M. HIRATA and W. PAKIDING

Grassland and Animal Production Division, Faculty of Agriculture, Miyazaki University, Miyazaki, Japan

Abstract

Dynamics in tiller weight and its association with herbage mass and tiller density were investigated for 2 years in a bahia grass (Paspalum notatum) pasture under cattle grazing, in an effort to characterise the dynamics in tiller weight and its components (live laminae, dead laminae and stem with leaf sheaths), to compare contributions of tiller density and tiller weight to herbage mass and to examine the existence of the self-thinning rule in bahia grass. Tiller weight (range = 67–257 mg DM/tiller) was high from late spring (May) to mid-autumn (October) and low in the other half of the year. The rate of change in tiller weight (range = – 4.28 to 4.31 mg DM/tiller/d) reflected high positive rates of change in live lamina weight in April–May and high negative rates of change in stem weight in October–November. The high positive rates in April–May represent a spring flush achieved by consuming reserve substances in stolons and roots as the main energy pools. The high negative rates in October–November may indicate the translocation of reserve substances stored in stems during summer into stolons and roots before the dormant winter season. Variations in herbage mass (range = 23–560 g DM/m²) were largely explained by the variations in tiller weight, with no significant contribution by tiller density (range = 3859–4875 tillers/m²). The tiller weight:density relationship, when combined with previous data having a broader range of tiller density, was in close agreement with the –3/2 self-thinning rule (slope = – 1.63).