Nutrient leaching and water quality from agricultural observation fields during 50 years of environmental monitoring in Sweden

Throughout the last 50 years, 16 agricultural fields in Sweden have been monitored fornutrient leaching losses and water chemistry via subsurface drainage water andgroundwater. The fields represent various climatic regions, soil types, and farmingpractices. Twelve fields were equipped with groundwater pipes. Typically, the shallow(1–2 m) groundwater varied due to weather and agricultural management, whilst thedeeper (4–5 m) groundwater stayed at a steadier level. Long-term mean annual lossesof total nitrogen (N) ranged between 2.8 and 58.0 kg N ha−1 yr−1 across the 12 fieldsoperated with flow-proportional water sampling. This variation was primarily due tothe location in Sweden, as higher losses of N could be monitored in the southern partcompared to further north in the country. For the same 12 fields, the mean annuallosses of total phosphorus (P) ranged between 0.01 and 1.48 kg P ha−1 yr−1. Here, thevariation was mainly due to soil type, with higher losses from clay soils and lowerlosses from sandy soils, but with apparent exceptions. The well-known sites with long-term monitoring that the observation fields offer is a profound opportunity forassessing and understanding current nutrient losses and making predictions of waterquality in the face of climate change.