Kálmán Rajkai - Academia.edu (original) (raw)
Papers by Kálmán Rajkai
HAL (Le Centre pour la Communication Scientifique Directe), 2009
Random forest based pedotransfer functions and geostatistical methods for mapping soil moisture retention capacity at 100 m resolution
EGUGA, Apr 1, 2019
The effects of cadmium (Cd) stress and arbuscular mycorrhizal fungus (AMF) inoculation were inves... more The effects of cadmium (Cd) stress and arbuscular mycorrhizal fungus (AMF) inoculation were investigated in wheat [Triticum aestivum L. cv. TC-33] under controlled conditions. The experiments aimed to reveal what stress responses belong to the different levels of Cd load in the growth medium (0; 1; 2,5 and 5 mg Cd kg-1 substrate). To detect the effect of Cd stress, we compared plant physiological and growth indicators measured with both in situ and destructive methods. Electrical capacitance (CR) was evaluated during the experiments as a method to indicate stress responses through of Cd-induced root system changes.During the growth period, the photosynthetic activity (Fv/Fm), the chlorophyll content index (CCI) of the leaves, and the CR of the root-soil system were monitored in situ. After harvest, the membrane stability index (MSI), the cadmium and phosphorus concentrations of the plants, the root dry mass (RDM), the shoot dry mass (SDM) and the leaf area (LA) were measured. The ro...
Comparative measurements with sand box, pressure membrane extractor and pressure plate extractor
Mathematical description of water retention (pF) curves
Soil moisture measurements using a microwave Michelson interferometer
Sand mixture density
Unsaturated Soils: Research & Applications, 2014
International Agrophysics, 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 observa...
Journal of Agricultural Informatics, 2011
Calibration of a TDR probe in an expansive soil
Unsaturated Soils, 2010
Hungarian Agriculture: Development Potential and Environment
Sustainable Development of Agriculture, 1988
Two comprehensive research projects were recently completed by the Hungarian Academy of Sciences ... more Two comprehensive research projects were recently completed by the Hungarian Academy of Sciences on the development problems of the Hungarian food and agricultural sector. In these studies agroecological factors were stressed.
The Soil Water Characteristics of Two-Component Sand Mixtures
Springer Proceedings in Physics 113, 2007
During an ongoing research the water retention curves of three sand fractions and 12 continuous a... more During an ongoing research the water retention curves of three sand fractions and 12 continuous and gap-graded two component sand mixtures with various composition ratio is measured. Due to the unexpectedly long equalization times in the low suction range complete data sets are not available yet. The existing data were used to test the newly set up sand box, an
Electrical impedance and capacitance method: A new approach for detection of functional aspects of arbuscular mycorrhizal colonization in maize
European Journal of Soil Biology, 2013
ABSTRACT Applicability of root electrical impedance (EI) and electrical capacitance (EC) measurem... more ABSTRACT Applicability of root electrical impedance (EI) and electrical capacitance (EC) measurements for the detection of arbuscular mycorrhizal fungal (AMF) colonization was studied. AMF-inoculated and non-inoculated maize plants were compared whilst growing them under well-watered and drought-stressed condition with regular measurement of root EI and EC. AMF-colonized maize plants showed lower EI and higher EC than control counterparts independently of moisture condition, indicating an enhanced root–soil interface. Root scanning revealed lower root surface area in mycorrhizal plants than in non-mycorrhizal ones growing under well-watered condition, while in plants exposed to drought no significant difference between root surface areas was detected. Since fungal colonization didn't provoke an increase in root surface area, the higher root–soil interface showed by EI and EC values was apparently due to the increased absorption surface area caused by the growth of AMF hyphae. Consequently, the simple, non-destructive EI and EC method is considered an appropriate technique for in situ investigation of AMF-colonization and function, which may partially substitute the intrusive techniques commonly used in mycorrhizal research.
