This article contains Tasmanian rules and guidelines for the use of various waste products as alternative fertilisers, including the laws on restricted animal materials and swill feeding.
Restricted animal materials, swill feeding and blood & bone:
Feeding Restricted Animal Materials (RAM) to ruminant animals (for example cattle, sheep, and goats) is illegal in Australia. RAM is any animal product other than milk or milk protein, tallow and gelatine. Feeding RAM to cattle caused the outbreak of Mad Cow Disease (BSE) in the UK.
Feeding swill to pigs is illegal in Australia. Swill is any material containing material of placental mammal origin (other than milk and milk by-products, properly rendered meat meal, or tallow). This ban on swill feeding is a most important part of Australia's efforts to keep Foot and Mouth Disease out of the country.
Swill feeding has been the cause of several exotic disease outbreaks, including the Foot and Mouth epidemic in the UK in 2001. Many exotic animal disease viruses are highly resistant to chilling, freezing and curing. Boiling swill may not destroy all disease organisms.
The general public has an important role in maintaining Australia's freedom from exotic diseases. If you believe someone is feeding swill or RAM to livestock or someone is supplying swill to pig owners or RAM for feeding to ruminants, please report your concerns to DPIW on (03) 6336 5306.
Standards allow for blood and bone meal to be used as pasture fertiliser but NOT as stock feed. It is highly advisable to keep stock from the fertilised paddock for at least three weeks to minimise the risk of developing botulism, salmonellosis or mastitis. Ideally, the blood and bone meal should be ploughed into the soil and time given for the grass to grow to a height where grazing close to the ground will not occur. The risk when used sensibly as fertiliser are considered insignificant in terms of BSE transmission.
For more information visit the DPIW website (www.dpiw.tas.gov.au).
Poultry litter as a fertiliser:
Most poultry feeds contain a significant amount of RAM. So do most pig feeds. Poultry litter inevitably contains significant amounts of spilled poultry feed and, usually feathers. The spreading of poultry litter on paddocks is acceptable providing all ruminant stock are successfully kept out of those paddocks until there has been sufficient pasture regrowth to absorb the litter.
In good growing conditions, the withholding period is 21 days after the poultry litter has been spread and longer if pasture growth is slow.
The poultry litter should only be spread on the paddock at the rate of 15 cubic metres per hectare or less, so as to allow it to be absorbed quickly. Spreading at a higher rate means that some of the poultry litter will probably still be on the pasture when stock are returned to the paddock.
If the litter contains any carcases, they should be removed before spreading, otherwise grazing animals are exposed to the risk of botulism
It is a farmer's responsibility to make sure the poultry litter is not eaten by ruminants. The following steps are encouraged:
- Make sure your load of poultry litter is covered with a tarp while transporting.
- When you get the load home, store it in an area that cannot be accessed by any ruminant animal and fence off any stack of poultry litter or composting area.
If you handle poultry litter as suggested above, you'll be within the law.
For more information visit the DPIW website (www.dpiw.tas.gov.au) or call 1300 368 550.
Wastewater - Human effluent:
Wastewater is part of the total water cycle. Like rainfall or groundwater, it is a resource available for use. Wastewater recycling brings positive benefits in the areas of water conservation and pollution abatement. While there are environmental and public health issues associated with wastewater - whether recycled or discharged to waterways - appropriate management techniques will minimise risk to acceptable levels.
Wastewater is a valuable resource for agricultural activities such as food, crop and wine grape production. Use of wastewater on food crops that require processing before eating is preferable to use on those eaten unprocessed. Irrigation of pasture for cattle or sheep grazing, fodder crops or cereals are other common uses of wastewater.
Constituents of wastewater, such as nitrogen and phosphorus, are beneficial to crops and can readily be used to produce protein and fibre, to enhance grass and other vegetation or to produce processed food crops. Much agricultural irrigation needs can be met by wastewater re-use.
The Clarence city council has developed a system where treated effluent that was once released from the Rosny sewerage plant into the Derwent River is now pumped up a 20 kilometre pipeline to the Coal Valley, where it is used on farms.
The Brighton council also has a similar system where effluent from the Brighton municipality, which would otherwise be pumped into the Derwent River, is pumped directly to farm dams for storage before being used for irrigation.
Environmental and public health protection:
Irrespective of use, minimisation of risk to the public and the environment requires that recycling of wastewater must comply with the following performance requirements:
- Use of wastewater for direct domestic portable purposes is not permitted.
