Swedish long‐term experiments

Abstract

In 1996 there were 124 individual long‐term experiments in Sweden financed by the Swedish University of Agricultural Sciences to a cost of 648.000 Euro. Of these 39 were plant nutrition and soil fertility experiments distributed between the 54th to the 63rd latitude. At three sites, south, central and north, N mineralization in cropping systems with ley and manure was investigated. Approximately 90 kg N per ha and year was removed by the crops at all three sites. Temperature, cropping history and ley proportions are factors that influenced the N mineralization. In rotations without ley and manure at the central and south sites the N uptake was around 30 kg per ha and year. Soil C content decreased during 35 years in the south but changed insignificantly at the central and north sites, 31 and 28 years respectively. Only minor effects on soil C content were observed by increased biomass production due to N fertilization. The efficient C metabolism of the heterotrophic microflora emphasises the significance and importance of the simultaneous ongoing N mineralization for the N supply of crops and for the environment.