Smith P.C.,Air Pollution and Climate Group |
Calanca P.,Air Pollution and Climate Group |
Fuhrer J.,Air Pollution and Climate Group
Water (Switzerland) | Year: 2012
This paper presents a simple approach for estimating the spatial and temporal variability of seasonal net irrigation water requirement (IWR) at the catchment scale, based on gridded land use, soil and daily weather data at 500 × 500 m resolution. In this approach, IWR is expressed as a bounded, linear function of the atmospheric water budget, whereby the latter is defined as the difference between seasonal precipitation and reference evapotranspiration. To account for the effects of soil and crop properties on the soil water balance, the coefficients of the linear relation are expressed as a function of the soil water holding capacity and the so-called crop coefficient. The 12 parameters defining the relation were estimated with good coefficients of determination from a systematic analysis of simulations performed at daily time step with a FAO-type point-scale model for five climatically contrasted sites around the River Rhone and for combinations of six crop and ten soil types. The simple scheme was found to reproduce well results obtained with the daily model at six additional verification sites. We applied the simple scheme to the assessment of irrigation requirements in the whole Swiss Rhone catchment. The results suggest seasonal requirements of 32 × 106 m3 per year on average over 1981-2009, half of which at altitudes above 1500 m. They also disclose a positive trend in the intensity of extreme events over the study period, with an estimated total IWR of 55 × 106 m3 in 2009, and indicate a 45% increase in water demand of grasslands during the 2003 European heat wave in the driest area of the studied catchment. In view of its simplicity, the approach can be extended to other applications, including assessments of the impacts of climate and land-use change. © 2012 by the authors.
Felber R.,Air Pollution and Climate Group |
Leifeld J.,Air Pollution and Climate Group |
Horak J.,Slovak University of Agriculture |
Neftel A.,Air Pollution and Climate Group
European Journal of Soil Science | Year: 2014
We compared (i) nitrous oxide (N2O) fluxes from a 9-month field experiment established on a temperate, newly sown, intensively managed meadow using automated chambers with fine time resolution, and (ii) fluxes measured at several occasions throughout the experiment under controlled laboratory conditions. Twenty tonnes dry matter ha-1 greenwaste biochar were added to three plots and compared with three control plots. Cumulated N2O field measurements revealed a reduction of 21.5% in the plots with biochar. The reductions for samples where the biochar was added at the beginning of the experiment in the field and samples which were collected each month and measured in the laboratory were in the same range (11.4-39.2%). Emission reductions from laboratory incubations when biochar was freshly mixed with soil in the laboratory were about twice as large (46.5-58.0%). Our results indicate provisionally that, at our site, biochar controls N2O emission through its capacity for reducing NO3- availability to denitrifiers, with the efficiency being related to the effectiveness of mixing of biochar in soil. © 2013 British Society of Soil Science.