PhD: Reduction in diffuse phosphorus loss from dairy farms

Brad Harrison Picture For Umbraco


 Research Partner: University of Reading

 Start and End Date: February 2018 - February 2021

 PhD Student: Brad Harrison




Identification of barriers to and facilitators for reducing phosphorus losses from UK dairy farms

In recent years diffuse phosphorus (P) loss from concentrated animal holdings has received great attention as a major contributor to water quality degradation and reduced aquatic biodiversity (i.e. eutrophication). In the UK a decreasing trend in P fertiliser use associated with increasing inputs of manure P indicated that reducing manure P output could minimize P oversaturation in soil and subsequently P loss to watercourses. Since faecal P content and feed P supply in dairy cows are highly and positively correlated, reducing P overfeeding could reduce manure P input into soil. However, a recent AHDB-funded survey of UK dairy farms identified that we are feeding more P to our cows than the amount recommended for optimum production and performance. With no proved benefit of P overfeeding and obvious negative consequences of excess P in manure, we need to ask the question ‘why are we overfeeding P?’ Therefore the current project firstly aims to identify the barriers to reducing P overfeeding in dairy cows.

The UK dairy production is seeing increased P import as concentrate feed and greater concentration of production per unit of land available. This combined with previous heavy fertiliser application and associated legacy P, creates challenges for the appropriate use of P-dense manure and aggravates spatial imbalances in soil P status. The issue of on-farm P surplus and subsequently environmental P loading could be tackled by developing and implementing management strategies to improve P use efficiency on dairy farms. This project aims to assess on-farm P budget and identify management strategies to improve on-farm P use efficiency.

The results from this project will contribute towards developing guidelines for best on-farm P management strategies. It will also guide the focus of future research by highlighting the barriers we need to overcome to achieve precision P feeding on UK dairy farms.