N2 Use in Perennial Swards Intercropped with Young Poplars, Clone I-214 (Populus × euramericana (Dode) Guinier), in the Mediterranean Area under Rainfed Conditions

Intercropping perennial legumes with trees can reduce Nitrogen (N) losses, due to the high amount of N accumulated in stable forms soil and permanent cover during whole year. Although cycling improvement mature agroforestry systems (AFS) was well documented, there is a lack knowledge regarding transition AF. In this work, we studied association two forage crops, namely ryegrass (Lolium multiflorum Lam.) sulla (Hedysarum coronarium L.), 1-year old poplars, evaluate: (i) agronomic performance vs. without intercropped poplar trees; (ii) N-fixing ability (iii) transfer effect from growth promoting on poplar; finally (iv) nitrate leaching reduction presence associated crops. The layout arranged two-factor randomized complete blocks design (RCB) three replicates. first factor tested (crop species) implied different swards, ryegrass. second (cropping system) included systems: PAST i.e., pastoral system trees, SIPAST, silvo-pastoral one tree row beside sward. Sulla resulted more productive than when (+35%). No clear trend observed about influence N-fixation sulla, but fixed higher grown SIPAST near Poplar plants, even year after planting, effective yet reducing flux crops towards ditches. Further investigations are needed study other swards young AF better understand dynamics; particular, it could be worth assess nutrient solution.