ISSN:1025-6016    

DOI:10.1080/10256019808036352

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The nitrogen research contributes significantly in different ways to crop sciences. By the application of the15N tracer technique additional informations are obtained, especially during long-term trials. Three models are represented:

ISSN:1025-6016    

DOI:10.1080/10256019808036353

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

By using soil as substrate, white and yellow lupines (Lupinus albusL.,Lupinus luteusL.) assimilated higher N amounts than under quartz sand conditions. This was caused by spontaneous infection of lupines with wild Rhizobia strains and also by an additional N uptake from the soil. In yellow lupines without inoculation in non-sterile soil, only the additional N uptake played a role. Differences in P and K supply as the cause of different N acquisition from soil and quartz sand could be excluded. As compared with white lupines, yellow lupines inoculated with Rhizobia had a high N2fixation that exceeded the effect of spontaneous infections. This result as well as the positive effect of spontaneous infections with soil-borne Rhizobia on white lupines indicates insufficient effectiveness of the strains used for inoculation on this plant species.

ISSN:1025-6016    

DOI:10.1080/10256019808036354

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Glutamine synthetase (GS) and glutamate dehydrogenase (GDH) are both present inSphagnumand in principle both enzymes could be involved in the assimilation of ammonium.15NH4* application led to the formation γ-15N-glutamine, followed by α-amino glutamate/glutamine as observed byin vivo15N NMR. No assimilation was detected in the presence of the GS-specific inhibitor methionine sulfoximine. This labelling pattern suggests, that ammonium assimilation inSphagnumis mediated solely by the GS/glutamate synthase pathway. The application of15N-labelled glutamate led to the liberation of15NH4*, indicating that GDH mainly catalyses the deamination of glutamate. It was possible to record good-qualityin vivo31P NMR spectra ofSphagnum flexuosumtissue, and the chemical shift of the orthophosphate resonances indicated that cytoplasmic pH was not affected during the ammonium application, whereas the vacuolar pH was slightly reduced.

ISSN:1025-6016    

DOI:10.1080/10256019808036355

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In microplot experiments on two minerotrophic mire sites of northeastern Germany (a: highly degraded, shallow—Paulinenaue, Brandenburg; b: slightly degraded, deep-layer—Heinrichswalde, Mecklenburg-Vorpommern) the fate of15N-labelled fertilizer-N (120kg N ha−1as K15NO3, 46.94 at-%15Nexc) was investigated over one growing season. Only 53 to 69% of the applied fertilizer-N (63 to 82kg N ha−1) could be recovered. The plants had taken up about 70 to 79% of this portion, that is about 16% of their total N demand. At the end of the first year of experiment, about 21 to 30% of the fertilizer-N recovered were in the soil, more than 90% of which in 0–20 cm depth. It is assumed that the low rates of retrieval are due to gaseous losses of N-compounds (as N2; N2O).

ISSN:1025-6016    

DOI:10.1080/10256019808036356

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

As shown in field plot trials with application of15N on loamy sand (albic luvisol), winter oilseed turnip (Brassica rapaL.; ssp.oleifera(Dc.) METZG.) incorporated considerable N amounts during the winter period. By this a reduction of N percolation into deeper soil layers was achieved. After mulching, about 30% of the catch crop N was taken up by the following crop, maize (Zea maysL., cv. ‘BEKENOVA’). Maize covered 11% of its total N demand deriving from the catch crop.

ISSN:1025-6016    

DOI:10.1080/10256019808036357

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Uptake of weed-borne nitrogen by maize was tested with15N in field experiments on silty loam (haplic phaeozem) after common growth of maize andChenopodium albumL. and incorporating the weeds at the 4- to 6-leaf stage of maize. Maize took up 22–23% of the weed-borne N in the year of incorporating and residual 7–32% in the following year. Uptake of weed-borne N was higher in comparable pot experiments. Different soil humidity after different water supply was mainly reasonable for these differences. Weed-borne nitrogen contributed 7–16% to total N of maize in the year of incorporating and 4–11% in the following year. Yield and N uptake between weeded and unweeded maize differed partly significant.

ISSN:1025-6016    

DOI:10.1080/10256019808036358

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Lysimeter experiments (soil: sandy treposol, from the region “Havelländisches Luch”, Brandenburg, Germany) with application of15N labelled fertilizer (80 kg N per ha as15NH415NO3, 10 at.-%15N exc.; for simulating mineralization in the early autumn period) were carried out to determine to what extent the amount of mineral- N was temporary conserved by winter catch crops, taken up subsequently in the vegetation periods by following crops, taken by subsequently in the vegetation periods by following crops, or percolated in the leaching water, respectively. The results were as follows:

ISSN:1025-6016    

DOI:10.1080/10256019808036359

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presents the interests and the limits of the isotope exchange kinetic method to assess soil K, P, S and Zn availability for plants. This method allows to quantify the amount of nutrient present on the soil's solid phase which can arrive in the solution of a soil/solution system at a steady state. Three parameters characterize this exchange in addition to exchange time:R/r(1) which is the ratio between the total introduced radioactivity (R) and the radioactivity remaining in the soil solution after 1 minute of exchange (r1),nwhich describes the rate of disappearance of the radioactivity from the solution for exchange times longer than 1 minute, and C which is the concentration of the studied element in the soil solution. These three parameters can be used to calculate the amount of element isotopically exchangeable with time (E(t)values). This approach gives access to the three parameters characterizing the availability of inorganic nutrient: the intensity factor (the concentration of nutrient in the solution), the quantity factor (the quantity of nutrient which can be taken up by a plantE(t)), and the capacity factor which describes the relationship between the intensity and the quantity factors (R/r(1) andn). Results obtained by this approach are relevant to areas such as fertilizer management and organic matter mineralization. This method bears also a large potential for assessing the bioavailability of heavy metals, such as Zn, either in agricultural soils where those nutrients may be limiting or in polluted soils where they may be present in excessive concentrations. However, results obtained by this approach may be properly interpreted if and only if the basic assumptions underlying its use are fulfilled, and if the various parameters (C,R/r(1),n) are measured with enough precision.

ISSN:1025-6016    

DOI:10.1080/10256019808036360

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Male Wistar rats (17 wks. old, body weight ∼400 g), fitted with an intra gastric cannula and with a catheter in thevena jugulariswere divided into 3 groups and given a marginal ration of the feeding solution Nutrison Standard (1g protein and 350 kJ ME per day). Group 1 had ad lib. access to the drinking bottle, the groups 2 and 3 were pair fed by gastric infusion, splitted up into 2 greater meals for group 2 respectively into 6 smaller meals for group 3. After adaptation all animals get an i.p. injection of doubly labelled tracer solution (200μl) containing 2.5mg L-[15N]leucine (72 atom%15N) combined with either [1-14C]- or [U-14C] leucine (37 kBq).

ISSN:1025-6016    

DOI:10.1080/10256019808036361

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor