Inhibitory effect of high soil pH on growth and mineral metabolism of rice and its reversal by zinc

Increasing soil pH retarded growth, tillers and bio-mass production of rice cultivar Sarjoo-52. Application of 10 to 15 kgZn ha(-1) increased the bio-mass by 33 to 41% at pH 8.5 and 27 to 32% at pH 10.3. Panicle length, rachis branches, total spikelets, filled grains, grain size were all adversely affected to the tune of 19, 23, 40, 74 and 21%, respectively by higher soil alkalinity at pH 10.3. Alkalinity resulted in 19, 31 and 65% spikelet sterility which reduced to 3, 21 and 55% at pH 8.5, 9.5 and 10.3, respectively by Zn applied @ 15 kg ha(-1). Grain yield reduced to 50% at pH 10.3 but Zn in general, raised the yield levels by 1.6 to 2.3, times. The chlorophyll decreased by 36 to 50% whereas carbonic anhydrase activities decreased only by 13% due to increase in soil sodicity and alkalinity. Further, increase in pH caused significant decrease in Zn, Ca, Mg, P and K concentrations but phenomenal rise in Na content Zinc application, apart from increasing tissue Zn content, elevated Ca :Na and K :Na ratio resulting in improved growth and yield of rice under soil sodicity and alkalinity.     

Studies on seed germination and growth in weed species of rice field under salinity stress

An investigation was made to see the salt tolerance of 10 weed species of rice. Properly dried and treated seeds of weed species were placed on 9 cm diameter petridishes lined with Whatman No. 1 filter paper under 6 salinity regimes, viz. 0 (control), 4, 8, 16, 24 and 32 dS m(-1). The petri dishes were then kept in germinator at 25 +/- 1.0 degrees C and 12 hr light. The number of germinated seeds were recorded daily. The final germination percentage, germination index (GI), seedling vigour index, mean germination time and time for 50% germination were estimated. Root and shoot lengths of the weed seedlings were measured at 20 days after salt application and relative growth values were calculated. Results revealed that salinity decreased final germination percentage, seed of germination as measured by GI, and shoot and root length in all the species. Germination of most of the weed seeds was completely arrested (0) at 32 dS m(-1) salinity except in E. colona (12%) and C. iria (13.9%). The species C. iria, E. colona, J. linifolia and E. crusgalli showed better germination (above 30%) upto 24 dS m(-1) salinity level and were regarded as salt-tolerant weed species. J. linifolia, F. miliacea, L. chinensis and O. sativa L. (weedy rice) were graded as moderately tolerant and S. zeylanica, S. grosus and C. difformis were regarded as least tolerant weed species.     

NaCl胁迫对高粱成熟叶质外体和共质体中Na~ 、Ca~(2 )浓度的影响

在c（NaCl）＝200mmol／L，t＝14d胁迫条件下，盐敏感品种糖高粱（T）成熟叶生长抑制、含水量的下降和质膜透性均明显大于耐盐品种独角虎（D）；盐胁迫下，质外体和共质体中Na＋浓度明显增加，增加的幅度是质外体大于共质体，T大于D．相反，盐胁迫下质外体和共质体Ca2＋浓度均明显下降，研究结果表明：质外体Na＋浓度剧增并没有改变细胞膨压，而可能通过取代质膜上Ca2＋而破坏质膜选择透性，从而引发盐害     

中新天津生态城植物多样性分析

2008年对中新天津生态城规划区域植被进行调查,发现该区域以盐生植被为主,现存植被可分为4个类型15种植物群落;植物区系成分含38科101属135种。本区植被的分布受土壤盐碱度的制约,并受当代人为因素的严重影响,盐生植物资源丰富,其中26种耐盐植物具有较大开发利用价值。因此,建议采取保留与保护现存的盐生植被;利用耐盐植物进行盐碱地绿化及研究和发展本区盐碱地环境的生态管理。     

碱性矿化水灌溉的淋洗分数

耐盐碱试验表明,在生育期内,小麦耐盐能力强于玉米,而耐碱能力弱于玉米.利用0.5-3.5 g/L的碱性矿化水灌溉时,淋洗分数约为4.4%～7.5%.相应地,需要增加的补水量小麦地为3181～     

脱硫石膏改良中度苏打盐渍土施用量的研究

采用盆栽试验和田间试验相结合的方法,通过种植油葵(Helianthus annus),进行了脱硫石膏施用量的试验.结果表明,施用脱硫石膏能够有效降低土壤碱化度、总碱度和pH值,但却增加了土壤全盐量;施用脱硫石膏可显著提高油葵出苗率和产量,但施用量过高会抑制油葵的生长发育.施用11 250 kg·hm-2脱硫石膏对中度苏打盐渍土改良效果最佳,最有利于油葵的生长发育,耕作层土壤碱化度、总碱度和pH值分别降至6%、0.2 cmol·kg-1和8.5以下,油葵出苗率达到70%以上,田间试验中油葵产量高达2 031 kg·hm-2,与不施脱硫石膏处理相比,增产率达到16.2%.     

