Applications of biosolids to agricultural soils and their effect on soil biology and chemistry

Milburn, G. (2018) Applications of biosolids to agricultural soils and their effect on soil biology and chemistry. Doctoral thesis, Harper Adams University.

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Approximately 1.05 million dry tonnes of biosolids are produced each year in the UK. Their application to land has the potential to cause not only environmental pollution but result in the bioaccumulation of heavy metals in the food chain. Nevertheless, they are a viable option for crop fertilisation and could contribute to relieving the issues associated with hidden hunger. This thesis attempts to determine if the use of Bestways Fertiliser (granular biosolids) impacts on soil biology or chemistry, through the use of contrasting soils at Broxton Cheshire and Harper Adams University between 2007 and 2014, across a range of combinable and forage crops. Initial investigations focused on the changes biosolids had to metal fractionation within the soils. Sequential extraction procedures were designed to remove elements bound to different factions within the soil. Results demonstrated that biosolids did not increase heavy metals in any fraction of either soil type but did increase concentrations of phosphorus by 214% in the iron/manganese bound fraction. Long-term leaching studies evaluated elemental mobility following biosolids applications. Results showed that long term applications of biosolids increased Copper concentrations in Broxton soils by 110% and 315% in Harper soils. To assess changes in plant-available elemental concentrations, mesocosm studies were investigated together with a long-term field experiment. Mesocosm investigations demonstrated that biosolids could produce similar yields to conventional fertilisers and concentrations in plant tissues (grain) were not raised above those grown with conventional fertilisers. To determine the effect biosolids had on microorganism populations, a twelve-month soil respiration study was investigated. It was concluded that biosolids increased respiration at 100% and 200% application rates, but decreased respiration at 400%. Overall conclusions suggest that the risk to the food chain from heavy metals is low, but the impact of heavy metal leaching rates into ground water must be studied further.

Item Type: Thesis (Doctoral)
Keywords: sewage sludge, environmental contamination, heavy metals
Divisions: Crop and Environment Sciences (to 31.07.20)
Depositing User: Ms Kath Osborn
Date Deposited: 18 Oct 2018 20:42
Last Modified: 18 Oct 2018 20:42

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