Kálmán Rajkai - Academia.edu (original) (raw)
Papers by Kálmán Rajkai
Open Geosciences, 2015
This study discusses scientific contributions analyzingsoil-atmosphere relationships. These studi... more This study discusses scientific contributions analyzingsoil-atmosphere relationships. These studies dealwith both the biogeophysical and biogeochemical aspectsof this relationship, with biogeophysical aspects beingin the majority. All of the studies refer either directly orindirectly to the fundamental importance of soil moisturecontent. Moisture has a basic influence on the spatiotemporalpattern of evapotranspiration, and so 1) oncloud formation and precipitation events by regulatingthe intensity of convection, and 2) on the trace-gas exchangesin the near-surface atmosphere. Hungarian modelingefforts have highlighted that soils in the PannonianBasin have region-specific features. Consequently, shallowand deep convection processes are also, to some extent,region-specific, at least in terms of the diurnal changeof the planetary boundary layer height and the spatial distributionof convective precipitation. The soil-dependentregion-distinctiveness of these two phenomena has beenrecogni...
Soil & Tillage Research, May 1, 2005
A model to predict the mechanical strength of arable soils and its effect on physical properties ... more A model to predict the mechanical strength of arable soils and its effect on physical properties was developed and integrated within the framework of the SIDASS-project “A spatially distributed simulation model predicting the dynamics of agro-physical soil state within Eastern and Western Europe countries for the selection of management practices to prevent soil erosion based on sustainable soil–water interactions”.The mechanical
Biogeosciences, Mar 5, 2009
A major international experiment on ammonia (NH 3) biosphere-atmosphere exchange was conducted ov... more A major international experiment on ammonia (NH 3) biosphere-atmosphere exchange was conducted over intensively managed grassland at Braunschweig, Germany. The experimental strategy was developed to allow an integrated analysis of different features of NH 3 exchange including: a) quantification of nearby emissions and advection effects, b) estimation of net NH 3 fluxes with the canopy by a range of micrometeorological measurements, c) analysis of the sources and sinks of NH 3 within the plant canopy, including soils and bioassay measurements, d) comparison of the effects of grassland management options on NH 3 fluxes
Agrokémia és talajtan (Nyomtatott), Aug 1, 2004
Az erdészeti beavatkozásokkal együtt járó, a természetes lékdinamikát közelítő léknyitás talajned... more Az erdészeti beavatkozásokkal együtt járó, a természetes lékdinamikát közelítő léknyitás talajnedvesség-tartalomra gyakorolt hatását tanulmányoztuk bükkös állományban, a Börzsöny hegységben. A K-ÉK-i kitettségű lejtőn elhelyezkedő, kb. 80 éves állományban 2000 telén létrehozott, kör alakú lékeket vizsgáltuk. A terület talaja andezit alapkőzeten kialakult, átlagosan 20-30 cm termőréteg-vastagságú, erodálódott agyagbemosódásos barna erdőtalaj. Feltételeztük, hogy a talajnedvesség-viszonyok a zárt lombkorona alatt és a lékekben különböznek. A talajnedvesség-mérések egy kis (kb. 20 m átmérőjű) és egy nagy (kb. 35 m átmérőjű) lékben, ill. környezetükben, vegetációs időszakban háromhetente és a vegetációs időszakon kívül összesen két alkalommal történtek transzekt, ill. grid elrendezésben. Kimutattuk, hogy a felső 10 cm-es talajréteg nedvességtartalma esős időszakok után kis mértékben különbözött a lékben és a zárt lombsátor alatt. Száraz időszakok után pedig szignifikánsan nagyobb volt a lékekben, mint az állomány alatt. A talajnedvesség-tartalom átlaga mindkét lékben minden mérési időpontban közel volt a szántóföldi vízkapacitás értékhez. Vizsgálatainkból arra következtettünk, hogy a lékek nyitása megváltoztatja a talaj felső rétegének nedvességviszonyait, ahogy azt bükkös állomány lékeiben leírták (pl. Bauhus, 1996). Méréseink szerint is a talaj a lékekben nedvesebb, mint a zárt lombsátor alatt. A két vizsgált lékméret hatása a talajnedvesség-tartalom nagyságára hasonló volt, míg a léken belüli térbeli mintázat különbözött. A lékhatás általánosabb érvényű jellemzéséhez a talajnedvesség-tartalom több lékben és hosszabb időn keresztül történő vizsgálatára van szükség. A méréseket a talajnedvesség-tartalmon kívül a fényre, mint abiotikus tényezőre is tervezzük kiterjeszteni.