Reclamation techniques in southwestern wyoming

Bridger Coal Company operates a 5.8 million tpy surface coal mine thrity five miles northeast of Rock Springs. Wyoming. Approximately 20.000 acres are under permit, with disturbance over the life of the mine projected to reach 10,000 acres. Located on the western rim of the continental divide, the mine receives less than 8.5 inches of precipitation annually. Soils in the area are coarse-textured. and problems associated with elevated salinity and sodicity arc encountered.A variety of common reclamation techniques have been modified to reflect these conditions. Soil horizons are segregated during salvage operations (the surface six inches as topsoil and the balance as subsoil). Unsuitable materials are not salvaged. Direct application of soil is used (over 130 acres in 1983) to maximize native plant regeneration and conserve soil fertility. Inter-seeding of seeding failures has proven to be significantly more successful than chisel plowing and reseeding. Broadcast seeding has been ineffective because of strong winds, and a no till drill has been modified to handle diverse seed mixes and rock conditions. The utility of fertilization under typically xeric moisture regimes is being evaluated. A research project has been initiated to assess establishment of a predominately native, diverse seed mix under irrigation, as well as to determine irrigation rates and duration.     

Reclamation techniques in southwestern wyoming

Bridger Coal Company operates a 5.8 million tpy surface coal mine thrity five miles northeast of Rock Springs. Wyoming. Approximately 20.000 acres are under permit, with disturbance over the life of the mine projected to reach 10,000 acres. Located on the western rim of the continental divide, the mine receives less than 8.5 inches of precipitation annually. Soils in the area are coarse-textured. and problems associated with elevated salinity and sodicity arc encountered. A variety of common reclamation techniques have been modified to reflect these conditions. Soil horizons are segregated during salvage operations (the surface six inches as topsoil and the balance as subsoil). Unsuitable materials are not salvaged. Direct application of soil is used (over 130 acres in 1983) to maximize native plant regeneration and conserve soil fertility. Inter-seeding of seeding failures has proven to be significantly more successful than chisel plowing and reseeding. Broadcast seeding has been ineffective because of strong winds, and a no till drill has been modified to handle diverse seed mixes and rock conditions. The utility of fertilization under typically xeric moisture regimes is being evaluated. A research project has been initiated to assess establishment of a predominately native, diverse seed mix under irrigation, as well as to determine irrigation rates and duration.     

Association studies for agro-physiological and quality traits of triticale x bread wheat derivatives in relation to drought and cold stress

Correlation coefficient analysis conducted on 22 triticale x bread wheat derivatives along with six checks to select true- breeding derivative(s) for future hybridization programme with tolerance to drought and cold stress conditions as well as better quality traits revealed significant correlation of grain yield with spikelets per spike, biological yield, harvest index, leaf area index. Interestingly, the grain yield and drought susceptibility index showed no association. However, with cold tolerance it showed significant positive correlation indicating the desirability of certain plant traits under cold stress. The grain yield exhibited no association with quality traits which might assist in the predictability of high yielding varieties with high protein, total sugars, reducing sugars and non-reducing sugars. Path coefficient analysis revealed that biological yield had the highest positive direct effect on grain yield followed by harvest index, specific leaf weight, stomatal number, 1000 grain weight, stomatal size, spikelets per spike and days to heading. Therefore, indirect selection for these plant traits in order should be exercised in selecting drought tolerant genotypes. Two genotypes (RL-124-2P2 and RL 111P2) were found to be drought and cold tolerant with high grain yield, spikes per plant, spikelets per spike and leaf area index.     

Soil amendments and cultivar selection can improve rice yield in salt-influenced (tsunami-affected) paddy fields in Sri Lanka

The tsunami disaster in the Indian Ocean in December 2004 caused devastation of agricultural soils by salt water over wide areas. Many rice fields located close to the coast were affected by the flood of seawater. Electric conductivity (EC) of soils in tsunami-affected rice fields was found to be higher compared to unaffected fields 2 years after the tsunami. Four soil amendments (gypsum, dolomite, cinnamon ash and rice-husk-charcoal) were tested for their influence on improving the yield parameters of rice grown in a tsunami-affected and a non-affected area. Yield parameters were compared with an untreated control of the same cultivar (AT362) and with a salt resistant rice variety (AT354). The salt resistant variety had the highest grain yield. The two amendments gypsum and rice-husk-charcoal led to an increase in grain yield compared to the untreated control, whereas dolomite and cinnamon ash had no significant effect on grain yield.     

