In a split field trial in South West Wales, a slurry inoculant, SlurryForSoil, increased dry matter grass yields by 21.5% and fresh grass yields 16.4%, above additional nitrogen.
The trial, hosted by Sion Thomas at Drysgolgoch Farm in Pembrokeshire, saw treated and untreated slurry, together with high (120kg of urea/ha) and average (170kg of urea/ha) rates of urea applied to a 6 year old ley. The slurry inoculant, SlurryForSoil, was applied to the tank eight weeks before spreading.
“We farm 1,200 acres and have a 750 Shorthorn cow herd on an extensively grass-based system,” explains Sion.
“60% of calving takes place in spring, the remaining 40% in the autumn and we average 6,000l/cow, 4.25% fat and 3.5% protein.”
Sion first came across SlurryForSoil through his milk buyer, Leprino.
“We’d no idea whether it would work but were less sceptical once I understood the microbes and their function. The main reason we were keen to trial is environmental. As well as the carbon footprint of the fertiliser, there’s leaching and run off, neither are efficient. Then there’s the cost. Fertiliser prices have risen again and there is talk of taxing them. Anything we could do to reduce our reliance would be a big step forward.”
With two slurry tanks underneath the slated shed, Drysgolgoch Farm was ideally placed to host the split field trial.
“This is the first time we’ve directly compared the impact of SlurryForSoil’s microbes with additional synthetic fertiliser,” explains Romney Jackson, Director of SylgenBio, manufacturer of SlurryForSoil.
“While the soil science tells us that, in comparison with fertiliser, the microbes in SlurryForSoil should facilitate stronger, faster grass growth, these results are astounding.”
SlurryForSoil contains 18 different plant growth promoting bacteria and fungi, each chosen for its wide-ranging abilities to support healthy grass growth – from capturing nutrients within the slurry and transporting nutrients with soils, to inducing plant defences against pests and pathogens.
Throughout the winter Sion was monitoring the slurry and says it was fascinating.
“We could see that the treated slurry was bubbling, where the untreated was not,” he says. “When we started mixing it was clear that the treated slurry was moving quicker and took just 12 hours to mix. We saved ourselves 260l tank of diesel, at 70p per litre, that’s a saving of £182. We typically mix slurry two or three times a year.”
Analysis of the slurry revealed increases in phosphorous and potassium. Romney explains why: “When SlurryForSoil is used for the first time we typically see accumulated sludge being broken down.”
“The notable increase in in ammonium nitrogen is a result of the microbes capturing nitrogen and preventing losses to the atmosphere,” he explains.
Due to the field’s location both the treated and untreated slurry was applied using a splash plate at a rate of 33m3/ha.
“The treated slurry dried a lot quicker,” says Sion. “This potentially means less run off and leaching as well as more nutrients where the grass can use them. The cut off between the two slurry applications was obvious.”
Throughout the spring, Sion kept an eye on grass growth.
“The half of the field that received the slurry treated with SlurryForSoil was more consistent across the field and across the season,” he notes.
Romney explains that it is likely to be the wider benefits of the microbes, not the additional nutrient value they capture, that accounts for this consistent growth and dramatic rises in fresh and dry matter yields.
“In the soil, the bacteria and fungi perform many growth enhancing functions. Fungi are adept at breaking down the toughest of organic matter, lignin. Their mycelium also creates vast networks through the soils profile which the fungi use to transport water and nutrients. Plants are able to tap into this resource and it gives them greater access to the essential building blocks of growth. Bacteria are also highly effective scavengers and further enhance plants’ ability to get what they want and perhaps more importantly, when they want it.”
Although this trial is about the short-term benefits of the slurry inoculant, for Romney, it is the product’s longer-term impact on soil health that is key.
“Those networks together with the metabolic substances the fungi and bacteria exude, hold soil particles together and create the all-important pores. By increasing surface area and allowing water and air flow, the aggregates and the spaces between them simultaneously make soils more resilience to droughts and floods. If this spring is anything to go by, that’s going to become increasingly important.”
By decreasing ammonium losses from slurry stores, reducing the fuel needed to stir and the lowering the fertiliser requirements SlurryForSoil can reduce the carbon footprint of dairy production.
“Getting to net zero requires us to optimise production, and lower our greenhouse gas emissions. It’s not easy but where farmers are looking to push grass productivity, SlurryForSoil is undoubtedly a cost-effective and more sustainable option than using additional urea.”