Actual new results from the largest lysimeter in Europe – Agroscope Zürich Reckenholz/Switzerland – are published:
Germann, P.F., and V.Prasuhn. 2017. Viscous flow approach to rapid infiltration and drainage in a weighing lysimeter. Vadose Zone J. doi:10.2136/vzj2017.01.0020
Rapid infiltration and drainage in a free-draining weighing lysimeter are assessed with a viscous flow approach that is based on the concept of moving water films. The two parameters film thickness and specific contact area of the film per unit volume of the permeable medium together with the rate and duration of water input suffice to quantify viscous flow at the Darcy scale. The two parameters are deducible from wetting front velocities and water content variations during the passing of the film. Temporarily perching water tables at lysimeter bottoms are considered artifacts of the lysimeter method that may severely alter the biogeochemistry of the effluent. The viscous flow approach assesses the duration of water perching from drainage flow interpretation. Perching in the sense of viscous flow occurred at most 10% of the time during drainage flow. Drainage ceased completely during a 6-mo period that yielded only 46% of rainfall compared with the 30-yr average. During rewetting of the lysimeter soil, viscous flow applied to infiltrations of nine precipitation episodes, showing successive penetrations of wetting fronts shortly before the onset of drainage.
Oberholzer, S., Prasuhn, V., Hund A. 2017. Crop water use under Swiss pedoclimatic conditions – Evaluation of lysimeter data covering a seven-year period. Field Crops Research 211 (2017) 48–65. http://dx.doi.org/10.1016/j.fcr.2017.06.003
Due to climate change, agricultural production in Europe will be challenged by higher temperatures and shifts in precipitation distribution that will give rise to frequent summer droughts. An adaptation of agricultural systems to these changes requires detailed knowledge of crop water use characteristics. This study aimed to evaluate the
dynamics of evapotranspiration and water uptake in different crops under the typical edaphoclimatic conditions of Switzerland. Seven years (2009–2015) of high resolution lysimeter mass data including 70 lysimeter-by-year combinations were evaluated. The “adaptive window and adaptive threshold “-filter (AWAT) was used to determine
evapotranspiration (ET), precipitation (P), crop coefficient (Kc) and water use efficiency (WUE). Additionally, FDR sensors installed in the lysimeter soil core allowed recording the temporal dynamic of soil water extraction. The evaluation comprised grain maize, silage maize, rapeseed, sugar beets, winter barley, winter wheat and temporary ley. The AWAT filter was successfully used to determine lysimeter P that was inserted in the lysimeter water balance equation to calculate daily ET. It could be shown that the peak of daily crop coefficient coincided with the time of flowering for all flowering arable crops. WUE’s lay in the range given by standard literature, but daily crop coefficients were clearly higher than proposed by the Food and Agriculture Organization of the United Nations (FAO) which is partially due to an oasis and border effect of the lysimeters.
Years with limited water availability were characterized by a comparably low Kc. For example, rapeseed in 2011 and maize in 2015 showed substantially lower Kc values. In accordance with the reduced Kc, readily available water was totally removed down to soil depth of at minimum 0.85 m. The limited water availability led to significantly lower yields only in case of silage maize in 2015. These results show overall current water supply to be sufficient under Swiss conditions; however, if drought events like in 2015 become more frequent and even more intense, yield potential of typical Swiss arable crops will be limited by water availability.