Publication Date

1997

Description

Biomass production and nitrogen content of the native perennial grasses, Barley Mitchell grass (Astrebla pectinata ) and Kangaroo grass (Themeda triandra), were studied over the 1996 growing season. After 160 mm of rain, the biomass of T. triandra increased from 2 to 4 t/ha, while A. pectinata increased from 1.1 to 1.5 t/ha. N in aboveground biomass of T. triandra increased from 14.5 to 17 kg/ha and of A. pectinata from 8.5 to 10 kg/ha. A. pectinata leaves senesced quickly increasing the total amount of N in dead leaves. T. triandra senesced more slowly but dead leaves provided the major portion of the pool of N in the biomass. Net mineralization, nitrification and plant uptake were greatest in the middle of the year (Winter) for both species, correlating with peak biomass production and greatest amounts of total aboveground N. Soils supporting A. pectinata were consistently nitrifying, whereas immobilization limited the amount of ammonium available for nitrification in soils supporting T. triandra.

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Native Grasses in the Pilbara Region, Australia; Resource Acquisition, Allocation and Growth

Biomass production and nitrogen content of the native perennial grasses, Barley Mitchell grass (Astrebla pectinata ) and Kangaroo grass (Themeda triandra), were studied over the 1996 growing season. After 160 mm of rain, the biomass of T. triandra increased from 2 to 4 t/ha, while A. pectinata increased from 1.1 to 1.5 t/ha. N in aboveground biomass of T. triandra increased from 14.5 to 17 kg/ha and of A. pectinata from 8.5 to 10 kg/ha. A. pectinata leaves senesced quickly increasing the total amount of N in dead leaves. T. triandra senesced more slowly but dead leaves provided the major portion of the pool of N in the biomass. Net mineralization, nitrification and plant uptake were greatest in the middle of the year (Winter) for both species, correlating with peak biomass production and greatest amounts of total aboveground N. Soils supporting A. pectinata were consistently nitrifying, whereas immobilization limited the amount of ammonium available for nitrification in soils supporting T. triandra.