Selection of the best adapted legume types for relay intercropping in durum wheat

Weed presence in cereal-based cropping systems may be markedly reduced increasing temporal and spatial diversification (Liebman et al., 2001). Relay intercropping is an application of spatial diversification and consists of growing two or more crops simultaneously, during part of their life cycle (Vandermeer, 1989).
In the current study, legume subsidiary crops are intersown in an already established durum wheat crop stand. The delayed legume establishment is expected to maintain grain yield by limiting the legume-wheat interspecific competition, avoid the fallow period between wheat harvest and the following crop (up to 10 months in Mediterranean agroecosystems) and support weed control.
However, the simple delay in sowing may not be sufficient to prevent yield loss and contrast weeds; the appropriate choice of the associated legume, with specific morphological and phenological characteristics, is also essential for a successful application of this system (Uchino et al., 2011).
Perennial, annual and annual self-reseeding legumes can be used for relay intercropping. During the intercropping period, the three groups can support weed control by establishing a living mulch. After wheat harvest, weed control capacity changes according to the group. Perennial legumes, traditionally used in this practise, can be used as forage crop for 2-3 following years. Annual legumes with high self-reseeding capacity, may be able to re-germinate by their seeds in autumn and serve as cover crop until the subsequent cash crop, while, annual legumes support weed control as dead mulch until the following crop.
The objective of this study is the agronomic evaluation of legumes and the selection of the most suitable ones for relay intercropping with durum wheat in central Italy. The study focused on wheat performance and weed control before and after crop harvest.