Tóm tắt
Runoff (overland flow and A/B horizon interflow) was measured from 2
grazed dairy pastures at Flaxley, South Australia, from 1996 to 1998. Runoff
ranged from 0.4% to 10% of annual rainfall and
>90% of this was overland flow. Phosphorus and carbon were
measured in runoff. As much as 2.3 kg/ha of phosphorus and 10.7 kg/ha
of total dissolved carbon were lost from the subcatchments in the wettest
year. Over the study period, 98% of total phosphorus and
86% of total dissolved carbon were lost in overland flow. Around
45% of phosphorus was dissolved and 69% of total
dissolved carbon was dissolved organic carbon. The proportion of phosphorus
present in the particulate form decreased during each runoff season, and was
highest in the wettest year. There was no consistent trend in the proportion
of total dissolved carbon present as dissolved organic carbon because the
factors found to affect dissolved organic carbon loss were different from
those affecting dissolved inorganic carbon loss. Predictive relationships
based on factors such as the time of year when the storm occurred and runoff
volume have been developed from the 3 years of data and they explain a high
proportion of variability of phosphorus and carbon loads.
