Holger Rupp

Lysimeter studies in East Germany concerning the influence of set aside of intensively farmed land on the seepage water quality

Abstract Since 1990, the five new federal states of Germany have experienced a fundamental structural change in agriculture. As much as 10% of the 6.2 million hectares of the previously intensively farmed agricultural areas were abruptly set aside. In the spring of 1991, a lysimeter test, designed in 1983 to maximize yields, was adapted to these new agricultural conditions. The purpose of the test was to investigate the impact of the structural changes on water balance and budget of materials. Leaching of relevant cations (Ca 2+ , Mg 2+ , Na + , and K + ) and anions (total PO 4 3− , NO 3 − , Cl − , and SO 4 2− ) contained in the seepage water as well as the resulting pH-values were determined for various types of set aside. The reference treatment consisted of intensively farmed lysimeters following the principles of BMP (best management practices). The tests covered a period of three years. The studies proved that restricting agricultural usage on areas previously farmed heavily, by converting them into permanent or rotation fallow, will result in measurable changes of seepage water recharge and quality within less than one year. The permanent fallow showed large leaching losses of the measured cations even three years after set aside. In contrast, the leaching of the measured anions NO 3 − , SO 4 2− and Cl − decreased significantly compared with the initial level. If cation leaching decreases from lack of additional supply, a shift of the pH into the acid range is to be expected. A one year set aside in the form of a rotation fallow is connected with increased leaching of nitrate. Compared with intensively farmed agricultural land, nitrate leaching in the year of set aside is increased by approximately 55% and in the year of resuming intensive agricultural production by 30%.

Assessing the impact of agricultural land use changes on water quality

To study and predict environmental impacts of land use changes on water quality we conducted different types of lysimeter experiments. All of them are linked to representative experimental catchment areas in the field. This allows the verification and extrapolation of lysimeter results. The objective of this paper is to discuss a strategy for using and scaling-up of lysimeter results to a field and catchment scale. It will be shown that the N-loss determined with lysimeters falls within the variation of N-balance based model calculations, and also within ground water recharge rates calculated with models commonly used in hydrology. Extrapolation of lysimeter data to a catchment with similar soils provides a reliable basis for estimating the N-leaching caused by a change in agricultural land use. On the basis of the N-loss from the soil and the N-load of the stream, the calculations show that an increase in the proportion of one year rotation fallow from 10 to 25% results in nearly a 10% increase in the N-load of the stream. However, from the point of view of protecting drinking water quality, rotation fallow for one year is not recommended because of the resulting intensified leaching of nitrates.

Novel lysimeter techniques — a basis for the improved investigation of water, gas, and solute transport in soils

For many years lysimeters have been proven to be effective tools in assessing and predicting the effects of current land use and future land use changes in catchment areas on both water and solute balances. Although due to the diverse aspects of mass transport modelling, many different types of lysimeters exist, water and solute balances are by no means fully understood, especially in post-mining areas. To tackle this problem, a new piece of equipment has been developed which enables the actual weight of a lysimeter to be precisely measured. The newly designed device, which has been used for one of the experiments described in this paper, permits the weighing of for example a 2 m3 lysimeter vessel with an accuracy down to 30 g. The second newly developed appliance presented here is the GAMS (Gas-Migration-Simulator). Basically comparable to a lysimeter, the difference is that the GAMS allows the detailed investigation of soil-gas migration processes and their dependence on parameters like the diffusion coefficient and the gas permeability of the soil, alterations of the groundwater level and on various external influences such as changes of the actual meteorological conditions. These two newly developed techniques are described in this paper, and their respective suitability is demonstrated on the basis of data sets recorded during initial experiments. Neue Lysimetertechniken — eine Grundlage zur verbesserten Untersuchung des Wasser-, Gas- und Stofftransportes in Boden Lysimeter haben sich als effektives Hilfsmittel zur Bewertung und Voraussage der von gegenwartigen Landnutzungen und kunftigen Landnutzungsanderungen in Einzugsgebieten ausgehenden Wirkungen auf den Wasser- und Stoffhaushalt bewahrt. Obwohl fur die modellhafte Beschreibung von Stoffbilanzen verschiedene Lysimeteranlagen verfugbar sind, konnte der Wasser- und Stoffhaushalt in Bergbaufolgelandschaften bisher nicht vollstandig aufgeklart werden. Zur Losung dieses Problems wurde eine neue Generation von Lysimetern entwickelt, mit denen beispielsweise die Wagung von 2 m3 grosen Bodensaulen mit einer Genauigkeit von 30 g moglich ist. Bei der zweiten hier vorgestellten Neuentwicklung handelt es sich um einen Gas-Migrations-Simulator (GAMS). Der grundsatz-lich mit dem Bauprinzip eines Lysimeters vergleichbare GAMS ermoglicht im Gegensatz zu herkommlichen Lysimetern die detaillierte Untersuchung der Bodengasmigration bzw. der Abhangigkeit dieser Migrationsprozesse von verschiedenen Einflussgrosen. Relevante einflussnehmende Parameter sind beispielsweise der Diffusionskoeffizient und die Gaspermeabilitat des Bodens, Ande-rungen des Grundwasserstandes oder externe Einflusse wie tageszyklische oder langerfristige Schwankungen der meteorologischen Verhaltnisse. Die beiden Neuentwicklungen werden anhand erster Untersuchungsergebnisse beschrieben, und es werden Schlussfolgerungen fur die weitere Arbeit abgeleitet.

N-, P- and DOC-dynamics in soil and groundwater after restoration of intensively cultivated fens

Most fens in Northeast-Germany have been drained since the late 18th century with a consequent increase in intensity of agricultural land use until the early 1990s. This cultivation resulted in severe peat degradation. Nowadays schemes are introduced to restore such degraded wetland sites. However, little is known about the impact of these restoration schemes on nutrient dynamics in soil and water.

Phosphorus input by nordic geese to the eutrophic Lake Arendsee, Germany

Phosphorus import by nordic geese (Anser fabalis and Anser albifrons) was investigated in Lake Arendsee, located in the Saxony-Anhalt region, Altmark, Germany during the period 1996 to 1997. Phosphorus contained in geese excrement on the ice was measured in the winters 1996 and 1997. In February 1996 (after 9 days of frozen lake surface) two excrement fields amounted to 80 ha and 30 ha in area and in January 1997, 10 days after ice closure, the excrement field was 106 ha large. The weight of excrement was estimated to be 148 to 266 g m -2 fresh weight (mean 201 g m -2 ) in 1996 and 83 g m -2 to 408 g m -2 (mean of 243 g m -2 ) in 1997. The average of phosphorus content was 8.5 mg g -1 dry weight in 1997 and 9.2 mg g -1 in 1996. Based on these values the phosphorus input attributed to nordic geese was calculated. Our results demonstrated a phosphorus import in 1996 after 9 days of frozen lake surface of 251 kg and in 1997 after 10 days of freezing of 173 kg. During 100 days of wintering, the nordic geese on Lake Arendsee produced a phosphorus load of 2.8 t in 1996 and 1.7 t in 1997. Compared with the annual phosphorus import from different sources, the contribution by nordic geese was 88 % in 1996 and 92 % in 1997. Its yearly phosphorus load during the winter months appears as a significant eutrophication factor for the trophic level of Lake Arendsee. However, the annual external load is approximately 10 % of the phosphorus poolsize in the lake water, and even less when considering the amount lodged in the bottom sediments.

Advanced Technologies in Lysimetry

The ability to quantify soil water flow is a prerequisite for the accurate prediction of solute transfer within the unsaturated zone. Monitoring these fluxes is a challenge because the results are required for answering not only scientific but also practical questions regarding the protection of groundwater, the sustainable management of agricultural, forestry, mining or set aside industrial areas, the reduction of leachate loss from landfills, and for explaining the fate of environmentally harmful substances. Both direct and indirect methods exist for estimating water flux rates; these have been applied with varying success. In Europe, the use of direct lysimetry methods for measuring water and solute fluxes in soils has increased significantly in recent years. Although this technique generates reliable drainage data, it involves relatively high investment and maintenance costs. New lysimeter techniques have been developed to tackle this problem. It is now possible to collect large monolithic soil columns and to measure the soil water balance of these monoliths (surface area 0.03–2 m2 and depth to 3 m) with a high degree of precision (±20 g). Furthermore, progress in lysimetry enables us to ascertain experimentally the mass input of dew and to calculate actual evapotranspiration, precipitation and seepage rates. Weighable groundwater lysimeters have been developed in addition to gravitation lysimeters. Different lysimeter types and their usage will be presented and explained using practical examples.

Analysis of the effect of meteorological factors on dewfall.

