important mechanism of tolerance to heavy metals.     

Growth and metal accumulation potential of Vigna radiata L. grown under fly-ash amendments

The study was undertaken with the aim of testing the feasibility of growing Vigna radiata on fly-ash dykes or on fly-ash contaminated soil. Experiments were conducted in earthen pots (12″) having various amendments of fly-ash with garden soil, press mud and farm yard manure and harvested after 60 days of growth. Various growth variables were analyzed, viz., root-shoot length, biomass yield, number of branches, photosynthetic area and pigments, protein content, in vivo nitrate reductase activity and nodulation frequency. The metal accumulation potential (Fe, Zn, Cu, Cr, Cd) in roots and shoot tissues of plants was determined in various fly-ash amendments and seeds were also examined for their metal content so that they can be utilized for growing in fly-ash-contaminated areas. Our results show that the plants grown in 100% fly-ash accumulated significant amounts of metals due to which general vigor and development of plant are affected. V. radiata grown on ameliorated fly-ash showed tolerant characteristics. Plants accumulated metal in the order Fe > Cu > Zn > Cr > Cd. However, their concentration was more in shoot than root tissue except in the case of Fe, which was found to have accumulated more in root tissues. Press mud (25%) amended with fly-ash was found to be the best ameliorant to support plant growth. It may be concluded from the present study that V. radiata was an ideal crop for growing in fly-ash-contaminated areas for the revegetation of fly-ash landfills.     

Effect of sewage wastewater treated byNostoc muscorum andAnabaena subcylindrica on the growth ofZea mays andPhaseolus vulgaris

Zea mays (Sakha 321 ) andPhaseolus vulagris (Giza 6) were irrigated with sewage wastewater treated withNostoc muscorum andAnabaena subcylindrica. The results showed that irrigation of plants by untreated or treated wastewater caused stimulation in the measured growth parameters of both plants. In addition pigmentation as well as protein and carbohydrate contents were stimulated. This stimulation was attributed to the presence of high levels of essential nutrients such as nitrogen, phosphorus, and organic matters in wastewater. On the other side, there was a slight inhibitory effect of wastewater on some measured growth parameters of the plants. This effect may be due to the presence of some heavy metals in wastewater.     

Ammonium Nutrition as a Strategy for Cadmium Mobilisation in the Rhizosphere of Sunflower

Ammonium nutrition of higher plants results in rhizosphere acidification due to proton excretion by root cells. The acidification induced by ammonium-fed plants can be exploited to promote a localised metal mobilisation in neutral to alkaline polluted soils and therefore to improve phytoextraction. The effects of ammonium uptake by sunflower (Helianthus annuus L.) plants on the external medium pH, aerial and root growth and tolerance to soluble Cd were studied in hydroponic culture. The ammonium-fed sunflowers induced a strong acidification of the solution and, compared to the nitrate-fed sunflowers, a small modification in mineral nutrition and a different Cd partitioning between root and shoot. Moreover, ammonium nutrition was found to induce a great mobilisation of a sparingly soluble form of cadmium (CdCO₃). A pot experiment studied the ability of different ammonium-based fertilisers (ammonium sulphate, ammonium thiosulphate, urea) to modify bulk and rhizo-soil pH, compared to the effect of calcium nitrate and to the unfertilised soil. Furthermore, in order to promote the persistence of ammonium in soil, a combined treatment of ammonium sulphate and DMPP, a nitrification inhibitor, was tested. Soil pH was strongly modified by chemical and biological processes involved in fertiliser transformations. In particular, due to nitrification, all ammonium-based treatments showed a bulk soil acidification of over 1.5 pH units and a relative increase in rhizo-soil pH as a consequence of nitrate uptake. The treatment with DMPP showed an opposite trend with a lower pH in rhizo-soil than in bulk soil. The ability of ammonium-fed plants to mobilise heavy metals from the non-labile pool was studied in another pot experiment using three soils with different properties and at different degree and type of heavy metal contamination. Whatever the soil, the metal concentrations in shoots were higher in plants fed with ammonium (ammonium sulphate plus DMPP treatment). Our results support the hypothesis that ammonium nutrition with nitrification inhibitors is a viable strategy to improve heavy metals phytoextraction while protecting bulk soil from acidification and presumably from metal leaching. An erratum to this article is available at .     

