The safe use of manure fertiliser

Safe use of manure as fertiliser on a livestock farm

Authors: Dr Hayden Morrow, District Veterinary Officer and Dr John Phelps, Principal Veterinary Officer, Agriculture Victoria.

Livestock manure can provide a valuable and cost-effective source of nutrients and organic matter for improving soil fertility and structure for crop or pasture production. The Environment Protection Authority (EPA) Victoria defines livestock manures as livestock faecal matter including any mixture with biodegradable animal bedding such as straw or sawdust.

In 2021, EPA Victoria introduced Livestock Manure and Effluent Determination (or regulatory standard) detailing the conditions for receiving livestock manures from other properties. Important conditions of this determination are that the receiver must inspect each consignment to ensure it contains only livestock manure and it must only be accepted on-farm for the purpose of application to land as a soil amendment.

Good management practices are needed to gain maximum benefit from the use of manure as fertiliser, while also protecting animal, human and environment health. Inappropriate manure use can have significant animal and human disease risks and cause adverse environmental effects such as soil nutrient imbalances, chemical and heavy metal residues, run-off and ground water pollution and public concerns from dust or odour generation.

Potential Risks

A range of biosecurity/animal health risks need to be managed when using manures as fertilisers on livestock properties. These risks need to be evaluated before bringing manure onto the farm and precautions then need to be taken with manure handling, storage, application and grazing management.

When introducing animal manure there is potential to introduce certain pathogens such as bacteria, viruses and parasites. Examples of disease agents that can be present in different types of manure include Salmonella, Clostridia (including botulism), E. coli strains, Cryptosporidium, Q fever, and Johne’s Disease.

Effective composting can significantly reduce or eliminate many pathogens in manure. However some more resistant pathogens such as Johne’s disease, Clostridia, Q fever and transmissible spongiform encephalopathies (TSEs) including mad cow disease may survive at infectious levels.

When selecting a suitable manure or compost it is important to ask where it is from and whether it could contain ‘restricted animal material’ (RAM) or ‘prohibited pig feed’ (swill). RAM is defined as any material taken from a vertebrate animal other than tallow, gelatin, milk products or treated oils. It includes rendered products, such as blood meal, meat and bone meals, fish meal, poultry meal, eggs, feather meal, and compounded feeds made from these products.

In Victoria it is illegal to feed materials containing RAM to ruminants (including cattle, sheep, goats, deer, alpacas and llamas) or to allow them access to piles of manure containing RAM due to the risks associated with TSEs. To avoid the risk of ingestion, all piles of manure must be stored in fenced off areas to prevent access by livestock.

Where manure containing RAM is spread onto ruminant grazing paddocks, livestock must be kept out of the paddock until there has been sufficient pasture growth to limit any ingestion of potentially contaminated waste. Access should not be allowed for at least 21 days after last application, and a minimum pasture height of four centimetres must be sustained at all times, even after grazing.

Prohibited pig feed (swill) refers to any mammalian product or material that has been in contact with any mammalian product. Legislation in Victoria prohibits pigs from having access to swill because of the risk of introducing or spreading exotic diseases such as African swine fever and Foot and Mouth disease.

The use of manure as fertilisers should be based on sound agronomic advice including nutrient budgeting and soil testing, to ensure that soil nutrient balances are maintained. Animal manures may also contain significant levels of heavy metals such as zinc and copper or carry antimicrobial residues and resistant bacteria as a result of supplementary feeding or treatment programs conducted on the source property.

Managing the Risk

• Ensure livestock never have access to manure stockpiles
• Do not graze pastures for at least 21 days after spreading manure. If pasture regrowth is slow or manure is still viable on pasture a longer period maybe required. Pasture should have grown well above manure to ensure no manure is consumed.
• Consider the use of composted instead of raw manure
• Inspect and remove foreign material or poultry carcases if present
• Seek agronomic advice to avoid excess nutrients and application rates. If high rates are applied, a longer period may be needed until grazing can occur safely
• Seek information/declarations from supplier:
  • - Test results
  • - Composting process specifications
  • - Quality Assurance Programs
  • - Chemical inputs and treatments on source farm/s
  • - Disease history on source farm/s
• Always implement good hygiene and personal protective equipment when handling manure.

Further Reading

• Agriculture Victoria 2021, Compost and farm biosecurity
• Australian Pork Limited 2015, Piggery Manure and Effluent Management and Reuse Guidelines project 2012/1028,(PDF, 134 pages, 2.3 Mb)
• Environment Protection Authority Victoria 2021, 2006: How to comply with the livestock manure and effluent determination,
• Griffiths, N. (2011) ‘Best practise guidelines for using poultry litter on pastures’ NSW Department of Primary Industries Primefact 534.
• Wiedemann, S.G. (2015) ‘Land Application of Chicken Litter: A Guide for Users’ (PDF, 26 pages, 2.3 Mb) Rural Industries Research and Development Corporation. Publication No. 14/094