Forage yield and N2 fixation of Trifolium alexandrinum in pure stand and in mixture with Lolium multiflorum.

The efficiency of grass-legume intercrop systems is affected by various agronomic factors such as crop density, plant spacing and arrangement that may alter the competitive relationships between component crops. This study was aimed to evaluate yield, N concentration, and symbiotic N2 fixation of berseem clover (Trifolium alexandrinum L.) grown in pure stand or in mixture with annual ryegrass (Lolium multiflorum Lam) either in alternating rows or in the same row. The experiment was conducted in two consecutive growing seasons in a semi-arid Mediterranean environment (Sicily, Italy). Dry matter (DM) yields were similar in the mixed stands and in the berseem pure stand; the annual ryegrass pure stand produced the lowest yields. Plant arrangement did not significantly affect the yield of the mixtures, but it did influence the proportion of the two components. Intercropped berseem had a significantly higher percentage of N derived from atmosphere than the monocropped berseem, but no differences were observed by plant arrangement. The apparent transfer of fixed N from berseem to ryegrass was not detected in any arrangement treatment.