Cobalt and the Contribution of Crown and Lateral Nodules to Nitrogen Fixation of Lupinus Angustifolius L.

Summary The contribution of crown and lateral nodules to the nitrogen supply of inoculated cobalt deficient and sufficient narrowleaf lupin (Lupinus angustifolius L.) was studied in a glasshouse experiment using cobalt‐deficient Lancelin sand. As found earlier, cobalt deficient plants bore more lateral nodules but fewer crown nodules, than normal plants and the nitrogen fixing ability of the deficient plants improved throughout the growth period. This improved nitrogen fixing ability resulted solely from the increased lateral nodulation of cobalt deficient plants. Nitrogenase specific activity of the lateral nodules did not improve with time and crown nodule activity fell to effectively zero.