INFLUENCE OF ALFALFA (MEDICAGO-SATIVA L) INTERCROPPING AND POLYETHYLENE MULCHING ON EARLY GROWTH OF WALNUT (JUGLANS SPP) IN CENTRAL ITALY

Combined production of timber and forage species is considered to be a desirable land-use system to offset some of the current land manageme nt problems of Italy. This paper reports the early results of a study on intercropping young plants of walnut with alfalfa (Medicago sativa L.), with or without polyethylene mulching, in an experimental plantat ion in central Italy, Two genotypes of walnut were used: Juglans regia L. and the French hybrid NG23 x RA. The seasonal changes of absolute and relative growth rates of walnut stem diameter and apical shoot len gth were investigated. During both growing seasons, alfalfa intercropp ing strongly decreased walnut growth, whereas polyethylene mulching pr omoted stem height and diameter growth. Stem growth of intercropped-an d-mulched walnut was the same as that of sole walnut under clean culti vation management. The use of polyethylene mulching reduced or avoided the competitive effect of associated alfalfa on walnut growth. During both growing seasons, the intercropped-and-mulched walnut had higher relative growth rates than intercropped-unmulched walnut. The results show the effectiveness of polyethylene mulching in promoting early gro wth of walnut, even when intercropped with alfalfa during early stages of plantation establishment.