Release of phosphorus from sheep faeces on grazed, hill country pastures

Abstract

The breakdown of sheep faeces enclosed in mesh bags and placed on 3 slopes of varying steepness on grazed hill country was monitored in both winter and summer. Samples had completely decomposed within 28 days in winter, but lasted for over 75 days in summer. The rate of breakdown was most rapid on the flat camp site areas and slowest on steep slopes. The concentration of both total phosphorus (P) and water-extractable P in the dung samples remained relatively constant with time. Thus the major mechanism controlling movement of P from faeces into the soil was the rate of physical breakdown of the dung rather than the leaching of P from the dung sample. This contrasted with laboratory studies which demonstrate a high water-extractable P content in the dung samples at all stages of the trial. There was no detectable increase in water-extractable P levels in soil samples collected from immediately beneath the decomposing dung.

Keywords:

• phosphorus
• sheep
• faeces
• hill country
• decomposition
• leaching