摘要:

Abstract13N‐Iabelled experiments were carried out with barley and squash seedlings to analyse the effect of methionine sulphoximine (MSO), as an inhibitor of the ammonium assimilation, on NH4+fluxes in the roots at the level (150 μM NH4+) of the high affinity uptake system (HATS). MSO pretreatment in the root medium significantly accelerated NH4+influx and efflux in NH4+‐fed plants of both species. Concomitantly, the level of NH4+extracted from the root and shoot tissues was strongly elevated whereas the translocation of13N‐Iabelled organic substances (presumably amino products) into the shoots was markedly reduced. The onset of the increased NH4+influx did not occur immediately but was indicated about 1 h after the application of MSO to the nutrient solution. Also, MSO did not directly affect the uptake of13NO3−. The reason why MSO treatment leads to an acceleration of the NH4+influx against an increasing level in the cell tissue remains obscure. In squash, an intermediate of NO3−metabolism is thought to suppress NH4+uptake since NH4+influx was high in N‐free‐ and NH4+‐grown seedlings but was reduced about threefold in NO3−‐fed squash plants; the suppression was not elimina

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610102

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractIm 9. und 10. Versuchsjahr des 1986 angelegten Dauerdüngungsversuches wurden Mikroparzellen in den Feldparzellen des Winterweizens eingerichtet. In drei Prüfgliedern wurden 160 bzw. 110 kg/ha N, unterteilt in drei Gaben, als15N‐markiertes Ammoniumsulfat verabfolgt.Zu 5 Terminen wurde Nminim Boden gemessen, die oberirdische pflanzliche Biomasse geerntet und die N‐Aufnahme als Entzug aus dem Boden bestimmt. Über die15N‐Analyse konnte in beiden Fällen nach Herkunft des Stickstoffs aus Dünger‐N und bodenbürtigem N unterschieden werden.Dünger‐N wird bis Anfang Juni mehr oder weniger von der Pflanze aufgenommen, aber auch in erheblichem Maße im Boden immobilisiert. Der festgelegte N wird in der Folgezeit teilweise wieder remineralisiert und von der Pflanze assimiliert. Dagegen wird der native Nmin− Gehalt des Bodens in der Anfangsentwicklung des Weizens nur minimal in Anspruch genommen, so daß diese lösliche N‐Menge durch die Mineralisierung der organischen Bodensubstanz zwischenz

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610103

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractSeedlings ofBetula papyriferawere grown in sand/nutrient solution cultures in rhizotrone growth containers under elevated (700 ppm) or ambient (375 ppm) atmospheric CO2concentrations for approximately 10 weeks. Thirty seven days after the begin of the experiment the plants were exposed to a 10 day pulse of 400 or 1200 μM Al. Elevated atmospheric CO2increased both root production and loss. Exposure to Al reduced root production and slightly reduced root loss. The reduced root production due to Al was amplified after the pulse had receded, resulting in a significantly lower net and gross root production at the end of the experiment. There were no clear CO2× Al interaction

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610104

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe quantities of earthworm surface casts were monitored in traditional bush fallow regrowth (BFR),Pueraria phaseoloideslive mulch (PLM),Leucaena leucocephalaalley cropping (LAC) and undisturbed forest. The fallow systems were planted to maize/cassava intercrop either permanently or for one year after three years of fallow i.e. at 100 and 25% cropping frequencies. Earthworm casting activity was lower in fields cropped after clearing three year old fallow than in the respective permanently cropped fallow management system. The reduction in casting was related both to the degree of biomass removed through burning and to re‐establishment of cover crops. Higher exchangeable cation concentration in the soil did not cause increased casting activity.Concentrations of organic C, total N and exchangeable Ca and Mg in casts were significantly higher than in the 0–15 cm topsoil. Exchangeable Ca and Mg in casts did not significantly differ between treatments, with the exception of significantly higher Mg in casts after three years ofP. phaseoloidesfallow. Topsoil (0–15 cm) exchangeable Ca and Mg were not correlated with cast exchangeable Ca and Mg, but concentrations of organic C and total N in casts were significantly correlated with organic C and total N in the topsoil. Coefficients of variability of organic C, total N and exchangeable Ca and Mg were about twice as high in the soil than in casts. Significant negative correlations between the cast to soil ratio (cast enrichment factor) of organic C, total N and exchangeable Ca and Mg and the respective concentrations in the soil show that earthworms are increasingly selective in organic carbon and nutrient uptake as these parameters of soil fertility are decl

