Intensive rural industry is developing rapidly in parts of inland Australia. The usually nutrient and salt rich effluent from these sources has traditionally been disposed to both land and water bodies. Since direct water discharge is no longer permitted, a challenge now exists when applying effluent to land especially where the rate of application exceeds crop requirements. Effluent of high volume and concentration of nutrients and/or salts can easily contaminate land and water resources. Predicting the optimum rate of land application of effluent is complicated by the physical, chemical and biological properties of soils.
This paper addresses the characteristics of effluents from various intensive rural industries and their potential environmental impacts when irrigated to agricultural land in New South Wales, Australia. To assess the environmental sustainability of effluent reuse in land application, a mathematical model (ERIM) has been developed based on a monthly water balance. ERIM includes historical rainfall and evaporation; the amount of nitrogen and phosphorus introduced; their yearly removal by plants to be grown; amount of applied organic matter; and water holding capacity of soil.