柳树幼苗渗透调节物质对中、碱性钠盐响应的差异性

世界土壤盐渍化问题日益严重.中国拥有面积广大的盐碱地,它严重地制约着中国农业的可持续发展.中国北方内陆盐碱地土壤含有NaCl、Na2SO4、Na2CO3、NaHCO3 多种盐分,类型复杂多样.柳树是我国重要的造林绿化和水土保持乡土树种,对改良盐碱地美化生态环境具有重要作用,因此研究柳树耐碱性及其适应盐碱生理差异性具有重要意义.以盐柳1号（Salix psammophila）为试验材料,分别以中性盐NaCl 和Na2SO4、碱性盐NaHCO3 和Na2CO3 混合模拟盐、碱胁迫（两者物质的量比均为9∶1）,各设计了5 个梯度处理,总共胁迫14 d 后,研究盐与碱胁迫下柳树幼苗叶片含水量、脯氨酸、可溶性糖和可溶性蛋白的变化情况.结果表明：随着盐浓度的升高柳树叶片中的含水量呈减少趋势,在碱性盐胁迫下叶片含水量下降趋势更大,盐浓度达到200 mmol·L^-1 时,叶片含水量达到最低为23.8%,仅为对照的32%（P〈0.01）达到极显著性差异,并且相比于中性盐在碱性盐胁迫下叶片损失水分更多.同样在碱性盐胁迫情况下随着盐浓度升高,柳树叶片中的三种渗透调节物质脯氨酸、可溶性糖和可溶性蛋白含量均增加,其中,碱性盐浓度达到200 mmol·L^-1 时植物叶片中脯氨酸质量分数为100.38 μg·g^-1 达到最大值为对照的3.18 倍（P〈0.01）达到极显著性差异,为同浓度中性盐胁迫下的1.57 倍（P〈0.05）.当碱性盐浓度达到150 mmol·L^-1 时,柳树叶片可溶性糖质量分数是2.4 mg·g^-1 为对照的1.86 倍（P〈0.05）达到显著性差异水平,为同等浓度中性盐胁迫下的1.69 倍（P〈0.05）,叶片可溶性蛋白质量分数为7.84 mg·g-1 为对照的1.67 倍（P〈0.05）差异显著,为同等浓度中性盐胁迫下的1.56 倍（P〈0.05）.综上所述,从渗透胁迫角度分析,碱性盐胁迫比中性盐胁迫是两种不同性质的胁迫,并且碱胁迫对柳树造成的危害损伤更大.     

Photosynthetic sulfur bacteria from Zimapan Reservoir (Mexico): Seasonal variations and toxic effects of zinc in a microcosm system

Photosynthetic sulfur bacteria oxidize the sulfide produced by dissimilatory sulfate-reducing bacteria, thus preventing the occurrence of pollution by these compounds in the oxygenic zone of aquatic systems. Zinc is one of the most abundant heavy metals. Its toxic effects have been documented in various organisms that can photosynthesize, but a lack of information prevails in this respect, about photosynthetic sulfur bacteria. The aim of the present study was to evaluate the toxic effects of zinc on green sulfur bacteria (Chlorobiaceae) and purple sulfur bacteria (Chromatiaceae) in a microcosm as well to explore the possible relationships between the bacterial population growths with the physicochemical properties of the metalimnion of Zimapan Reservoir (Mexico) during a 1-year period. Hydrosoluble organic carbon (HOC) and light availability in the metalimnion were the limiting factors for growth in these bacteria. Higher HOC levels occurred in Spring, at the end of the wet season and in Winter. Current zinc levels in the reservoir seem to elicit toxic effects. At lethal zinc concentrations, the best concentration-response relationship was shown. The biomarker for purple sulfur bacteria was the bacteriochlorophyll content, while total reducing sugar was the best biomarker for green sulfur bacteria. At sublethal concentrations, zinc alters adenosine triphosphate levels, total reducing sugar, total protein content, and bacteriochlorophyll content. The observed responses indicate that green sulfur bacteria are more sensitive than purple sulfur bacteria and are suitable target organisms for use in establishing the accepted threshold concentration of zinc (NOEC 0.056–0.097 mg L^?1 of Zn) in anoxic deep water.     

