Fig. 4. Nitrogen fertilizer recovery (%) of ¹⁵N labeled fertilizer (N_R) and N derived from ¹⁵N fertilizer (N_F) in the whole plant at maturity for durum wheat as affected N timing in a experiment at Andalucía region. Mean 3 yr (1999–2000, 2000–2001 and 2001–2002). For each indices treatment means followed by the same letter are not significantly different at P < 0.05 according to LSD.