Long-term nutrient leaching from a Swedish arable field with intensified crop production against a background of climate change

Abstract

Leaching of nutrients was studied at a tile drain outlet and in two pairs of groundwater pipes in an arable field in central Sweden in order to identify trends and impacts of the climate. In the study period (1973–2005), crop production was dominated by spring barley, winter wheat, rape and, in later years, potatoes. Winter crops were cultivated 60% of the time. Leaching of total nitrogen (TotN) and total phosphorus (TotP) to drain water was low, on average 10 kg ha−1 year−1 for TotN and 0.07 kg ha−1 year−1 for TotP based on measurements. Nitrogen fertilisation increased slightly from 121 to 142 kg ha−1 year−1 during the period in a balanced way in line with increasing crop yields of cereals, from 5.8 to 6.6 tonnes year−1. For the entire study period, the temperature was estimated to increase significantly by a total of +2 °C for the growing season (April–September). Precipitation (+16 mm) and humidity (+11%) were also estimated to have increased significantly, mainly in June. Simulations with a deterministic and coupled N-leaching database model (SOILN-DB) indicated an increased rate of mineralisation (+2 kg ha−1 year−1) and increased N leaching to the drain pipes (+0.06 kg ha year−1) as a result of climate changes. In this simulation spring tillage instead of autumn tillage was estimated to reduce N leaching by 10%. Mineral P fertilisers were applied to winter crops in autumn until 1999, but thereafter all mineral P fertilisers were applied in spring by drilling in bands. A weak trend for decreasing concentration of dissolved reactive phosphorus was indicated based on the measurements in the tile drain outlet.