Manure and mulch warning update

Last October I updated the warning about pyridine herbicides that can damage or kill both food crops and decorative plants. Unfortunately, some readers have since had plant damage after inadvertently purchasing manures or mulch that contain one of these herbicides, despite a NSW government website stating that no damage has occurred in Australia.
As a result, I am posting a reminder.
Pyridine herbicides are only effective on broad-leaf plants, but the chemicals remain active in mulch cut from sprayed pastures and in manure from animals that have grazed on sprayed pastures until the chemicals are broken down by soil microbes. Of particular concern to home gardeners and councils that recycle waste into compost for agricultural and domestic use are the products containing aminopyralid, clopyralid and picloram because they are quite persistent, and residue from these herbicides can damage plants for up to 24 months. However, because the Australian Pesticides and Veterinary Medicines Authority (APVMA) regards the person who sprays the herbicide as the ‘end user of the product’, any warnings are limited to product labels without any regard for unsuspecting gardeners who, in good faith, purchase mulch, compost or manures contaminated with the herbicide, and who may not recognise the cause of the damage to their crops because they have not personally used any herbicides.
A recent check of their website shows that the APVMA has registered 233 herbicides that contain at least one of the pyridine group of herbicides – an impossible list to check through before purchasing mulches, manures or compost. The entire tomato family, lettuces, sunflowers, spinach, strawberries and legumes are particularly susceptible to damage from these herbicides, which can also affect a range of ornamental plants.
To protect your garden from pyridine herbicide damage: only use aerobically composted manures on gardens. Aerobic composting requires weekly turning or stirring to ensure the composting process is carried out by microbes that require oxygen. Breakdown of the herbicide will be very slow in compost heaps that are not aerated.
Mulch that carries an organic-registered label does NOT contain any herbicides. Mulches from uncertified sources are high-risk products because the drying and baling of mulch materials eliminates microbial action, and the herbicide will still be active. The only safe compost to purchase is organic-registered compost.

If you are unable to purchase certified-organic manures or mulch, test the safety of the product by sowing some seasonally suitable peas or beans in pots containing certified-organic potting mix (with the manure mixed through it) or covered with the purchased mulch. (Water this pot through the mulch). Keep the test pots well-watered to eliminate other sources of stress. You should be able to see if an input is contaminated within 21-28 days. Dispose of any affected plants and potting mix with household garbage.
Symptoms to look for are:
Poor germination or death of seedlings, twisted, cupped or elongated leaves and twisted growth, misshapen pods.

Return remaining contaminated inputs to your supplier. If this is not an option, aerobic composting is the quickest way to break down these herbicides. Test the mature compost for herbicide residue.
If you find that the mulch has been affected, use it on beds that you can leave fallow until aerobic microbes in topsoil break down the herbicide or, if space is limited, compost it aerobically. if you find that garden beds have been affected, dig organic-registered compost through the bed and keep it damp to keep soil microorganisms breaking down the herbicide as quickly as possible.
Notify your supplier of the problem as pyridine herbicide product labels state that treated crops are not to be used for hay, silage or animal bedding, and manures are not to be spread on land used for growing susceptible crops.

Please also take a minute or two to notify the APVMA of problems with these herbicides. The APVMA encourage the public to report pesticide problems through their new Adverse Experience Reporting Program (AERP) by e-mail: aerp@apvma.gov.au, phone 1800 700 583, or fax: 612 6210 4813.

Further information:
Examples of pyridine herbicide damage

You can find Australian product names of these herbicides by going to the APVMA’s Public information (PUBCRIS) page. Under product type select ‘herbicide’, then type aminopyralid, clopyralid or picloram in the active constituent panel. Click ‘Search’.

The NSW Government has been aware of the problems with these herbicides in Australia since 2005.

Herbicide damage

Broad-leaf weed killers that contain the pyridine herbicides have caused widespread damage to many gardens in New Zealand, the UK and the US in recent years, and these herbicides are now being sold in Australia.
Pyridine herbicides include aminopyralid, clopyralid, fluroxypyr, picloram, and triclopyr. They are only effective on broad-leaf plants, but the chemicals remain active in mulch cut from sprayed pastures and in manure from animals that have grazed on sprayed pastures until the chemicals are broken down by soil microbes. Of particular concern to home gardeners and councils that recycle waste into compost for agricultural and domestic use are the products containing aminopyralid, clopyralid and picloram because they are quite persistent in compost (particularly anaerobic compost), and residue from these herbicides can damage crops for up to 24 months.