To get an insight into when dewfall will occur and how much to expect we carried out extensive calculations with the energy balance equation for a crop surface to 1) identify the meteorological factors which determine dewfall, 2) establish the relationship between dewfall and each of them, and 3) analyse how these relationships are influenced by changes in these factors. The meteorological factors which determine dewfall were found to be air temperature (T(a)), cloud cover (N), wind speed (u), soil heat flux (G), and relative humidity (h(r)). Net radiation is also a relevant factor. We did not consider it explicitly, but indirectly through the effect of temperature on the night-time radiation balance. The temperature of the surface (T(s)) where dew forms on is also important. However, it is not a meteorological factor, but determined by the aforementioned parameters. All other conditions being equal our study revealed that dewfall increases linearly with decreasing N or G, and with increasing h(r). The effect of T(a) and u on dewfall is non-linear: dewfall initially increases with increasing T(a) or u, and then decreases. All five meteorological factors can lead to variations in dewfall between 0 and 25 W m(-2) over the range of their values we studied. The magnitude of the variation due to one factor depends on the value of the others. Dewfall is highest at N=0, G=0, and h(r)=1. Ta at which dewfall is highest depends on u and vice versa. The change in dewfall for a unit change in N, G or h(r) is not affected by the value of N, G or h(r), but increases as T(a) or u increase. The change in dewfall for a unit change in Ta or u depends on the value of the other four meteorological factors.

Estimating the effects of set‐aside on water quality: scaling‐up of lysimeter studies

Since 1990, agriculture in the five new federal states of Germany has experienced a fundamental structural change. As much as 10 per cent of the 6·2 million ha of previously intensively farmed agricultural land were set-aside abruptly. In the spring of 1991, a lysimeter trial (filled with soils common in the catchment area of the Elbe River), was set up to investigate the impact of set-aside on the water and solute balance. The studies proved that restricting agricultural use in areas previously farmed intensively by converting them into permanent or rotation fallow will result in measurable changes in deep percolation (ground-water recharge) and water quality in less than one year. The results of the lysimeter studies were extrapolated to calculate the effects of set-aside in a catchment area (about 2 500 ha) with similar meteorological and soil conditions. The calculations showed that increasing the area under rotation fallow from 8 to 15 per cent increases the nitrogen load of the stream draining the catchment by about 5 per cent. Copyright

Hochwassergebundener Schadstoffeintrag in Auen der Elbe und der Oka: Aktueller Stand eines BMBF- und UFZ-geförderten russisch-deutschen Kooperationprojektes

Im Rahmen des BMBF-geforderten Vorhabens „Wirkung von Hochwasserereignissen auf die Schadstoffbelastung von Auen und kulturwirtschaftlich genutzten Boden im Uberschwemmungsbereich von Oka und Elbe“ werden in einer weidewirtschaftlich genutzten Aue im Bereich der mittleren Elbe (Strom km 437 – 440) und in einem Auenabschnitt der Oka in der Nahe von Ryazan, ca. 700 km vor der Mundung in die Wolga, der Eintrag, die Verteilung, Retention und Wirkung von Schadstoffen untersucht. Dazu werden bei Hochwasserereignissen die Wasserphase und die Schwebstoffe kontinuierlich, i.d.R. taglich beprobt und auf ihre Gehalte an Schwermetallen analysiert. Daruberhinaus werden auf detailliert hohenvermessenen Transekten an exponierten Standorten Sedimentmatten ausgelegt, auf denen die Retention des sedimentierten und von der Grasnarbe ausgekammten Materials nach Menge und Gute (Hochflutsedimente) untersucht wird. Die Transekte sind im dichten Raster bodenkundlich kartiert und im Elbauenbereich an besonders ausgewiesenen Referenzmesstellen mit Saugkerzen in 4 Tiefen (15, 30, 60, 90 cm) zur Gewinnung von Bodenwasserproben ausgestattet. Die Untersuchung der Schadstoffbelastung wird erganzt durch Arbeiten zur Identifizierung der okotoxikologisch relevanten Verbindungen und deren mikrobiologischer Abbaubarkeit sowie zur Akkumulation von Schwermetallen in Pflanzen.

CALCULATION OF WATER BALANCE FOR THE SOUTH DESERT AREA OF WESTERN SIBERIA BY INTERNATIONAL MONITORING NETWORK DATA

The study of the water balance is not only of great practical importance, but also of interest from the standpoint of basic science for the researchers of the steppe zone, which has traditionally attracted people for its climate and soil resources. The article presents the results obtained from a network of automatic stations deployed in the framework of the Russian-German scientific cooperation in the field of climate, soil, and hydrological monitoring for 2012-2015. The instrumental data were obtained and the method of soil water balance calculation was performed on the basis of data of automatic weather station observations and lysimetric stations of new generation in the conditions of Western Siberia.