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Pot Experiment (pot + experiment)

Distribution by Scientific Domains

Earth and Environmental Science	51%
Life Sciences	34%
Chemistry	10%

Selected Abstracts

Procedure for separating the selection effect from other effects in diversity,productivity relationship

ECOLOGY LETTERS, Issue 6 2001
paèková
In a greenhouse pot experiment we cultivated six meadow species in a replacement series design. The plants were grown at two sowing densities in monocultures and all possible species combinations. Our aim was to separate the selection effect from other diversity effects. This distinction is based on the notion that true overyielding is not a consequence of the selection effect. We suggest a hierarchical procedure, which is based on a repeated division of samples into the pots with the most productive species present and missing. Overyielding can be then demonstrated by a positive dependence of productivity on species richness in the subsets with the most productive species present. Although we found a strong dependence of biomass on species richness in the entire data set, the hierarchical method revealed no evidence of overyielding. Above-ground biomass in a monoculture was a good predictor of species success in a species mix. [source]

Uptake and transport of roxarsone and its metabolites in water spinach as affected by phosphate supply

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010
Lixian Yao
Abstract Roxarsone (ROX) is widely used as a feed additive in intensive animal production. While an animal is fed with ROX, the As compounds in the manure primarily occur as ROX and its metabolites, including arsenate (As[V]), arsenite (As[III]), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Animal manure is commonly land applied with phosphorous fertilizers in China. A pot experiment was conducted to investigate the phytoavailability of ROX, As(V), As(III), MMA, and DMA in water spinach (Ipomoea aquatica), with the soil amended with 0, 0.25, 0.50, 1.0, and 2.0,g PO4/kg, respectively, plus 2% (w/w manure/soil) chicken manure (CM) bearing ROX and its metabolites. The results indicate that this species of water spinach cannot accumulate ROX and MMA at detectable levels, but As(V), As(III), and DMA were present in all plant samples. Increased phosphorous decreased the shoot As(V) and As(III) in water spinach but did not affect the root As(V). The shoot DMA and root As(III) and DMA were decreased/increased and then increased/decreased by elevated phosphorous. The total phosphorous content (P) in plant tissue did not correlate with the total As or the three As species in tissues. Arsenate, As(III), and DMA were more easily accumulated in the roots, and phosphate considerably inhibited their upward transport. Dimethylarsinic acid had higher transport efficiency than As(V) and As(III), but As(III) was dominant in tissues. Conclusively, phosphate had multiple effects on the accumulation and transport of ROX metabolites, which depended on their levels. However, proper utilization of phosphate fertilizer can decrease the accumulation of ROX metabolites in water spinach when treated with CM containing ROX and its metabolites. Environ. Toxicol. Chem. 2010;29:947,951. © 2009 SETAC [source]

Re-evaluation of the liming-fertilization interaction in grasslands on poor and acid soils

GRASS & FORAGE SCIENCE, Issue 2 2010
V. Poozesh
Abstract The effect of surface liming on herbage production in permanent grasslands is rather uncertain. To better understand the effect of liming on the grassland, a study was made with a field experiment and a pot experiment with soil from the same field. In the field, the effects of liming and NPK fertilization on the production and composition of the vegetation were studied. In pots, the effects of liming and phosphate fertilization on different grass species were analysed. The effect of NPK fertilization (+3·96 t ha,1) on the production of the original grassland was greater than that of liming (+0·68 t ha,1), which was only observed (P < 0·05) on the unfertilized plots. Liming increased the total number of species and the proportion of dicotyledons. After replacing the semi-natural community with Dactylis glomerata L., the effects of liming (+2·37 t ha,1) and fertilization (+6·52 t ha,1) were increased. These results, together with those of the pot trial, show the important role of phosphorus in the fertilization effect, and are interpreted as a protective effect of P against aluminium toxicity. [source]

Neotyphodium endophyte infection affects the performance of tall fescue in temperate region Andisols

GRASSLAND SCIENCE, Issue 1 2006
M. Hasinur Rahman
Abstract A pot experiment was conducted for 75 days to observe the effect of Neotyphodium coenophialum endophyte on three tall fescue (Festuca arundinacea Schreb.) ecotypes grown in two Andisols viz. Black Andisol and Red Andisol. Black Andisol with a naturally low content of P was high in other nutrients such as N, K, while Red Andisol, with a naturally high content of P, was low in other nutrients. Tiller number, plant height, chlorophyll content, shoot dry weight and agronomic efficiency of water use (WUEag) showed higher values in endophyte-infected (E+) plants than noninfected (E,) plants. Plants growing in Black Andisol performed better than those in Red Andisol. Among the three tall fescue ecotypes, one of them (ecotype Showa) had the best performance regardless of soils and endophyte infection. When considering the effect of endophyte infection in different soil conditions, higher WUEag was observed in endophyte-infected plants grown in Black Andisol. Endophyte infection significantly enhanced all plant parameters in Black Andisol but they were reduced in Red Andisol. Our results indicate that infected plants grew better in soil that was naturally low in P whereas uninfected plants had increased vegetative growth in soil that was naturally high in P. In nutrient poor soil with comparatively high P content (Red Andisol) the cost of endophyte infection may override its benefit. The presence of endophyte had a variable impact on plant performance and the effect of endophyte varied with ecotype of grass it infected into. [source]

Relationship between Carbon Isotope Discrimination, Mineral Content and Gas Exchange Parameters in Vegetative Organs of Wheat Grown under Three Different Water Regimes

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2010
L. Zhu
Abstract Carbon isotope discrimination (,) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for , analysis, attempts have been made to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for , in wheat and barley. A pot experiment was conducted to analyse the relationship between ,, mineral content and gas exchange parameters in seedlings and leaves of bread wheat (Triticum aestivum L.). Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate (T3), intermediate (T2) and severe drought (T1) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. , and ma in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between , and ma in seedlings and leaves at elongation and anthesis stages in severe drought stress (T1). , was negatively associated with potassium (K) content in intermediate drought stress (T2) and positively with magnesium (Mg) content in T2 and T3 (moderate drought stress) in flag leaf at anthesis. There were negative correlations between , and single-leaf intrinsic water-use efficiency (WT) in T2 and T3 at anthesis stage. Stronger positive associations were noted between , and stomatal conductance (gs) in T1 and T2 than in T3 at anthesis. These results suggested that , is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while ma is a possible alternative criterion of , in wheat vegetative organs, especially in stressed environments. Significant association was found between , and K, Mg and Ca contents that would merit being better investigated. [source]

