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Title: Investigation into the fate of nutrients and crop growth following application of sewage sludge to land
Author: Collins, O. J.
Awarding Body: Cranfield University
Current Institution: Cranfield University
Date of Award: 1996
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Investigations into nitrate leaching from sludge and sludge injection into grassland have been undertaken for many years, however phosphate leaching from soils and shallow injection of sludge into grassland are relatively new ideas. This lysimeter study sets out to investigate the influence of the type of slurry and application rate on the amount of phosphorus and nitrogen lost by leaching. The field trial assesses the influence of application methods on grass yield, sward damage and ritrogen loss by leaching through analysing the effects on a grass crop using two different methods of injection and comparing them with surface application and granular fertilizer. Losses of P from sandy loam soils were found to be minimal therefore contamination of groundwater is thought to be unlikely. Similar leacling patterns were observed from both the cake and liquid sludges at all four rates_ applied, however the liquid sludge released more phosphate than the cake sludge, resulting in higher concentrations recorded. The lysimeter study also found leaching losses of ritrate from both sludge types to be well above the EC maximum permissible level of 11.3 mg nitrate-N l`l at all four rates. Residual N from the previously cropped soil masked the nitrate concentrations during the initial stages of the study. Losses of N from the cake sludge was lower than from the liquid treated plots due to slow release. It was also found that environmental factors such as high temperatures and rainfall influence nitrate leaching. The field trial analysed various disposal methods in terms of nitrate leached, crop yield and sward damage. N losses from shallow injection were reduced compared to the deep injection plots, as the sludge was placed in closer proximity to the crop roots. Olibhe Collins, Silsoe College, 1996. In overall terms the shallow injection system yielded the greatest quantity compared to surface applied or the inorganic fertilizer. Damage caused by the tines during shallow injection was not evident compared to the deeper injection system where sward damage and dieback was considerable. The results from the field trial indicate that the shallow injection of sewage sludge has proved to the most environmentally friendly method for the disposal of sludge to farm land.
Supervisor: Hann, M. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available