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Report of water protection field trials 2018 & 2019 released, showing effects on nitrate leaching

Within the framework of German state-wide tasks around cooperative drinking water protection, several field trials are executed by the Chamber of Agriculture Lower Saxony (CALS), Germany. The results from 2018 and 2019 are now published, including the long-term rotation experiments monitored in DiverIMPACTS.

The experiments aim to develop and test measures to avoid nitrate leaching into the groundwater. For this purpose, all experiments are carried out within a fixed set of nitrogen fertilisation levels in different crop sequences and rotations. Besides intensive testing of soil nitrogen, additional leachate water tests on nitrate in 0.8 meter depth are carried out at four sites in Thülsfelde, Wehnen, Hamerstorf and Schickelsheim by the Lower Saxony Office for MiningEnergy and Geology (LBEG). The Lower Saxony Chamber of Agriculture (CALS) executes those field trials in the framework of state-wide tasks around cooperative drinking water protection. These experiments are financed by the water treatment charge granted by the Lower Saxony Ministry for Environment, Energy, Building and Climate Protection, and the Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN).

Unlike the weather of 2017 with a high precipitation rate, 2018 and 2019 were shaped by quite dry summers. The year 2018 was the warmest and sunniest year, but also the driest since the start of regular climate recordings. In many places, soils were too dry, resulting in significantly reduced yields. Some places in Lower Saxony only had half of the long-term average precipitation.

The year 2019 continued as the third warmest year since the start of regular climate recordings. Different from 2018, the May was relatively cold and wet, followed by the warmest and sunniest June ever. Precipitation rates again were far below the long-term average. At some sites no vertical water-transport could be observed during the turn of the year from 2018 to 2019, resulting in no nitrogen dislocations. In addition to this, a certain amount of fertilised nitrogen could not be used by the plants, resulting in partly very high left-over nitrogen rates after harvest. Depending on the site, this was still observable in spring 2019. This characteristic needs to be taken into account for the interpretation of the results.

This report also includes results from experiments about other crop production measures. The selection of sites takes into account the regional cropping practices and different leaching risks in Lower Saxony. The experiments with accompanying leachate investigations allow, besides the investigation of the N-dynamics in the soil, also nitrate concentrations in leachate water and the total nitrogen charge during groundwater recharge the assessment in different experimental variants.

A detailed and summarised presentation of results is available in the annual test report (pdf), published in September 2020 (LWK 2020). The report is only published in German and can be downloaded using the link below.

Further information



LWK - Landwirtschaftskammer Niedersachsen (2020): Versuchsbericht 2018 und 2019. Grundwasserschutzorientierte Landbewirtschaftung. LWK, Oldenburg. Available at