Is it just me, or do other people think it is crazy that there is widespread concern about the future of food production in Australia, and all levels of government are advising us to recycle and store carbon, yet the Australian Pesticide and Veterinary Medicines Authority (APVMA) continues to register more and more of these herbicides that damage food crops, and little if anything is being done to warn the public of the risk in using mulches, composts or manures contaminated by these herbicides.
Although there are only two pyridine herbicides containing aminopyralid (Hotshot and Grazon Extra), the APVMA has registered 59 herbicides containing clopyralid, 54 containing picloram, 27 containing fluroxypyr, and 77 containing triclorpyr, and there are several more of these herbicides awaiting approval – an impossible list to remember when purchasing mulches, manures or compost.

The problem with Australian regulating authorities is that they regard the person who sprays the herbicide as the ‘end user of the product’ and any warnings are limited to product labels without any regard for the unsuspecting gardeners who, in good faith, purchase mulch, compost or manures contaminated with the herbicide, and who may not recognise the cause of the damage to their crops because they have not personally used any herbicides.

I am very grateful to Jo T. who has sent me a link to photos of damage to vegetable plants caused by aminopyralid. These may help readers identify this herbicide problem in their gardens.
http://www.geologywales.co.uk/storms/summer-2011-aminopyralid.htm

If you are unfortunate enough to have garden beds affected by these herbicides, click here for treatment information.
See also Herbicide warning.

Further Information:
You can find Australian product names of these herbicides by going to APVMA’s Public Chemical Registration Information System page. Select herbicide and then type aminopyralid, clopyralid or picloram in the active constituent panel.
The NSW Government has been aware of the problems with these herbicides in Australia since 2005:http://www.environment.nsw.gov.au/resources/warr/SPD_ORG_ReduceRiskHerbCompost_FS.pdf
Jo has also provided a link to UK information about aminopyralid problems.

Herbicide warning

Before purchasing mulches or manures for your garden, ensure that they don’t come from pastures treated with a broad-leaf weed killer.
A relatively new herbicide (weed killer) ingredient, aminopyralid kills broad-leaf plants by disrupting plant cell growth. It does not affect grasses, but can remain active in them, and manures from animals that eat sprayed grasses, until it is completely broken down by composting or soil microbes.
Some readers may remember that, 16 months ago, I drew attention to the devastation this herbicide caused in UK gardens, rendering garden beds unusable for almost two years, after contaminated pasture was used as mulch, or uncomposted manures were dug into garden beds. UK residents were advised not to eat any produce from affected garden beds.
Despite extensive problems in the UK, and the fact that aminopyralid is highly mobile in soil, our Australian Pesticides and Veterinary Medicine Authority (APVMA) has approved herbicides containing aminopyralid under the names; ‘Hotshot’, ‘Starane’, and ‘Grazon’.
The APVMA Manager – Public Affairs told me that the APVMA requires products that contain aminopyralid to include on the label the following instructions: The herbicide is not be used on land to be cultivated for crops for up to 24 months. The herbicide is not to be applied to crops or pastures, which are intended to be cut for the production of compost, mulches or mushroom substrate to be used for susceptible crops or plants, as straw, hay or other plant material treated with this herbicide may damage the plants. Manure from animals grazing treated areas or feeding on treated hay is not to be used for growing broadleaf crops, ornamentals or orchards as injury to susceptible plants may occur.
However, these warnings do not help the many gardeners who are unlikely to ever see the herbicide label and, completely unaware of any potential problem, may inadvertently purchase contaminated products.
To test manures and mulch for herbicide residue, see: Manure and mulch warning update
If you are unfortunate enough to have beds affected by this herbicide, click here for treatment information.