Simulated and Measured Nitrogen Conditions in Tomato Culture
Communications in Soil Science and Plant Analysis, 2009
ABSTRACT Nitrogen (N) loss by nitrate leaching below the root zone may be great in N‐fertilized a... more ABSTRACT Nitrogen (N) loss by nitrate leaching below the root zone may be great in N‐fertilized and irrigated vegetable soils when root uptake does not deplete the mineral N content of the soil water, which percolates through the soil profile. Soil texture and root growth as well as the dynamics of mineral N concentrations in soil solution are major factors in these processes. Differences of nitrate transport in high productive tomato cultures were studied in different texture soils in an irrigated and fertilized lysimeter experiment. In soil 0–60 cm deep, hydraulic properties were determined and nitrate (NO3)‐N and ammonium (NH4)‐N contents were measured in the beginning and end of the experiment. The soil moisture content was monitored in the 0‐ to 60‐cm soil. Root distribution, the dynamics of shoot biomass, N content, leaf area, and fruit yield were also measured. Interactions of root activity and water and N dynamics were evaluated by fitting the SOIL and SOILN model outputs to measured data. Parameterization of different tomato treatments helps the generalization of experimental findings. Both measurements and simulation results show that N losses via nitrate leaching can be minimized by the use of slow‐release N fertilizer in the establishment period of the crop and by application quick release N fertilizer topdressings after the roots proliferated in the deeper layers. The coupled SOIL and SOILN general models were suitable for the simulation of soil water and N transport and crop growth in the conditions of intensive tomato production.
Sensitivity of the swat model to soil organic carbon content: A Lake Balaton catchment case study
Cereal Research Communications, 2005
Estimating soil water retention characteristics from the soil taxonomic classification and mapping informations: Consideration of humus categories
Cereal Research Communications, 2005
The main limiting factors of soil fertility in Hungary are related to soil water management. For ... more The main limiting factors of soil fertility in Hungary are related to soil water management. For this purpose the water management category systems was elaborated in the scale of 1: 100 000 and 1: 10 000 (Várallyay et al., 1980, Várallyay, 1989). Soil water-retention ...
Cereal Research Communications, 2008
Rock-Eval (RE) pyrolysis was designed for petroleum exploration to determine the type and quality... more Rock-Eval (RE) pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. The aim of our work was to present new fields of application of the RE pyrolysis for assessing the proportion of the organic components of different thermal stabilities, and also to apply this method for characterization of organic matter dynamics in polluted sediments, soil and paleosoil profiles.
Biology and Fertility of Soils, 1993
An expert system to predict climate change induced salinization processes in salt-affected soils
HAL (Le Centre pour la Communication Scientifique Directe), 2009
Random forest based pedotransfer functions and geostatistical methods for mapping soil moisture retention capacity at 100 m resolution
EGUGA, Apr 1, 2019
The effects of cadmium (Cd) stress and arbuscular mycorrhizal fungus (AMF) inoculation were inves... more The effects of cadmium (Cd) stress and arbuscular mycorrhizal fungus (AMF) inoculation were investigated in wheat [Triticum aestivum L. cv. TC-33] under controlled conditions. The experiments aimed to reveal what stress responses belong to the different levels of Cd load in the growth medium (0; 1; 2,5 and 5 mg Cd kg-1 substrate). To detect the effect of Cd stress, we compared plant physiological and growth indicators measured with both in situ and destructive methods. Electrical capacitance (CR) was evaluated during the experiments as a method to indicate stress responses through of Cd-induced root system changes.During the growth period, the photosynthetic activity (Fv/Fm), the chlorophyll content index (CCI) of the leaves, and the CR of the root-soil system were monitored in situ. After harvest, the membrane stability index (MSI), the cadmium and phosphorus concentrations of the plants, the root dry mass (RDM), the shoot dry mass (SDM) and the leaf area (LA) were measured. The ro...
Comparative measurements with sand box, pressure membrane extractor and pressure plate extractor
Mathematical description of water retention (pF) curves
Soil moisture measurements using a microwave Michelson interferometer
Sand mixture density
Unsaturated Soils: Research & Applications, 2014
International Agrophysics, 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 observa...
Journal of Agricultural Informatics, 2011
Calibration of a TDR probe in an expansive soil
Unsaturated Soils, 2010
Hungarian Agriculture: Development Potential and Environment
Sustainable Development of Agriculture, 1988
Two comprehensive research projects were recently completed by the Hungarian Academy of Sciences ... more Two comprehensive research projects were recently completed by the Hungarian Academy of Sciences on the development problems of the Hungarian food and agricultural sector. In these studies agroecological factors were stressed.
