BELOW-GROUND CARBON DISTRIBUTION IN BARLEY (HORDEUM VULGARE L.) WITH AND WITHOUT NITROGEN FERTILIZATION

The distribution of net assimilated C in barley (Hordeum vulgare L.) grown at two N-levels was determined in a growth chamber. The N-fertilization involved 0 and 3.61-mu-mol N g-1 dry soil. After growth for seven weeks in an atmosphere with continuously C-14-labelled CO2, C-14 was determined in shoots, roots, rhizosphere respiration and soil. At the low N-level, 32% of the net assimilated C-14 was translocated below ground, whereas at the high N-level 27% was translocated below ground. The release of C from roots (root respiration, microbial respiration originating from decomposition of C-14-labelled root material and C-14 remaining in soil) was greater with no N-supply (19% of net assimilated C-14) than in the treatment with N-supply (15%). Thus, the effect of N-supply on both translocation of assimilated C-14 below ground and the release of C-14 from growing roots was relatively small.