N-15 DISTRIBUTION IN WHEAT AND CHEMICAL FRACTIONATION OF ROOT-BORNE N-15 IN THE SOIL

Spring wheat plants were grown in split-root containers and labelled with N-15 by fertilizing one compartment of the container with (NH4NO3)-N-15-N-15 (95 at.-% N-15 exc.). After the harvest, approx. 90% of the N-15 incorporated by the plants were found in the shoots and 3% in the roots; approx. 7% had been released into the soil of the unlabelled compartment. The N-15 in the soil of the unlabelled compartment was extracted with KCl and hydrolysed with HCl. Approx. 60% of the N-15 was found in the hydrolysable organic N pool of the soil and 9% in the fraction of the soluble and exchangeable inorganic nitrogen.