Soil Science


Biowaste comprises unwanted material of biological origin, such as biosolids. Biowaste can contain high concentrations of organic matter and plantnutrients, making them valuable soil conditioners. However, biowaste can also contain pathogens and contaminants that present a risk to humans and ecosystems. Inappropriate disposal of biowaste is expensive and environmentally damaging. When correctly applied to degraded lands, biowaste can create both economic and environmental value.

The soil science branch of research investigates the effects on soil health and groundwater quality from biosolids land application, and develops sustainable management practices to best reuse biosolids, enhancing soil integrity for future generations. They also look into greywater re-use and its effects on the receiving environment as well as the risk to human health. Examples include:

  • Monitoring soil health indicators such as enzyme activity, biomass respiration, pH, metals.

  • Using molecular ecology techniques to monitor changes in soil microbial communities.

  • Assessing the carbon and nitrogen transformations and storages in soil and tree biomass when biosolids are applied to forested land.

  • Investigating the effects of native plants such as mānuka on soil health, including the effect on nitrogen movement in soil and groundwater.

Another method of looking at soil health are lysimeter studies. Lysimeter's contain intact soil cores collected from the study environment. These lysimeters then serve as a small-scale field replication to observe how soil health changes when irrigated or fertilised with various forms of wastewater effluent, greywater or biosolids. The lysimeters receive measured amounts of irrigation, rainfall, and effluent. Lysimeters drain into a container allowing regular determination of the leaching volume, chemical composition, and pathogen load.

The soil core itself can be destructively harvested to assess potential chemical and pathogen contamination within the soil and particularly within each soil horizon to further understand natural attenuation within soil. 

Alternatively, plants can be grown in small lysimeters to study the effect that plant growth has on soil biochemistry when soil is exposed to biowaste.


Above: Diagram of a standard lysimeter set-up.