Relationship between Carbon Isotope Discrimination and Mineral Content in Wheat Grown under Three Different Water Regimes

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2008
L. Zhu
Abstract Carbon isotope discrimination (,) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of the high cost for , analysis, attempts have been carried out to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for , in wheat and barley. A pot experiment was conducted to analyse the relationship between , and ma in flag leaf and grain. Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate, intermediate and severe drought stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity, respectively. , and ma in flag leaf and grain showed significant differences between the moderate, intermediate and severe drought stress levels. Significant correlations were found among genotypes for , and ma in flag leaf under severe drought stress, and for , and ma in grain under intermediate and moderate drought stress. In flag leaf at anthesis, , was negatively associated to K content and positively to Mg content. At maturity, , in grain was negatively correlated with Mg and Ca contents in flag leaf and grain, respectively. These results suggested that these traits may be potentially useful traits, which could be surrogates for ,. [source]

Strategies to Improve the Use Efficiency of Mineral Fertilizer Nitrogen Applied to Winter Wheat

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2002
K. Blankenau
Recovery of fertilizer nitrogen (N) applied to winter wheat crops at tillering in spring is lower than that of N applied at later growth stages because of higher losses and immobilization of N. Two strategies to reduce early N losses and N immobilization and to increase N availability for winter wheat, which should result in an improved N use efficiency (= higher N uptake and/or increased yield per unit fertilizer N), were evaluated. First, 16 winter wheat trials (eight sites in each of 1996 and 1997) were conducted to investigate the effects of reduced and increased N application rates at tillering and stem elongation, respectively, on yield and N uptake of grain. In treatment 90-70-60 (90 kg N ha,1 at tillering, 70 kg N ha,1 at stem elongation and 60 kg N ha,1 at ear emergence), the average values for grain yield and grain N removal were up to 3.1 and 5.0 % higher than in treatment 120-40-60, reflecting conventional fertilizer practice. Higher grain N removal for the treatment with reduced N rates at tillering, 90-70-60, was attributed to lower N immobilization (and N losses), which increased fertilizer N availability. Secondly, as microorganisms prefer NH4+ to NO3, for N immobilization, higher net N immobilization would be expected after application of the ammonium-N form. In a pot experiment, net N immobilization was higher and dry matter yields and crop N contents at harvest were lower with ammonium (ammonium sulphate + nitrification inhibitor Dicyandiamide) than with nitrate (calcium nitrate) nutrition. Five field trials were then conducted to compare calcium nitrate (CN) and calcium ammonium nitrate (CAN) nutrition at tillering, followed by two CAN applications for both treatments. At harvest, crop N and grain yield were higher in the CN than in the CAN treatment at each N supply level. In conclusion, fertilizer N use efficiency in winter wheat can be improved if N availability to the crops is increased as a result of reduced N immobilization (and N losses) early in the growth period. N application systems could be modified towards strategies with lower N applications at tillering compensated by higher N dressing applications later. An additional advantage is expected to result from use of nitrate-N fertilizers at tillering. Strategien zur Verbesserung der Effizienz von Düngerstickstoff in Winterweizen Aus früheren Versuchen mit Winterweizen ist bekannt, daß zur Ernte die Wiederfindung von im Frühjahr zur Bestokkung gedüngtem Stickstoff (N) geringer ist, als die von N aus Spätgaben. Die Ursachen liegen in einer höheren mikrobiell-bedingten Netto-N-Immobilisation, aber auch N-Verlusten zwischen Bestockung und Schoßbeginn im Vergleich zu späteren Wachstumstadien begründet. In den vorliegenden Versuchen wurden zwei Strategien getestet, um insbesondere die früh in der Vegetation auftretende Netto-N-Immobilisation zu vermindern. Die dadurch erwartete erhöhte N-Verfügbarkeit sollte zu einer erhöhten N-Effizienz (höherer N-Entzug/Ertrag bezogen auf die N-Düngung) führen. 1996 und 1997 wurden jeweils 8 Feldversuche mit Winterweizen durchgeführt, um den Einfluß einer reduzierten Andüngung bei gleichzeitig erhöhter Schossergabe im Vergleich zur konventionellen N-Düngung zu untersuchen. Tatsächlich wurden in dem Prüfglied 90-70-60 (N-Sollwertdüngung: 90 kg N ha,1, Schossergabe: 70 kg N ha,1, Ährengabe: 60 kg N ha,1) im Mittel bis zu 3.1 % höhere Erträge und 5.0 % höhere N-Abfuhren mit dem Korn im Vergleich zur konventionellen Variante 120-40-60 (N-Sollwertdüngung: 120 kg N ha,1, Schossergabe: 40 kg N ha,1 und Ährengabe: 60 kg N ha,1) erzielt. Die höhere N-Abfuhr kann auf eine erhöhte N-Verfügbarkeit infolge geringerer mikrobieller N-Festlegung zurückgeführt werden. Da die vornehmlich heterotrophen Bodenmikroorganismen bevorzugt NH4+ gegenüber NO3, immobilisieren, kann eine höhere N-Immobilisation bei Ammonium-Düngung erwartet werden. Tatsächlich wurden in einem Gefäßversuch nach Düngung von Ammoniumsulfat (+ Nitrifikationshemmer Dicyandiamid) geringere Trokkenmasseerträge und N-Aufnahmen von Weizenpflanzen erzielt als mit Calciumnitrat. Für die Ammoniumsulfatvariante ergab sich eine höhere Netto-N-Immobilisation. Danach wurde in fünf Feldversuchen mit Winterweizen der Einfluß einer Andüngung mit Nitrat (Calciumnitrat) im Vergleich zur Verwendung des ammoniumhaltigen Kalkammonsalpeters (KAS) auf die N-Aufnahme und den Kornertrag untersucht (beide Varianten erhielten KAS als Spätgaben). In der nitratangedüngten Variante wurden zum Teil signifikant höhere Ertäge und N-Aufnahmen in Korn und Stroh ermittelt. Aus den dargestellten Versuchen kann gefolgert werden, daß die Düngerstickstoff-Effizienz verbessert werden kann, wenn vor allem die N-Immobilisation (und eventuell auch N-Verluste) in frühen Wachstumsstadien zwischen Bestockung und Schoßbeginn verringert und so die N-Verfügbarkeit erhöht wird. Es kann empfohlen werden Winterweizenbestände mit geringeren N-Mengen , als nach N-Sollwert 120 kg N ha,1 vorgesehen , anzudüngen und die Schossergabe entsprechend zu erhöhen. Die Verwendung von nitrathaltigen Düngern bei der Andüngung ist von Vorteil. [source]

