Nutrient Budgeting as an Approach to Assess and Manage the Impacts of Long-Term Irrigation Using Abattoir Wastewater

Disposal and management of abattoir wastewater have been a long-term concern in a high meat-consuming country like Australia. Land-based application of wastewater is considered to be the most economically viable disposal method and is widely used by abattoirs. In this study, we assessed the effects of long-term abattoir wastewater irrigation on soil physical and chemical characteristics of calcareous soils. Soil samples were collected from 16 different locations with seven 5 cm depths intervals down to 35 cm. Soil properties including soil type, bulk density, moisture holding capacity, pH, electrical conductivity (EC), nitrogen (N), phosphorus (P), carbon (C) and micronutrients were measured. Soil characteristics were compared with non-irrigated soils. The study area receives annually about 327 ML of wastewater with high concentration of N and P (186 and 30.4 mg/L). Overall, the site retained 0.6 t N/ha, 0.1 t P/ha and 0.4 t of K per hectare. Irrigation for over a decade onto the study site has caused a significant change in the soil fertility. Soil total N was increased by 82% compared to non-irrigated. Similarly, soil total P concentration was increased more than sixfold. The overall results showed that the abattoir wastewater irrigation to soil caused very significant changes in soil nutrient levels. These changes indicate need to recapture the surplus nutrient, in particular N, to avoid potential leaching and off-site effects.