Enhancing Mediterranean forage legume production through inoculation with elite rhizobia

Aurelio Scavo¹Aurora Maio¹Francesca Calderone¹Tommaso La Malfa¹Calvin Trostle²Ronald J Yates³Stefania Toscano¹Carmelo Cavallo¹Marianna Oteri¹Maria Elena Furfaro⁴Antonino Nazareno Virga⁴Danilo Scordia^1*Fabio Gresta¹

• ¹University of Messina, Messina, Italy
• ²Texas A&M University AgriLife Research and Extension Center at Lubbock, Lubbock, Texas, United States
• ³Legume and Rhizobium Sciences, Food Futures Institute, Murdoch University, Murdoch, WA, Australia, Murdoch, Australia
• ⁴Consorzio di Ricerca Filiera Carni e Agroalimentare - Polo Universitario dell'Annunziata sn, 98168 – Messina, Italy, Messina, Italy

Forage legumes play a fundamental role in the sustainability of cropping systems, as rotating species with grain crops, intercrops or winter cover crops. However, their compatibility with rhizobial inoculants needs context-specific studies. The objectives were to evaluate the effectiveness of three species-specific inoculants (Australian granular (AUG), Australian peat (AUP) and American peat (USP)), compared with a non-inoculated control (CNT). These were applied at the recommended and double dose on five Mediterranean forage legumes (Vicia sativa, Medicago polymorpha, Trifolium michelianum, T. subterraneum and T. pratense). Plant growth, nodulation and relative N2 fixation were measured. Species-specific variations were observed for each inoculant. Across the average of legume species, AUG demonstrated the highest growth-and nodulation-promoting effects at both standard and double inoculum dose. The USP was the worst inoculant at standard dose but induced positive effects at double dose. The relative N2 fixation was only improved at double dose, especially by USP and AUG, whereas only AUP provided significant N2 fixation enhancements at standard dose. Overall, the double dose was the best strategy for all tested forage legumes. These findings suggest inoculating Mediterranean forage legumes with selected inoculants, especially at double dose, may be an effective solution to increase their N2 fixation ability, reduce the use of mineral N fertilizers and identify the optimal forage legume × inoculant combinations for intercropping systems with cereals.