- Primary treated wastewater is not considered acceptable for irrigation re-use in Tasmania.
- Wastewater may only be used where the quality achieves the level required for that particular beneficial use.
- Maintenance of high levels of pathogen reduction is required to safeguard health where domesticated grazing animals are present or public access is possible.
- The impacts of nutrients and other substances on the soil, water and plant environment need to be assessed and managed by the user to avoid adverse impacts.
Some guidelines:
- Warning signs with both a pictorial sign and words indicating that reclaimed water is being used should be placed in strategic positions.
- Spray systems must be designed to avoid misting from sprinklers and spray drift beyond the actual irrigation area.
- There must be no run-off of irrigant beyond the designated irrigation area.
- Livestock must be excluded from wastewater treatment and storage lagoons, channels, drains and tree belts.
- Livestock should not graze pastures that have been irrigated for at least three days.
For more information see: Environmental guidelines for wastewater (http://www.environment.tas.gov.au/index.aspx?base=106)
Feedlot waste:
The waste from intensive animal production (feedlots) is a good source of nutrients and can be used as a natural fertiliser or soil amendment when applied to crops. Although, if not carefully managed, these nutrients can have a negative impact on the environment, reducing environmental value and degrading our natural resources.
The removal and storage of manure prior to disposal is an important part of the waste management program of a feedlot. Between yard cleaning and manure removal, manure may be temporarily mounded within yards. Longer term, manure storage is often in stockpiles outside the yards.
Cattle in feedlots produce 1 to 2 tonnes of manure per head per year. Given that the removal of manure is a real cost to the feedlot operator, efficient removal of this product is important. Manure can be removed directly from the pad if the manure pack is 100 mm deep or deeper. Usually a front-end loader, scraper or grader would be used for primary yard cleaning. A bobcat may be useful for cleaning around troughs and under fences. However, if the manure pack is shallow or hard, a light ripping may be necessary to break up the manure prior to removal. It may also be necessary to scrape the manure into a mound prior to loading. During the removal of manure, the pad should be graded to ensure that the surface is uniform and any potholes are filled in.
Between the base soil and the manure layer is an interface layer. It consists of mixed compacted soil and manure and is about 50 mm deep. The interface layer forms an impermeable barrier, which prevents contamination of ground water by nitrates and salts in the manure. The interface layer must not be removed during yard cleaning.
Mounding of manure:
Some managers use short term mounding of manure as a waste management tool. During yard cleaning, manure is formed into a mound in the yard. This allows flexibility in manure management programs. It permits all yards to be quickly cleaned out while equipment is available or when other conditions are suitable. It also allows an increased interval between full-yard clean outs. The volume of manure to be disposed of may also be reduced by up to 50%. However storage of the manure in this way will reduce its nitrogen content and subsequent value as a fertiliser.
Stockpiling manure:
Although some managers like to spread manure removed from the yards immediately onto land utilisation areas, this is not always possible. Manure that has been removed from yards, but cannot be used productively straight away, must be stored in an appropriate manner, usually by stockpiling.
By maintaining a stockpile, yards can be cleaned out as frequently as required, even when spreading machinery is not available or when agricultural land is not ready for the application of manure. Stockpiling of manure also allows decomposition of the manure, which reduces the amount of manure that must be applied to land, but also reduces the nitrogen content of manure, making it less valuable as an organic fertiliser. The amount of stockpiled manure should, therefore, be kept minimal and manure utilised as soon as possible.
Manure containing rocks is unsuitable for immediate use since these objects can damage manure spreading and crop harvesting equipment. Manure may, therefore, need to be stored in stockpiles prior to screening.
Stockpiles that have been properly constructed and maintained have little potential to pollute the local environment:
- Manure should be added to the stockpile in thin even layers.
- The layers should be dry (25% moisture content) otherwise spontaneous combustion may occur. Manure usually has a moisture content of 45% or less when it is removed from yards and is usually at least partly stabilised.
- Following the addition of each layer, the stockpile should be compacted. This is particularly important if manure is to be stacked deeper than about 1.8 m.
- Stockpiles should also be shaped so that they shed rain.
- An even surface should be maintained by periodic grading. This helps to avoid ponding of water on the pile.
- Stockpiles must be built within a controlled drainage area. This means that they should be protected from external runoff by drains and/or diversion banks.
