Insect pests and parasites thrive in moist manure, particularly in warm weather. Intestinal worms and flies, particularly the stable fly (Stomoxys calcitrans), are the biggest concern to horses and horse owners.
Stable flies are blood-sucking insects that feed on all short haired mammals, including humans.
Fly bites can be stressful for livestock and can also spread animal diseases.
The irritation from stable flies may result in reduced grazing time, causing a decrease in daily weight gains.
Horses and cattle reject areas of a paddock which are contaminated by manure as a way of minimising their parasite burdens. When large areas are rejected for this reason, the paddock is referred to as being ‘sick’.
In this situation the pasture close to the manure thrives, becoming tall and rank and causing it to be even less desirable, while the unaffected areas are well grazed or often overgrazed.
Constant movement around the areas of contaminated pasture eventually causes the ground to become bare, increasing the risk of land degradation and enabling weeds to establish.
Stores of weed seeds may already exist in the soil or they may be introduced through the manure itself.
Consider possible weed invasion when selecting purchased fodder.
The end result of leaving manure undisturbed is a decrease in the available grazing area.
This is less of a problem with sheep and goats since their faeces are smaller and more scattered. Alpacas tend to have ‘toilet areas’ within a paddock and the grass in such areas may become rank.
Manure is a source of nutrients, including nitrogen and phosphorus, which can be transported in run-off and cause pollution of lakes, streams and other water resources if manure is not managed carefully.
Manure can also be used as a valuable source of plant nutrients. A 450kg horse will produce 5-9 tonnes of manure a year, containing around 50kg nitrogen, 5-10kg phosphorus, 40kg potassium, 45kg calcium, 8kg magnesium and 8kg sulphur.
Cattle produce 50-130kg nitrogen, 15-30kg phosphorus and 40-65kg potassium per year.
These amounts are sufficient to maintain the fertility of 1-2ha of pasture for a year.
Horses and cattle will also produce 15-40L of urine per day, but this is less of a problem as it infiltrates into the soil, unlike manure which remains on the surface harbouring flies and worms.
However it can add to the nitrogen concentration in groundwater which can be a problem for those that rely on groundwater for stock and house use.
Managing fly and worm problems
The most effective way to combat problems from flies and worms is to interrupt their breeding cycle. As their breeding cycles are very fast in warm, moist conditions, manure should be removed from stables and yards at least once a day.
Design your stables and feedlots to facilitate thorough cleaning and to prevent the continual accumulation of waste. This will make them relatively worm and fly free. Be sure to meet the conditions required by your local government authority for stables and keeping livestock.
If it is possible to remove manure from paddocks this will be beneficial. Collected manure should be disposed of, used or stored in ways that exclude flies.
For example the fresh manure can be composted or buried in garden beds. When manuring garden beds, remove the top 4cm of soil, spread the manure and replace the topsoil evenly over the area before watering.
Do not mix the topsoil and manure together. Having a layer of soil over the top of the manure prevents fly infestations.
Manure that is expected to contain many weed seeds (e.g. horse manure) – due to what the livestock have been fed – should be either well composted to kill the seeds or legally disposed of away from the property.
Manure which contains a large amount of wood shavings or sawdust from stables should be composted before applying to the garden bed or pasture. If these are applied fresh to the soil they can reduce available soil nitrogen.
For manure to be composted successfully, it requires regular turning to maintain aerobic conditions.
If it is not possible to collect manure from paddocks, harrowing or slashing the paddocks are options to spread the manure thinly and evenly and aid its drying.
In addition slashing will remove the build up of tall, rank grass clumps.
These operations are normally undertaken when livestock are removed from the paddock. Therefore implementing a rotational grazing system is a natural addition to pasture and manure management.
Certain conditions aid the harrowing operation:
- the pasture should be grazed to a height that permits contact between the harrows and the manure pats
- the ground should be dry enough to minimise damage to the soil by the harrowing
- the manure pats should be moist enough to break up (for example, following heavy dew or slight rainfall)
- forecast hot, dry conditions after harrowing will help to desiccate parasite larvae
- harrowing should be confined to those areas containing manure (to prevent contamination of ‘clean’ areas)
- spelling the paddock after harrowing or slashing until the worm risk is reduced. (Note: This can be four to six weeks in hot conditions and ten to twelve weeks in cold, frosty conditions.)