Improving <Emphasis Type="Italic">Casuarina</Emphasis> growth and symbiosis with <Emphasis Type="Italic">Frankia</Emphasis> under different soil and environmental conditions—review

Casuarinas are very important plants for their various uses and survival in adverse sites or harsh environments. As nitrogen fixation, in symbiosis with Frankia, is an important factor for the survival of these plants under various conditions, the basis for selecting both effective and tolerant Frankia strains and Casuarina spp., are provided. Enhancement of the symbiotic relationship between Frankia and Casuarina, by mycorrhizal infection and other biofertilizing microorganisms such as Bacillus and Azospirillum, is reflected by superior plant growth. Casuarina leaf litter is also a great source for both inorganic and organic nutrients. Therefore, careful management of the top soil layer under Casuarina trees is very important. Litter decomposition ratio is affected by many physical chemical and biological factors including temperature, moisture conditions, lignin, and C-to-N and N-to-P ratios in addition to soil biota. In general, here the above relations are discussed and an alleviation model is presented for important disturbances of natural and human origin made in soil and environment, especially in the dry regions. In conclusion, we suggest how to optimize the nitrogen fixation and plant growth under the prevalent conditions.     

垃圾填埋场渗滤液灌溉对土壤理化特征和草本花卉生长的影响

以草本花卉植物一串红和石竹为材料,通过盆栽试验研究了不同浓度垃圾渗滤液灌溉对土壤理化性质及生物学性质、植物生长、氮磷和重金属吸收的影响。渗滤液灌溉提高了土壤有机质、氮含量和电导率,其中,黄壤盐分积累速度大于紫色土,而对土壤磷和重金属含量的影响不明显,土壤脲酶活性随渗滤液浓度的提高呈先升高后降低趋势,紫色土和黄壤在渗滤液灌溉浓度分别为60%和40%时脲酶活性最强;随渗滤液浓度提高紫色土过氧化氢酶活性略为上升,黄壤过氧化氢酶活性降低。渗滤液灌溉使两种花卉根系生长受到抑制,但对植物地上部的生长发育存在低浓度促进高浓度抑制的双重作用。渗滤液灌溉可提高两种植物地上部的氮含量,对一串红磷含量影响不明显,使石竹磷含量降低,对Cu、Zn含量的影响因土壤和植物的不同而异,但高浓度渗滤液灌溉使两种植物Pb、Cr和Cd含量均提高。结果表明,适当浓度渗滤液灌溉具有改善土壤肥力,促进植物地上部生长发育的作用,渗滤液灌溉不会引起土壤和植物体内重金属过量积累,土壤氮过量积累导致的氮磷营养失调和盐分过度积累是高浓度渗滤液抑制植物生长的重要原因。从土壤性质变化和植物生长反应看,渗滤液灌溉浓度以20%—40%为佳。     

Temperature sensitivity of nitrogen productivity for Scots pine and Norway spruce

Environmental conditions control physiological processes in plants and thus their growth. The predicted global warming is expected to accelerate tree growth. However, the growth response is a complex function of several processes with both direct and indirect effects. To analyse this problem we have used needle nitrogen productivity, which is an aggregate parameter for production of new foliage. Data on needle dry matter, production, and nitrogen content in needles of Scots pine ( Pinus sylvestris) and Norway spruce ( Picea abies) from a wide range of climatic conditions were collected and needle nitrogen productivities, defined as dry matter production of needles per unit of nitrogen in the needle biomass, were calculated. Our results show that the nitrogen productivity for spruce is insensitive to temperature. However, for pine, temperature affects both the magnitude of nitrogen productivity at low needle biomass and the response to self-shading but the temperature response is small at the high end of needle biomass. For practical applications it may be sufficient to use a species-specific nitrogen productivity that is independent of temperature. Because temperature affects tree growth indirectly as well as through soil processes, the effects of temperature change on tree growth and ecosystem carbon storage should mainly be derived from effects on nitrogen availability through changes in nitrogen mineralization. In addition, this paper summarises data on dry matter, production and nitrogen content of needles of conifers along a temperature gradient.     

