British farmers could save millions of pounds a year by regularly analysing their slurry and manure, according to a recent review carried out by NRM Laboratories. With nearly 90 million tonnes produced on farms every year the average value of nutrients supplied by livestock manures equates to almost £304 million a year – but nutrient contents can vary significantly, underlining the value of laboratory analysis for accurately predicting manure nutrient supply.
The Bracknell-based firm, which carries out a significant proportion of the UK’s agricultural analytical tests, examined the nutrient content of thousands of samples analysed since January 2011. “The range between samples is staggering,” says Managing Director Nigel Patrick. “Farmers might rely on ‘typical’ figures such as in the Fertiliser Manual (RB209) when estimating the nutrient value of organic manures, but our analysis shows that they could be way off the mark.”
RB209 guidelines put the typical nitrogen content of cattle farmyard manure at 6kg/t, with phosphate and potash at 3.2kg/t and 7.2kg/t, respectively. But NRM’s analysis reveals that nitrogen contents in cattle FYM ranged from 1.3kg/t to 32.6kg/t, phosphate contents from 0.5kg/t to 21.9kg/t and potash from 0.2kg/t to 35.0kg/t. “When looking at crop-available nutrient levels, the value of that manure could be anywhere between 44p/t and £28/t,” says Mr Patrick. “This means that farmers could either be under-supplying crop needs; and thereby hampering yields, or over-fertilising and wasting both money and precious resources, while increasing the risk of nutrient losses to the environment.”
Similar results can be seen in livestock slurries as well as in solid pig and poultry manure. “In fact, the range in broiler and turkey litter is even greater than in cattle manure, with a £54/t difference in value between the highest and lowest samples,” he adds.
Nutrient levels can vary according to the dry matter content of the manure and the way in which it is handled, he explains. “Readily available nitrogen such as ammonium nitrate-N and uric acid-N is particularly susceptible to loss through leaching or volatilisation, so storage, management and application practices will have a significant impact on the ultimate value of your manure.”
The mean value of an autumn application at 50m3/ha of pig slurry to winter wheat has been estimated at £161/ha, with the same application of cattle slurry worth £124/ha – although those figures will vary depending on the actual nutrient content of the muck. However, manure only carries a financial value if the soil and crop require the nutrients, warns John Williams, Principal Research Scientist at ADAS. “It’s therefore important to match crop requirements with the nutrients present in your soil and manure before drawing up a nutrient plan.”
Unfortunately, only a very small percentage of the nation’s farmers analyse their manure, so the potential for improvement is vast. “Inorganic fertilisers are expensive – and when over-used can be damaging to the environment – so no farmer would willingly apply too much to their crops,” says Lord Curry, chairman of NRM, one of the divisions of Cawood Scientific. “But by not analysing their slurry and manure, they could be doing exactly that. This research is a real wake-up call to the industry: Manure is a valuable resource and we’ve got to start treating it as such. It really does confirm the old adage; where there’s muck there’s money.”