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

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 (Ca2+, Mg2+, Na+, and K+) and anions (total PO43-, NO3-, Cl-, and SO42-) 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 NO3- SO42- 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%. (C) 1998 Elsevier Science B.V.