Nine-out-of-ten UK dairy farms are thought to be missing out on boosting the value of slurry at minimal cost. Among progressive RABDF members, of course, the picture is probably not this extreme. Nevertheless, there’s a long way to go before producing ‘microbe enriched’ slurry is widespread even among this enlightened group.
As long ago as 2011, independent research by Kingshay found that treating slurry with five different forms of slurry bugs increased total nitrogen by about 14%. For ammonium (NH4), which is readily available for plant uptake, the average was 12% higher than untreated. In both, these differences were statistically significant. The launch at 2017’s Grassland Event of AHDB’s updated Nutrient Management Guide (RB209) heralded a renewed focus on making best use of home-grown organic fertilisers.
Right now, Liz Russell from Envirosystems says exploiting the full plant nutrient content of slurry for silage crops and grazing alike can help reduce fertiliser costs markedly. “One early adopter we know in north west Lancashire reduced their bagged-N use from 270 to 150kg/ha,” she says. “Financially, this saves £80/ha and a five-figure total annually.
“In addition, microbe enrichment reduces odours, digests stubborn crusts with minimal mechanical stirring, and inhibits new crust formation.
“This is due to trillions of friendly bacteria that digest slurry’s fibre content, which otherwise floats to the surface and forms a crust. These bugs utilise nitrogen and sulphur, for example, converting them into available plant nutrients.”
The Kingshay study also found that treatment increased the ratio of aerobic-to-anaerobic bacteria in slurry. Liz Russell says this makes it more friendly to soil microbes and thereby better for earthworms, soil health and productive capacity.
“For anyone thinking about trialling slurry bugs, this is a good time of year to start,” she explains. “In slurry stores less than half full, warmer weather gives bugs a chance to make a rapid visible impact, with the resulting material available for after-cut use this summer.
“For maximum value and compliance with environmental limits, AHDB’s RB209 explains how to incorporate enriched slurry’s nutrients into fertiliser plans,” Liz adds. “To gauge the contribution of plant nutrients, we recommend and can provide laboratory analysis.
“Amid the uncertainty that surrounds dairy farming right now, here is a way to make better use of material that is available in large quantities, and is already bought and paid for.” In 10 years time, this microbial revolution might just have become mainstream. Where innovative RABDF members lead today, others will surely follow…eventually.