Effetti del diverso ritmo di utilizzazione sulla persistenza in coltura di 16 cultivar di Medicago sativa L.

ALFALFA (Medicago sativa L.) CULTIVARS COMPARISON UNDER DIFFERENT CUTTING FREQUENCES: EFFECTS ON PERSISTENCE A field trial plot was carried out for three years (2005-2007) at the experimental Farm of Padova University to study the relationship between cutting interval and plant persistence of 16 cutivars of alfalfa (Medicago sativa L.). The cultivars were subjected to two cutting intervals: 1) 25 days between consecutive cuts (corresponding to pre-bloom stage harvest schedule); 2) 30 days between consecutive cuts (corresponding to first bloom stage harvest schedule). Plant density (plants/m2) and root diameter (at three levels: 3, 8, and 15 cm of depth) were measured in spring and autumn of each year. Dry weight and Water Soluble Carboidrate content in both taproot and crown were measured and analyzed at the last cut of 2007. Forage yield was determined at each cut. The presence of spring weeds before the beginning of cuts in 2007 was also estimated by visual rating. Persistence, root diameter, taproot dry weight, crown dry weight, forage production, and competition against weeds decreased under shorter cutting interval. Cultivars showed different concentration of Water Soluble Carboidrate (total and low weight WSC). But these differences are not related to persistence. A negative relation between plant density and root size (diameter, crown dry weight, and taproot dry weight) was also observed. The relationship between plant density and yield (only in the case of harvest at pre-bloom stage), could be explained by the major stress due to the shorter cutting frequence. ‘Delta’ and ‘PR57N02’ showed high persistence in both cutting intervals, so these cultivars could be used for modern alfalfa employments involving frequent cutting interval.