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Influence of humic acids on soil environment is still subject of scientific discussions. The aim of above studies was to investigate the relationships between selected physicochemical properties of eleven peaty-muck soils and properties of humic acids isolated from these soils. The following parameters were determined for soils: total and organic carbon, density, ash, humifi- cation, and the water absorption index. Humic acids were described by: absorbance at 280 nm, absorbance ratios at 465 and 665 nm, at 260 and 665 nm, elemental composition and atomic ratios: H/C, O/H, O/C, C/N, the degree of internal oxidation, and the content of carboxylic and phenolic groups. Statistical analyses showed that an increase in density, humification, and water absorption indices of soils caused a significant increase in the humic acid parameters: absorbance at 280 nm, the oxygen content, O/H, O/C ratios, inter- nal oxidation degree, and functional groups. Statistically signifi- cant negative correlations were found for the same parameters of soils and for the hydrogen and carbon content as well as the H/C ratio of humic acids. The relationships showed that there was a pos- sibility to express the properties of humic acids on the basis of more simple parameters measured for soil and without time-consuming isolation of humic acids.
Effects of the climate change appear in several fields of the economy and agriculture can be considered as one of the most affected among them. In a country, where almost 10% of the total GDP is produced by the agricultural sector and more than 30% of the total work force is employed in this field, these changes may have severe economic impacts. As in Romania almost 65% of the agricultural production is represented by vegetal production, we concentrate our investigations on this agricultural sector. Our aim is to present, basing on econometric modeling, how the climate changes will affect the Romanian crop production in the next 20 years, highlighting the territorial differences which appear between the Romanian NUTS2 development regions. This paper presents some of the first results of the FP6 research project “CLAVIER – Climate Change and Variability: Impact on Central and Eastern Europe”, contract no. 037013 (2006-2009).
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The paper presents an analysis of wheat yields variability in the voivodeships of Poland. The main aim of the study was to find out what are the statistical relationships between the wheat yield variability and the following factors: arable area, size of wheat production area, share of arable land used for wheat production, land quality and average yield. For that purpose a multiple linear regression was applied. It was found out that the detected spatial autocorrelation of wheat yields variability measured by standard deviations can be explained in 75% by the fitted model. Two of the considered variables showed a significant negative effect on this variability: the logarithm of arable area and the land quality, while the other two: the average wheat yield and the wheat production area displayed a significant positive effect on the variability. The effect of share of arable land used for wheat production itself was not significant.
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