Response of Black Nightshade (Solanum nigrum L.) to Phosphorus Application

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2000
M. M. A. Khan
A pot experiment was conducted to study the effect of phosphorus (P) on the vegetative and reproductive growth of black nightshade (Solanum nigrum L.). Single superphosphate was applied at 0, 0.15, 0.30, 0.45, 0.60 and 0.75 g P/pot containing 3.5 kg of soil. Seeds were sown directly in pots and plant samples were taken at fortnightly intervals for recording growth and yield parameters. In addition, the solasodine content in fruit and N, P and K levels in leaves were also estimated. Most parameters were significantly influenced by P, with0.45 g/pot generally proving optimal. The data also established that the berries should be harvested between 160 and 190 days (days after sowing), preferably at 175 days for maximum fruit yield and solasodine production. Most parameters showed consistent and positive correlations with leaf P content. Interestingly, the correlation between leaf P content at 40 days and solasodine yield at 175 days was highly significant (r = 0.888), implying that the former is predictive of the latter. Thus, if low leaf P content was noted at 40 days corrective measures like foliar application or top dressing may be adopted to increase the leaf P content to ensure maximum solasodine at harvest. Zusammenfassung Es wurde ein Gefäßexperiment mit Nachtschatten (Solanum nigrum L.) durchgeführt, um den Einfluß von Phosphor (P) auf das vegetative und reproduktive Wachstum zu untersuchen. Einfach-Superphosphat wurde mit Mengen von 0, 0,15, 0,30, 0,45, 0,60 und 0,75 gP/Gefäß mit 3,5 kg Boden angewendet. Die Samen wurden direkt in die Gefäße ausgesät und die Pflanzenproben wurden 14-tägig für Untersuchungen hinsichtlich Wachstum und Ertragsparameter genommen. Zusätzlich wurde der Solasodine-Gehalt in der Frucht sowie N, P und K in den Blättern bestimmt. Die meisten Parameter waren sig-nifikant beeinflußt durch P, wobei sich 0,45 g/Gefäß als optimal erwies. Die Ergebnisse zeigen, daß die Beeren 160,190 d (Tage nach der Aussaat), am günstigsten 175 Tage, für maximalen Fruchtertrag und Solasodine-Produktion zu ernten sind. Die meisten Parameter zeigten konsistente und positive Korrelationen mit dem Blatt-P-Gehalt. Es ist interessant, daß die Korrelation zwischen Blatt-P-Gehalt nach 40 Tagen sowie Solasodine-Ertrag nach 175 Tagen hochsignifikant war (r = 0,888), was für eine Zeitvoraussage genutzt werden kann. Es erscheint daher möglich, falls geringer Blatt-P-Gehalt nach 40 Tagen festgestellt wird, Blattanwendungen oder Düngungen zur Erhöhung des Blatt-P-Gehaltes vorzunehmen, um ein Maximum an Solasodine zur Ernte zu erreichen. [source]

Studies on Symptom Development, Phenolic Compounds and Morphological Defence Responses in Wheat Cultivars Differing in Resistance to Fusarium Head Blight

JOURNAL OF PHYTOPATHOLOGY, Issue 4-5 2002
E. SIRANIDOU
Abstracts Development of Fusarium head blight, caused by Fusarium culmorum, was evaluated in seven winter wheat cultivars and one spring wheat cultivar in an outdoor pot experiment. Of the cultivars studied, only the spring wheat cultivar Frontana exhibited resistance against initial infection by the fungus. Significantly higher amounts of free phenolic compounds were found in the glumes, lemmas and paleas of Frontana prior to and at all sampling times after inoculation, in comparison to the winter wheat cultivar Agent. Furthermore, the amount of p -coumaric acid increased significantly in the glumes, lemmas and paleas of the cultivar Frontana 2 days after inoculation compared to that in uninoculated spike tissues. However, the amounts of ferulic acid between inoculated and healthy plant tissues did not differ. Ultrastructural studies indicated more pronounced structural defence responses, such as cell wall appositions, in the infected lemma tissue of the resistant cultivar Frontana compared with the susceptible Agent 3 days after inoculation. Immunogold labelling of lignin revealed no differences in the density of gold particles on the cell walls of healthy lemma tissue in the two cultivars. However, density of particles increased in the infected lemma tissue of the resistant cultivar Frontana on cell walls adjacent to the fungal cells, 3 days after inoculation. The susceptible cultivar Agent showed little or no response to the infection. Phenolic compounds appear to play a role in the resistance of the cultivar Frontana to F. culmorum. [source]

Phosphate buffer,extractable organic nitrogen as an index of soil-N availability for sorghum and pearl millet

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2010
Asako Mori
Abstract The availability of soil nitrogen (N) is usually quantified by the amount of mineralized N as determined after several weeks of soil incubation. Various alternative methods using chemical solvents have been developed to extract the available organic N, which is easily mineralized. We compared one such solution, neutral phosphate buffer (NPB), with conventional incubation and 0.01 M,CaCl2 extraction, as measures of soil N available to two major cereal crops of the semiarid tropics, based on the total N uptake by plants in a pot experiment. Mineralized N had the highest correlation with N uptake by pearl millet (Pennisetum glaucum L., r = 0.979***) and sorghum (Sorghum bicolor [L.] Moench, r = 0.978***). NPB-extractable N was also highly correlated with N uptake (pearl millet, r = 0.876***; sorghum, r = 0.872***). Only one major peak was detected when NPB extracts were analyzed using size-exclusion high-performance liquid chromatography, regardless of soil properties. In addition, the organic N extracted with NPB was characterized by determining the content of peptidoglycan, the main component of bacterial cell walls. Although the characteristics of NPB-extractable organic N are still unclear, it offers a promising quick assay of available N. [source]

Cadmium and zinc accumulation in willow and poplar species grown on polluted soils,

