A BALMORAL farmer has turned to the Glenelg River for an unlikely source of fertiliser.
Justin Weaver has started using carp as organic fertiliser as a way to improve his soil health, while reducing pest numbers in the region.
The Balmoral property consists of about 80 per cent cropping, with some sheep as well.
"We also do a lot of contract sowing in both autumn and spring," Mr Weaver said.
Last summer, Mr Weaver was at a Vic No-Till Association field day at Rupanyup, which focused on liquid fertilisers.
He said from there, he realised how easy it was to make fertiliser and started researching it some more.
"I started chatting to Steve Ryan from the Glenelg Hopkins CMA, who is a mate of mine, and I mentioned this field day and he suggested we catch some carp and have a go," he said. "So from that thought bubble, it turned into a pilot project."
Mr Weaver said over time the idea had snowballed.
"We don't know whether it's going to be a silver bullet - it's not going to change the world but it's something we can do," he said.
"It's a way to get carp out of the river, make something useful out of them that's cheap and effective, and make us a bit more sustainable at the same time.
"And it's not that hard - we were amazed by how simple the whole process was."
Mr Weaver started working with Dion from Austral Fisheries to catch the carp.
"We use electrofishing, which is a good way to catch a large amount of carp in a short period of time," he said.
"We got Dion from Austral on board, who also wants some fertiliser for his garden.
"Dion as worked across waterways all around Australia and he hates carp with a passion - he is sick of death of pulling carp out of waterways when he is looking for native fish."
After the fish are caught, they are then put into a large garden mulcher.
"It's a mulcher that is definitely not going back into the garden after this - the smell is not pleasant," Mr Weaver said.
"It's a bit confronting to put carp into the machine and see mince come out the bottom."
The mince is then put into a drum and mixed with water, molasses and a bacterial inoculant.
The drum is sealed, but carbon dioxide is able to escape.
It sits for a few months and the bacteria breaks down the protein and fatty acids in the fish.
Mr Weaver said it was very similar to brewing beer, so he named the fertiliser Glenelg River Bitter.
"After a few months we then strain it so it is a liquid, then we put it in a spray bottle and put it out on the pasture," he said.
The project is still in its infancy.
"We have stumbled along the way and we are still working out dosage rates," Mr Weaver said.
"Once you go looking, there is quite a bit of information out there - the Koreans have been doing this for hundreds of years.
"Trying to incorporate it into our system is the tricky part - working when to apply it and what to apply it to.
"We are having fun though."
Mr Weaver said the fertiliser didn't smell once it had fermented.
"However, we had one batch where the drums didn't seal as well as we had hoped and that was a rather smelly process," he said.
"That's when the smell really hits you - when something goes horribly wrong."
Mr Weaver said to fill one 200-litre drum, he needed about 80 litres of carp mince.
"That's about 20 to 30-odd big carp," he said.
The project has gained quite a bit of interest already.
Mr Weaver said he had been contacted by people all over wanting to be involved.
"I've had dairy guys getting in contact, wanting to know if they can do some trials," he said.
"I've had a couple of soil ecologists, one from New Zealand, get in contact - the amount of information we've been able to get and the assistance we've received has been fantastic."
Mr Weaver said the best part of the project was getting carp out of the river.
"Every little bit help. Carp are really lazy in the Glenelg system, they tend to be in groups and they don't move around a lot," he said.
"The Wimmera system is slightly different - they tend to breed more often and they are different sizes, which makes them hard to catch. One day we were fishing for about three to four hours in the Glenelg River and we got a tandem-trailer load of carp, which was a heck of a lot.
"They were all about 40-centimetres long and about three-quarters were female, and every one of them were full of eggs. That was depressing."
Mr Weaver said anything he could do to lighten the load of carp was a good thing.
"I would like to see every farmer along the river fermenting carp so we can take the river-rabbits out of the system," he said. "Even if we are making a small impact, at least it's an impact."
Mr Weaver said he already tried to farm in a regenerative way.
"We are into no-till and holistic management, so this was right up our alley," he said.
"Once we started looking into it, we realised it was really simple, cheap and it could be effective.
"It's something different - if it makes an impact on the river and the farm becomes less reliant on fertiliser, then I've done my bit. There is no downside, except for a pair of overalls that will never go back into rotation - the smell on them will outlast time."