Bright sunshine duration (BSD) data are required for simulating biomes using process-based vegeta... more Bright sunshine duration (BSD) data are required for simulating biomes using process-based vegetation models. However, monthly global paleoclimate datasets that can be used in paleo data–model comparisons do not necessarily contain BSD or radiation data. Considering the theoretical and practical aspects, the scheme of Yin, X. (1999) is here recommended to estimate monthly time series of relative BSD using only monthly climate and location data. As a case study for the Carpathian Region, the efficiency of both the original and a variant of that scheme is analysed in this paper. The alternative scheme has high applicability in paleoenvironmental studies. Comparison of the estimated and observed BSD data shows that from May to August, the value of relative root mean squared error in more than 90 percent of the study area does not exceed the threshold of 20 percent, indicating an excellent performance of the original estimation scheme. It is also found that though the magnitude of overe...
The superior agronomic and human nutritional properties of grain legumes (pulses) make them an id... more The superior agronomic and human nutritional properties of grain legumes (pulses) make them an ideal foundation for future sustainable agriculture. Legume-based farming is particularly important in Africa, where small-scale agricultural systems dominate the food production landscape. Legumes provide an inexpensive source of protein and nutrients to African households as well as natural fertilization for the soil. While the consumption of traditionally grown legumes has started to decline, the production of soybeans (Glycine max Merr.) is spreading fast, especially across southern Africa. Predictions of future land-use allocation and production show that the soybean is poised to dominate future production across Africa. Land use models project an expansion of harvest area, while crop models project possible yield increases. Moreover, a seed change in farming strategy is underway. This is being driven largely by the combined cash-crop value of products such as oils and the high nutrit...
There are several estimation methods to calculate daily global radiation using different input da... more There are several estimation methods to calculate daily global radiation using different input data. The Szasz method uses the daily sum of sunshine hours, the Ritchie-Fodor method uses the daily thermal oscillation. It was investigated whether global radiation estimated by the Szasz method or Ritchie-Fodor method can substitute the measured global radiation for biomass and yield predictions in the 4M crop simulation model. The reliability of estimated global radiation is much greater if the data is used for yield prediction than for biomass prediction. The global radiation estimated by the Szasz method can substitute measured data in 4M and other CERES based crop models with 89-96% of reliability, when yield prediction is the goal. The Ritchie-Fodor method made less reliable radiation estimations. This method needs further development.
Model simulations aimed to estimate yields of some major agricultural crops with respect to the c... more Model simulations aimed to estimate yields of some major agricultural crops with respect to the climate changes are presented. 4M, a CERES-based cropping systemmodel, developed in RISSAC is used incorporating long records of field experiments under semi-industrial circumstances and several input generators. Sequence of years can be run continuously with the same crop or crop rotations. Retarded adjustment of a few soil parameters is also included into the numerical experiments. Two types of model runs have been performed. First, model testing and parameter adjustment is fulfilled with present climate series. Next, climate-forced projections are considered referring to ca. 50 years ahead, i.e. to a global warming of 0.75 K. Daily weather is considered as a variable input parameter of the crop model. Down-scaling of climate, i.e. derivation of these input parameters is processed in a 3 steps: (1) Downscaling in space: to express the global warming into site-specific seasonal averages....
Weather generators (WG) became significant modules of crop models and decision support systems in... more Weather generators (WG) became significant modules of crop models and decision support systems in the past decade. Using a large meteorological database from North America; two basic problems, related to the applicability of WGs in case of short or lacking data series, were investigated in the framework of the Multivariable weather generator (MVWG). First, the minimum data series length, required for adequate parameterization of the WG, was determined. Our results suggest that 15 years of observed data are enough for adequate parameterization of the MVWG. We then investigated a possibility of spatial interpolation of WG parameters using the outputs of the WG for sites with no meteorological observations. Coupled with the presented interpolation technique, MVWG was able to generate realistic weather data for sites with no measurements situated in climatically and geographically homogeneous regions.
