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Soil microbes & carbon for compost amended dairy pastures

Soil microbes & carbon for compost amended dairy pastures

  • Author: SWCC
  • Date Posted: Jun 13, 2016
  • Category:

Project Details

Project Delivery: University of Western Australia

Contact: Wendy Wilkins (SWCC – Bridgetown).  Ph: 9761 4184


Website: SWCC Sustainable Agriculture

Start Date:  May 2016                     End Date: Sept 2017

Site ID:  IN2.1.013

Size Are Ha: 12

Project Aim

The project’s aims are to compare different composts (compost produced on-farm dairy and commercially produced compost), manure (manure/effluent) and synthetic fertiliser treatments on three WA dairy farms in collaboration with a three-year study funded through current SWCC Project IN2.1.002. This project is also a continuation of an identical project that occurred from May 2015 to April 2016, and will enable longer analysis.  Value will be added by evaluating soil biological processes associated with soil carbon storage in these pastures receiving different fertiliser inputs including synthetic fertiliser, dairy effluent/manure, dairy compost (windrow system prepared by dairy farmer) and commercial MAF C-WISE compost (made from different waste streams). The fertiliser, composts and manures are already being characterized in terms of nutritive value as part of Project IN2.1.002. The project will determine whether applying compost to land promotes soil carbon and its associated microbes (community diversity, resilience, population size). Soil microbial community diversity will be determined using community profiling techniques (pyrosequencing or ion-tag sequencing of amplicons generated from the V4 region of bacterial 16S rRNA genes).

The project’s objectives are to quantify:

  • microbial dominance associated with soil carbon retention in three dairy soils in response to compost application under field conditions; and
  • microbial dominance associated with soil carbon retention in three dairy soils in response to compost application under controlled glasshouse conditions.


Soil carbon is an important issue in south-western Australia and it will become even more important with projected reductions in rainfall and increasing temperatures. The need to build and retain carbon in soil has many benefits in this environment for sustaining high quality agricultural productivity. Current research into the long-term addition of organic amendments to soil have been shown to improve carbon storage and nutrient availability, crop yield, soil microbial diversity and function, and soil resilience to heat and drought stress.

Dairy effluent and manures contain significant amounts of carbon and essential plant nutrients but these nutrients are often in a relatively dilute form making the transportation of large volumes of organic matter impractical and uneconomical. Low-cost composting technologies, such as, the Mobile Aerated floor (MAF) system being used at C-WISE converts different forms of organic waste material into high quality, carbon–rich, concentrated, balanced fertiliser/soil improver that have a higher economic and agronomic value and are easy to handle and transport. The MAF system requires minimal space and operational management (limited turning/machinery), making it a very attractive option to dairy farmers.

Soil organisms are involved in soil carbon transformations in soil. These processes are important for increasing and retaining soil carbon, but some are also involved in loss of soil carbon. Soil microbial communities respond to the addition of organic matter such as compost, and they play a role in the incorporation of carbon from compost into soil. Soil organisms also play a role in the breakdown of organic matter in soil and the balance of these processes leads to either the retention or loss of soil carbon over time. Compost addition to soil is expected to positively support soil microbial communities and contribute to resistance and resilience of the soil community.  Resistance is the ability of the microbial community to maintain its structure, and resilience is the ability of the microbial community to respond to severe impacts or disturbances.

Analysis on soil carbon is based on recent comprehensive evaluation of methodology and analyses.

To exploit the opportunity of on-farm composting of effluent on dairy farms, we will evaluate and quantify the extent to which composting enhances soil carbon and identify soil microbial processes associated with soil carbon retention following application of soil carbon.

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“Composting manure” by Prof Lynette Abbott & Sasha Jenkins – Farm West News – May 2016, p12


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