Determining manure deposition in free range sheds and free range areas

Poultry farmers have an environmental duty of care to manage manure nutrients to minimise the risk of environmental impacts. Previous research on free range farms showed that nutrients are concentrated within a short distance (0–10 m) from sheds despite birds having the opportunity to range much further (Wiedemann et al. 2018). This manure distribution pattern interacts with site features (such as climate, soil profile, ground water depth and distance to waterways) to determine the risk of nutrient loss.

Accordingly, the objective of this research was to determine manure nutrient excretion in a free range shed via mass balance. That is, to predict manure nutrient excretion in the range area by the difference between predicted nutrients excreted by the bird and measured nutrients deposited in the shed.

Using the results presented in this report, it is relatively simple for industry to estimate the deposition of manure in range areas. The rates and masses of nutrients excreted in the range area were consistent with previous observations of ranging behaviour and international research, which supports the continued use of current industry practices for managing nutrients in range areas. The findings of this research should be used to update the next edition of the industry environmental guidelines, particularly the observation of unexpectedly high manure ash and silica concentrations and their potential implications. The inferred rate of soil transport out of the range and into the shed has potential implications for range management