ABSTRACT Plant cover can influence the hydraulic characteristics of soil considerably. Water repe... more ABSTRACT Plant cover can influence the hydraulic characteristics of soil considerably. Water repellency, which commonly evolves in sandy soils during longer dry spells, can result in water infiltration retardation. Water infiltration into natural-meadow, pine-forest, glade and fallow sandy soils was evaluated after during several wet and dry spells in respect of: soil porosity, hydraulic conductivity and sorptivity estimated by mini-disc infiltrometer, water drop penetration time, effective contact angle and water repellency index. Bare aeolian sand containing practically no organic matter was taken as etalon material. All materials have similar texture and pore-size distributions but their wettability and hydraulic properties differed considerably. Long dry spells enhanced the infiltration capacity in wettable etalon material because of sorptivity increase. Sorptivities of meadow and fallow soils, however, remained restrained during both, wet and dry seasons either due to higher water content (when wet) or to stronger water repellency (when dry). For this reason no temporal variability of infiltration capacity was observed in these soils unlike the etalon material. It was confirmed (for the fallow soil) that subcritical water repellency can significantly retarded water infiltration. The infiltration rate vs. time relationships measured both in the laboratory and field for the grass site revealed different behaviour in the initial phase of infiltration. In the laboratory, the onset of infiltration depended on the water ponding depth. As is often found in water repellent soil, the infiltration rate increased with time as a result of fingered flow. In the field, infiltration started immediately after the water application. This was the result of temporarily stable wetting patterns observed in all studied water repellent soils. Important founding is also that substantial part (71%) of the hydraulic conductivity variation in meadow soil could be explained by the variation of mean WDPT observed around the installed infiltrometer. The same was observed also for some other types of vegetation examined (pine forest, mosses and lichens on glade). However, no correlation existed between hydraulic conductivity and water repellency index possibly due to macropore flow dominating over the saturated hydraulic conductivity measurements.
Bright sunshine duration (BSD) data are required for simulating biomes using process-based vegeta... more Bright sunshine duration (BSD) data are required for simulating biomes using process-based vegetation models. However, monthly global paleoclimate datasets that can be used in paleo data–model comparisons do not necessarily contain BSD or radiation data. Considering the theoretical and practical aspects, the scheme of Yin, X. (1999) is here recommended to estimate monthly time series of relative BSD using only monthly climate and location data. As a case study for the Carpathian Region, the efficiency of both the original and a variant of that scheme is analysed in this paper. The alternative scheme has high applicability in paleoenvironmental studies. Comparison of the estimated and observed BSD data shows that from May to August, the value of relative root mean squared error in more than 90 percent of the study area does not exceed the threshold of 20 percent, indicating an excellent performance of the original estimation scheme. It is also found that though the magnitude of overe...
The superior agronomic and human nutritional properties of grain legumes (pulses) make them an id... more The superior agronomic and human nutritional properties of grain legumes (pulses) make them an ideal foundation for future sustainable agriculture. Legume-based farming is particularly important in Africa, where small-scale agricultural systems dominate the food production landscape. Legumes provide an inexpensive source of protein and nutrients to African households as well as natural fertilization for the soil. While the consumption of traditionally grown legumes has started to decline, the production of soybeans (Glycine max Merr.) is spreading fast, especially across southern Africa. Predictions of future land-use allocation and production show that the soybean is poised to dominate future production across Africa. Land use models project an expansion of harvest area, while crop models project possible yield increases. Moreover, a seed change in farming strategy is underway. This is being driven largely by the combined cash-crop value of products such as oils and the high nutrit...
