Screening of perennial and annual self-reseeding legume cover crops for their potential application as permanent living mulch in organic vegetable system

The objective of this experiment is to screen perennial and annual self-reseeding legumes cover crops for investigating their potential role as permanent living mulch in organic vegetable systems. This study focuses on the screening of legumes based on their morphology, phenology and weed suppression capacity. This is the first phase of a trial in which 28 different legume cover crops are tested as sole crop in order to select the most interesting ones for the local environmental condition. A reduced number of selected legumes will then be tested as permanent living mulch in a vegetable cropping system. Both perennial and annual self-reseeding legumes may be suitable for the target system. Perennial legumes are expected to exert weed control all over the year as living mulch. Annual self-reseeding legumes are able to re-generate from the soil seed bank in autumn and therefore improve weed control during winter as living mulch, while during summer they act as dead mulch, hence limiting the potential water competition during this season. This preliminary experiment was necessary because one of the main challenges to establish successfully a permanent living mulch is the appropriate choice of legume species and/or varieties. Indeed, specific morphological, physiological and phenological traits are crucial in order to obtain the benefits of living mulch and avoid over-competition with the main crop (Ciaccia et al., 2017). Unfortunately, the availability of suitable legumes for this system seems limited, because the cultivars available on the market are normally selected for other uses, e.g. high biomass production and, hence, they are likely highly competitive with the main crop. A specific legume ideotype selection is therefore necessary.