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2007
Maria N. Dos Santos Utmazian
Abstract Woody plant species that produce high biomass have been proposed for use in phytoremediation technology. We investigated the accumulation of cadmium (Cd) and zinc (Zn) in Salix babylonica, S. caprea, S. dasyclados, S. matsudana × alba, S. purpurea, S. smithiana, Populus tremula, and P. nigra clones grown in a pot experiment on a Calcaric and a Eutric Cambisol (pH 7.2 and 6.4) of different levels of contamination (total metal concentrations in mg,kg,1 in soil A: 32.7 Cd, 1760 Zn; soil B: 4.34 Cd, 220 Zn). Generally, the tested clones tolerated large metal concentrations in soils and had larger Cd and Zn concentrations in leaves compared to the roots. The largest Cd concentrations in leaves were found in two clones of S. smithiana (440 mg,kg,1 on soil A; 70 mg,kg,1 on soil B). One of the S. smithiana clones had also the largest Zn concentrations (870 mg,kg,1) on soil B but accumulated slightly less Zn than a S. matsudana × alba clone (2430 mg,kg,1) on soil A. The Cd concentrations in leaves of both S. smithiana clones on soil A are the largest ever reported for soil-grown willows. The bioconcentration factors of the best performing clone reached 15.9 for Cd and 3.93 for Zn on the less contaminated soil B. Also based on the metal contents in leaves, this clone was identified as the most promising for phytoextraction. The metal concentrations in leaves observed in the pot experiment do not reflect those found in a previous hydroponic study and the leaf-to-root ratios are clearly underestimated in hydroponic conditions. This demonstrates the need for testing candidates for phytoextraction crops on soils rather than in hydroponics. Our data also show that the phytoextraction potential should be tested on different soils to avoid misleading conclusions. [source]

Influence of Tithonia diversifolia and triple superphosphate on dissolution and effectiveness of phosphate rock in acidic soil

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2006
Isaac Savini
Abstract An incubation and a pot experiment were conducted to evaluate the dissolution and agronomic effectiveness of a less reactive phosphate rock, Busumbu soft ore (BPR), in an Oxisol in Kenya. Resin (anion and anion + cation)-extractable P and sequentially extracted P with 0.5 M NaHCO3, 0.1 M NaOH, and 1 M HCl were analyzed. Dissolution was determined from the increase in anion resin (AER),, NaHCO3 -, and NaOH-extractable P in soil amended with PR compared with the control soil. Where P was applied, resin P significantly increased above the no-P treatment. Busumbu-PR solubility was low and did not increase significantly in 16 weeks. Anion + cation (ACER)-extractable P was generally greater than AER-P. The difference was greater for PR than for triple superphosphate (TSP). The ACER extraction may be a better estimate of plant P availability, particularly when poorly soluble P sources are used. Addition of P fertilizers alone or in combination with Tithonia diversifolia (TSP, BPR, TSP + Tithonia, and BPR + Tithonia) increased the concentration of labile inorganic P pools (NaHCO3 - and NaOH-Pi). Cumulative evolved CO2 was significantly correlated with cumulative N mineralized from Tithonia (r, 0.51, p < 0.05). Decrease in pH caused NH -N accumulation while NO -N remained low where Tithonia was incorporated at all sampling times. However, when pH was increased, NH -N declined with a corresponding rise in NO -N. Tithonia significantly depressed soil exchangeable acidity relative to control with time. A significant increase (p < 0.05) was observed for P uptake but not dry-mass production in maize where BPR was applied. The variations in yield and P uptake due to source and rates of application were statistically significant. At any given P rate, highest yields were obtained with Tithonia alone. Combination of Busumbu PR with TSP or Tithonia did not enhance the effectiveness of the PR. The poor dissolution and plant P uptake of BPR may be related to the high Fe content in the PR material. [source]

Effects of nitrate-, ammonium-, and organic-nitrogen-based fertilizers on growth and yield of tomatoes

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2005
Anuschka Heeb
Abstract Mineral and organic fertilizers contain different forms and amounts of nitrogen (N), which can affect yield and product quality. The aim of this study was to determine appropriate amounts of N applied as nitrate (NO), ammonium (NH), and organic N (a mixture based on chicken manure) for optimal growth and quality of tomatoes. A pot experiment with sand as substrate was established in a greenhouse with six-week-old tomato plants (Lycopersicon esculentum Mill. cv. "Armada"). Nitrogen was applied in nutrient solutions at different NO : NH ratios combined with different chloride levels (NO -dominated, NO = NH at low Cl,, NO = NH at high Cl,, and NH -dominated, respectively) or as organic N at four N-application rates (250, 500, 750, 1000 mg N plant,1 week,1). No significant differences in shoot biomass and yields of red tomatoes were observed between NO - or NH -fed plants. Nitrogen rates above 750 mg N plant,1 week,1 did not significantly increase marketable fruit yield, but enhanced shoot-biomass production. The NH -N-dominated treatments (which also had high Cl, concentrations) showed increasing incidence of blossom-end-rot (BER)-infected fruits. In the organic-N treatments, shoot-biomass production and yields were lower than in the inorganic-N treatments, but fruit quality was good with few BER-infected fruits. The results show that with a total N supply below 750 mg N plant,1 week,1, NH can be used as equivalent N source to NO, resulting in equivalent yields of marketable fruit under the conditions in this experiment. Einfluss von Nitrat, Ammonium und organischem Stickstoff auf Wachstum und Ertrag von Tomaten Mineralische und organische Dünger enthalten verschiedene Formen von und Mengen an Stickstoff (N), welche den Ernteertrag und die Produktqualität beeinflussen können. Das Ziel dieser Arbeit war es, geeignete N-Mengen , appliziert als Nitrat, Ammonium oder organischer Stickstoff , für optimales Wachstum und Qualität von Tomaten zu bestimmen. Dazu wurde mit sechs Wochen alten Tomatenpflanzen (Lycopersicon esculentum Mill. cv. "Armada") unter Gewächshausbedingungen mit Sand als Substrat ein Gefäßversuch angelegt. Die Applikation von N erfolgte in Form von Nährlösungen mit verschiedenen NO:NH -Verhältnissen, kombiniert mit unterschiedlichen Chlorid (Cl)-Konzentrationen (NO -dominiert, NO = NH bei niedrigem Cl,, NO = NH bei hohem Cl, und NH -dominiert) bzw. als organischer N. Jede dieser Behandlungen wurde mit vier verschiedenen N-Mengen angelegt (250, 500, 750, 1000 mg N Pflanze,1 Woche,1). Zwischen den mit Nitrat und Ammonium gedüngten Pflanzen konnte kein signifikanter Unterschied in Sprosswachstum und Ertrag an erntereifen Tomaten festgestellt werden. Stickstoffmengen über 750 mg N Pflanze,1 Woche,1 steigerten den Ertrag verkaufsfähiger Tomaten nicht signifikant, obwohl die Produktion an Sprossbiomasse noch anstieg. In den NH -dominiert gedüngten Gefäßen mit gleichzeitig hohen Cl-Konzentrationen in den Nährlösungen wurden häufiger Tomaten mit Blütenendfäule beobachtet. In den Behandlungen mit organischem Stickstoff waren die Sprossbiomasseproduktion und der Ertrag geringer als in den mineralisch gedüngten Behandlungen, aber die Qualität der Früchte war gut, mit nur wenigen durch Blütenendfäule geschädigten Tomaten. Die Ergebnisse zeigen, dass bei einer Stickstoffversorgung unter 750 mg N Pflanze,1 Woche,1 Ammonium anstelle von Nitrat verwendet werden kann. Im vorliegenden Versuch wurden unter diesen Bedingungen vergleichbare Erträge verkaufsfähiger Früchte erzielt. [source]