Shading and the capture of localized soil nutrients: nutrient contents,carbohydrates, and root uptake kinetics of a perennial tussock grass

Summary The ability to exploit spatial and temporal heterogeneity in soil resources can be one factor important to the competitive balance of plants. Competition above-ground may limit selective plant responses to below-ground heterogeneity, since mechanisms such as root proliferation and alterations in uptake kinetics are energy-dependent processes. We studied the effect of shading on the ability of the perennial tussock grassAgropyron desertorum to take up nutrients from enriched soil microsites in two consecutive growing seasons. Roots of unshaded plants selectively increased phosphate uptake capacity in enriched soil microsites (mean increases of up to 73%), but shading eliminated this response. There were no changes in ammonium uptake capacity for roots in control and enriched patches for either shaded or unshaded plants. The 9-day shade treatments significantly reduced total nonstructural carbohydrate (TNC) concentrations for roots in 1990, but had no apparent effect on root carbohydrates in 1991 despite dramatic reductions in shoot TNC and fructan concentrations. Enrichment of the soil patches resulted in significantly greater phosphate concentrations in roots of both shaded and unshaded plants, with less dramatic differences for nitrogen and no changes in potassium concentrations. In many respects the shaded plants did surprisingly well, at least in terms of apparent nutrient acquisition. The effects of aboveground competition on nutrient demand, energy requirements, and belowground processes are discussed for plants exploiting soil resource heterogeneity.     

Competition for alfalfa nodulation under metal stress by the metal‐tolerant strain Ochrobactrum cytisi Azn6.2

Legume plants, in association with rhizobia, are gaining increasing interest for heavy metal rhizoremediation. This symbiotic interaction combines the advantages of rhizoremediation and soil nitrogen enrichment. In metal polluted soils, Ochrobactrum cytisi can elicit non‐fixing nodules on legumes, including Medicago sativa. Nodulation kinetics was much slower when M. sativa plants were inoculated with O. cytisi Azn6.2 compared with the natural symbiont Ensifer meliloti 1021 and nodules were ineffective in nitrogen fixation. A competition experiment was performed using alfalfa grown on heavy metals, and co‐inoculated with equal amounts of the metal‐sensitive E. meliloti 1021 and the metal‐resistant O. cytisi Azn6.2. When plants were inoculated in non‐polluted substrates, all nodules were formed by E. meliloti 1021. Nevertheless, under increasing metal concentrations, the number of nodules occupied by O. cytisi grew. At the highest metal concentration, all nodules were elicited by O. cytisi, suggesting that the resistant species can take the place of the natural symbiont. This fact has important ecological and environmental implications when proposing legume–rhizobia symbioses for rhizoremediation and highlights the need of selecting highly resistant rhizobia in order to be competitive in polluted soils.     

羊草基因型数目与氮添加对土壤微生物群落的交互影响

物种多样性(或同一物种遗传多样性)减少和氮富集都是影响陆地生态系统进程的主要因素,它们之间的交互作用是否对土壤微生物群落产生显著影响已成为研究者关心的主要科学问题。研究羊草基因型数目(1、2、4三种基因型数目组合)和氮添加(无氮添加、低氮添加和高氮添加3种水平)对土壤微生物群落的总磷脂脂肪酸(PLFA,Phospholipid Fatty Acid)含量、细菌PLFA生物标记含量、真菌PLFA生物标记含量、真菌/细菌比、以及基于每个PLFA生物标记相对含量百分比所得微生物群落的Shannon-Wiener多样性指数和Simpson优势度指数的影响。结果表明:氮添加对细菌PLFA生物标记含量,以及土壤微生物PLFA生物标记的Shannon-Wiener多样性指数和Simpson优势度指数具有显著影响(P0.05);基因型数目对所测变量无显著影响(P0.05),但基因型数目和氮添加的交互作用对细菌PLFA生物标记含量和真菌/细菌比具有显著影响(P0.05)。研究结果为全球变化背景下氮沉降及重要物种种群数量减少对土壤微生物群落的影响提供了科学数据,为合理解释群落动态变化提供了数据支持。     

Effects of Chromium Ore Tailings on Growth and Physiological Activities of Mesua ferrea L.