Cereal Research Communications, Mar 1, 2006
Agrokémia és talajtan (Nyomtatott), Dec 1, 2015
Agrokemia es Talajtan, Aug 14, 1979
Agrokemia es Talajtan, 1980
Acta Agronomica Hungarica, Aug 1, 2005
The electrical capacitance method was applied for the examination of living root systems in a pot... more The electrical capacitance method was applied for the examination of living root systems in a pot experiment. The measured root capacitances gave an unambiguous indication of the development of root mass and length. The root capacitances measured using needle and clamp plant electrodes were closely similar when the roots of whole plants were placed in water, while increasing differences were observed with a decrease in soil water saturation. The difference in capacitance between the plant electrodes is outlined by interpreting the action mechanism of the clamp electrode. The capacitance and electrical impedance spectra (30 Hz-1 MHz) were determined for roots in soil, for pieces of roots washed free of soil, and for the soil itself. The root capacitance was smaller than that of the soil and higher than that of root pieces at 1 kHz, while the capacitance of the soil became equal to that of roots in soil at about 2 kHz. This calls attention to the importance of the measuring frequency when determining root capacitance. A capacitor model with two dielectric media is proposed besides Dalton's model in order to interpret the behaviour of root and soil capacitances. However, its validity requires further verification.
Soil Science, Dec 1, 1996
ABSTRACT A Swedish soils database containing soil-water retention data, particle-size fractions, ... more ABSTRACT A Swedish soils database containing soil-water retention data, particle-size fractions, dry bulk density, and organic matter content, was analyzed in order to find a relatively simple predictor of the soil-water retention curve (SWRC). As a SWRC model we chose a three-parameter function selected from nine van Genuchten-type retention models that were fitted to the measured retention data by nonlinear parameter optimization. Cumulative particle-size (CP) data were described by a logistic distribution model. Additionally, the mean and standard deviation of the CP distribution were estimated directly from the measured particle-size data. Regression equations were subsequently used to estimate the parameters in the selected SWRC model from available soil properties, particle-size data, and CP distribution parameters. Four alternative pedotransfer models were formulated to estimate the SWRC curve from the basic soil properties. These models predicted the SWRC curves from either the original soil data or from the CP distribution parameters. A mean estimation error of less than 2.5% was used to indicate a good estimation. The highest ratio (67%) of good estimations and the lowest ratio (12%) of poor estimations were obtained when both the original soil properties and the CP model parameters were used. Our study shows that the resulting simple SWRC model gives a good description and a usable prediction of the retention properties of Swedish soils for a wide range of soil textures.
Journal of Agricultural Informatics, Mar 22, 2011
Agrokemia es Talajtan, Jan 27, 2005
Agrokémia és talajtan (Nyomtatott), Dec 1, 2011
CRC Press eBooks, Aug 26, 2010
International Agrophysics, Dec 1, 2013
Importance of phase angle measurement during the application of electrical impedance spectroscopy... more Importance of phase angle measurement during the application of electrical impedance spectroscopy was studied by executing pot experiments with maize. Electrical impedance, phase angle (strength of capacitive character), and dissipation factor in the plant-soil system were scanned between 100 and 10 000 Hz current frequency. The frequency-dependent change in the phase angle could be described by optimum curves culminating within 920-3 650 Hz. Since the rate of energy dissipation is independent of root extent, the higher phase angle and lower energy dissipation were associated with the higher coefficient of determination achieved for the root electrical impedance-root system size (root dry mass and root surface area) regressions. The characteristic frequency selected on the basis of phase angle spectra provided a higher significance level at statistical comparison of plant groups subjected to stress conditions influencing root development. Due to the physicochemical changes observable in aging root tissue, the apex of phase angle spectra, thus the characteristic frequency, shifted continuously toward the higher frequencies over time. Consequently, the regularly repeated phase angle measurement is advisable in time-course studies for effective application of the electrical impedance method, and the systematic operation at the same frequency without determination of phase angle spectra should be avoided. K e y w o r d s: dissipation factor, root capacitance, electrical impedance spectroscopy, phase angle, root surface area
Agrokémia és talajtan (Nyomtatott), Nov 28, 2020
International Agrophysics, 1996
Cereal Research Communications, 2008
Open Geosciences, 2015
This study discusses scientific contributions analyzingsoil-atmosphere relationships. These studi... more This study discusses scientific contributions analyzingsoil-atmosphere relationships. These studies dealwith both the biogeophysical and biogeochemical aspectsof this relationship, with biogeophysical aspects beingin the majority. All of the studies refer either directly orindirectly to the fundamental importance of soil moisturecontent. Moisture has a basic influence on the spatiotemporalpattern of evapotranspiration, and so 1) oncloud formation and precipitation events by regulatingthe intensity of convection, and 2) on the trace-gas exchangesin the near-surface atmosphere. Hungarian modelingefforts have highlighted that soils in the PannonianBasin have region-specific features. Consequently, shallowand deep convection processes are also, to some extent,region-specific, at least in terms of the diurnal changeof the planetary boundary layer height and the spatial distributionof convective precipitation. The soil-dependentregion-distinctiveness of these two phenomena has beenrecogni...
