Effects of Cutting Date and Cutting Height before Overwintering on the Spring Regrowth of Summer-planted Napiergrass (Pennisetum purpureum SCHUMACH)

Abstract

This study was made to obtain some information on the spring regrowth of summer-planted napiergrass (Pennisetum purpureum SCHUMACH) subjected to different cutting dates and heights before overwintering. The plants were cut to -3,0 or +20 crn in early December in Experiment 1, and to 0 or +20 cm in late October or late November in Experiment 2. Plant characteristics before and after the overwintering were measured with a particular attention to the individual tillers and tiller buds. The regrown percentage of plant and the dry weight (DW) of regrown tillers in May increased as the cutting height was raised and the cutting was delayed. Increasing the cutting height raised the number of tillers grown from the overwintered tiller buds (RT_<otbs>), owing mainly to the increase in the survived percentage of emerged tiller buds (SPETB) and the total number of tiller buds. Delaying the cutting date, in contrast, raised the number of daughter tillers of RT_<otbs>. Death, survival and regrowth of the buds were dependent on the position of the buds in the soil. The dead tiller buds were located in the shallowest position, and the survived tiller buds were in the deepest position. The regrown tillers were in an almost intermediate position. There was a highly significant positive linear relationship between the SPETB in early April and the regrowth percentage of plant in early May, which indicated the importance of the SPETB to the spring regrowth of napiergrass.