The Soil Water Characteristics of Two-Component Sand Mixtures
Springer Proceedings in Physics 113, 2007
During an ongoing research the water retention curves of three sand fractions and 12 continuous a... more During an ongoing research the water retention curves of three sand fractions and 12 continuous and gap-graded two component sand mixtures with various composition ratio is measured. Due to the unexpectedly long equalization times in the low suction range complete data sets are not available yet. The existing data were used to test the newly set up sand box, an
Electrical impedance and capacitance method: A new approach for detection of functional aspects of arbuscular mycorrhizal colonization in maize
European Journal of Soil Biology, 2013
ABSTRACT Applicability of root electrical impedance (EI) and electrical capacitance (EC) measurem... more ABSTRACT Applicability of root electrical impedance (EI) and electrical capacitance (EC) measurements for the detection of arbuscular mycorrhizal fungal (AMF) colonization was studied. AMF-inoculated and non-inoculated maize plants were compared whilst growing them under well-watered and drought-stressed condition with regular measurement of root EI and EC. AMF-colonized maize plants showed lower EI and higher EC than control counterparts independently of moisture condition, indicating an enhanced root–soil interface. Root scanning revealed lower root surface area in mycorrhizal plants than in non-mycorrhizal ones growing under well-watered condition, while in plants exposed to drought no significant difference between root surface areas was detected. Since fungal colonization didn't provoke an increase in root surface area, the higher root–soil interface showed by EI and EC values was apparently due to the increased absorption surface area caused by the growth of AMF hyphae. Consequently, the simple, non-destructive EI and EC method is considered an appropriate technique for in situ investigation of AMF-colonization and function, which may partially substitute the intrusive techniques commonly used in mycorrhizal research.
Simulated and Measured Nitrogen Conditions in Tomato Culture
Communications in Soil Science and Plant Analysis, 2009
ABSTRACT Nitrogen (N) loss by nitrate leaching below the root zone may be great in N‐fertilized a... more ABSTRACT Nitrogen (N) loss by nitrate leaching below the root zone may be great in N‐fertilized and irrigated vegetable soils when root uptake does not deplete the mineral N content of the soil water, which percolates through the soil profile. Soil texture and root growth as well as the dynamics of mineral N concentrations in soil solution are major factors in these processes. Differences of nitrate transport in high productive tomato cultures were studied in different texture soils in an irrigated and fertilized lysimeter experiment. In soil 0–60 cm deep, hydraulic properties were determined and nitrate (NO3)‐N and ammonium (NH4)‐N contents were measured in the beginning and end of the experiment. The soil moisture content was monitored in the 0‐ to 60‐cm soil. Root distribution, the dynamics of shoot biomass, N content, leaf area, and fruit yield were also measured. Interactions of root activity and water and N dynamics were evaluated by fitting the SOIL and SOILN model outputs to measured data. Parameterization of different tomato treatments helps the generalization of experimental findings. Both measurements and simulation results show that N losses via nitrate leaching can be minimized by the use of slow‐release N fertilizer in the establishment period of the crop and by application quick release N fertilizer topdressings after the roots proliferated in the deeper layers. The coupled SOIL and SOILN general models were suitable for the simulation of soil water and N transport and crop growth in the conditions of intensive tomato production.
Sensitivity of the swat model to soil organic carbon content: A Lake Balaton catchment case study
Cereal Research Communications, 2005
Estimating soil water retention characteristics from the soil taxonomic classification and mapping informations: Consideration of humus categories
Cereal Research Communications, 2005
The main limiting factors of soil fertility in Hungary are related to soil water management. For ... more The main limiting factors of soil fertility in Hungary are related to soil water management. For this purpose the water management category systems was elaborated in the scale of 1: 100 000 and 1: 10 000 (Várallyay et al., 1980, Várallyay, 1989). Soil water-retention ...
Cereal Research Communications, 2008
Rock-Eval (RE) pyrolysis was designed for petroleum exploration to determine the type and quality... more Rock-Eval (RE) pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. The aim of our work was to present new fields of application of the RE pyrolysis for assessing the proportion of the organic components of different thermal stabilities, and also to apply this method for characterization of organic matter dynamics in polluted sediments, soil and paleosoil profiles.
Biology and Fertility of Soils, 1993
An expert system to predict climate change induced salinization processes in salt-affected soils