摘要:

AbstractWhen investigating the reversibility of soil and water acidification due to a reduction of SO42−deposition, the size and stability of the reversibly bound SO42−fraction in soils are important parameters. The desorption behaviour of SO42−in three acid forest soils was investigated using columns with undisturbed and disturbed (<5 mm sieved) soil material. The results were compared to batch experiments.A comparison of the undisturbed and the disturbed soil samples showed that the soil structure had no effect on the chemistry of the soil solution, the S‐mineralisation rates or the SO42−desorption rates. A comparison of the batch and the column method showed only minor differences in desorption rates. However, fitting the measured desorption rates to a modified Langmuir equation showed a more distinct difference between both methods. It was concluded that the batch method was more suitable to establish SO42−desorption isotherms.When investigating SO42−dynamics of soils, the heterogeneity of the soils has to be considered because the spatial variability of isotherm parameters was found to be greater than differences between the investigated methods. Furthermore, SO42−sorption showed a distinct hysteresis. While most of the sorbed SO42−was desorbed at concentrations<5–10 mg SO42−1−1, a sorption of SO42−was observed only at concentr

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610112

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractCa deficiency disorders are common in micropropagated plantlets but little is known regarding the uptake of Cain vitro.Ca uptake byinvitra‐grown potato (Solanum tuberosumL. cvs. Bintje and Norland) plantlets was investigated when Ca levels were maintained but the total macroelement salts or just NH4, the major competing cation, were reduced in Murashige and Skoog (MS) medium. This increased the ratio of Ca:cations or Ca:NH4as well as the osmotic potential of the medium. The increased Ca‐cations improved Ca uptake of shoot tips, leaves, and stems while increased Ca:NH4had no effect. MS medium macroelement dilution may improve Ca uptake by micropropagated plantlets and prevent Ca deficiency disord

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610113

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractTurnover and fluxes of C and N through microbial biomass were investigated on a research site in the grassland region of southwestern Germany. For a period of twelve months, biomass C was determined every 2 weeks and biomass N every 4 weeks (Fumigation‐Extraction). This was done at fertilized plots as well as on plots, which had not been fertilized for eight years. Biomass C and N accounted for 1.5–7.5% of the soil C and 2–9% of the soil nitrogen. Unfertilized plots contained more biomass C and N than fertilized plots. No seasonal influence on the amount of the microbial biomass was visible. C/N ratios were not related to fertilization events. An increase of the C/N ratio with depth suggests a dominance of fungi in the subsurface horizons.Estimates of biomass C and N turnover were calculated by dividing the total measured losses of biomass by the average quantity of biomass present (McGillet al., 1986), annual fluxes of carbon and nitrogen were calculated by dividing annual mean C(N) by the average C(N) in biomass (JenkinsonandLadd, 1981). Average turnover rates for biomass C varied between 1.4 and 4.5 a−1, turnover rates for nitrogen were slower (1.2–3.3 a−1). Carbon Ruxes through the microbial biomass range from 5000 to 8000 kg ha−1a−1, while nitrogen fluxes range from 400 to

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610114

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610115

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

ISSN:0044-3263    

DOI:10.1002/jpln.1998.3581610101

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY