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Value of Cattle Manures
NRM Laboratories have reported on the mean average and range of N, P and K nutrient values in cattle manures and slurries, based on samples going back to 2011.
Importantly, their results reiterate variability between manures, and the influence of factors such as application method and timing on nutrient value. The analysis includes a breakdown of how nutrients are supplied to current and future crops in year one (present) and two, and reports on N use efficiency.
An example for grassland in a 2-cut scenario, based on broadcasting 25t/ha of 23.9% DM FYM in mid-February amounted to a potential fertiliser value of £141/ha. Much of the fertiliser value is gained from the P and K supplied, with 86kg/ha total P2O5 and 197kg/ha total K2O, providing all of the P and K required for two cuts at the adequate soil indices in the example. A modest amount of available N is also supplied, 15kg/ha in the first year with a further 5kg in the following year, which also offsets some fertiliser requirement.
More information for nutrient planning for silage is available from The Fertiliser Manual (RB209) here
Considering the relationship between slurry DM and nutrient value, one example the report provides is that a 50 m3/ha application of 10% DM slurry, applied in mid-September by trailing-shoe and ploughed-in in a winter wheat scenario was calculated to be worth £124/ha, but reduced to £61 for 2% DM slurry, as the same volume of a more dilute slurry contains less nutrient. Given this variation, its vital to factor in the wetness of slurries when planning nutrient supply. If you are not getting slurries analysed or using an on-farm DM meter, guides such as the images in Think Manures are useful for estimating DM, whilst the Farm Crap App may also be suitable for some users (Android or Apple), both are available on the SWARM Hub here
NRM used MANNER NPK to calculate the financial values, software which is freely available here
The full report is available here
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