Uptake of soil nitrogen by soybean as influenced by symbiotic N2-fixation or fertilizer nitrogen supply
Jensen, E.S.; Sorensen, L.H.
Soil Biology and Biochemistry 20(6): 921-925
ISSN/ISBN: 0038-0717 DOI: 10.1016/0038-0717(88)90104-6
Nodulated and N2-fixing soyabean plants (Glycine max L.) grown in a pot experiment took up significantly more soil N (labelled with 15N) than non-nodulated control plants. The organic matter in the experimental soil was labelled with 15N during a previous incubation, and the pool of labelled inorganic N originated mainly from mineralization of organic matter. Addition of non-labelled ammonium or nitrate-N to non-nodulated plants did not increase their uptake of labelled soil N. Plants grown with the various N-sources exhausted the soil for KCl-extractable N to almost the same low concentration. Where non-nodulated plants were grown, 60-75% of the inorganic N initially present could be accounted for in plants and KCl-extracts at harvest.