δ¹³C values (‰±SD) of soil carbon (C_t) and microbial biomass (C_mic) in pots with barley plants kept at ambient conditions or labelled with ¹³C. Pulse-labelling took place 19 days after inoculation of 0 (control), 2000, 4000, and 8000 Meloidogyne incognita and soil was harvested after a chase period of 3 days. Means with the same or no letters are not significantly different from Tukey's HSD (P<0.05).