Effects of stubble height and cutting frequency on regrowth of berseem clover in a Mediterranean semiarid environment

Defoliation management of forage crops affects endogenous reserves (in the root and in the stubble), the residual leaf area, and, consequently, the regrowth and biomass yield. The aim of this study was to evaluate the effect of cutting frequency (28-d vs. 35-d intervals) and stubble height (3 vs. 6 cm) on forage yield, regrowth, and persistence of berseem clover (Trifolium alexandrinum L.). Neither cutting interval nor cutting height affected plant survival during the crop cycle. Frequent clipping reduced crop yield. Residual biomass and leaf area were less when plants were cut at a height of 3 cm compared with 6 cm, but stubble height did not affect the total amount of dry matter (DM) removed. However, with a cutting interval of 28-d, DM yield was greater with a stubble height of 6 cm compared with 3 cm, whereas stubble height generally had no effect with a cutting interval of 35-d. This study shows that severe defoliation, which substantially reduces residual photosynthetic area, forces berseem clover plants to mobilize reserves from the taproot. With frequent clipping, taproot reserves are depleted and regrowth is impaired, whereas less frequent clipping enables taproot reserves to be restored. In contrast, less severe defoliation, which results in a considerable residual leaf area, promotes rapid regrowth regardless of the frequency of defoliation.