Water erosion is a challenge faced by the modern farmer but the costs of preventative measures to halt the loss of topsoil has been investigated in a new trial recently completed by NRM North.
Four plots of paddocks at Weetah were subjected to the trial between June and September, over the winter and spring months, with each of the plots under a different preventative measure.
NRM North land program manager Adrian James said this year had seen a reasonable dry winter and spring but erosion was still present across all three plots.
"The results were very interesting considering we didn't have as much rain this year, each of the plots still did see topsoil loss, which would have been exacerbated."
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The plots were under different intervention conditions: bare fallow, re-sown withe grass as a sacrificial cover crop, deep-ripped with a single line across the contour and ripper-mulched across the contour.
The area used was previously in a pasture phase and was described by the owner as highly erodable.
Bamboo pegs were used to measure the expected erosion by being inserted into the plots at 50cm intervals across the slop at the level of the existing soil.
The bare fallow paddock lost 65 cubic metres of soil per hectare, the mulched rip lines lost 63 metres of soil per hectare, deep ripping lost 59 cubic metres of soil per hectare and cover crops lost 40 cubic metres of soil per hectare during the trial months.
Mr James said in conjunction with the erosion data collection, the trial also aimed to provide farmers with monetary information, providing details on how much it would cost to intervene with these techniques and to replace the topsoil loss due to water erosion.
A sacrificial cover crop such as grass was the most cost-effective option; the trial revealed it would cost $1831 per hectare factoring in the cost of the crop versus the loss of the topsoil.
Mr James said he did not believe a trial that included the calculated cost of intervention had been done before but the work did build on a similar trial conducted about a generation or so ago that measured the loss of erosion using sediment traps.
"This trial is being done for a new generation...the message we want to send is that it might cost money to do things like a cover crop but it saves money in the long run," he said.
Ripper-mulcher was the most expensive technique to improve water soil erosion, costing a farmer $2629 per hectare, while deep fallow ($2464) and deep ripped ($2354) cost a similar amount.
"The results indicate that on hilly soil these techniques save money for the long term," Mr James said.
Cover crops were the most effective option by far, the trial result report said there were unresolved issues with machinery, seedbed tilth and decomposing plant matter that made subsequent fine-seeded crops a challenge.
"Each production system has its own challenges and options. Where producers understand the scale of their problem and associated costs, they can identify the best solutions for their circumstances. There are ways and means to reduce erosion in any circumstance," the report said.
Farmers attended a soil erosion trial end of results day at Weetah on December 3.
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