Yen-Yiu Liu (PhD Student)
University of Queensland

Project title
Effects of land application of contaminated effluents on soil propreties and the size, activity and diversity of soil microbial communities.

Start date
July 2008

Biography
In 2005 Yen Yiu graduated form Bachelor of Biotechnology from Queensland Univeristy of Technology and in 2006 she graduated from Bachelor of Applied Science (Hon) from the University of Queensland. Her honours project invovled studying the application of differential scaning calorimeter in determing heat resistance of bacterial spores. After graduation Yen-Yiu worked in a quality control laboratory in a pharmaceutical company performing physical and chemical analysis of pharmaceutical products.

Project details
The project investigates the long-term (>10 y) and shorter term effects of land application of dairy factory effluent, meat processing effluent and other effluents (e.g. Pulp and Paper industry effluent) on soil quality. This includes effects on salinity/sodicity, organic matter status and the size, activity and diversity of the soil microbial community.

Despite the importance of the dairy and meat producing industries to Australia and the widespread irrigation of liquid wastes to land (particularly under pasture), there is little information about changes in soil properties under long-term irrigation with effluents. The objective of this study is to investigate how the chemical and physical properties of soils have changed and more particularly how this has effected the size,activity and diversity of the soil microbial community. Within one type of factory (e.g. dairy factory) the nature of effluent can vary greatly depending on the main end products produced (e.g. milk, butter, cheese, milk powder) as well as operational parameters at individual factories. Thus, the effects on soil microbial activity are also likely to differ.

Previous work in New Zealand has shown the effects of dairy factory effluent application can involve a downward movement of organic matter in the soil profile (due to the caustic nature of some effluents), accumulation of organic matter and microbial activity (especially in high C effluents), increases and/or decreases in soil enzyme activities, some increases in soluble salts and sodicity, increases in pH and increased pasture growth. No such studies have been carried out in Australia so effects on Australian soils are unknown.

The project will involve identifying paired sites around (a) dairy factories and (2) meat works where effluent and no effluent has been applied. Fields close to the factories which have a known history of effluent apllication (5-10 y or more) will first be identified. A “non-irrigated” control will be identified closeby which has had no effluent application. For each soil, matched sites with comparable profiles will be selected (same soil type, same land use, comparable land use history prior to effluent irrigation, vegetation, slope, elevation,land form, parent material and drainage class). Four replicate plots will be set up at each of the sites on irrigated and non-irrigated fields. Twenty soil cores (0-10 cm) will be taken per plot, devided into 0-5, 5-10, 10-15 and 15-20 cm depths and bulked. Measurements to be made will include: organic C, total N, soluble C and N, microbial biomass C and N, basal respiration, metabolic quotient, catabolic diversity, enzyme activity, exchangeable cations and extractable P, NH4 and NO3. In addition , other measurements such as bulk density, infiltration capacity and earthworm numbers may also be made. The effects of effluents from various factory types will then be determined. Other methods may also be used to measure the structure of the soil microbial community including PLFA profiles and molecular techniques (e.g. PCR-DGGE).

Subsequent experiments may involve application of selected, collected effluents to soils in laboratory and greenhouse studies to further understand their effects on soil microbial activity in the short term.