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610105

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe occurrence of terrestrial algae on two beech sites was determined qualitatively and quantitatively in the litter, organic and mineral layer. Both sites are beech stands of different age and the soil type is a Cambisol. On the site with young beech the maximal value determined was 1.0 · 108algae g−1dw in the litter layer. With increasing soil depth the number of algae decreased on both sites, and at the young beech stand site no algae were found in the mineral soil.Chlorophyceaewere the dominant algae group and at the young beech standBacillariophyceaewere prese

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610106

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractDrei Weidelgras‐Inzuchtlinien (A, B, C) und ihre Hybriden (AB, AC, BC) wurden auf ihre Sproßtrockenmassebildung, P‐Aufnahme (mg P je Gefäß), P‐Verwertung (mg Sproßtrockenmasse je mg P im Sproß) sowie ihren P‐Influx durch Kultivierung für maximal 92 Tage in einem Lößlehm‐Boden (Gefäßversuch) geprüft. Für die Bestimmung der Phosphataseaktivität wurden die Pflanzen der Linien A und C in Nährlösungen (1.10.100 μmol P · L−1) angezogen und die Hydrolyserate von Nitrophenylphosphat (NPP) gemessen.Verglichen mit dem Mittelwert der Inzuchtlinien produzierten die Hybriden bei hohem P‐Angebot 8%, bei niedrigem P‐Angebot 12% mehr Sproßmasse. Die Hybride BC bildete jeweils 14 bzw. 25% mehr, zeigte also den größten Heterosiseffekt. Die Biomassebildung korrespondierte mit dem P‐Entzug, deshalb gab es bei der P‐Verwertung keine Unterschiede zwischen Hybriden und Inzuchtlinien. Der erhöhte P‐Entzug der Hybriden korrespondierte mit größerer Wurzellänge. Das bedeutet, daß die Effizienz der P‐Aufnahmerate je Wurzeleinheit (Influx) durch die Hybridisierung nahezu unbeeinflußt war. Daraus kann der Schluß gezogen werden, daß der Heterosiseffekt mit einer erhöhten P‐Aufnahme verbunden ist, die durch ein vergrößertes Wurzelsystem verursacht wird. Die Phosphataseaktivität (Pase) der Wurzeln steigt mit sinkenden P‐Gehalten der Sprosse deutlich an, wobei die Absolutwerte bei Linie A fast doppelt so hoch wie bei C waren. Beide Linien reagierten mit einer signifikanten Erhöhung der Pasewenn das P

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610107

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractVon Februar 1985 bis Juli 1987 wurden in vier hessischen Forslämtern auf den 1983 begründeten Düngungsversuchsflächen in Buchenaltbeständen chemische Bodensickerwasser‐Untersuchungen durchgeführt. Darüber hinaus wurden in diese Arbeit auch die wichtigsten Ergebnisse der bodenchemischen Analysen der nachfolgenden Jahre 1988 und 1991 aufgenommen. Vordergründiges Ziel dieser Arbeit war es, den Einfluß der Kalkung und K/Mg‐Düngung auf die chemische Beschaffenheit des Bodens und der Bodenlösung unter verschiedenen Standortbedingungen näher zu untersuchen.Im Bodensickerwasser erbrachte die Kalkung in den nachfolgenden Jahren insgesamt keine eindeutige Erhöhung der pH‐Werte. In einigen Fällen sind die pH‐Werte im Durchschnitt sogar um 0.1 bis 0.2 Einheiten gesunken und die Al‐Konzentrationen dementsprechend angestiegen.Bei den Metallkationen Kalium. Kalzium und Magnesium hat die Düngung in den meisten Fällen zu einer deutlichen Erhöhung der Konzentrationen in der Bodenlösung geführt, insbesondere in 50 cm Bodentiefe. Auf den Versuchsparzellen mit den gesunkenen pH‐ Werten sind die K‐, Ca‐ und Mg‐Konzentrationen nicht oder nur geringfügig angestiegen.Darüber hinaus hat die Kalkung auf einigen Versuchsstandorten mil vermehrt durchlässigen Böden eine beschleunigte Mineralisierung der Humusauflage bewirkt und damit die Nitratgehalte im Bodensickerwasser von durchschnittlich rd. 1–2 bis auf 10–20 mg/l erhöht. Ferner sind durch die mobilisierende Wirkung der Ca‐Düngung die Gehalte an Sulfat und zumeist auch an Schwermetallen (Mn, Zn. Cu, Cd) in der Bodenlösung angestiegen. Insgesamt konnte bei den meisten chemischen Parametern eine etwas erhöhte Mobilität durch Kalkung mit Bodenbearbeitung nachgewiesen werden.Im Boden wurden als Folge der Kalkung und Düngung auch noch nach 5 bis 8 Jahren deutlich höhere pH‐Werte und Basensättig

