Flooding on the German Rhine during the 20th century was tested for trends and assessed to identify causal mechanisms driving worsening of flooding. A review of previous research outlines the range of impacts due to climate change, land-use shifts, and river regulation. Analysis of hydrologic data, especially of the long record at Cologne, documents statistically significant increases in both flood magnitudes and frequencies. Specific-gauge analysis, which isolates the effects of channel modification, documents that 20th century river engineering has caused little of the observed increase in flooding on the German Rhine. Precipitation records from the Rhine basin confirm that flood magnification has been driven by upstream factors, including an increase in flood-producing precipitation of roughly 25% during the past 100 years and increases in runoff yields. In addition, agricultural land-use records suggest that flood magnification can be partially explained by 20th century trends documenting intensification and industrialization of German agriculture. Copyright (c) 2005 John Wiley & Sons, Ltd.

To control the groundwater contamination by NO3, monitoring programs have been developed during the past 17 years in German drinking water catchments. The monitoring programs are using data of the NO3 content of the soils and of the groundwater. In Baden-Wurttemberg, between 1987 to 2002, soil NO3 decreased significantly by 50%. Atmospheric influences and irregularities of sampling complicate the interpretation of NO3 values in the soil. This is especially true for areas, where values are available only for about one decade or less. To take such complications into account, NO3 time series from a drinking water catchment in Lower Saxony(Germany) were analyzed by multiple regression. A strong correlation between the weather conditions (precipitation and temperature during the fall) and the NO3 content of the soil was found While the raw data of NO3 content of the soil did not decrease significantly over time, a highly significant yearly decrease of about 3kg N (.) ha(-1) or 50% from 1.992 to 2002 was observed after atmospheric influences were taken into account. This result was confirmed by the trend of NO3 concentration of the groundwater near the surface. It decreased yearly by about 10mg (.) L-1 or 55% from 1994 to 2001. It is concluded that a multiple regression analysis is indispensable in interpreting soil NO, time series of restricted length.

Confined animal production, in Germany for instance found in the Vechta/Cloppenburg area, can have various impacts on the environment. Both reactive nitrogen (N) and phosphorous (P) compounds from the animal manure are a threat to the regional soils and the groundwater. Agricultural politics is advocating a less intensive form of animal production, but occasionally it may take years before this policy becomes effective. In order to accelerate the relief of the environment, the use of technical means can be considered. To this end, the application of aluminum salts and drinking water treatment residues containing aluminum has been studied, particularly in the USA. These investigations have shown that the water-soluble P content in organic fertilizers and in soils can be reduced significantly. If applied in the field, a decrease of the P concentration in the runoff from soils can be achieved. By treating organic fertilizers. also the NH3 emission as a result of the decreased pH-values was reduced. Simultaneously, a better health of the animals in poultry production, and a better economic efficiency was achieved. Other positive effects are lower concentrations of heavy metals and hormones in the runoff. The results suggest, that also in Germany a reduction of non-point pollution may be achieved in the subject areas just mentioned. More research is needed, however, especially with respect to the optimally required quantity, as well as regarding the usefulness of other industrial by-products.

To control the groundwater pollution by NO3-, different monitoring programs have been carried out during more than a decade in drinking water catchments in Germany. The monitoring programs are based on agricultural and hydrological data. Atmospheric influences and irregularities of sampling complicate the interpretation of NO3- values in the soil and in the groundwater. To take such complications into account, NO3- time series from a drinking water catchment in Lower Saxony were analyzed by multiple regression. A strong correlation between the precipitation during the fall season and the NO3- content of the soil was found. The NO3- content of the soil is also influenced by the October temperature. While the raw data of NO3- content of the soil did not decrease significantly over time, a highly significant yearly decrease of about 3 kg N ha(-1) or 50 % from 1992 to 2002 was observed after atmospheric influences were taken into account. The variability due to precipitation was amplified by changing the date at which samples were taken. The NO3- concentration of the groundwater near the surface decreased yearly by about 10 mg 1(-1) or 55 % from 1993 to 2001. Beside this decrease, influences of the October temperature and the sampling depth on the NO3- concentration of groundwater were identified. It is concluded that a multiple regression analysis is indispensable in interpreting soil and groundwater NO3- time series of restricted length.

