W ith 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 .”
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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 overfertilising 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
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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
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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 .”
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