Organ-Level Nutrient Partitioning in Legume Green Manures Grown under Calcareous Mediterranean Field

Green manuring with legumes is widely used to enhance nutrient recycling in Mediterranean agroecosystems, especially under calcareous soil conditions where nutrient availability is commonly constrained. This study examined growth performance and organ level macro and micronutrient distribution in four legume species chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), forage pea (Pisum sativum L.), and vetch (Vicia sativa L.) grown as sole green manure crops under field conditions in in a calcareous Mediterranean field soil. Growth parameters, nodulation traits, and nutrient concentrations were quantified in roots, stems, leaves, flowers, and nodules. Plant organ had a highly significant effect on all macro- and micronutrients analyzed, whereas species effects were limited and significant only for N, Fe, and B. Significant species × organ interactions were observed for Ca, Mg, Fe, Cu, Mn, and B, indicating context-dependent nutrient allocation among organs. Nitrogen was preferentially concentrated in nodules (measurable in chickpea and faba bean, but weak in forage pea and vetch) and flowers, consistent with symbiotic N fixation in nodules and high metabolic demand in reproductive tissues. In contrast, Fe and Mn were enriched primarily in roots and nodules and, for Mn, also in photosynthetically active leaves, whereas B was predominantly enriched in leaves and, in some species, roots under calcareous, alkaline soil conditions. Overall, the results indicate that organ-level nutrient partitioning is the primary determinant of nutrient distribution in legumes grown under calcareous Mediterranean conditions (soil pH=7.49), whereas species-specific effects are secondary and element-dependent. These findings show that organ composition and biomass distribution, together with soil constraints, should be considered when evaluating legume species for green manure use.