Myerscough College Trial Data

Slurry Analyses

Background

Myerscough college contains a dairy unit at Lodge farm which houses a 300 cow herd, and has the slurry booster system installed to their slurry lagoon. To test the effectiveness of the SBS in enhancing liquid nitrogen retention in slurry, initial trials were undertaken at Lodge farm that measured the Total Kjeldahl Nitrogen (TKN) of slurry prior to installation of the SBS, followed by subsequent measurements after installation. Furthermore, these measurements were also taken of fresh slurry contained in the slats, representing the total potential nitrogen retention prior to loss of nitrogen in the form of gaseous compounds. The purpose of the latter sample was for comparison purposes with treated and untreated slurry samples. These analyses were carried out at the laboratories of the Environment Agency (EA). Following these analyses, further samples to measure total nitrogen amount per fresh tonne were taken of treated slurry and fresh slurry since TKN does not take into account the nitrate and nitrite content of slurry, both of which are valuable nitrogen constituents. These analyses were implemented at the external laboratory of Natural Resource Management (NRM).

Results

 

The EA TKN results illustrated in graph 1 show the TKN values following various days of application of SBS (blue) compared with the maximum nitrogen available for retention (red), a figure derived from the nitrogen content of fresh slurry. Before installation of SBS a significant proportion of nitrogen has been lost from the initial slurry whilst stored in the lagoon, with just 8.5% of the TKN remaining in the slurry. Following 30 days of treatment with SBS this value had risen to 29% and after 90 days 62%. This signifies a substantial rise in the proportion of available nitrogen retained as a direct result of the action of slurry bugs.

The installation of this system was dated 29^th May 2008 and the first NRM analyses were implemented in August as detailed in graph 2. These analysed the total nitrogen content in kilograms per fresh tonne of slurry as opposed to TKN. Once again these readings were taken at regular intervals and compared to the total nitrogen content in fresh slurry. Since the first reading was taken 3 months after installation the total nitrogen retained was already valued at 52%, but in the subsequent months as illustrated in graph 2 this value rose to 63% and finally 85%. This demonstrated the significant impact of total nitrogen retention in the 8 months following installation of the SBS.