Excess nitrogen from farming has led to a rise in nitrate concentrations in groundwater. Since the late eighties, measures have been undertaken to reduce nitrate (NO3)- inputs. In order to document their success, the levels of mineral soil nitrogen (N-min, mostly NO3-N) in drinking water catchment areas threatened by leaching are often checked early in the second half of the year. Any reduction in N-min overtime would then be attributable to reduced NO3 inputs into the ground-water. However, as the N.; level is closely dependent on climatic influences, these become superimposed on any possible downward trend in the levels which might otherwise be recorded. Consequently, in many drinking-water catchment areas where regular recording of levels is still in its early stages, no downward trend has yet been detected.In the article under review, the author employs multiple-regression computations to identify the climatic influences affecting the long-term recording of N-min levels, and to compute trends adjusted for climatic trends. These interrelationships were analysed in three series of measurements. The results can be discussed using the example of a ten-year record kept in Lower Saxony (1992-2001): This record from Lower Saxony is dependent to a very significant degree on the precipitation Occurring from October to the time the sample was taken, the October temperature and the precipitation in September. Adjusted for climatic effects, the N-min contents sank annually by the highly significant figure of 4.3 kg/ha. Although after 7 years the trend exhibited by the climate-adjusted data was significant, the raw data, in contrast, displayed no significant downward trend, even after 10 years. Similar climatic influences and a downward trend in the climate-adjusted data were detected using a seven-year record kept in Bavaria, and a twenty-year one in Lower Saxony.These result show that, in terms of drinking-water protection, much more weight can be given to N-min records taken in autumn as a measurement of the result or success of Nitrogenreduktion aktivities if the influence of climate has been identified, and the climate-adjusted trends computed. In the field of overall groundwater protection, moreover, N-min readings taken in spring for manuring strategic purposes can be similarly analysed and thus also used as agricultural environmental indicators.

Physical degradation of agricultural soils is a widespread and persistent problem, and it is a problem that is now increasingly recognized in Germany. It causes damages and external costs that are estimated at several hundred million Euros per year. If, and to what extent, Tschernosem cropland soils of the so-called Hildesheimer Borde (Hildesheim Loess Belt) are subject to physical soil degradation has been examined little to date. Therefore we studied the deterioration of soil structure in the plow layer as well as soil compaction below the plow pan at a number of arable field locations in the Borde region. As a measure of soil structure, we chose the aggregate stability, and for soil compaction we chose the relative Proctor density. In order to assess the development of soil degradation over time, we compared our present measurements with those from the same sites made during the 1960s. We found that already in the 1960s, evidence of physical soil degradation could be detected in the cropland soils of the Hildesheimer Borde. This tendency, however, increased in the following decades. The relative aggregate stability of the plow layer presently amounts to only about 10%, and the soil density below the plow pan shows values of about 95% of the Proctor density. To protect the soil and the environment, measures against further degradation promoting reestablishing of lost functionalities of the Borde soils appear appropriate. The relative aggregate stability (qGMD) seems to be a proper criterion for imposing the new Federal Soil Protection Act. Furthermore, reduced soil cultivation, together with a restriction in the size and power of farm machinery, would be helpful. A restriction in the size and the length of single fields might also be considered. We show that such restrictions may lead to farm income losses, but because such restrictions are economically and environmentally beneficial, they could be compensated by diverting existing financial farm subsidies.

The present agricultural production system in Germany is characterized by a high degree of commercial N-fertilizer and imported fodder use. Because the N use efficiency is low, a large part of the applied N is emitted in a reactive form into the environment. The possible damage caused in the environment so far has been investigated only partly. The objective of the present study therefore was to quantifiy this environmental damage. To this end, the yearly N surplus in German agriculture since 1951 was estimated with the use of statistical data on national agriculture. With the use of literature data, we showed how, and to which extent, surplus N is emitted into the environment. We also evaluated monetarily the environmental damage. To judge the magnitude of the environmental damage, the monetary damage was compared with the economical output of agriculture. Our calculations aim at directing ways to develop a sustainable agricultural production system, to which Germany has committed itself by signing the Agenda 21.For the period under study (1951 to 2000), we calculated from the difference between the N input by commercial fertilizers and imported fodder, and the N output by animal and crop products the annual N surplus. This surplus increased from about 10 kg/ha in the 1950s to 120 kg/ha in the 1980s, and amounted to 70-80 kg/ha in the 1990s. In case additional N inputs are considered, such as N fixation by legume crops, N deposition from the atmosphere, or N input by compost and sludge, and if the lay-off cropland area is subtracted from the total agricultural land area, the calculated N surplus per hectare of cropland is considerably larger. For 1995, for example, in this case a N surplus of nearly 150 kg/ha is calculated, which is emitted largely into the environment (ground and surface waters, atmosphere). The annual external costs caused by these emissions are estimated at 2.5 to 10.0 billion DM (approximate to 1.25 to 5.0 EU$). Furthermore we point out, that particularly animal products are consumed to such an extent that it harms the population's health. Stimulating and subsidizing organic farming may help to reduce the excessive use of nitrogen in today's agriculture. It appears, that in view of the present state of science and technology, the NO3 and agricultural N surplus problem in Germany can be solved enduringly only with a significant reduction in animal production.

Collectivization of farmland since the 1950s has changed the agricultural land use in former East Germany. Single fields on the collective farms became increasingly large and were cultivated with increasingly heavy farm equipment. This led to large-scale physical degradation of arable soils, enhancing the formation of surface runoff in periods with prolonged and excessive precipitation. The extent to which this development may have affected the discharge behavior of the main East German river, the Elbe, has so far not been studied. We analyzed the flood peaks of the Elbe during the past century (1900–2000). The flood discharge behavior of the Elbe has apparently changed significantly since the 1950s. Although climate changes may be involved, we conclude that the Elbe flood peaks, recorded since 1950, are related to the changes in postwar agricultural land use in former East Germany. To restore the degraded farmland soils, a change in agricultural land use may be necessary.

Nitrogen (N) fertilization in agriculture has been discussed controversially in Germany for almost two centuries. The agronomist Carl Sprengel, who published his theory on the mineral nutrition of plants in 1828, advocated the use of mineral N fertilizers. Chemist Justus von Liebig, on the other hand, vehemently denied around 1850 the need for N fertilization. Although it soon became evident that Sprengel was right and Liebig was wrong, not much synthetic N fertilizer was used in German agriculture until around 1915, when the Haber-Bosch technique enabled the commercial production of NH3. The use of N fertilizers since then has grown, especially since 1950. To increase agricultural productivity, German governments have promoted, directly and indirectly, the use of N in crop and in animal production. Unfortunately, it was overlooked that N surpluses in agriculture increased rapidly; around 1980 they amounted yearly to more than 100 kg ha-1. The extensive use of N in agriculture is causing environmental damage and is contributing substantially to the external costs of present agriculture. The main N compounds that affect the environment are N2O, NH3, and NO3. These compounds are considered to contribute one third to the external costs of agriculture. Additionally, the high rate of human intake of animal proteins and lipids has adversely affected the health of the country’s population. Fundamental corrections in German farm policy appear inevitable.

The frequency of extreme stages and floods along rivers like Rhine and Danube seems to have increased after the second World War. The question, as to whether this increased frequency is due to climate changes or human impacts, has been raised repeatedly. We hypothesize that the increased frequency is related to the intensification of German agriculture. For the pre-sent study, we analyzed developments in German agronomy after World War II, especially in soil tillage. We also analyzed flood stages of the river Rhine at Cologne, both for prewar and postwar times. The analysis revealed that the relation between peak discharge of a flood wave on one side, and catchment rainfall on the other, has changed after the war. Our calculations show, for example, that an extreme rainfall amount of 200 mm in the Rhine catchment within one month results in a mean peak discharge at Cologne that presently is 1544 m(3) s(-1) higher than before the war. Simultaneously, our analysis indicates that conventional soil tillage after World War II was intensified. During heavy or long lasting rainstorms, this intensified conventional tillage seems to promote surface runoff. We assume that postwar intensified tillage has led to a physical soil degradation that at least partly explains the increased frequency of extreme stages and floods along Germany's rivers. To reduce the threat of flash floods, it seems recommendable to extend conservation tillage subsidies.

Simple multiple regression models were derived to describe the relation between the mineral nitrogen content (Nmin) of agricultural soils and the weather conditions in the months before the date of measurement. The data, which are needed for the regression models are the Nmin values of a few years, the monthly precipitation an the monthly temperature. It can be used Nmin values of spring and of autumn. Calculations can be made for mean values of whole areas, but also for single fields. There are three fields of application, which are resulting from the knowledge of the influence of weather on Nmin: The prediction of Nmin for optimizing the N fertilization, the analysis of trends for identifying changings of the Nmin level, which are not caused by weather as well as the the estimating of leaching of nitrate from agricultural soils during winter.