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Seventy-two Lysimeters for Measuring Water Flows and Nitrate Leaching under Arable Land
Abstract
At the agricultural research station Agroscope in Zurich-Reckenholz (Switzerland), a large lysimeter facility was built in 2009. Totally 72 lysimeters, each with 1 m2 surface area and a depth of 150 cm, were monolithically excavated at three agricultural sites differing in soil type. All lysimeters can be operated from a walkable basement. Twelve of the lysimeters are weighable and are instrumented with tensiometers, temperature sensors, suction cups and FDR probes in four depths (10, 30, 60, and 90 cm), each with two replicates. The other 60 lysimeters are non-weighable. Seepage water is measured by tipping counters. All lysimeters are used for agronomic experiments. The main focus is on water flows and nitrate leaching under different cropping systems, soil tillage intensities, fertilization regimes, and soil types. All treatments are replicated three times. The results of the first seven experimental years (2009-2015) show that water flows of the lysimeters are subject to large annual variations, depending on climatic conditions and crops grown. Annual seepage volumes fluctuated between 116 mm and 754 mm. Results on nitrate leaching are shown by the example of an experiment on the ploughing-in time of a cover crop. Ploughing up in spring led to reduced N leaching compared to ploughing up already in autumn. Tracer experiments with bromide show that the mass transport through the soil profile takes about 0.5 to 1.5 years. A large lysimeter facility has large advantages and offers many opportunities, but is also a challenge in terms of financial and human resources.
... The following hypotheses can be formulated in this context, based on previous research (e. g., Chervet et al., 2006;Oberholzer et al., 2017;Prasuhn et al., 2016): ...
... In general, the results show that differences in SMS are big between different sites and different years: comparing a specific md over different sites and years shows that SMS values can cover the whole measurable range between 0 and 80 cbar. The big annual differences in SMS are in line with results from similar research (Gut et al., 2015;Prasuhn et al., 2017Prasuhn et al., , 2016Wyler, 2010). The following discussion mainly focuses on results from the analysis of the subset 01 -06/11 -16 -e. ...
... ET rates are crop-specific and change during the different stages of seasonal plant growth (e. g., Allan et al., 1998;Oberholzer et al., 2017;Prasuhn et al., 2016). Furthermore, different rooting depths of the crops influence SMS at certain soil depths. ...
... The reference data used in this study was obtained from the lysimeter facility of Agroscope Zürich-Reckenholz (Prasuhn et al. 2016). Additional data on averages of flowering days and crop yield was obtained from silage maize variety trials in Zürich-Reckenholz (Baux et al. 2010;Hiltbrunner et al. 2014;. ...
... For this study, the lysimeter setup was used, implying that surface runoff was disabled and therefore all rainfall water eventually infiltrates the soil profile. The depth of the soil profile was set at 135 cm, and an additional 15 cm of coarse sand was assumed at the bottom boundary, as described by Prasuhn et al. (2016). CANDY allows the usage of different plant modules, some of which are N-uptake driven and require the 2 | APEX model parameters calibrated to simulate silage maize aboveground biomass. ...
Pedotransfer functions (PTFs) are widely used empirical relationships to estimate soil hydraulic parameters. PTFs are usually derived from point soil samples analysed in the field or laboratory; thus, they contain uncertainties at different levels (i.e., from sampling and measuring techniques, as well as empirical approaches chosen to quantify relationships). When PTFs are used to parametrize agro‐hydrological models, both the choice of PTF and the choice of the model may influence the simulation results. Both sources of variance (PTF choice and model structural differences) were found to be relevant in previous studies, but how they relate to each other has rarely been investigated. In this study, we addressed this research gap by conducting a systematic analysis of the variance in selected agro‐hydrological model outputs (i.e., seepage water, soil water content, actual evapotranspiration, transpiration, biomass production) based on an ensemble of 18 PTFs applied to four agro‐hydrological models, namely: APEX, CANDY, DAISY and SWAP. The models were calibrated for aboveground biomass and phenology of silage maize and evaluated using data of actual evapotranspiration, seepage water and soil water content obtained from a lysimeter facility in Switzerland. ANOVA‐based variance partitioning was applied to attribute variance in model outputs to two uncertainty sources (PTF choice, model choice). Overall, we found that agro‐hydrological model structural differences had a larger influence on the variance in model outputs than PTF differences. Further analyses undertaken per model showed that the sensitivity of the simulated outputs to the choice of PTF differed between the models; our results showed that the models integrating the Richards equation (SWAP, DAISY) were more sensitive to the choice of PTF than those using a reservoir cascade approach (APEX, CANDY). Our results also showed that simulated outputs using the mean of a PTF ensemble performed better than when using a single PTF, irrespective of the model and output variable. We therefore recommend using PTF ensembles in agro‐hydrological modelling studies. The benefit of using large PTF ensembles is, however, likely to be reduced in larger ensembles of agro‐hydrological models, as structural model uncertainties will dominate over PTF uncertainties, according to the four‐member model ensemble investigated here.
