Berseem-annual ryegrass intercropping: effect of plant arrangement and seeding ratio on N2 fixation and yield

Various agronomic factors can affect the productivity and the efficiency of legume-grass intercropping systems. This research was carried out in a Mediterranean semi-arid environment (37°30’N; 13°31’E; 178 m a.s.l.) with the aim to study on berseem clover- annual ryegrass mixture (Trifolium alexandrinum L. – Lolium multiflorum Lam subsp. wersterwoldicum) the effects of different plant arrangement (sowing of the two components in alternate rows or in the same row) and seeding ratios (100:0; 75:25; 50:50; 25:75; 0:100) on forage yield, nitrogen content and nitrogen fixation. The experimental design was a split-plot with four replications. The 15N isotope dilution technique was used to estimate nitrogen fixation by berseem clover. All plots were cut four times (first cut 85 DAS; rest period of four weeks). The DM yield of mixtures and pure stand clover were similar; annual ryegrass in pure stand produced the lowest yields. No significant differences for DM yield were observed due to the plant arrangement and seeding ratio in the mixture. Intercropping berseem had always a significant higher percentage of Ndfa than monocropped berseem. The %Ndfa of mixed berseem was not influenced by plant arrangement but gradually decreased when proportion of berseem in the mixture increased.