Soil & Tillage Research, May 1, 2005
A model to predict the mechanical strength of arable soils and its effect on physical properties ... more A model to predict the mechanical strength of arable soils and its effect on physical properties was developed and integrated within the framework of the SIDASS-project “A spatially distributed simulation model predicting the dynamics of agro-physical soil state within Eastern and Western Europe countries for the selection of management practices to prevent soil erosion based on sustainable soil–water interactions”.The mechanical
Biogeosciences, Mar 5, 2009
A major international experiment on ammonia (NH 3) biosphere-atmosphere exchange was conducted ov... more A major international experiment on ammonia (NH 3) biosphere-atmosphere exchange was conducted over intensively managed grassland at Braunschweig, Germany. The experimental strategy was developed to allow an integrated analysis of different features of NH 3 exchange including: a) quantification of nearby emissions and advection effects, b) estimation of net NH 3 fluxes with the canopy by a range of micrometeorological measurements, c) analysis of the sources and sinks of NH 3 within the plant canopy, including soils and bioassay measurements, d) comparison of the effects of grassland management options on NH 3 fluxes
Agrokémia és talajtan (Nyomtatott), Aug 1, 2004
Az erdészeti beavatkozásokkal együtt járó, a természetes lékdinamikát közelítő léknyitás talajned... more Az erdészeti beavatkozásokkal együtt járó, a természetes lékdinamikát közelítő léknyitás talajnedvesség-tartalomra gyakorolt hatását tanulmányoztuk bükkös állományban, a Börzsöny hegységben. A K-ÉK-i kitettségű lejtőn elhelyezkedő, kb. 80 éves állományban 2000 telén létrehozott, kör alakú lékeket vizsgáltuk. A terület talaja andezit alapkőzeten kialakult, átlagosan 20-30 cm termőréteg-vastagságú, erodálódott agyagbemosódásos barna erdőtalaj. Feltételeztük, hogy a talajnedvesség-viszonyok a zárt lombkorona alatt és a lékekben különböznek. A talajnedvesség-mérések egy kis (kb. 20 m átmérőjű) és egy nagy (kb. 35 m átmérőjű) lékben, ill. környezetükben, vegetációs időszakban háromhetente és a vegetációs időszakon kívül összesen két alkalommal történtek transzekt, ill. grid elrendezésben. Kimutattuk, hogy a felső 10 cm-es talajréteg nedvességtartalma esős időszakok után kis mértékben különbözött a lékben és a zárt lombsátor alatt. Száraz időszakok után pedig szignifikánsan nagyobb volt a lékekben, mint az állomány alatt. A talajnedvesség-tartalom átlaga mindkét lékben minden mérési időpontban közel volt a szántóföldi vízkapacitás értékhez. Vizsgálatainkból arra következtettünk, hogy a lékek nyitása megváltoztatja a talaj felső rétegének nedvességviszonyait, ahogy azt bükkös állomány lékeiben leírták (pl. Bauhus, 1996). Méréseink szerint is a talaj a lékekben nedvesebb, mint a zárt lombsátor alatt. A két vizsgált lékméret hatása a talajnedvesség-tartalom nagyságára hasonló volt, míg a léken belüli térbeli mintázat különbözött. A lékhatás általánosabb érvényű jellemzéséhez a talajnedvesség-tartalom több lékben és hosszabb időn keresztül történő vizsgálatára van szükség. A méréseket a talajnedvesség-tartalmon kívül a fényre, mint abiotikus tényezőre is tervezzük kiterjeszteni.