Uptake of residual phosphate and freshly applied diammonium phosphate by Lolium perenne and Trifolium repens,

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2003
Anne Gallet
Abstract Residual fertilizer phosphorus (residual P) may significantly contribute to crop P nutrition. To test this hypothesis, a pot experiment was conducted with ryegrass (Lolium perenne) and clover (Trifolium repens) grown separately on three different soils which either had not received P fertilizer for at least nine years (0F) or had received P fertilizer equivalent to crop P off-take (F). Soils in the pot experiment were given either none (0F, F) or a single rate of 15 mg P (kg soil),1 as diammonium phosphate (0F+DAP, F+DAP). In the treatments 0F+DAP and F+DAP DAP had been labeled with 33PO4 while in the treatments 0F and F the pool of available soil P had been labeled with carrier-free 33PO4. This allowed estimating the quantities of P in plant dry matter that derived from native soil P, residual fertilizer P or fresh fertilizer P. Fourteen to 62,% of the P in the above ground biomass of white clover or perennial ryegrass were derived from residual P whereas 7 to 28,% were derived from freshly applied DAP. The proportion of P derived from residual P was correlated to the total amount of P fertilizer added to the soils, while the proportion of P derived from DAP was correlated to the concentration of P in the soil solution of the 0F and F soils. Aufnahme von Phosphat aus Rückständen von früherer Düngung und aus frisch ausgebrachtem Diammoniumphosphat durch Lolium perenneund Trifolium repens In Düngerrückständen enthaltener Phosphor (P) kann möglicherweise signifikant zur P-Ernährung von Kulturpflanzen beitragen. Um diese Hypothese zu prüfen, wurde im Topfversuch die P-Aufnahme durch Lolium perenne und Trifolium repens untersucht. Als Substrat dienten drei Böden, die entweder seit mindestens 1989 keine P-Gabe mehr erhalten hatten (0F) oder die jährlich P-Gaben im Umfang der P-Entzüge durch die vorgängigen Kulturen erhalten hatten und deshalb P-Rückstände enthielten (F). Es ergaben sich folgende Verfahren: 0F: ohne P aus Düngerrückständen und frischer Düngung; 0F+DAP: mit P aus frischer Düngung (Diammoniumphosphat, 15 mg P (kg Boden),1); F: mit P aus Düngerrückständen; F+DAP: mit P aus Düngerrückständen und frischer Düngung. In den Verfahren 0F + DAP und F + DAP war DAP mit 33PO4 markiert. In den Verfahren 0F und F war der verfügbare P des Bodens mit carrier-freiem 33PO4 markiert. Dies ermöglichte die Erfassung der Aufnahme von P durch die Pflanzen differenziert nach Herkunft aus Boden, Düngerrückständen und frischem Dünger. Von Düngerrückständen stammten 14,62,%, von frischem Dünger 7,28,% des in den Sprossen der Pflanzen gefundenen P. Der von Düngerrückständen stammende Anteil P in den Pflanzensprossen war korreliert mit dem gesamten Gehalt an P das dem Boden als Dünger zugeführt worden war. Der von frischem DAP stammende Anteil war korreliert mit der P-Konzentration in der Bodenlösung. [source]

Soil properties, but not plant nutrients (N, P, K) interact with chemically induced resistance against powdery mildew in barley

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2003
Joachim Wiese
Abstract Chemically induced resistance is a promising method of plant protection against diseases, which can be triggered by systemically acting chemical inducers such as BTH (benzo(1, 2, 3)thiadiazole-carbothioic-acid-S-methylester). BTH is commercially distributed as a 50,% formulation, called Bion®. The uncertain success of Bion® application in controlling infection by powdery mildew is a major obstacle in using induced resistance for plant protection in agriculture. This study aimed to investigate the effect of soil properties, selected macronutrients (N, P, and K), and addition of organic matter on induced resistance and to identify possible factors responsible for the high variability of BTH effect under field conditions. A pot experiment under open-air conditions was set up using the pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei race A6. The different soils strongly affected the resistance of barley plants against powdery mildew after BTH treatment. The infection of barley by powdery mildew was lower than on all other soils when grown on an acid forest soil which was limed up to pH 4.9, even after BTH treatment. A reproducible induction of pathogen resistance by BTH was shown only on a mineral soil (Kleinlinden) with a negligible C content. Application of N, P, and K did not consistently affect the induction of resistance by BTH. The addition of green manure and compost led to an enhanced variability of resistance induction on the soil "Kleinlinden". Possible effects of soil microflora on resistance induction are discussed. Bodeneigenschaften, aber nicht Pflanzennährstoffe (N, P, K) interagieren mit der chemisch induzierten Resistenz gegen Gerstenmehltau in Gerste Chemisch induzierte Resistenz ist eine viel versprechende Methode im Pflanzenschutz, welche durch systemisch wirkende Substanzen wie BTH (Benzo(1, 2, 3)-thiadiazolcarbothion-Säure- S -Methylester) induziert werden kann. BTH ist die wirksame Komponente des kommerziell erhältlichen Produkts Bion®. Allerdings ist die Wirksicherheit von Bion® im Feld gering, wodurch die Anwendung des Produkts im Pflanzenschutz eingeschränkt ist. Das Ziel der vorliegenden Arbeit war es, den Einfluss verschiedener Böden, ausgewählter Makronährstoffe (N, P und K) und des Zusatzes von organischem Material zum Boden auf die induzierte Resistenz zu untersuchen und Faktoren zu identifizieren, die für die unsichere BTH-Wirkung im Feld verantwortlich sind. Dafür wurden Gefäßexperimente unter freilandähnlichen Bedingungen durchgeführt. In diesen wurde das Pathosystem Hordeum vulgare cv. Ingrid / Blumeria graminis f. sp. hordei Stamm A6 verwendet. Es wurde ein starker Einfluss des Bodens auf die Resistenz der Gerste gegen Gerstenmehltau nach BTH-Behandlung ermittelt. Die Mehltauinfektion von Gerste, welche auf einem sauren Waldboden kultiviert wurde, der auf einen pH-Wert von 4, 9 aufgekalkt worden war, war niedriger als auf allen anderen Böden, selbst nach BTH-Behandlung. Eine reproduzierbare Induktion der Pathogenresistenz durch BTH konnte nur auf einem Mineralboden mit vernachlässigbarem C-Gehalt gezeigt werden. Die Ernährung mit N, P und K hatte keinen konsistenten Einfluss auf die Resistenzinduktion mittels BTH. Der Zusatz von Kompost und Gründünger zum Boden ,Kleinlinden" erhöhte die Variabilität der Resistenzinduktion. Der mögliche Einfluss der Bodenmikroflora auf die Resistenzinduktion wird diskutiert. [source]

