Yield and nitrogen fixation capacity by inoculated white lupin (Lupinus albus L.).

White lupin (Lupinus albus L.) crop can gain a renewed interest due to its higher crude protein yield than other rainfed grain legumes, and for the request as an ingredient of functional or healthy food products. It is a new crop in Sardinia (Italy) and very few studies provide information about the N fixation ability of this species which needs to be preferably evaluated at local level from direct measurements. This study was aimed at quantify the DM yield and the N fixed by white lupin, using the Isotopic Dilution method, in three Sardinian sites. Grain dry matter yield and its N proportion did not differ between sites whereas the proportion of N derived from the fixation showed a wider variation. The aerial DM of white lupin fixed from 140 to about 270 kg ha-1 of N. Even if results differed among sites, very high percentages of N derived from the atmosphere were found and a relationship of 53.7 kg of fixed N per tonne of grain DM produced by this legume was established.