Introducing techniques to prevent soil erosion is a crucial on-farm task, according to a new soil trial by Tasmanian researchers, which estimates that farmers could lose up to $2000 of soil per hectare.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
The informal soil trial was undertaken by the Cradle Coast Authority's Natural Resource Management (NRM) team who partnered with the Tasmanian Institute of Agriculture (TIA) at the Forthside Vegetable Research Station.
Over a period of three months the team used three different techniques to create contour gaps in the soil and attempt to prevent erosion in a commercial five hectare paddock.
The techniques included using a ripper mulcher, a single tine ripper and an agroplow to create accurately mapped gaps, while a fourth section of the paddock went untreated.
Cradle Coast Authority agricultural facilitator Tom O'Malley said the untreated plot of the paddock showed that a possible 41 cubic metres of soil per hectare washed downhill.
"We might get 20 to 30 mills of rain overnight and a good bit of soil gets washed away. The steeper the slope the more speed the water can build up moving downhill. The faster it goes the more soil it takes with it," he said.
"To that end we have put in erosion control treatments across the contours of the paddock, five meter gaps in elevation, so that a portion of the soil that does get washed downhill will get trapped.
"The action of opening up the soil and allowing water to enter the profile along the contour lines reduced surface water runoff, and also the soil which may be eroded along with it.
"The channels or rills in the paddock that were above and below the erosion control measures were counted, and their volume measured, to try to give a sense of how effective the treatments were at reducing the formation of rills and at reducing the movement of soil within the paddock."
Mr O'Malley said that the ripper mulcher and the agroplow both resulted in a 50 per cent decrease in rills, the single tine treatment showed no difference while the non treated area showed a 167 per cent increase in the number of rills.
"The ripper mulcher tows behind a tractor and rips open one single rip line in the soil, and then we stuffed that line with straw, effectively installing a store drain along the contour lines of the paddock. It is quite an effective implement but the agroplow might be more adoptable because you don't need straw, you can do it faster, and you only need one person to operate the machinery," he said.
"The trial presents a couple of control options for farmers to consider using, and shows that doing something to control soil erosion and benefit your farm in the long run is better than doing nothing which will ultimately end up losing quite a lot of soil from your paddock."
He said the trial provided some basic numbers on the potential cost of soil erosion.
"The non treated plot showed up to 41 cubic metres of soil per hectare could be eroded downhill. If a conservative value of $50 per cubic metre was applied to cover cost of nutrients and topsoil, this equates to $2,048 worth of eroded soil lost per hectare in one season.
"Using a ripper mulcher or an agroplow can reduce in-paddock soil movement by 92% and 76% respectively and keep our valuable soil in the paddock where it should be."