Soil solution chemistry of two reclamation sites in the Lusatian lignite mining district as influenced by organic matter application

Due to a large reclamation (recultivation) demand in the Lusatian lignite mining district, efficient strategies for the rehabilitation of abandoned mine sites are needed. A field study was conducted for comparing the effects of three different fertilizer treatments (mineral fertilizer, sewage sludge and compost) on soil solution chemistry of both a lignite and pyrite containing spoil as well as a lignite and pyrite free spoil. The lignite and pyrite containing spoil was ameliorated with fly ash from a lignite power plant (17–21 t ha⁻¹ CaO), whereas the lignite and pyrite free site received 7.5 t ha⁻¹ CaO in form of limestone. Fertilizer application rates were: mineral fertilizer 120 N, 100 P and 80 K kg ha⁻¹. 19 t ha⁻¹ sewage sludge and 22 t ha⁻¹ compost were applied. Soil solution was sampled in 20, 60 and 130 cm depth for the period of 16 months. Solution was collected every fortnight and analysed for pH, EC, Ca²⁺, Mg²⁺, K⁺, Na⁺, Feⁿ⁺, Alⁿ⁺, Mn²⁺, Zn²⁺, NO₃ ⁻, NH₄ ⁺, SO₄ ²⁻, Cl⁻, PO₄ ³⁻, C_inorg and DOC. Lignite and pyrite containing spoil differed clearly from lignite and pyrite free spoil regarding soil solution concentrations and composition. Acidity (H⁺) produced by pyrite oxidation led to an enhanced weathering of minerals and, therefore, to at least 10 fold higher soil solution concentrations compared to the lignite and pyrite free site. Major ions in solution of the lignite and pyrite containing site were Ca²⁺, Mg²⁺, Feⁿ⁺, Alⁿ⁺ and SO₄ ²⁻, whereas soil solution at the lignite and pyrite free site was dominated by Ca2+, Mg²⁺ and SO₄ ²⁻. At both sites application of mineral fertilizer led to an immediate but short term (about 1 month) increase of NO₃ ⁻, NH₄ ⁺ and K+ concentrations in soil solution down to a depth of 130 cm. Application of sewage sludge caused a long term (about 16 months) increase of NO_{3 3} ⁻ in the topsoil, whereas NO₃ ⁻ concentrations in the subsoil were significantly lower compared to the mineral fertilizer plot. Compost application resulted in a strong long-term increase of K+ in soil solution, whereas NO₃ ⁻ concentrations did not increase. Concentrations of PO₄ ³⁻ in soil solution depend on solution pH and were not correlated with any treatment. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of N-enriched rock powder on soil chemistry,organic matter formation and plant nutrition in lignite-poor sandy mine spoil in the forest reclamation practice

The effects of a slow-release N-enriched rock powder on soil chemistry, on the development of the soil vegetation (field layer vegetation), on the nutritional status of pine seedlings (Pinus sylvestris L.), and on decomposition rates of cellulose in lignite-poor mine spoils were studied. In the initial phase after afforestation fertilization caused a significant increase in NO₃ ⁻-N concentrations in the soil solution of the top-soil (0–60 cm). Subsequently, NO₃ ⁻-N concentrations of all N fertilized treatments decreased with the exception of the highest N application area (500 kg N ha⁻¹). This decrease of NO₃ ⁻-N concentrations was related to the establishment of a field layer vegetation, which developed according to the amount of N applied. In the above-ground phytomass of the field layer vegetation a maximum N accumulation amount of 22 kg ha⁻¹ was measured. Cellulose decomposition increased with higher N application rates. In the second year after N-fertilization, the pine needles indicated insufficient supply for almost all nutrients except for N. The deficiency symptoms were most pronounced at the plots that had received the highest amounts of nitrogen. This phenomenon appears to be related to the competition by the field layer vegetation. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investigations on pyrite oxidation in mine spoils of the Lusatian lignite mining district