Nitrogen release dynamics and transformation of slow release fertiliser products and their effects on tea yield and quality

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2008
Dr Wen-Yan Han
Abstract BACKGROUND: Tea (Camellia sinensis (L.) O. Kuntze) is a perennial leaf harvested crop. It requires more nitrogen than most other crops and preferentially utilises NH4+ to NO3, when both are available in the soil. It is expected that slow release fertilisers coupled with a nitrification inhibitor could improve the N use efficiency and simultaneously reduce environmental pollution. In this study, three slow release fertilisers were developed and tested: CaMg phosphate coated urea with dicyandiamide (DCD) as a nitrification inhibitor and polyolefin coated urea with and without DCD. The main aim was to compare the nitrogen release dynamics and transformation of these fertilisers and their effects on tea yield and quality. RESULTS: The results showed that the coatings significantly slowed N release and kept mineral N in soils at a higher concentration for a longer time compared to uncoated urea. Polyolefin was a superior coating to CaMg phosphate. DCD was an effective nitrification inhibitor and significantly reduced the ratio of nitrate to total mineral N in a highly acidic tea soil. The 15N use efficiency was 29% where uncoated fertiliser was applied and 46% where polyolefin coated fertiliser with DCD was applied. The application of slow release fertilisers increased the chlorophyll content in mature leaves and enhanced the uptake of mineral elements by tea plants. Bud sprouting, shoot growth and mature leaf longevity were significantly improved, resulting in higher biomass of tea plants. Slow release fertilisers increased the yield of shoots by 51,143% (mean, 106%) in a pot experiment and 4,14% (mean, 9%) in a field experiment compared to uncoated urea. Tea quality parameters, especially free amino acids, were also significantly increased. CONCLUSION: Slow release fertilisers, especially polyolefin coated urea with DCD could significantly increase the N use efficiency and improve tea growth. Their uses in tea fields not only improved the profit margin, but possibly reduced environmental pollution. Copyright © 2008 Society of Chemical Industry [source]

Leaf dry matter content and lateral spread predict response to land use change for six subalpine grassland species

JOURNAL OF VEGETATION SCIENCE, Issue 2 2007
Nicolas Gross
Abstract Question: Land-use change has a major impact on terrestrial plant communities by affecting fertility and disturbance. We test how particular combinations of plant functional traits can predict species responses to these factors and their abundance in the field by examining whether trade-offs at the trait level (fundamental trade-offs) are linked to trade-offs at the response level (secondary trade-offs). Location: Central French Alps. Methods: We conducted a pot experiment in which we characterized plant trait syndromes by measuring whole plant and leaf traits for six dominant species, originating from contrasting subalpine grassland types. We characterized their response to nutrient availability, shading and clipping. We quantified factors linked with different land usage in the field to test the relevance of our experimental treatments. Results: We showed that land management affected nutrient concentration in soil, light availability and disturbance intensity. We identified particular suites of traits linked to plant stature and leaf structure which were associated with species responses to these environmental factors. Leaf dry matter content separates fast and slow growing species. Height and lateral spread separated tolerant and intolerant species to shade and clipping. Discussion and Conclusion: Two fundamental trade-offs based on stature traits and leaf traits were linked to two secondary trade-offs based on response to fertilization shade and mowing. Based on these trade-offs, we discuss four different species strategies which could explain and predict species distributions and traits syndrome at community scale under different land-uses in subalpine grasslands. [source]

Indirect facilitation and competition in tree species colonization of sub-Mediterranean grasslands

JOURNAL OF VEGETATION SCIENCE, Issue 3 2006
Georges Kunstler
Abstract: Questions: In the absence of herbivores, what is the importance of shrub facilitation for the colonization of grasslands by Fagus sylvatica and Quercus pubescens? Is there an indirect facilitative effect of shrubs on tree seedlings by limiting herb competition? Location: Causse du Larzac, southern Massif Central, France. Methods: We conducted field experiments on the facilitative role of shrubs in seedling emergence and survival, in relation to potential negative effects of shading and the presence of herbs. The effects of shade and herbs on allocation and root morphology were analysed in a pot experiment. Results: According to these experiments, the establishment of both tree species was facilitated by shrubs, but the two species differed in the processes underlying this facilitation. Shade directly facilitates the emergence rate of both species. Shade also indirectly facilitates Fagus survival by limiting herb competition. No indirect facilitation of Quercus survival was detected. These differences reflect variation in the tolerance of herb competition by seedlings of the two species. The tolerance of herb competition by Quercus seedlings allows regeneration over a wide area under each shrub and some regeneration events in grasslands at low grazing intensity. In contrast, for Fagus, only a narrow area under each shrub is suitable; regeneration is zero in grassland. The high tolerance of herb competition by Quercus seedlings may result from the avoidance of root competition. Conclusions In grasslands with severe drought stress, and almost obligatory shrub facilitation for tree seedling regeneration, the tolerance of herb competition may alter the precise role of facilitation in the colonization process. [source]

Interspecific and intraspecific interactions between salt marsh plants: integrating the effects of environmental factors and density on plant performance

