Abstract
Orchardgrass plants of a single clone were transplanted 10cm apart on Nov. 23rd 1969, and were cutted 5cm above ground level when plants got about 30cm, 40cm or 50cm in height (named 30cm cut, 40cm cut or 50cm cut sward, respectively) between 1970 and 1972. Seasonal fluctuation of tiller numbers of each plant was investigated during the years, and the dates of emergence of tillers and death of them were observed between Apr. 14 and Oct. 9 in 1972. 1) With the start of rapid plant growth at the beginning of Apr. in 1970, vigorous tillering occurred, and it continued until the first of May (Fig.1). As many of tillers were cutted at culm at the first cutting of each treatment, the number of shoots being capable of regrowth decreased, but tiller numbers per plant were immediately recovered by active tillering, which continued until the time of summer depression. In contrast, poor tillering was observed from spring to early summer in 1971 and 1972, when tiller populations were greater than at the same season of 1970. The increase of tiller numbers was most abundant in automn, especially in 30cm cut sward, during 3 years. 2) From heading to late Aug. of 1972 the rate of tiller emergence was largest in 50cm sward, and little in 30cm cut sward, but most of these tillers died at the early stage after emergence, thus the greater part of tillers which emerged after Apr. 14 disappeared during the summer (Fig.5). 3) Though the sward was constituted with the plants genetically identical in this experiment, the fluctuation in size arose among plants of same cuting treatment. The basal area of plants in 50cm cut sward was most uneven after 3-year-treatment (Fig.8). One of the probable reasons that caused this phenomenon may be related with the repetition of frequent emergence and death of tillers during growing seasons.