A greenhouse pot experiment was conducted to evaluate the feasibility of using a native ornamental plant, Mesua ferrea L. as phytostabilizer for chromium ore tailings (COT) and to assess the metal accumulation capacity. Different ratios of soil and COT were taken in pots and sowed with seeds of M. ferrea. Plants were harvested at various intervals and separated into roots and shoots for analysis of metal concentrations and physiological characteristics of the plants. The study revealed that the plant has great tolerance and stronger ability to accumulate Cr. The results suggested an increase in growth, chlorophyll content, antioxidant activities, as well as metal accumulation capacity of M. ferrea with increasing proportion of COT in the soil. This indicates the plant's efficiency to overcome any stress generated due to excess of chromium as well as other heavy metals. The order of accumulation of heavy metals was observed to be Fe>Cr>Ni>Cd>Co. The accumulation of Cr was higher in root compared to that in shoot. M. ferrea has found to be potential as a native species candidate for phytostabilization of chromium mine tailings.     

混合生物结皮对土壤养分的影响与群落结构之关联——以黄土丘陵区的生物结皮为例

自然条件下生物结皮是藻、藓及地衣等结皮类型以不同比例组成的混合群落,显著影响土壤养分含量,目前混合生物结皮对土壤养分的影响与其群落结构的关系尚不清楚,限制了混合生物结皮土壤养分的评估。为此,研究通过测定单一组成的藻结皮、藓结皮以及80%藻+20%藓、60%藻+40%藓、40%藻+60%藓和20%藻+80%藓4个不同藻藓比例的混合生物结皮土壤有机碳、全氮、全磷、速效磷、铵态氮和硝态氮含量,研究了混合生物结皮土壤养分与其群落结构之间的关联。结果显示：(1)藓结皮层土壤有机碳、全氮、速效磷、铵态氮和硝态氮含量显著高于藻结皮,分别高出166.4%、77.2%、55.1%、56.2%和42.2%。(2)藻藓混合生物结皮土壤有机碳、全氮、速效磷和铵态氮含量与组成和盖度等结构特征有关,可以通过单一类型生物结皮土壤养分含量与盖度加权预测混合生物结皮土壤养分储量。(3)混合生物结皮土壤有机碳、全氮、速效磷和铵态氮储量实测值(x)与预测值(y)拟合的线性函数分别为y=0.97x、y=0.96x、y=1.18x和y=0.92x。(4)混合生物结皮对全磷和硝态氮含量的影响与群落结构无关。生物结皮对下层0—5 ...     

Interaction Between Golden Nematode Globodera Rostochiensis (Woll.), Behrens and Soil Saprophytic Fungi - Its Influence on The Processes of Gaseous Exchange and Crop Yield of Potato (Solanum Tuberosum L.)

During a three-year pot experiment on potato cv. Mila, an effect of Globodera rostochiensis, occurring alone and in conjunction with saprophytic soil fungi (Aspergillus versicolor, Penicillium frequentans, P. verrucosum var. cyclopium, Stachybotrys chartarum, and Trichocladium asperum), on the processes of gaseous exchange (i.e. transpiration and assimilation). Relationships between these parameters and potato crop yield were established as well. It was found that the symptoms of the nematosis had been alleviated as a result of G. rostochiensis interaction with the saprophytes. The effect is connected with a reduction in G. rostochiensis cysts density in the presence of antagonistic saprophytes, which directly contributes to crop increase. The studies demonstrated that soil infection by G. rostochiensis alone, and by this nematode together with fungi, modifies the course of physiological processes in potato plants, which is expressed by reduced assimilation and transpiration intensity, as compared with the control. In the plants that grew on infected soil, assimilation and transpiration ran independently from each other, while positive correlations between the intensities of these processes were demonstrated in the control plants.