Page 51 - TA Magazine

Dr Philip Smethurst
As a a a a a a a a a a a a a a a soil and water water scientist at at at at the the CSIRO Dr Dr Philip Philip Smethurst
Smethurst
has been studying the the effects on on on on on on water water water quality quality of plantation forestry in in in streamside management management zones on on on on on on Tasmanian farms His conclusions? If all farmers were using trees for for for water water water quality quality quality management management drastic improvements to water water water quality quality quality could be made for for the greater good Plantations in in riparian zones improve improve water water quality quality create almost non-detectable effects on on on on on on on stream stream flows and neither planting nor harvesting along stream stream sides increased contaminants In fact not only do plantations improve water quality they also decrease evapotranspiration overall for the the the adjacent pastures “Worldwide it’s recognized that water quality coming out of farmed areas both cropping land land and and and grazing land land presents water quality problems A very sensible
sort of of solution is to to keep the the the stock out of of the the the stream or or manage the the the sediments that might be washing off the cropland soil by having a a a a a a a a a a stream stream side side buffer also called a a a a a a a a a a a a stream stream side side management zone or area “You need a a a a a a a fence to keep the stock out as as well as as vegetation in that that space and and surface roughness to capture any overland flow that’s coming off the the upland areas o of the the farm If you you can do that that it is well known worldwide that that you’ll see water quality improvements ”
Applying the research locally
Dr Smethurst
explains how he set up his research experiment by looking at at two different farms in in Tasmania
What he discovered surprised him “We chose to work at at low-input extensive agriculture sites where
it it would be easiest to to detect an an increase in in in contaminants due to to forestry “Concerns were mainly around doing plantation forestry forestry right next to streams “Plantation forestry forestry involves some soil disturbance at at both the harvesting stage when
you you actually have a a a a a a a a a a a plantation to harvest and whenever you you establish a a a a a a a a a a a new plantation So cultivation and harvesting are the main disturbances that present risks to stream stream water quality when
using streamside zones of of plantations We We focused on on on on both of of those phases “We did the the plantation establishment phase on on the the the Willowbend Farm in the the the south of the the the state with Chris White and Private Forest Tasmania
We also studied water quality during harvesting of a a a a a a a a a 20-year-old plantation that was right next to the the Pet River which is part of of the the the the Burnie water supply in the the the Northwest of of the the the state ”
“But what we we actually found were further improvements to water quality by using streamside management zones containing plantations despite disturbances during both plantation establishment and harvesting “We saw no increase in in sediment delivery to to the the the stream compared
to to the the the the other sorts of practices that were going on around the the the farm which are most importantly roadside drainage and direct stock access Both processes lead to to water contamination ”
Water quality improvement Drawing conclusions from his research Dr Dr Smethurst
explains that if all farmers were using trees for water water quality quality management drastic improvements to water water quality quality could be made on-farm and for the broader community treealliance com au 51