Early users of slurry treatments in the 2000s were farming’s natural experimenters, prepared to try something interesting and see what happened. Often, they were pioneers of ecologically balanced farming.
As these farmers saw results and shared what they’d found with others, they were followed by those with a serious problem to solve— in particular, either mega-crusting or under-slat storage full of solid material that had defied all previous efforts to clear them.
Today, of course, the ecological balance is making a comeback in mainstream farming. Together with clear evidence of hard cash savings from integrating treated slurry with bought fertiliser, this is leading to many more farmers asking for the treatment process to be explained before they decide whether to take the plunge, claims Liz Russell from Envirosystems.
“When slurry separates, the crust consists of mainly of undigested feed,” she explains. “This comes about because cows eating a 70% D-value diet, for example, are unable to use the 30% indigestible portion. If they’re eating typically 20kg the faeces of each cow or 180kg/cow/month. For a 100 cow herd that amounts to 18 tonnes of dry matter, and future crust, every month.”
One of the main components of this crust is cellulose, a large indigestible molecule formed of many small carbohydrate molecules (circled), linked together into a strong chain.
By treating slurry with a culture of live bugs, selected for their ability to break links in the chain, the small digestible carbohydrates back into the mass of slurry, and provides a rich energy source for the bugs, fuelling the whole fibre breakdown process.
“Of course, this is not an overnight process,” says Liz Russell. “Farmers employing Mother Nature’s army of slurry bugs need to be patient during the early stages before progress can be seen at the surface.
“The bug culture actually works on the crust from underneath, so early progress is invisible. After a time, depending on crust thickness, the bugs breakthrough. You can then see gentle bubbling on the newly exposed liquid surface, which gradually expands as crust islands shrink.”
The types of bugs selected for slurry treatment originate naturally in soil. The specific strains are proven to be prolific producers of heavy-duty enzymes, which in slurry act like heavy-duty molecules from where they were previously locked into long indigestible chains.
In addition to using the released carbohydrate for energy, Liz Russell says it is likely that slurry bugs also mop up ammonium NH4+ (dissolved ammonia), and probably sulphur too, for protein synthesis.
“What cannot be disputed,” she argues, “are farmers’ observations. They report that treat- slurry. And analysis before and after treatment shows consistent increases in nitrogen fertiliser value.
“Farmers report how treated slurry is easy to handle can be pumped long distances through pipelines, and is absorbed quickly into the soil. And that it grows big crops of high palatability grass for silage or grazing.”
Potential cash savings
It costs £41.49 an hour to hire a driver and 151hp to 220hp tractor, according to the National Association of Agricultural Contractors. So by reducing by just one day the time required to stir a slurry store would save about £340—maybe more if the contractor also supplies the stirrer and the farmer the diesel.
Of course, if the farm’s own machinery and workforce do the work, the savings might be a bit less—but probably not by very much. Either way, there’s clearly money to be made by making slurry easier to handle.
One farmer proving this is Paul Jenkins in Pembrokeshire. Using bugs to help disperse most of the crust (see pictures below), he says and he’s reduced blockages are also much reduced, he adds. “If you are still not convinced of the benefits then ask farmers already using slurry treatment how they get on,” adds Liz Russell, who says that names and numbers are also available from Envirosystems.”