Winter growth of a glycine-green panic pasture in a tropical upland environment

Abstract

In a tropical upland environment, with a predominantly summer rainfall, Glycine wightii CV. Tinaroo (glycine) produced 17 to 40 lb DM an acre per day over periods of five to seven weeks during winter, under dryland conditions. An associated grass, Panicum maximum var trichoglume (Petrie green panic) gave practically no increase in shoot dry matter during winter, although it was less susceptible to frost damage. Partial or complete defoliation of glycine by frost occurs in this environment in about 60 per cent of winters, predominantly in the period mid-June to mid-August. Good recovery occurs in the winter months in frostfree periods. At such times, regrowth is limited primarily by low rainfall, and the availability of stored subsoil moisture is important. A pot study showed that root growth continued during the pre-seeding flowering period and that its relative growth rate was apparently not reduced relative to that of the shoot. Nodule development and nitrogen fixation also continued during this period. Leaf fall and a concurrent cessation of growth were associated with the prolific seeding that occurs in July. Pod development can be delayed by defoliation during flowering.