Effect of water quality on yield of sugar beet and sweet sorghum

To study the effects of quality of water on soil and plant, an experiment was conducted at Rudashat Drainage and Reclamation Experiment Station in 1999. Four irrigation water salinities (2, 5, 8 and 11 ds m(-1)) and two sugar crops (sugar beet and sweet sorghum) were used in this experiment. The results showed that under the same water quality, sweet sorghum used 2700 cubic meter per hectare less water than sugar beet. As the quality of irrigation water decreased, the soil salinity and exchangeable sodium percent increased which caused yield reduction for both plants. Sugar beet by accumulating Na and Cl in its leaves tolerated salinity but its usage as a forage crop caused some limitations, whereas sweet sorghum by not accumulating Na and Cl escape salinity and it can be used as a forage crop without any limitation.     

磷肥施用量对缺锌土壤上水稻生长的影响

磷肥施用量对缺锌土壤上水稻生长的影响李延，潘伟彬（福建农业大学土化系，福州３５０００２）（闽西职业大学，龙岩３６４０２１）ＥｆｆｅｃｔｏｆＰｈｏｓｐｈａｔｉｃＦｅｒｔｉｌｉｚｅｒｏｎＧｒｏｗｔｈｏｆＲｉｃｅｏｎＺｉｎｃＤｅｆｉｃｉｅｎｔＳｏｉｌ￥Ｌｉ...     

Microbial community and functional genes in the rhizosphere of alfalfa in crude oil-contaminated soil

A rhizobox system constructed with crude oil-contaminated soil was vegetated with alfalfa (Medicago sativa L.) to evaluate the rhizosphere effects on the soil microbial population and functional structure, and to explore the potential mechanisms by which plants enhance the removal of crude oil in soil. During the 80-day experiment, 31.6% of oil was removed from the adjacent rhizosphere (AR); this value was 27% and 53%higher than the percentage of oil removed from the far rhizosphere (FR) and from the non-rhizosphere (NR), respectively. The populations of heterotrophic bacteria and hydrocarbon-degrading bacteria were higher in the AR and FR than in the NR. However, the removal rate of crude oil was positively correlated with the proportion of hydrocarbon-degrading bacteria in the rhizosphere. In total, 796, 731, and 379 functional genes were detected by microarray in the AR, FR, and NR, respectively. Higher proportions of functional genes related to carbon degradation and organic remediation, were found in rhizosphere soil compared with NR soil, suggesting that the rhizosphere selectively increased the abundance of these specific functional genes. The increase in water-holding capacity and decrease in pH as well as salinity of the soil all followed the order of AR>FR>NR. Canonical component analysis showed that salinity was the most important environmental factor influencing the microbial functional structure in the rhizosphere and that salinity was negatively correlated with the abundance of carbon and organic degradation genes.     

多种盐分离子作用下苋菜对重金属的吸收累积特征

模拟不同淋洗脱盐阶段滩涂土壤孔隙水中盐分和重金属含量,通过苋菜水培试验,研究多种盐分离子（SO42-、Cl-、NO3-、CO32-、Na＋、Ca2＋、K＋和Mg2＋等）的共同作用下,苋菜对Zn、Cu、Ni、Cr、Pb和Cd 6种重金属的吸收、累积和转运的变化。结果表明,与对照相比,在不同盐分离子浓度影响下,苋菜茎叶中Cd的累积增幅为69.2%～146.2%,而茎叶中其他重金属的含量无显著变化,苋菜根系中Cd、Pb、Cr、Ni和Cu含量的最大增幅分别为187.8%、197.7%、305.7%、228.1%和58.2%,但根系中Zn含量未受到显著影响。在相对较高的盐分离子浓度（〉1 312.4 mg.L-1）范围内,不同盐分离子浓度处理间苋菜茎叶和根系中6种重金属含量差异均不显著。盐分处理显著降低了苋菜对Pb、Cr、Ni和Cu的转移系数,但未显著影响苋菜对Cd和Zn的转移系数。     

Phytoavailability and potential transfer of Pb from a salt-affected soil to Atriplex verucifera,Salicornia europaea and Chenopodium album