In and around Perth, the conditions described above are most likely to occur following early autumn rains.
In areas which remain warm and moist throughout the year, harrowing is not recommended as a means of worm control since it can take six to eight months to reduce the worm risk.
Manure management for improved pastures
Following the guidelines given above for controlling fly and worm problems will help to avoid the negative impacts of manure on pastures.
For improved pastures also:
- Lime the pastures when pH falls below 5.5. This will stimulate the soil bacteria and actinomycetes that assist in the breakdown of manure.
- Apply composted manure during the pasture growing season, but not during periods of heavy rain and not in areas prone to storm water run-off or flooding.
- Spread manure and compost in the mornings when warming and rising air will dilute odours.
- Rotationally graze the pasture.
Horses can be rotated with other livestock.
Sheep and cattle will graze areas rejected by horses and ingest and kill worm eggs and larvae that affect horses. Sheep and cattle will also even out the fertility of a paddock by depositing manure more evenly.
Free-range poultry can be used on small holdings to spread manure.
Management of beneficial beetles and worms
Establishing dung beetles on the property is another way to reduce the problems associated with manure build up on pasture.
Dung beetles quickly break up and bury manure pats, causing them to dry out. This restricts the development of fly and intestinal worm larvae, allows more rapid recycling of nutrients from the manure to the pasture and decreases the occurrence of ‘sick’ pasture.
Dung beetles may become established naturally in areas of high rainfall or where pastures are irrigated. If dung beetles are not already established they can be obtained from people on properties where they already exist.
Worm drenches can kill non-target species such as dung beetles and earthworms when leached out of manure.
Minimise the use of worming drenches between November and February in the south-west when dung beetles are active, and only drench those stock that essentially need it.
Ask your supplier to help you choose drenches that have particularly low detrimental effects on the environment. Carefully follow the manufacturer’s instruction to minimise the effect on the environment and wastage of the chemical.
Managing manure more effectively saves money and time otherwise spent on maintaining pasture cover and reducing weeds.
Properly managed manure can benefit pastures by returning nitrogen and phosphorus to the soil and improving the physical and chemical properties of the soil through additional organic matter.
Manure improves soil structure, increases the water and nutrient holding ability of the soil and boosts the soil’s resistance to compaction and crusting. However, when spreading manure on paddocks, always follow the guidelines above to minimise parasite breeding.
Preventing contamination of water bodies
It is important to prevent pollution by run-off or leaching of manure into waterbodies. Fence off the watercourses and waterbodies on your property to prevent livestock directly depositing manure in or around them.
Other ways to avoid water pollution through good manure management include:
- yards, stables and manure storage areas should be located away from waterlogged soil and at least 50m away from natural drainage lines and waterbodies. They should be constructed to prevent surface run-off flowing through them
- the floors of yards and stables should contain sand or sawdust overlying compact soil or limestone
- use gutters, downpipes and drains to divert rainwater away from stables, manure composting areas and wastewater storage ponds (an application to the Department of Health is required for the installation of a wastewater storage pond)
- when conditions are dry manure can be applied up to 10m from a waterbody, however, if rain is expected or the soil is wet this distance should be increased to 100m.
Vegetation buffers along the banks of drainage lines and waterbodies are an important means of filtering and removing nutrients from run-off before they enter a waterbody. A simple grassed filter strip of 3m wide can reduce phosphorus run-off to waterways by 90%.
Vegetation buffers should be established down-slope from where horses and other livestock are kept.
Open drains and waterbodies on the property should have well established buffer zones of vegetation. If these are not already in place a revegetation program could be established.
Contact your local government authourity or the Water Corporation for permission if open drains are to be revegetated.
(Note: Guidelines on widths of buffer zones may vary between shires and environmental agencies.)
Manure management outside your property
This applies particularly to horses. When riding your horse in areas outside your property, it is important to prevent the spread of weeds, via manure, into bushland.
Stay on well maintained and located bridal paths, collect as much of the manure as possible and feed the horse processed food rather than hay overnight.
Manure management on small properties is vital to prevent degredation of your small property.