Comparisons between applied biosolids and inorganic fertiliser under canola production in a red Dermosol in northeast Victoria, Australia

Management of biosolids is a major environmental issue for Victoria. In 2003, VicWater (a consortium of water authorities in Victoria) and the Victorian Department of Primary Industries (DPI) established a 4 year trial investigating applications of biosolids at Dookie in northern Victoria, to address the issues of metal contaminants and nutrient bioavailability in soil amended with biosolids. Data from the Dookie site is contributing to the CSIRO coordinated National Biosolids Research Program (NBRP), where similar field experiments are occurring around Australia. Biosolids are rich in organic matter and essential plant nutrients, and thus are useful amendments in agriculture. However, biosolids can contain significant amounts of pathogenic microorganisms, metals and other chemical residues that can cause toxicity in plants and animals if they are inappropriately processed and recycled back into the environment. State and Federal regulatory agencies have released draft guidelines for sustainable reuse and land application of biosolids; both documents provide biosolids classification and ceiling levels of nutrients and contaminants. One of the aims of the NBRP is to determine if these ceiling levels could be better adapted for local soil environments. This paper reports the effects of land application of biosolids from two urban water authorities on canola production and soil N and P status in an acid soil in north east Victoria. Canola grown in soils treated with increasing rates of biosolids produced equivalent or better yields than conventional fertiliser. The overall difference between the biosolid treatments and the fertiliser control was significant for two sources of biosolids for canola oil seed yields and soil Colwell P at the end of the first cropping season.