A b s t r a c t. Erosion processes can strongly influence the dissipation of glyphosate and aminomethylphosphonic acid applied with Roundup Max® in agricultural soils; in addition, the soil structure state shortly before erosive precipitations fall can be a key parameter for the distribution of glyphosate and its metabolite. Field rain simulation experiments showed that severe erosion processes immediately after application of Roundup Max® can lead to serious unexpected glyphosate loss even in soils with a high presumed adsorption like the Cambisols, if their structure is unfavourable. In one of the no-tillage-plot of the Cambisol, up to 47% of the applied glyphosate amount was dissipated with surface run-off. Moreover, at the Chernozem site with high erosion risk and lower adsorption potential, glyphosate could be found in collected percolation water transported far outside the 2x2 m experimental plots. Traces of glyphosate were found also outside the treated agricultural fields.K e y w o r d s: glyphosate, aminomethylphosphonic acid, erosion, adsorption, soils

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A b s t r a c t. The results showed that glyphosate is initially adsorbed mostly in the upper 2 cm. It is than transported and adsorbed after few days in deeper soil horizons with concomitant increasing content of its metabolite aminomethylphosphonic acid. Moreover, Fe-oxides seem to be a key parameter for glyphosate and aminomethylphosphonic adsorption in soils. This study confirmed previous studies: the analysis showed lower contents of dithionite-soluble and Fe-oxides for the Chernozem, with consequently lower adsorption of glyphosate and aminomethylphosphonic as compared with the Cambisol and the Stagnosol.K e y w o r d s: adsorption, glyphosate, aminomethylphosphonic acid, soils

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Despite the importance of soil organic matter (SOM), very few long-term data concerning soil organic-C dynamics are available for calibrating and evaluating C models. The long-term 14 Cturnover field experiment, established in 1967 in Fuchsenbigl, Lower Austria, offers the unique opportunity to follow the fate of labeled C under different crop-management systems (bare fallow, spring wheat, crop rotation) over a period of more than 35 y. Compared with the crop-rotation and spring wheat treatments, the decline of total organic C was largest in the bare-fallow treatments, because no significant C input has occurred since 1967. Nonetheless, the decline was not as fast as predicted with the original RothC-26.3-model decomposition rate constants. In this work, we therefore calibrated the Roth-C-26.3 model for the Pannonian climatic region based on the field-experiment results. The main adjustment was in the decomposition rate constant for the humified soil C pool (HUM), which was set to 0.009 instead of 0.02 y -1 as determined in the original Rothamsted field trial. This resulted in a higher HUM pool in the calibrated model because of a longer turnover period (111 vs. 50 y). The modeled output based on the calibrated model fitted better to measured values than output obtained with the original Roth-C-26.3-model parameters. Additionally, the original decomposition rate constant for resistant plant material (RPM) was changed from 0.3 to 0.6 y -1 to describe the decomposition of 14 C-labeled straw more accurately. Application of the calibrated model (modified HUM decomposition rate) to simulate removal of crop residues showed that this can entail a long-term decline of SOM. However, these impacts are strongly dependent on the crop types and on environmental conditions at a given location.Key words: decomposition rate constants / model calibration / soil organic carbon / soil carbon pools / soil organic matter / Roth-C-26.3 model