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610108

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe interlaboratory variations in the fumigation extraction method and the analytical procedures for measuring C and N in the soil microbial biomass were tested with one soil sample, and two soil extracts (non‐fumigated and fumigated) sent to 25 different laboratories. Four groups of analytical procedures for organic C, i.e. (1) oven oxidation/ IR detection, (2) UV‐persulfate oxidation/lR detection, (3) UV‐persulfate oxidation/colorimetric detection and (4) dichromate oxidation/ titration, and three groups for total N, i.e. (1) Kjedahl reduction to NH4+, (2) UV‐persulfate and (3) persulfate‐borate oxidation to NO3−were used by the different laboratories.The coefficient of variation for C and N measurements between different laboratories and analytical procedures varied between 15 and 34% in non‐fumigated samples, between 13 and 20% in fumigated samples, and between 12 and 24% in the differences Ecand EN. The average coefficients of variation between the replicate measurements within one laboratory were much smaller, i.e. they varied between 3.0 and 9.2% in non‐fumigated samples, between 2.4 and 5.5% in fumigated samples, and between 4.5 and 12.8% in the differences Ecand En. Extraction and fumigation were not the major source of the variations observed. They were mainly a result of differences in the analytical procedures used to measure the low concentrations of C and N in the extracts. However, all of these analytical procedures should be able to measure correct values if they are properly calibrate

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610109

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe primary aims of the present investigation were to determine the proportion of microbial driven soil processes associated with acidification in coniferous forest soils, and the response of microbial communities with respect to soil acidification and to acidification processes. Lysimeters containing undisturbed soil columns from five forest sites in Europe were installed in a spruce forest in the Soiling (northern Germany) and exposed to the same input and climatic conditions. In the present study root uptake was excluded.Under these conditions, during the 21 months of the experiment, acid load by microbial N‐transformations especially mineralization and subsequent nitrification were the most important processes ranging from 50.2% to 79.1%. Except for one soil the balances showed, that increasing levels of soil acidity decreased the potential of mineralization. This agreed with the observation that microbial biomass Cmic decreased. The biomass Cmic (kg ha−1a−1) was significantly correlated to N‐output. The caloric quotient qW increased parallel to decreasing pH.During the experiment the PH caCl 2in all mineral soil horizons decreased significantly. This change in soil chemical conditions did not affect the microbial biomass Cmic but the caloric quotient increased during the experiment, especially in the upper m

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610110

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractEmploying four mathematical models (first‐order, parabolic‐diffusion, Elovich and zero‐order), kinetics of potassium desorption from eight soils with and without cropping were studied to evaluate their ability in explaining K release from soils. The decline in the soil test K in cropped soils over original soils was drastic in easily desorbable forms compared to that of strongly held forms like 3 M H2SO4K. Results showed that parabolic diffusion as well as first‐order kinetic equation explained the K release data well for both original and K depleted (cropped) soils. Elovich and zero‐order equations were not suitable to describe the kinetic data. However, zero‐order equation explained K release data better in case of K‐depleted soils as compared to original soils. Soils with higher initial K contents registered higher release rate constants. Over the entire period of cropping the range of release rate (b) decreased from 1.26 to 1.53 × 10−2to values ranging from 1.12 to 1.30 × 10−2h−1. In contrast, the first‐order equation, parabolic diffusion showed higher b values for cropped soils as they represent the diffusion gradient. Mica and its biotite content in both silt and clay fractions showed significant correlation (r) with b values. Similarly with the rate of K release, clay content of soils maintained significant r whereas t

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610111

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY