Abstract
Population dynamics of harvestable tillers and their generation after harvest were investigated on each cutting time of reed canarygrass (Phalaris arundinacea L.) swards that were grown under different cutting (3 and 4 cuttings per year) and nutrient (standard and low fertilization) treatments in 1984 and 1985 (Table 1). During two growing periods in 1984-1985, population of total productive tillers (TPT, the harvested tillers at each cutting) which consisted of both culm elongating (CET) and non-elongating (NET) tillers stayed rather invariable, fructuating around 800-900 shoots/m^2 in each sward with different cutting frequencies and nutrient levels (Table 3). In most cases TPT tillers composed of CET whose internodes had elongated above cutting height (5 cm above ground) ; the density of CET was at ca. 500 shoots/m^2 or more. On the contrary, NET was at lower level excepting that of last cutting in 4 C (cutting 4 times/year) swards with both nutrient levels. New tillers originated in abundance from the CET stubbles during ten days after each cutting, although their sprouting rate in autumn (especally that of last cuttings in 4 C swards) decreased to half. The underground new tillers UST, which had been dormant in the axils of underground stems of growing CET and started rhizomatous growth just after cutting, emerged with greater population, almost 3 times or more as compared with that of AST which sprouted from aerial nodes of the stubbles (Table 4). The dry matter yield of swards revealed high, positive correlations with plant height and mean dry matter yield per tiller, whereas it rather correlated negatively with TPT density (Fig. 1). Herbage production of reed canarygrass swards may be, therefore, exclusively dependent upon the leaf and internode growth of individual regrowing tillers, an essential and enough amount of which generates rather instantly and stably just after every cutting irrespective of growing seasons and managements.