OIKOS, Issue 2 2002
Jonathan M. Huckle
There has been much debate about the role of plant interactions in the structure and function of vegetation communities. Here the results of a pot experiment with controlled environments are described where three environmental variables (nutrients, sediment type and waterlogging) were manipulated factorially to identify their effects on the growth and intensity of interactions occurring between Spartina anglica and Puccinellia maritima. The two species were grown in split-plot planting treatments, representing intraspecific and interspecific addition series experiments, to determine individual and interactive effects of environmental factors and plant interactions on plant biomass. Above-ground growth of both species involved interactions between the environmental and planting treatments, while below-ground, environmental factors affected the biomass irrespective of planting treatments. It was suggested that this difference in growth response is evidence that in our experiment plant interactions between the two species occur primarily at the above-ground level. The intensity of plant interactions varied in a number of ways. First, interactions between Spartina and Puccinellia were distinctly asymmetrical, Puccinellia exerting a competitive effect on Spartina, with no reciprocal effect, and with a facilitative effect of Spartina on Puccinellia in low nutrient conditions. Second, the interactions varied in intensity in different environmental conditions. Interspecific competitive effects of Puccinellia on Spartina were more intense in conditions favourable to growth of Puccinellia and reduced or non-existent in environments with more abiotic stress. Third, intraspecific competition was found to be less intense for both species than interspecific interactions. Finally, the intensity of plant interactions involving both species was more intense above ground than below ground, with a disproportionate reduction in the intensity of interspecific competition below relative to above ground in treatments with less productive sediments and greater immersion. This is interpreted as reflecting a potential mechanism by which Spartina may be able to evade competitive neighbours. [source]

Size-dependent sex allocation in Aconitum gymnandrum (Ranunculaceae): physiological basis and effects of maternal family and environment

PLANT BIOLOGY, Issue 6 2008
Z.-G. Zhao
Abstract Theory predicts size-dependent sex allocation (SDS): flowers on plants with a high-resource status should have larger investment in females than plants with a low-resource status. Through a pot experiment with Aconitum gymnandrum (Ranunculaceae) in the field, we examined the relationship between sex allocation of individual flowers and plant size for different maternal families under different environmental conditions. We also determined the physiological base of variations in plant size. Our results support the prediction of SDS, and show that female-biased allocation with plant size is consistent under different environmental conditions. Negative correlations within families showed a plastic response of sex allocation to plant size. Negative genetic correlations between sex allocation and plant size at the family level indicate a genetic cause of the SDS pattern, although genetic correlation was influenced by environmental factors. Hence, the size-dependency of sex allocation in this species had both plastic and genetic causes. Furthermore, genotypes that grew large also had higher assimilation ability, thus showing a physiological basis for SDS. [source]

Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009
Mehmet Senbayram
The attribution of nitrous oxide (N2O) emission to organic and inorganic N fertilizers requires understanding of how these inputs affect the two biological processes, i.e. denitrification and nitrification. Contradictory findings have been reported when the effects of organic and inorganic fertilizers on nitrous oxide emission were compared. Here we aimed to contribute to the understanding of such variation using 15N-labelling techniques. We determined the processes producing N2O, and tested the effects of soil moisture, N rates, and the availability of organic matter. In a pot experiment, we compared soil treated with biogas waste (BGW) and mineral ammonium sulphate (Min-N) applied at four rates under two soil moisture regimes. We also tested biogas waste, conventional cattle slurry and mineral N fertilizer in a grassland field experiment. During the first 37 days after application we observed N2O emissions of 5.6,kg N2O-N,ha,1 from soils supplied with biogas waste at a rate of 360,kg,N,ha,1. Fluxes were ca. 5-fold higher at 85% than at 65% water holding capacity (WHC). The effects of fertilizer types and N rates on N2O emission were significant only when the soil moisture was high. Organic fertilizer treated soils showed much higher N2O emissions than those receiving mineral fertilizer in both, pot and field experiment. Over all the treatments the percentage of the applied N emitted as N2O was 2.56% in BGW but only 0.68% in Min-N. In the pot experiment isotope labelling indicated that 65,95% of the N2O was derived from denitrification for all fertilizer types. However, the ratio of denitrification/nitrification derived N2O was lower at 65% than at 85% WHC. We speculate that the application of organic matter in conjunction with ammonium nitrogen first leads to a decrease in denitrification-derived N2O emission compared with soil receiving mineral fertilizer. However, at later stages when denitrification becomes C-limited, higher N2O emissions are induced when the soil moisture is high. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Nematicidal activity of powder and extracts of Melia azedarach fruits against Meloidogyne incognita

ANNALS OF APPLIED BIOLOGY, Issue 2 2010
N.G. Ntalli
Pulverised lyophilised (dehydrated) Melia azedarach (Meliaceae) fruits (PMF) were tested in a dose,response pot experiment against juveniles (J2) of the root-knot nematode Meloidogyne incognita. Successively, with different extraction procedures, a polar (melia methanol extract, MME) and a non-polar (melia oil, MO) fragments were obtained and their effects were tested on nematode motility and development, in dose and time response bioassays and pot experiments. An EC50 value was calculated for all experiments. A dose,response effect was found in pot bioassays using PMF and, after an incubation period of 24 and 48 h, the EC50 values were calculated at 0.41% and 0.34% w/w, respectively. Motility bioassays revealed a dose and time dependent response effect, after exposure to MME, but not to MO. Doses of MME higher than 0.08% were nematicidal, whereas lower ones were nematostatic (the loss of motility as a result of the presence of the substance was reversible). In a pot experiment, MME doses higher than 2.5% w/w caused 100% nematode control with EC50 value of 0.916% w/w. [source]

Effects of spatial aggregation on competition, complementarity and resource use

AUSTRAL ECOLOGY, Issue 3 2008
KAREL MOKANY
Abstract The spatial distributions of most species are aggregated to varying degrees. A limited number of studies have examined the effects of spatial aggregation on interspecific and intraspecific interactions, generally finding that spatial aggregation can enhance coexistence between species by reducing the capacity for interspecific competition. Less well studied are the effects of spatial aggregation on complementarity (i.e. differences in resource use strategies) and resource use. Our primary hypothesis was that spatial aggregation reduces the complementarity between species owing to: (i) less interspecific interactions as a result of spatial separation; and (ii) less differences between species as a result of phenotypic plasticity. We further postulate that these negative effects of spatial aggregation on complementarity will reduce resource use by the community. Here we test these hypotheses in a pot experiment in which we applied three levels of spatial aggregation to three sets of two-species mixtures of herbaceous perennial plant species from native grasslands of south-eastern Australia. Both root and shoot biomass were significantly affected by spatial aggregation, although the nature of these affects depended upon the species involved, and the relative strengths of interspecific versus intraspecific competition. Complementarity between species in the distribution of their green leaves decreased significantly as spatial aggregation increased for one of the species mixtures, providing some evidence in support of our hypothesis that aggregation reduces complementarity through phenotypic plasticity. Spatial aggregation also altered light interception and use of soil moisture resources, although these effects were dependent on the species involved. We suggest that clear effects of spatial aggregation on complementarity and resource use may be obscured by the idiosyncratic way in which neighbour identity influences plant growth and hence plant size, limiting the ability to generalize, at the community level, any underlying effects of spatial pattern on ecological process. [source]

