R.C. BRUCE1 and J.P. EBERSOHN2
1Agricultural Chemistry Branch, Department of Primary Industries, Meiers Road, Indooroopilly, Queensland, 4068.
2Coolum Research Station, Department of Primary Industries, Coolum Beach, Queensland, 4573.
Litter was measured in two grazed pastures in coastal south-east Queensland. The pastures were pangola grass (Digitaria decumbens) which was medium-heavily, and continuously grazed and tropical species (Panicum maximum var. trichoglume, Setaria sphacelata var. sericea, Desmodium intortum and Macroptilium atropurpureum) which were lightly and intermittently grazed. Sampling was done at 28-day intervals over 112 days (from January to May) and 2 years respectively.
The amount of litter under pangola varied from 81 to 209 g m-2. Under mixed tropical species it varies from 284 to 902 g m-2 being highest in spring and lowest in early autumn.
For pangola, litter accumulation during a 28-day period ranged from 59 to 76 g m-2 28 d-1, or, assuming uniform accumulation rates, 3 to 6 mg g-1 d-1 relative to the amount of standing crop. For tropical species accumulation varied from 66 to 452 g m-2 28 d-1 with the highest amounts in spring.
Pangola litter disappeared at rates from 9 to 54 g m-2 28 d-1 or 3 to 10 mg g-1 d-1relative to litter on the ground, if a uniform disappearance rate is assumed over 28 days. For tropical species the corresponding figures were 12 to 422 g m-2 28 d-1 and to 20 mg g-1 d-1. The highest rates of disappearance were in summer and lowest in winter. Sampling errors were high in all litter measurements, especially in pangola.
Chemical composition of litter from each pasture was relatively constant over the sampling periods with little difference between recently accumulated and older litter. Nitrogen concentrations in pangola litter were relatively high when compared to the standing dead material from which it derived.