Nitrate leaching:: comparing conventional, integrated and organic agricultural production systems

The impact of conventional, integrated and organic practices on groundwater quality were studied in northwestern Germany. Between 1993 and 1997 nitrogen budgets and the nitrate content of the unsaturated zone (soil sampling and porous suction cups) were measured in two field trials located on a clayey loam and a loamy sand. In each year of investigation three main crops per fanning system were compared according to the defined site(soil)adapted crop rotation. Shifting from conventional practice to integrated farming resulted in little decrease in the NO3-concentration of the percolate and the amount of leached N (15% less). Converting to organic farming reduced leaching losses of nitrogen by more than 50%. Yields of the organic field plots were lower, but comparing the cash crop yields in relation to the amount of leached nitrate, the production efficiency (nitrate-N leached related to yield of crops) of the organic fanning system was still clearly higher.