Acacia species turnover in space and time in an African savanna

JOURNAL OF BIOGEOGRAPHY, Issue 1 2001
William J. Bond
Aim Patterns of species turnover along environmental gradients are better studied than their causes. Competitive interactions, or physiological tolerance are most often cited as determinants of turnover. Here we investigate differential tree species response to disturbance by fire and mammal browsing as causes of changing dominance of species within and among sites along an altitudinal gradient. Methods We documented the distribution of two Acacia species using maps and sample transects. We explored possible causes of species turnover by studying differences between the species in tolerance to grass competition using pot experiments, to browsers by observing patterns of shoot damage, and to fire by comparing the size structure of populations burnt at different frequencies and intensities. Results Acacia karroo woodlands were rare and occur at higher elevations than the much more common A. nilotica woodlands. Woodland composition seems set to change in future since the pattern of dominance was reversed in juvenile stages. A. karroo juveniles were very widespread and far more abundant than A. nilotica juveniles. A. karroo juveniles were most abundant in tall fire-prone grasslands and were rare on grazing lawns whereas A. nilotica showed the reverse pattern. In the pot experiments, growth of both species was suppressed by grasses but there were no significant differences in response between the two species. Juveniles of A. karroo were more heavily browsed than those of A. nilotica. However juveniles of A. nilotica were less tolerant of frequent intense burns than juvenile A. karroo. Main conclusions Disturbance gradients, from high fire frequency and low herbivore density at high altitudes, to lower fire frequency and higher herbivore density at low altitudes, are responsible for the shift in community structure along the spatial gradient. Differential responses to browsing and fire may also explain temporal turnover from A. nilotica in the past to A. karroo in the present. Changes in the area burnt annually, and in faunal composition, suggest a landscape-scale shift from grazing-dominated short-grass landscapes in the 1960s, favouring A. nilotica, to fire-dominated tall grasslands in the 1990s favouring A. karroo. We suggest that species turnover due to differential responses along disturbance gradients may be much more widespread than the current paucity of studies suggests. [source]

Influence of environmental factors on the growth and interactions between salt marsh plants: effects of salinity, sediment and waterlogging

JOURNAL OF ECOLOGY, Issue 3 2000
Jonathan M. Huckle
Summary 1,Artificial environmental gradients were established in a series of pot experiments to investigate the effect of salinity, sediment type and waterlogging on the growth, and interactions between Spartina anglica and Puccinellia maritima. In each experiment, one environmental variable was manipulated and plants grown in pairwise combinations to examine the effect of the environmental factor on the intensity of intra- and interspecific interactions, quantified using the Relative Neighbour Effect (RNE) index. 2,Puccinellia was found to exert an asymmetric, one-way competitive dominance above ground over Spartina in experiments where gradients of sediment type and waterlogging were established. The intensity of the competition was highest in conditions with the least abiotic stress and lower or non-existent where stress was increased. 3,The intensity of the above-ground competition was greatest in loam and least in sand sediments. Reduction in competitive intensity in sand was accompanied by an increase in below-ground Spartina biomass and it is suggested that the production of rhizomes is a potential mechanism by which this species can expand vegetatively into areas without competition. 4,Interspecific competition on Spartina from Puccinellia also varied in intensity in the waterlogging experiment, being more intense in non-immersed treatments, where abiotic stress was reduced. 5,The competitive dominance of Puccinellia and the competition avoidance mechanism shown by Spartina in these experiments help to explain the successional interactions between the species along environmental gradients in natural salt marsh communities. [source]

Arsenic accumulation by rice grown in soil treated with roxarsone

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2009
Chen-Wuing Liu
Abstract Poultry litter is widely used as a fertilizer for lowland rice in Taiwan and China. However, the organic-arsenic compound roxarsone (additive of poultry feed) in poultry litter can be absorbed by the plants and the resulting arsenic (As) contamination may pose a serious threat to human health. This study used various amounts of poultry litter contaminated with roxarsone in pot experiments to evaluate the effect of roxarsone on rice agronomic parameters and the bioaccumulation of total and inorganic As in rice-plant tissues. Rice-grain yield decreased significantly with increasing As content of the soil, and the critical threshold that killed rice was 200 mg roxarsone (kg soil),1. The As concentrations in root, straw, leaf, husk, and grain increased with increasing soil As (p < 1%). At 100 mg roxarsone per,kg of soil, the As concentration in the rice grain exceeded the statutory permissible limit of 1.0 mg As (kg dry weight),1 and at 25 mg roxarsone (kg soil),1, the inorganic As concentrations in grains exceeded the statutory limit of 0.15 mg of inorganic As,kg,1 in China. For all treatments, the As concentrations in various plant tissues at maturity follow the order: root > stem > leaf > husk > grain. Arsenite was the predominant species in root, straw, and grain, while arsenate was the predominant species in leaf and husk. No significant difference existed between the amounts of arsenite and arsenate when various amounts of poultry litter were applied. This result illustrates that large amounts of added roxarsone are not only toxic to rice but also accumulate in grains in the inorganic As forms, potentially posing a threat to human health via the food chain. [source]

Marc concentration of sugar beet (Beta vulgaris L) in relation to sucrose storage

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2005
Christa M Hoffmann
Abstract Pulp as a feed stuff produced in the sugar factory is estimated by the marc concentration in sugar beet, which consists of the insoluble cell wall compounds. To identify factors affecting level and development of marc concentration during the growing season, several field trials and pot experiments were carried out in 2000, 2001 and 2002. The results show that marc concentration decreased until 100 days after sowing, but then did not change markedly until October, when it ranged between 34 and 45 g kg,1 beet. Marc concentration was affected more by site and variety than by year. Differences in marc concentration were already established very early in the season (65 days after sowing). This was attributed to the formation of cambial rings and parenchyma cells in the root during this period, which determine sucrose storage. There was a positive correlation between marc and dry matter, sucrose and betaine, but a negative correlation to root yield and amino N. Marc concentration was about 10% lower than reported in the past, which is supposed to be due to a change in the optimal cell volume for sucrose storage and the cell wall thickness of new sugar beet varieties. Copyright © 2004 Society of Chemical Industry [source]