- Runoff from stockpiles must also be controlled to prevent runoff from contaminating watercourses.
For more information visit DPI&F Queensland (www2.dpi.qld.gov.au)
Piggery effluent:
Much of the pig industry relies on flushing systems to keep piggeries clean. The process of flushing away the 2.5 to 3.0 kg/day of manure produced for each standard pig unit typically results in the creation of large volumes of effluent that must eventually be disposed of. Disposal of final pond effluent can be achieved by evaporation in drier areas, however, land application is the most effective method of re-using effluent, and is also probably the best method of disposal. Unfortunately, soils do not have an unlimited capacity for effluent re-use, and effluent application has to be carefully managed to avoid natural resource degradation, in addition to ensuring maximum benefit to the producer.
Reuse of piggery effluent and sludge can have many beneficial effects:
- Altered soil organic content, possibly resulting in decreased soil density, and improved water infiltration. Infiltration tends to reduce erosion and makes more water available to crops.
- Effluent application can provide a proportion of the requirements of a crop or pasture for nitrogen, phosphorus and potassium, leading to better crop growth.
- Effluent irrigation provides a proportion of the water requirement of a crop. This effect should be considered after calculation of appropriate nutrient application rates.
The potential for environmental harm:
Unfortunately, effluent application can have a wide range of negative environmental effects. Producers, who want to take advantage of land application as a means of reusing effluent/sludge, and all the benefits that this can entail, have a moral and legal obligation to ensure that all actions are undertaken in an environmentally sustainable manner.
Excess application can result in on-farm soil damage:
- Soil sodium concentrations may be elevated, possibly resulting in increased soil dispersion, degraded soil structure, reduced workability, and reduced soil permeability.
- Soil salinity may be increased to levels where productivity is reduced.
- Where the hydraulic loading exceeds the irrigation demand of the crop or pasture, soil water logging may occur, reducing soil productivity, and possibly mobilising phosphorus.
- Excessive nitrate levels in soils may result in toxic levels of nitrate in forage or reduced forage palatability.
Excessive or poorly planned application can have serious off-farm effects on ground or surface water, through the following mechanisms:
- The increased phosphorus in surface soils due to effluent application is vulnerable to mobilisation by erosion or dissolution in run-off water. This is currently thought to be the primary pathway for effluent-phosphorus entry into surface water, where phosphorus is often the limiting nutrient for algal growth. Algal blooms have already caused problems worldwide, due to the toxins produced by some algae, or depletion of the water's oxygen supply. The end results of these problems include fish kills, stock deaths, and sickness in humans.
- Where the soil's safe phosphorus-storage capacity is exceeded, phosphorus may enter surface water resources through leaching to ground water.
- Nitrate- and nitrite-nitrogen are readily mobilised by leaching or transport in run-off, linked to "blue baby" syndrome, and other negative health effects. While final pond effluents tend to not contain high concentrations of nitrate or nitrite, ammonium is rapidly converted to these nitrogen forms in soil.
- Effluent-nitrogen may also play an important role in triggering harmful algal blooms.
Some guidelines:
- It is recommended that effluent should not be applied to sandy soils. Where application to sandy soils is unavoidable, careful monitoring and responsive management should accompany effluent application. Ideal application sites should have slopes that promote infiltration rather than runoff and erosion.
- Application rates should be determined from the nutrient or hydraulic factor that is most limiting (that is, the nutrient that limits the amount of effluent/sludge that can be applied).
- Maximum total applications should be calculated for each sludge or effluent nutrient (N, P and K) according to the following formula:
Maximum total application = safe soil storage + amount removed in crop + allowable losses.
- Effluent potassium should be managed in a similar manner to potassium fertiliser, with the aim of applying effluent-potassium at the rate of uptake by the crop where possible.
- In addition to good soil conservation practices, it may be necessary to use Vegetated Filter Strips (VFS) to reduce nutrient load transport to surface water by run-off. This type of management is appropriate where effluent application areas are close to surface water or gullies (whether permanently flowing or not). Vegetated Filter Strips (VFS) are a strip of dense grass between a nutrient source and the protected area.
- Avoid using effluent irrigation techniques that promote surface saturation such as flood or contour irrigation.
- Applications of effluent with an electrical conductivity of up to 8 Ds/m should have no long or short-term negative salinity effects.
For more information see Queensland DPI & F (www2.dpi.qld.gov.au)