A comparison of surface applied granulated biosolids and poultry litter in terms of risk to runoff water quality on turf farms in Western Sydney, Australia

Abstract

A simulated rainfall study was carried out on couch ( Cynodon dactylon cv) turf on a Haplic Lixisol soil at Camden in South Western Sydney, Australia, to compare surface applications of a new granulated biosolids product with poultry litter (the current turf farm practice) in terms of runoff water quality impacts. The granulated biosolids were surface applied to the turf at a total N loading of 240 kg N ha −1, equivalent to the current turf farm practice of applying 18.9 m 3 ha −1 of poultry litter. One week after the application of the organic fertiliser treatments, simulated rainfall was applied to each plot at an intensity of 90 mm h −1 for a period of 0.5 h, and all runoff water was collected and analysed for a range of important water quality parameters. The most significant result from this study was the finding that runoff water samples from the poultry litter treatment plots were found to contain 10 times more total P (12.3 mg l −1 compared to 1.2 mg l −1) and dissolved P (8.3 mg l −1 compared to 0.6 mg l −1) than that found in the runoff water samples from the biosolid treatment. The relationship between application total P loading (TPA) and runoff water total P concentration (RO-P) was significantly ( P < 0.05) different between the biosolids (RO-P:TPA ratio = 0.01) and poultry litter (RO-P:TPA ratio = 0.16) products, reflecting the importance of the chemical nature of the applied P in addition to the total loading. The phosphorus in the poultry litter was much more easily mobilised and transported in runoff than the biosolids P. For surface applications of these organic wastes, bicarbonate extractable P loading provided a better indication of runoff P contamination risk in the first flush of runoff, than total P loading. The runoff from the biosolid treatment plots also had lower levels of NH 4-N and salinity than the poultry litter plots, although both treatments had moderate levels of dissolved organic carbon in their runoff. Heavy metal levels in the runoff were below guideline limits for both organic amendments, while runoff pathogen levels were highly variable. Our findings highlight the potential benefits of using granulated biosolids as an alternative surface applied organic N fertiliser on turf farms for its lower risk to surface water quality as compared to poultry litter, the current practice.