Publication Date

1993

Description

Heteropogon contortus is a palatable pasture grass which is being threatened by , increases in grazing pressure, particularly during drought. This paper presents interim results plant population dynamics of H. contortus., as affected by stoc.1s tak. legume augmentation (mainly Stylosanthes sabra cv. Seca) and p1 Jvision of a dry-season supplement for cattle. The study began in 1%8. By 1991, basal ara of H. co11tortus was highest at the light .. Jt stocking rate of 0.187 steers/ha and declined linearly to be longest at the heaviest stocking rate of 0,5 steers/ha. Similarly, survival of the H. contortus tussocks initially present was' highest at the lighest stocking rate and declined linearly with increasing stocking rate, H. contortus plants has occurred in all years but by,991 was highest at 0.187 steers/ha. The size of the germinable seed bank varied between years but by 1991 tended to be greatest in paddocks grazed at 0.187 steers/ha, The effects of legume augmentation and dry-season supplementation have been small compared with that of stocking rate, However, it is expected that the legume population will continue to increase and may affect populations of H. contortus, The results suggest that H. contortus is favoured by light grazing pressure.

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Impact of Grazing Pressure on the Plant Population Dynamics of Heterpogon contortus (black speargrass) in Subtropical Queensland

Heteropogon contortus is a palatable pasture grass which is being threatened by , increases in grazing pressure, particularly during drought. This paper presents interim results plant population dynamics of H. contortus., as affected by stoc.1s tak. legume augmentation (mainly Stylosanthes sabra cv. Seca) and p1 Jvision of a dry-season supplement for cattle. The study began in 1%8. By 1991, basal ara of H. co11tortus was highest at the light .. Jt stocking rate of 0.187 steers/ha and declined linearly to be longest at the heaviest stocking rate of 0,5 steers/ha. Similarly, survival of the H. contortus tussocks initially present was' highest at the lighest stocking rate and declined linearly with increasing stocking rate, H. contortus plants has occurred in all years but by,991 was highest at 0.187 steers/ha. The size of the germinable seed bank varied between years but by 1991 tended to be greatest in paddocks grazed at 0.187 steers/ha, The effects of legume augmentation and dry-season supplementation have been small compared with that of stocking rate, However, it is expected that the legume population will continue to increase and may affect populations of H. contortus, The results suggest that H. contortus is favoured by light grazing pressure.