Long-term fertilization effects on soil carbon under permanent swards

In a long-term study with four rates each of fertilizer N, P, and K in factorial combination on timothy (Phleum pratense L.), soil C concentration in the 0- to 15-cm layer of an Orthic Dystric Brunisol in New Brunswick ranged from 25 to 37 g C kg−1 after 26 yr, and from 26 to 44 g C kg−1 after 35 yr. Soil C concentration was not related to the wide range of aboveground net productivity resulting from contrasted long-term fertilization treatments. Soil C concentration, however, was negatively correlated to soil pH. Key words:Phleum pratense L., timothy, carbon, fertilization