The phytoavailability and potential transfer of Pb to Atriplex verucifera, Salicornia europaea and Chenopodium album in two calcareous soils with different salinity/sodicity were compared. The soils were spiked with 0, 250, 500 and 1000 mg Pb kg^?1 soil. Plant shoots were harvested and analysed for total Pb after they had been grown in the contaminated soils. Visual MINTEQ 3.0 was used to calculate the speciation of soluble Pb in the experimental soils. Results showed that although the concentrations of 1 M NH₄NO₃-extractable Pb were relatively similar, speciation of Pb in the soils were not the same. Salicornia europea was found to be the most salinity/sodicity-tolerant plant. When the plants were grown in non-saline soil, the Pb tolerance of the three plants was as follows: A. verucifera > C. album >S. europea, whereas in saline (sodic) soil, Pb tolerance was in the order S. europea > C. album > A. verucifera. Lead phytotoxicity to A. verucifera and C. album was higher in the saline soil, whereas for S. europea, Pb toxicity was higher in the non-saline soil. It could be concluded that the phytoavailability of Pb and its interactions with plants are widely dependent on soil salinity level and type of plant.     

Zinc and copper induced changes in physiological characteristics of Vigna mungo (L.)

The effect of deleterious concentration of zinc and copper provided either individually or in combination in the nutrient media was investigated in order to assess the effect of metal interaction in Vigna mungo (L.). Both metals showed negative effect and led to a marked decrease in seed germination (20%), seedling growth (91.7%) and nitrate reductase activity (85.7%) with the increase in metal concentrations. The present study also emphasizes on the response of catalase and peroxidase enzyme under zinc and copper stress. Both antioxidant enzymes exhibited an increasing trend under different treatment conditions but it was reverse at highly toxic metal concentration. The results showed active involvement of peroxidase enzyme in regulating oxidative stress rather than catalase enzyme, as the specific activity of peroxidase enzyme got increased by 8.94% under the combined metals stress whereas catalase activity got declined by 60.97% in comparison to control due to excessive stress. The combined effect of copper and zinc metal was more pronounced in comparison to their individual effects.     

Trace elements in wild grasses: a phytoavailability study on a remediated field

There have been significant efforts to establish a widely usable method for the prediction of trace element bioavailability in soil. In this work, we used extraction with 0.01 M CaCl₂ and 0.05 M ethylenediaminetetraacetic acid (EDTA) to estimate bioavailable concentrations of As, Cd, Cu, Pb, and Zn in a soil moderately contaminated with trace elements 1 and 2 years after the application of three amendments. The experiment took place in a field plot of a soil affected by the toxic spill of the Aznalcóllar mine. Four treatments were established: three with amendments (biosolid compost, sugar beet lime, and a combination of leonardite plus sugar beet lime) and a control without amendment. Trace element concentrations of two representative species in each year (Lamarckia aurea and Poa annua in 2004 and Lamarckia aurea and Bromus rubens in 2005) were analyzed. The results showed a positive effect of the amendments both on soil and vegetation. Trace element concentrations in plants growing in the amended subplots were lower than those in plants from nonamended subplots. As a rule, concentrations of CaCl₂-soluble Cd, Cu, and Zn in soil were positively correlated with trace elements in plants, whereas EDTA extraction was scarcely correlated with plant concentration. For species of grasses, especially L. aurea, CaCl₂ seems to be a more suitable extractant to predict trace element bioavailability in this contaminated soil.     

Type of disturbance and ecological history determine structural stability.

This study aims to reveal whether complexity, namely, community and trophic structure, of chronically stressed soil systems is at increased risk or remains stable when confronted with a subsequent disturbance. Therefore, we focused on a grassland with a history of four centuries of patchy contamination. Nematodes were used as model organisms because they are an abundant and trophically diverse group and representative of the soil food web and ecosystem complexity. In a field survey, a relationship between contaminants and community structures was established. Following, two groups of soil mesocosms from the field that differed in contamination level were exposed to different disturbance regimes, namely, to the contaminant zinc and a heat shock. The zinc treatment revealed that community structure is stable, irrespective of soil contamination levels. This implies that centuries of exposure to contamination led to adaptation of the soil nematode community irrespective of the patchy distribution of contaminants. In contrast, the heat shock had adverse effects on species richness in the highly contaminated soils only. The total nematode biomass was lower in the highly contaminated field samples; however, the biomass was not affected by zinc and heat treatments of the mesocosms. This means that density compensation occurred rapidly, i.e., tolerant species quickly replaced sensitive species. Our results support the hypothesis that the history of contamination and the type of disturbance determine the response of communities. Despite that ecosystems may be exposed for centuries to contamination and communities show adaptation, biodiversity in highly contaminated sites is at increased risk when exposed to a different disturbance regime. We discuss how the loss of higher trophic levels from the entire system, such as represented by carnivorous nematodes after the heat shock, accompanied by local biodiversity loss at highly contaminated sites, may result in detrimental effects on ecosystem functions.