Cereal Research Communications, Mar 1, 2006
Agrokémia és talajtan (Nyomtatott), Dec 1, 2015
Agrokemia es Talajtan, Aug 14, 1979
Agrokemia es Talajtan, 1980
Acta Agronomica Hungarica, Aug 1, 2005
The electrical capacitance method was applied for the examination of living root systems in a pot... more The electrical capacitance method was applied for the examination of living root systems in a pot experiment. The measured root capacitances gave an unambiguous indication of the development of root mass and length. The root capacitances measured using needle and clamp plant electrodes were closely similar when the roots of whole plants were placed in water, while increasing differences were observed with a decrease in soil water saturation. The difference in capacitance between the plant electrodes is outlined by interpreting the action mechanism of the clamp electrode. The capacitance and electrical impedance spectra (30 Hz-1 MHz) were determined for roots in soil, for pieces of roots washed free of soil, and for the soil itself. The root capacitance was smaller than that of the soil and higher than that of root pieces at 1 kHz, while the capacitance of the soil became equal to that of roots in soil at about 2 kHz. This calls attention to the importance of the measuring frequency when determining root capacitance. A capacitor model with two dielectric media is proposed besides Dalton's model in order to interpret the behaviour of root and soil capacitances. However, its validity requires further verification.
Soil Science, Dec 1, 1996
ABSTRACT A Swedish soils database containing soil-water retention data, particle-size fractions, ... more ABSTRACT A Swedish soils database containing soil-water retention data, particle-size fractions, dry bulk density, and organic matter content, was analyzed in order to find a relatively simple predictor of the soil-water retention curve (SWRC). As a SWRC model we chose a three-parameter function selected from nine van Genuchten-type retention models that were fitted to the measured retention data by nonlinear parameter optimization. Cumulative particle-size (CP) data were described by a logistic distribution model. Additionally, the mean and standard deviation of the CP distribution were estimated directly from the measured particle-size data. Regression equations were subsequently used to estimate the parameters in the selected SWRC model from available soil properties, particle-size data, and CP distribution parameters. Four alternative pedotransfer models were formulated to estimate the SWRC curve from the basic soil properties. These models predicted the SWRC curves from either the original soil data or from the CP distribution parameters. A mean estimation error of less than 2.5% was used to indicate a good estimation. The highest ratio (67%) of good estimations and the lowest ratio (12%) of poor estimations were obtained when both the original soil properties and the CP model parameters were used. Our study shows that the resulting simple SWRC model gives a good description and a usable prediction of the retention properties of Swedish soils for a wide range of soil textures.
Journal of Agricultural Informatics, Mar 22, 2011
Agrokemia es Talajtan, Jan 27, 2005
Agrokémia és talajtan (Nyomtatott), Dec 1, 2011
CRC Press eBooks, Aug 26, 2010
International Agrophysics, Dec 1, 2013
Importance of phase angle measurement during the application of electrical impedance spectroscopy... more Importance of phase angle measurement during the application of electrical impedance spectroscopy was studied by executing pot experiments with maize. Electrical impedance, phase angle (strength of capacitive character), and dissipation factor in the plant-soil system were scanned between 100 and 10 000 Hz current frequency. The frequency-dependent change in the phase angle could be described by optimum curves culminating within 920-3 650 Hz. Since the rate of energy dissipation is independent of root extent, the higher phase angle and lower energy dissipation were associated with the higher coefficient of determination achieved for the root electrical impedance-root system size (root dry mass and root surface area) regressions. The characteristic frequency selected on the basis of phase angle spectra provided a higher significance level at statistical comparison of plant groups subjected to stress conditions influencing root development. Due to the physicochemical changes observable in aging root tissue, the apex of phase angle spectra, thus the characteristic frequency, shifted continuously toward the higher frequencies over time. Consequently, the regularly repeated phase angle measurement is advisable in time-course studies for effective application of the electrical impedance method, and the systematic operation at the same frequency without determination of phase angle spectra should be avoided. K e y w o r d s: dissipation factor, root capacitance, electrical impedance spectroscopy, phase angle, root surface area
Agrokémia és talajtan (Nyomtatott), Nov 28, 2020
International Agrophysics, 1996
Cereal Research Communications, 2008