The impact of organic waste material and fly ash on microbial and chemical pyrite oxidation was investigated in a field experiment, as well as in column tests under laboratory conditions. For the field experiment, pyritic mine spoil was ameliorated with fly ash and treated either with mineral fertiliser, with sewage sludge or with compost. Independent of treatment, during the 18 months following application, the pyrite-S contents decreased steadily in the top spoil (0–30 cm depth). However, high variations of the pyrite-S content were observed. Compared to other pyrite oxidation studies, the pyrite content of the mine spoil at the experimental site was low. Therefore, a model spoil with a higher pyrite content, derived from Tertiary strata of the overburden sequence in the same open-cast mine, was used for the column experiments. For the first column experiment, the model spoil was mixed with fly ash and mineral fertiliser, reflecting the common reclamation practice in the Lusatian open-cast lignite mining district. Columns with this spoil were either inoculated with different cell numbers of autochthonous acidophilic bacteria, isolated from the model spoil, or with a commercial strain of Thiobacillus ferrooxidans. The ratio of sulphate-S to total S was used as a measure for the degree of pyrite oxidation. The ratio of sulphate-S to total S increased within 28 days of incubation. The increase was related to the inoculated cell numbers of bacteria, but independent of the origin of the bacteria. It can be stated, that autochthonous bacteria from the model spoil oxidised pyrite at a similar rate as did the commercial T. ferrooxidans strain. For the second column test, mineral fertiliser, sewage sludge or compost were applied to the model spoil. The columns were inoculated with autochthonous bacteria, isolated from the model spoil. Application of sewage sludge and compost seemed to promote the weathering of pyrite, as the ratio of sulphate-S to total S increased more rapidly in these treatments compared to control or mineral fertiliser application. Both experiments showed an increase of cell numbers of inoculated bacteria, independent of the ratio of sulphate-S to total S. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ground beetle communities on reclaimed mine spoil: Effects of organic matter application and revegetation

On a study site in the Lusatian lignite mining region (Germany), sandy mine spoil was ameliorated with either sewage sludge, compost or mineral fertilizer. Plots were sown with the grass Secale multicaule and planted with pine seedlings except for a control that was not meliorated and not revegetated. Pitfall catches of ground beetles in 1996/97 yielded high numbers of species and individuals directly after revegetation. The dominant beetles were xerophilic species, known to prefer open sandy sites. Catches in different plots were positively correlated with the amount of vegetation cover and declined as follows: amelioration with sewage sludge > compost > mineral fertilizer > untreated control. Even beetles characteristic of open sandy sites showed a distinct preference for plots with high vegetation cover treated with organic waste. For the dominant species, an attraction to shelter and a more balanced, humid microclimate is assumed. A year-to-year comparison showed an increase in beetles typical of dry grasslands and ruderal sites in the second year, while characteristic species of open sandy sites decreased. Application of organic waste combined with revegetation led to an immediate increase in beetle numbers. In the long term, revegetation would be expected to reduce suitable habitats for endangered ground beetles which prefer open sites with poor sandy soils. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impacts of long-term application of organic fertilizers on soil quality parameters in reclaimed loess soils of the Rhineland lignite mining area

On the basis of long-term field experiments, the impact is demonstrated of the periodic application of organic fertilizers on the accumulation of organic matter and the development of the micro-pollutant content of reclaimed loess soils of the Rhineland lignite mining area under agricultural use. The oldest of these experiments (‘Berrenrath Humus Accumulation Experiment’) was begun in 1969. The results show that the regular input of organic matter (e.g. manure, waste compost, sewage sludge) favors the accumulation of soil organic matter (SOM). However, the type of organic material applied seems to be less important to the long-term accumulation process than the application rate. This is also true for composted and uncomposted manure, if the decay of organic matter during the composting process is taken into account. Nevertheless, the application of similar amounts of organic C in the form of manure resulted in a higher accumulation of SOM in a nitrogen-reduced farming system. Depending on the treatment, accumulation rates were between 0.02 and 0.08% SOM per year with values decreasing with time. From these results, it is estimated that reclaimed soils will take much longer to reach the former SOM level than was previously assumed. However, it is important to determine which SOM level is adequate for different soil functions (e.g. production function, filter and buffer function, transformation function), and whether the young SOM of reclaimed soils has the same properties as older SOM in undisturbed topsoils. As was expected, long-term fertilization with sewage sludge and waste compost led to an accumulation of some micro-pollutants in the topsoils treated. Nevertheless, the observed concentrations are quite low compared to background levels in topsoils of rural regions in North Rhine-Westphalia. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

The simulation of soil organic matter and nitrogen accumulation in Scots pine plantations on bare parent material using the combined forest model EFIMOD

The individual-based combined forest model EFIMOD including the soil-sub model SOMM has been used for the simulation of Scots pine stand growth and soil organic matter (SOM) accumulation on a humus-free bare mineral surface. The growth of Scots pine plantation, with an initial density of 10 000 trees ha⁻¹ and average tree biomass of 0.01 kg was simulated for 50 yr under Central European climatic conditions (i) with varying atmospheric nitrogen inputs and (ii) different rates of initial application of raw undecomposed organic material or compost, on humus-free parent material. The accumulation of typical raw humus was simulated in all cases. The accumulation was most intensive in the simulation of high atmospheric nitrogen input. The humus pool in the mineral topsoil was small but achieved its maximum value with compost application. SOM nitrogen accumulation was scant in all cases, except the compost applications with low atmospheric nitrogen input. No statistically significant differences of SOM and stand parameters were found between variants without organic matter and those with low input of organic manure. However, the maximum relative rate of SOM and nitrogen accumulation was found in the scenario without organic manure, under slowly growing unstable Scots pine plantation. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phosphorus availability in different types of open-cast mine spoil and the potential impact of organic matter application

Greenhouse experiments were conducted in order to determine for carboniferous and non-carboniferous mine spoil substrates from the Lusatian lignite mining area (i) the suitable extraction method for plant available P, (ii) the soil capacity for immobilisation of P and (iii) the impact of sewage sludge and compost on P availability. Ca-lactate extraction (DL) and NH₄F-extraction (Bray) were both suited equally well for the determination of plant available P as they extracted similar amounts of P on both spoils, they showed a close correlation with each other (R=0.97 ²) and they showed a close relation with plant P uptake (R²=0.63 and R²=0.66, respectively). Phosphorus recovery from limed carboniferous mine spoil five days after mineral fertiliser application was only 50%, and decreased to 30% after 54 days. As pH was increased from 3.0 to 5.0 the amount of P immobilised decreased only by about 5%. Several pH dependent processes of P immobilisation and release could occur concurrently counteracting each other. One process could be P sorption to newly formed hydroxy-Al-surfaces but P desorption could also take place as pH increases by decreasing surface positive charge. Finally, due to high Ca concentrations in spoil solution formation of Ca-phosphates, even at lower pH values, cannot be excluded as a possible mechanism of P immobilisation. As part of the P is bound in organic matter, application of P with organic matter resulted in a lower P recovery compared to mineral P-fertiliser. However, the amount of P recovered did not differ between carboniferous and non-carboniferous mine spoil, if P was applied in the form of organic matter, indicating that the application of P with organic matter might be a measure to overcome P immobilisation in carboniferous mine spoils. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Temporal and spatial development of soil solution chemistry and element budgets in different mine soils of the Lusatian lignite mining area

Lignite and pyrite contents in the dump materials of the Lusatian opencast mining district in East Germany result in high acidification and salinization potentials. These extreme conditions require considerable amounts of alkaline materials like ash or lime to enable recultivation and revegetation. Investigations at chronosequence sites on different mining substrates show characteristic developments of the soil solution chemistry. Processes like weathering of primary and formation of secondary mineral phases, acid production and buffering, and their impacts on both the solid and the liquid soil phase result in high temporal and spatial dynamics especially in the initial phase of soil and ecosystem development. To study these processes we continuously collected soil solutions from different soil depths at seven sites with two representative soil substrates. All sites were afforested with pine and cover stand ages from 1 to 60 yr. The results show that actual pyrite oxidation occurs at the youngest sites on lignite and pyrite containing substrates leading to extremely low pH values and high Feⁿ⁺ and SO₄ ²- concentrations. The considerable acid production causes weathering of aluminium silicates resulting in high Alⁿ⁺ concentrations. Ca²⁺ concentrations are unexpectedly high even at low pH showing no correlation to amelioration amounts or depths. Therefore it seems most probable that these mining substrates contain geogenic Ca sources. The transport of dissolved weathering products is limited due to low leaching rates enabling formation of secondary phases which control the actual composition of the soil solution. Depth gradients of the soil solution composition at the chronosequence sites point to a gradual transport and leaching of these secondary phases from the soil profiles. Soil solution composition and dynamics at lignite and pyrite free sites show completely different patterns and have a higher potential for successful sustainable recultivation. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Deep placement of Mn fertiliser on a sandy soil increased grain yield and reduced split seed in Lupinus angustifolius

Experiments were conducted over two years with Lupinus angustifolius L. on a site with acid sandy soil near Esperance, Western Australia to determine if deep placed manganese fertilizer increases lupin grain yield. Manganese at 4 and 8 kg ha⁻¹ was placed below the surface immediately before sowing at 4, 20 and 30 cm and 4, 8, 12, 16 and 20 cm in 1987 and 1988 respectively. Foliar Mn applied at 1 kg ha⁻¹ when the first order laterals were in mid-flowering stage, was also compared. Increasing the depth of Mn placement increased grain yield in both years. The deepest placed Mn increased grain yields by 255 kg ha⁻¹ (10%) and 430 kg ha⁻¹ (106%) in year 1 and year 2 over the shallow (4 cm) placed Mn. The higher responses to deep placed Mn occurred in year 2, the year with the driest spring and most intense aphid infestations. Foliar applied Mn was as effective as most deep placed Mn treatments, except for the highest rate (8 kg ha⁻¹) at the greatest depth (20 cm) in year 2. The higher rate of applied Mn gave the best grain yields. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agricultural reclamation of disturbed soils in a lignite mining area using municipal and coal wastes: the humus situation at the beginning of reclamation

Soils disturbed by long-term opencast mining were treated with organic waste materials for reclamation. Humic substances were extracted from waste and soil samples and analysed using pyrolysis-gas chromatography/mass spectrometry and electrofocusing. Furthermore, analytical pyrolysis permits to study all starting materials in situ. According to structural similarities, the statistical evaluation of the pyrolysis results clearly indicates three sample groups. The first group, called compost, implies the waste materials compost and composted sewage sludge. Moreover, pyrolysis revealed that coal humic substances are predominant in brown coal sludge, pure mine soils and mine soils treated with the different organic waste materials. They constitute the second group. The sewage sludge contains a high nitrogen potential, as expected, and represents the third group. Finally, pyrolysis generally showed the specific structural characteristics of humic and fulvic acids, respectively. Electrofocusing yielded for all samples a signal pattern that is typical of humic substances. However, number and ratio of the signals differ according to the special structural features of the samples. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Contribution of Lolium perenne rhizodeposition to carbon turnover of pasture soil

Carbon rhizodeposition and root respiration during eight development stages of Lolium perenne were studied on a loamy Gleyic Cambisol by ¹⁴CO₂ pulse labelling of shoots in a two compartment chamber under controlled laboratory conditions. Total ¹⁴CO₂ efflux from the soil (root respiration, microbial respiration of exudates and dead roots) in the first 8 days after ¹⁴C pulse labelling decreased during plant development from 14 to 6.5% of the total ¹⁴C input. Root respiration accounted for was between 1.5 and 6.5% while microbial respiration of easily available rhizodeposits and dead root remains were between 2 and 8% of the ¹⁴C input. Both respiration processes were found to decline during plant development, but only the decrease in root respiration was significant. The average contribution of root respiration to total ¹⁴CO₂ efflux from the soil was approximately 41%. Close correlation was found between cumulative ¹⁴CO₂ efflux from the soil and the time when maximum ¹⁴CO₂ efflux occurred (r=0.97). The average total of CO₂ Defflux from the soil with Lolium perenne was approximately 21 μg C-CO₂ d⁻¹ g⁻¹. It increased slightly during plant development. The contribution of plant roots to total CO₂ efflux from the soil, calculated as the remainder from respiration of bare soil, was about 51%. The total ¹⁴C content after 8 days in the soil with roots ranged from 8.2 to 27.7% of assimilated carbon. This corresponds to an underground carbon transfer by Lolium perenne of 6–10 g C m⁻² at the beginning of the growth period and 50–65 g C m⁻² towards the end of the growth period. The conventional root washing procedure was found to be inadequate for the determination of total carbon input in the soil because 90% of the young fine roots can be lost. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impact of CO2 Enrichment and Variable Nitrogen Supplies on Composition and Partitioning of Essential Nutrients of Wheat

This study was conducted to determine effects of nitrogen supply (75 and 150 kg(N) ha⁻¹) and CO₂ enrichment on partitioning of macro and micro nutrients in wheat (Triticum aestivum L. cv. HD-2285). Plants were grown from seedling emergence to maturity inside open top chambers under ambient CO₂ (CA, 350 ± 50 μmol mol⁻¹) and elevated CO₂ (CE, 600 ± 50 μmol mol⁻¹). Leaves, stems and roots of the same physiological age were analyzed for carbon, nitrogen, calcium, copper, iron, zinc and manganese content at 40, 60 and 90 d after germination. C, Cu, Mn and Zn content was higher in the stem, leaves and roots on dry mass basis under CE than CA. However, N and Fe contents decreased in CE grown plants. Ca content was unaffected due to CE and variable N supplies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selenium accumulation by sequentially grown wheat and rice as influenced by gypsum application in a seleniferous soil

A field experiment was conducted for 2 years on an alkaline calcareous seleniferous soil to study the effect of different levels of gypsum (0.2 – 3.2 t ha⁻¹) applied to wheat only in the first year on Se accumulation by wheat (Triticum aestivum L.) – rice (Oryza sativa L.) cropping sequence. With gypsum application, grain yield of both rice and wheat crops increased by 0.4 – 0.5 t ha⁻¹; the increase in straw yield was 0.4 – 1.1 t ha⁻¹. Significant reduction in Se accumulation by wheat was observed with gypsum application up to 0.8 t ha⁻¹ and its residual effect was evident on the following crops for 2 years. Reduction in Se accumulation varied from 53 to 64% in wheat grain, 46 to 49% in wheat straw, 35 to 63% in rice grain and 36 to 51% in rice straw with an application of gypsum at 0.8 t ha⁻¹. A corresponding increase in S concentration was observed. In the gypsum-treated plots, the ratio of S:Se increased by 6 – 8 times in wheat and 3 – 6 times in rice. Reduction in Se accumulation by crop plants through gypsum application may help in lowering the risk of Se over-exposure of animals and humans that depend on diet materials grown on high selenium soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Salicylic Acid Influences Net Photosynthetic Rate,Carboxylation Efficiency,Nitrate Reductase Activity,and Seed Yield in Brassica juncea

Aqueous solutions of salicylic acid (SA) were applied to the foliage of 30-d-old plants of mustard (Brassica juncea Czern & Coss cv. Varuna). The plants sprayed with the lowest used concentration (10₋₅ M) of SA were healthier than those sprayed with water only or with higher concentrations of SA (10⁻⁴ or 10⁻³ M). 60-d-old plants possessed 8.4, 9.8, 9.3, 13.0 and 18.5 % larger dry mass, net photosynthetic rate, carboxylation efficiency, and activities of nitrate reductase and carbonic anhydrase over the control, respectively. Moreover, the number of pods and the seed yield increased by 13.7 and 8.4 % over the control. This revised version was published online in August 2006 with corrections to the Cover Date.     

Alleviation of Ultraviolet-B Radiation-Induced Growth Inhibition of Green Gram by Triadimefon

Supplementary UV-B (12.2 kJ m⁻² d⁻¹ UV-B_BE) provided to Vigna radiata for 2 h d⁻¹ suppressed the length of root, shoot and whole plants, number of leaves, total leaf area, leaf area index, specific leaf mass, fresh and dry mass of leaves and shoot, relative growth rate and net productivity. In unstressed green gram plants (10 kJ m⁻² d⁻¹ UV-B_BE), triadimefon (TRIAD) (20 mg dm⁻³) enhanced growth in all parameters over control. The growth promoting effect of TRIAD enabled the UV-B impacted plants to overcome the growth inhibitions to varying degrees indicating its protective potential against UV-B stress. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of phosphorus in the rhizosphere of maize and rape grown on synthetic,phosphated calcite and goethite

In calcareous soils the dynamics of phosphorus is controlled by calcite and iron oxides such as goethite which strongly retain P and consequently maintain low P concentrations in soil solution. Plants can drastically change chemical conditions in the rhizosphere, in particular by releasing H⁺ or OH⁻ or by excreting organic anions. By modifying the dissolution/precipitation and desorption/adsorption equilibria, roots can influence the mobility of soil P. The aim of this work was to test whether H⁺ or OH⁻ release can induce the mobilization of P in the rhizosphere of maize and rape supplied with NO₃-N or NH₄-N and grown on synthetic phosphated calcite or goethite as sole source of P. With P-calcite, the mobilization of P was generally related to the acidification of the rhizosphere. With P-goethite, rhizosphere acidification induced some increase of DTPA-extractable Fe and hence dissolution of goethite. Rhizosphere P was concomitantly depleted but the mechanisms involved are less clear. The difference in behavior of the two species is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of Boron on Somatic Embryogenesis in Papaya

Influence of boron on somatic embryogenesis in papaya (Carica papaya L.) cv. Honey Dew was investigated. Immature zygotic embryos were grown in the induction medium containing Murashige and Skoog basal salts, with B₅ vitamins, picloram (1 mg dm⁻³) or 2,4-dichlorophenoxy acetic acid (2 mg dm⁻³) and different concentrations of boric acid (30 to 500 mg dm⁻³). Maximum somatic embryo initiation was observed at 62 mg dm⁻³ boric acid irrespective of the growth regulator used. The cotyledonary stage somatic embryos were germinated on MS basal medium devoid of growth regulators. The regenerated plantlets were hardened under greenhouse conditions and transferred to field. This revised version was published online in July 2006 with corrections to the Cover Date.     

Recombinant protein production using the Semliki Forest Virus expression system

We report here the successful scale up of transient recombinant protein expression to litre scale using Semliki Forest Virus System. The expression of bacterial β-galactosidase was initially compared in BHK and CHO cells and the conditions for optimal infection of BHK cells were identified. 10% FCS in a medium at pH 6.9 and infection in small volumes were found to be optimal. A high MOI results in an increased recombinant protein yield. Stirring does not affect the infection process. Finally we applied these optimal conditions to the production of a microsomal enzyme, human cyclooxygenase-2 in suspension spinners. Five independant productions at the 1 litre scale yielded reproducible substantial amounts of recombinant protein (16 mg microsomal protein 10⁹ cells⁻¹) with an average specific activity of 3942 ± 765 pg PGE₂ μg⁻¹ microsomal protein 5 min⁻¹. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contribution of N2 fixing cyanobacteria to rice production: availability of nitrogen from 15N-labelled cyanobacteria and ammonium sulphate to rice

This study investigate the potential contribution of nitrogen fixation by indigenous cyanobacteria to rice production in the rice fields of Valencia (Spain). N₂-fixing cyanobacteria abundance and N₂ fixation decreased with increasing amounts of fertilizers. Grain yield increased with increasing amounts of fertilizers up to 70 kg N ha^-1. No further increase was observed with 140 kg N ha^-1. Soil N was the main source of N for rice, only 8–14% of the total N incorporated by plants derived from ¹⁵N fertilizer. Recovery of applied ¹⁵N-ammonium sulphate by the soil–plant system was lower than 50%. Losses were attributed to ammonia volatilization, since only 0.3–1% of applied N was lost by denitrification. Recovery of ¹⁵N from labeled cyanobacteria by the soil–plant system was higher than that from chemical fertilizers. Cyanobacterial N was available to rice plant even at the tillering stage, 20 days after N application. This revised version was published online in June 2006 with corrections to the Cover Date.     

A study on floral biology of seedlings in vitro in Orychophragmus violaceus: Induction of flowers in seedlings of O. violaceus cultured in vitro

Seedlings of O. violaceus were cultured on MS media and treated at low temperature. Cold treatment at 5–7 °C for more than 7 days was needed for flower induction of seedlings in vitro originated from germinated seeds. When cultured on MS media supplemented with 2.5 mg l⁻¹ zeatin and 2 mg l⁻¹ gibberellin (GA₃), seedlings in vitro did initiate flowers without cold treatment. When MS media was used with a reduced amount of NH₄NO₃, flower induction of seedlings in vitro could be accelerated. This revised version was published online in June 2006 with corrections to the Cover Date.