... Over the last ten years, most crops of the traditional Swiss crop rotation have been grown. The three soil types are loamy soils and widely used for farming in Swiss lowlands (Prasuhn et al., 2016, Oberholzer et al., 2017. ...
... The tipping bucket had a volume of 100 ml and this volume was interpolated to 5 min values between two tippings. For detailed information about the lysimeter facility and the installed devices, we refer to a recent publication (Prasuhn et al., 2016). ...
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.
... Über eine Sickerwasserhilfe von 15 cm aus Quarzsand am Lysimeterboden entwässern die Lysimeter frei dränend in Kippwaagen von 100 ml. 12 Lysimeter sind wägbar und mit verschiedenen Messsonden (FDR, Tensiometer, Saugkerzen, Temperatur) in vier verschiedenen Tiefen (10, 30, 60, 90 cm) in zweifacher Wiederholung ausgestattet. Alle Messdaten werden alle fünf Minuten aufgezeichnet(Prasuhn et al. 2016). Die Vegetationsperioden der Jahre 2009 bis 2015 wurden analysiert. ...
Fertile soils are crucial for human well-being, yet the intensification of agriculture and use of heavy machines increasingly threatens their quality. Agricultural practices with heavy machines expose soils to a high risk of irreversible subsoil compaction. Research has shown that from a sustainable land management perspective, soils should not be trafficked with heavy machines when soil conditions are wet (soil moisture suction <6 cbar at a soil depth of 35 cm). However, there is a lack of knowledge about the frequencies of wet soil conditions in Swiss agricultural soils and about potential influences of soil management systems on soil moisture. This study aims at closing these research gaps by analyzing the long-term (1996-2019) dataset of the Canton Bern including 13 different locations on six sites in the Swiss Central Plateau. Soil moisture suction data measured with five tensiometers per location at a soil depth of 35 cm and precipitation sums per site for three measurement days (md) per week are used. On every site, at least one permanent grassland and one crop rotation location are present. Furthermore, two tillage systems (no-till and mouldboard plough) and 11 different crops occur in the dataset. After data correction and validation , 22'947 md with available soil moisture suction data are analyzed. To put the results into a larger context, spade tests are performed at every location, and a climate and weather characterization of the years 1996-2019 is undertaken. Periods with wet soil conditions (<6 cbar at 35 cm soil depth) during the vegetation period from April to October range from 41 to 48% of the md for different locations (average over all sites), while site-specific differences range from 31 to 76% on permanent grassland locations. The duration of wet soil conditions can exceed three months in extreme cases. Furthermore, a seasonal curve in soil moisture suction is found and influences of the longer-term (≥3 months) weather conditions, as well as of single precipitation events on soil moisture suction fluxes are apparent. Differences in soil moisture suction fluxes are big between different sites and years: comparing a specific md over different sites and years shows that soil moisture suction values can cover the whole measurable range between 0 and 80 cbar. While the seasonal curve and the annual fluctuations likely originate from climate and weather influences, the differences between the sites cannot be attributed to a specific influence factor. Differences between permanent grassland and crop rotation locations can mostly be attributed to different crops' seasonal evapotranspiration rates. Other systematic differences which hold for all sites and years cannot be identified. Differences between no-till and mouldboard plough are present, but non-systematic based on the analysis on one site. The spade tests show that tillage systems impact physical soil properties. In conclusion, the results point to a highly complex human-climate-soil-system. This study lays a valuable basis for future research, among others, by providing concrete recommendations for future study designs. Further research about soil moisture suction is needed to promote sustainable land management in Switzerland.
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