Changes during growth in the nutritive value of components of berseem clover (Trifolium alexandrinum L.) under different cutting treatments in a Mediterranean region

Abstract

AbstractThe nutritive value of berseem clover (Trifolium alexandrinum L.) may be influenced by changes in the nutrient concentrations of morphological fractions as a consequence of cutting treatment. The aim of this study was to evaluate the effects of different cutting treatments on the nutritive value of herbage and leaf and stem components in two Mediterranean berseem genotypes during growth in order to develop management approaches for harvesting forage with a high nutritive value. Spring growth of genotypes of Egyptian (cv. Giza 10) and Italian (cv. Sacromonte) origins was harvested in each of 2 years beginning 196 days after sowing and thereafter every 6 days (twelve harvests in total) to measure dry matter (DM) yield and nutritive value. Cutting treatments were initiated at sixth internode elongation (A) and early flowering (B) and there was an uncut control treatment (C). In vitro digestibility of organic matter (IVOMD) and crude protein (CP) concentration were determined for leaf, stem and total forage of each cultivar at each harvest. For both cultivars, in the uncut treatment (C), DM yield increased linearly to a maximum of 14 800 kg ha−1, on average, by 250 days after planting, the same time at which stem DM accumulation peaked, whereas the nutritive value, in terms of IVOMD and CP concentration, declined with age, coinciding with a reduction in leaf:stem ratio (LSR) from 1·00 to 0·30. Plant parts differed (P < 0·01) in nutritive value with stems being of lower nutritive value than leaves, in the two cutting treatments. There were strong positive correlations between LSR and herbage IVOMD and CP concentration, in both cutting treatments, indicating that, during growth, part of the changes in IVOMD and CP concentration of berseem clover plants was due primarily to the changes in the LSR. Defoliation induced a considerable reduction in DM yield, but an increase in the LSR and a small increase in nutritive value. Plants cut at the sixth internode elongation (A) showed a small proportional decrease (0·19) in total DM yield, but higher LSR values and similar or higher IVOMD and CP concentration than initiating cutting at early flower (B). Delaying defoliation to the early flowering stage (B) increased the proportion of stems and, therefore, decreased nutritive value. Therefore, harvest management in which cuts are applied at the stage of sixth internode elongation appears to be the most favourable for obtaining relatively high yields of forage with high nutritive value in berseem clover grown in Mediterranean regions.