There are several estimation methods to calculate daily global radiation using different input da... more There are several estimation methods to calculate daily global radiation using different input data. The Szasz method uses the daily sum of sunshine hours, the Ritchie-Fodor method uses the daily thermal oscillation. It was investigated whether global radiation estimated by the Szasz method or Ritchie-Fodor method can substitute the measured global radiation for biomass and yield predictions in the 4M crop simulation model. The reliability of estimated global radiation is much greater if the data is used for yield prediction than for biomass prediction. The global radiation estimated by the Szasz method can substitute measured data in 4M and other CERES based crop models with 89-96% of reliability, when yield prediction is the goal. The Ritchie-Fodor method made less reliable radiation estimations. This method needs further development.
Model simulations aimed to estimate yields of some major agricultural crops with respect to the c... more Model simulations aimed to estimate yields of some major agricultural crops with respect to the climate changes are presented. 4M, a CERES-based cropping systemmodel, developed in RISSAC is used incorporating long records of field experiments under semi-industrial circumstances and several input generators. Sequence of years can be run continuously with the same crop or crop rotations. Retarded adjustment of a few soil parameters is also included into the numerical experiments. Two types of model runs have been performed. First, model testing and parameter adjustment is fulfilled with present climate series. Next, climate-forced projections are considered referring to ca. 50 years ahead, i.e. to a global warming of 0.75 K. Daily weather is considered as a variable input parameter of the crop model. Down-scaling of climate, i.e. derivation of these input parameters is processed in a 3 steps: (1) Downscaling in space: to express the global warming into site-specific seasonal averages....
Weather generators (WG) became significant modules of crop models and decision support systems in... more Weather generators (WG) became significant modules of crop models and decision support systems in the past decade. Using a large meteorological database from North America; two basic problems, related to the applicability of WGs in case of short or lacking data series, were investigated in the framework of the Multivariable weather generator (MVWG). First, the minimum data series length, required for adequate parameterization of the WG, was determined. Our results suggest that 15 years of observed data are enough for adequate parameterization of the MVWG. We then investigated a possibility of spatial interpolation of WG parameters using the outputs of the WG for sites with no meteorological observations. Coupled with the presented interpolation technique, MVWG was able to generate realistic weather data for sites with no measurements situated in climatically and geographically homogeneous regions.
ABSTRACT Plant cover can influence the hydraulic characteristics of soil considerably. Water repe... more ABSTRACT Plant cover can influence the hydraulic characteristics of soil considerably. Water repellency, which commonly evolves in sandy soils during longer dry spells, can result in water infiltration retardation. Water infiltration into natural-meadow, pine-forest, glade and fallow sandy soils was evaluated after during several wet and dry spells in respect of: soil porosity, hydraulic conductivity and sorptivity estimated by mini-disc infiltrometer, water drop penetration time, effective contact angle and water repellency index. Bare aeolian sand containing practically no organic matter was taken as etalon material. All materials have similar texture and pore-size distributions but their wettability and hydraulic properties differed considerably. Long dry spells enhanced the infiltration capacity in wettable etalon material because of sorptivity increase. Sorptivities of meadow and fallow soils, however, remained restrained during both, wet and dry seasons either due to higher water content (when wet) or to stronger water repellency (when dry). For this reason no temporal variability of infiltration capacity was observed in these soils unlike the etalon material. It was confirmed (for the fallow soil) that subcritical water repellency can significantly retarded water infiltration. The infiltration rate vs. time relationships measured both in the laboratory and field for the grass site revealed different behaviour in the initial phase of infiltration. In the laboratory, the onset of infiltration depended on the water ponding depth. As is often found in water repellent soil, the infiltration rate increased with time as a result of fingered flow. In the field, infiltration started immediately after the water application. This was the result of temporarily stable wetting patterns observed in all studied water repellent soils. Important founding is also that substantial part (71%) of the hydraulic conductivity variation in meadow soil could be explained by the variation of mean WDPT observed around the installed infiltrometer. The same was observed also for some other types of vegetation examined (pine forest, mosses and lichens on glade). However, no correlation existed between hydraulic conductivity and water repellency index possibly due to macropore flow dominating over the saturated hydraulic conductivity measurements.
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