By David Shambrook, Agriculture Victoria dairy extension officer
YOU can use farm effluent, manure and materials such as wasted feed, wood chips, rice hulls, fouled bedding materials and tree prunings to produce compost.
Compost, if made correctly, will allow you to:
• Handle, store, transport and spread organic by-products back to land.
• Recycle high carbon low nitrogen materials back to the land without tying up as much soil nitrogen while going through biological processes.
• Produce a safe, stable soil amendment with slow-release nutrients in organic forms.
• Improve soil fertility, soil structure and general soil health.
If you choose on-farm composting, you need to plan to do the process properly. It requires costly, specialised equipment, an area of land set aside for compost making and storage of materials, and the time to perform the tasks required.
Additionally, the end product will have a lower volume, lower carbon and nitrogen than the original materials with high C:N ratios.
Composting is a biological process, carried out by microorganisms that are naturally present in the environment. Therefore, no special inoculants are required.
You need to provide organic materials in the right proportions, with moisture, and the microbes will do the rest.
Microorganisms have three basic needs and when these are provided, the composting process will proceed, and the mix will heat up as required.
These needs are:
• Oxygen (greater than 5 per cent).
• Adequate moisture (45 to 65 per cent moisture).
• Suitable food supply (material with carbon to nitrogen ratio of 30-40:1).
This is called the thermophilic stage where intensive decomposition of organic residues occurs, reaching temperatures of between 45C and 65C.
The use of a gauge to monitor the temperature and regularly checking moisture content by squeezing handfuls of the material will help maintain appropriate temperatures.
The temperature needs to hold for at least three days to ensure sterilisation of pathogens, diseases and weed seeds occurs.
At the end of this stage, all the readily available organic substrate has been exhausted and the temperature cools down, allowing the compost to cure or mature.
The whole process could take several months depending on how quickly the material heats up and when all the readily available substrate has decomposed.
The whole composting process needs to be monitored, making sure the conditions for the microbes are kept reasonably constant for them to break down the material.
Providing a balance of smaller and larger particle sized materials will allow effective aeration for microbes to access oxygen.
Regular turning of the material for aeration and addition of water to maintain the moisture levels, particularly as moisture is lost in the heating process, will also aid the process.
On-farm production of compost is best suited to the windrow method.
It involves creating windrows of the organic material around 1.5 metres high and 2 to 3 metres wide at the base.
Ideally, the site should have a level compacted surface such as concrete, crushed rock or gravel, or compacted soil.
It allows easier turning of the material and watering, as required, to maintain the temperature within the windrow.
When selecting a site for compost making, also consider the potential for runoff, odour, groundwater reserves and movement of windborne particles.
Before embarking on large scale production of compost, it’s recommended you do a test stack or small windrow, using organic waste materials you have ready access to on the farm.
If you intend to bring in green waste materials for the composting process, you may need to seek Environmental Protection Authority approval.
For more information, visit epa.vic.gov.au/for-business/find-a-topic/agricultural-guidance, plus designing, constructing and operating composting facilities at epa.vic.gov.au/about-epa/publications/1588-1.
If you are considering bringing organic material onto the farm to assist with composting, refer to the information note ‘Compost and farm biosecurity’ on the Agriculture Victoria website: agriculture.vic.gov.au/farm-management/soil/compost-and-farm-biosecurity.
If you are planning to compost livestock mortalities as well as organic waste materials, refer to the information note ‘On-farm composting of stock mortalities’ at agriculture.vic.gov.au/livestock-and-animals/dairy/managing-effluent/on-farm-composting-of-cattle-mortalities.
For more information on composting, contact your local agronomist, reputable compost making advisors, or refer to the information note ‘Composting Spoiled Hay’ at agriculture.vic.gov.au/livestock-and-animals/dairy/managing-effluent/composting-spoiled-hay.