The potential for grain yield and nitrogen fixation by faba bean (Vicia faba L.) cultivars of contrasting plant types was studied at ICARDA's main research station at Tel Hadya in northern Syria during 1985–88. The cultivars included indeterminate landraces, determinate and independent vascular supply (IVS) plant types sown at two seeding densities.
In 1985/86, the cultivars with indeterminate growth habit (ILB 1811, ILB 1819, ILB 1814), which are adapted to the Mediterranean basin, produced the highest grain yield, followed by the determinate cultivar FLIP 84–230F and the lowest yield was obtained from IVSFG–IVS 6, a cultivar with an independent vascular supply to each flower. In 1986/87, ILB 1814 again outyielded two determinate faba bean cultivars (FLIP 84–230F and FLIP 84–239F) and IVSFG–IVS 6. Similarly, in 1987/88, ILB 1814 significantly outyielded the determinate faba bean cultivars FLIP 84–239F, FLIP 84–240F and FLIP 84–241F; and also the indeterminate cultivar IVSFG–IVS 6.
Seeding at 44 plants/m2 as opposed to the recommended rate of 22 plants/m2 gave a slight but non-significant reduction in grain yield for the indeterminate cultivars from the Mediterranean environment (ILB 1814, ILB 1811, ILB 1819). Grain yields were increased significantly in the determinate plant type FLIP 84–39F in 1986/87 and 1987/88, and in IVSFG–IVS 6 in 1986/87.
Grain yield was strongly and positively correlated with total dry matter (r = 0·93) and also to mean weight per bean (r = 0·83) and harvest index (r= 0·47). The correlations between grain yield and pods/m2, seeds/m2 and seeds/pod were negative.
Total nitrogen uptake and nitrogen derived from atmospheric fixation followed a similar pattern to the results for grain yield: high in the high yielding cultivar, ILB 1814, and low in cultivars with low grain yields. In 1986/87, N2 derived from fixation was 77% in ILB 1814, 68% in FLIP 84–239F, 63% in FLIP 84–230F and 62% in IVSFG–IVS 6; and in 1987/88 the values were 88% in ILB 1814, 86% in FLIP 84–239F and 82% in IVSFG–IVS 6.