Horse manure

Magic1One of our SA readers wants to know what to do about the weeds that sprout from their horse manure pile, as she is concerned about spreading the weeds through her garden. She also has a problem with millipedes. Interestingly, manure and millipedes have a relationship because millipedes feed on decaying organic matter and they can lay their eggs in faecal matter. Millipedes are related to slaters. See Slaters and earwigs for controlling them in the garden.
Horse manure is often the easiest manure to obtain close to metropolitan areas. We have found horse manure to be a good source of plant nutrients and our miniature Shetland, Magic, works 24/7 to keep up supplies. Small amounts can be fermented in a bucket of water, then diluted, to produce a fertiliser tea for plants that need a boost.
But, adding uncomposted horse manure to the garden can encourage millipedes, slaters and earwigs. This is more common if you use sheet composting for the manure, a process of spreading a layer of manure on an unused garden bed, dampening it and covering it with mulch.
The best way to use fresh horse manure is to put it into the compost heap as it is a good source of nitrogen and generates a lot of heat, but there is a big difference between an active compost heap and a pile of horse manure. The manure should be mixed with dry ingredients such as straw, mulch, shredded newspapers, or dry leaves to create a good nitrogen to carbon balance. The heap should also be turned regularly to aerate the heap because aerobic bacteria require nitrogen, moisture and oxygen to work efficiently. When the compost heap is turned, newly germinated weed seeds get turned into the mixture and provide more organic matter for the bacteria to feed on. In its early stages, the heap should generate enough heat to kill off pathogens and seeds. As the composting process continues, the heap reduces in volume. As it gets cooler, you will occasionally see earwigs, slaters or millipedes in the mix but they are helping to break it down so don’t spray them with anything. When the organic matter reaches a favourable stage, earthworms move into the heap if it has contact with soil, and they digest the decomposing organic matter and turn it into worm castings. The final product, ready to be used on garden beds, is about one quarter of the volume of the original heap, friable, very dark brown in colour, and has a earthy, rainforest smell.
If you just leave horse manure in a pile to break down, it will tend to pack down and anaerobic (without oxygen) composting will occur. This is much slower, and can generate unpleasant smells. A lot of the nitrogen can be lost to the air and other nutrients can leach away when it rains.
To get horse manure to work even more quickly in a compost heap, tip it onto a hard surface and mince it a bit with the edge of a spade, because bacteria only work on the surface area of the ingredients. Producing more surface areas to feed on by chopping ingredients will greatly speed up the process.

Herbicide problems

Aminopyralid
A cousin in the UK contacted me recently concerning a major problem that UK organic gardeners and farmers are experiencing. I would like to draw your attention to it because a similar problem could occur here.
The cause of the problem is a hormone-based herbicide (weed killer) Aminopyralid, which is an ingredient in several brands of herbicides produced by Dow Agrosciences. Aminopyralid has become popular because it is only effective against broad-leaf weeds and does not kill grasses. However, the herbicide binds to woody tissue in grasses and remains active in the grass, hay and silage fed to animals. The herbicide survives passage through mammalian digestive systems and remains active in manure produced by animals that consume contaminated feed.
Consequently, the herbicide affects a range of vegetable crops planted where contaminated manures have been added to beds, or where contaminated hay or straw is used as mulch. As soil bacteria begin to decompose the mulch or manure, the herbicide is released into the soil and absorbed by roots of broad-leafed plants.
Symptoms of affected crops are dying seedlings or curled leaves and gross deformity of plants and produce. Susceptible crops include peas, beans and other legumes, carrots and parsnips, potatoes and tomatoes, and lettuce and similar crops. The affected beds remain unusable until soil bacteria have completely broken down the herbicide. As you can imagine, there are a lot of angry gardeners in England and Wales where this problem is endemic, and there are calls to for this product to be banned.
The best Dow Agrosciences can offer is: the levels of amylopyralid in crops “are unlikely to cause a problem to human health”, although the Dow website says: “As a general rule, we suggest damaged produce (however this is caused) should not be consumed.”
Originally the Royal Horticultural Society (RHS) advised allotment gardeners that contaminated soil would not be usable for two years. However, more recent information indicates that it can be used as soon as soil bacteria break down the herbicide, so the faster you can get them to do this, the better. Aerobic bacteria that break down organic matter faster than anaerobic bacteria require moisture, air and nitrogen for fast consumption. They work faster in a soil pH that is close to neutral. If soil is acidic, raise soil pH to close to neutral (6.5-7) by watering in agricultural lime. Start with a generous handful per square metre, and mix it through the topsoil. This will also aerate the soil to provide air for the bacteria. Don’t use hydrated or slaked lime (builder’s lime) as this will lose nitrogen from the soil, and the bacteria will work more slowly when soil is low in nitrogen. Check soil pH every six weeks because manures produce hydrogen ions as they break down (making soil more acidic), and turn the topsoil regularly to maintain good aeration. Keep soil just damp. If uncontaminated mulch can be sourced, it can be applied to the bed surface to maintain consistent moisture content and keep soil warmer through the colder months, especially if mulch is applied in the middle of the day when the soil is warmest.

Other herbicide problems
Other herbicides, including glyphosate, increase the risk of soil diseases by damaging the good fungi in soils that keep soil diseases under control. Recent research published by the United States Department of Agriculture (USDA), found that herbicide-resistant GM crops are causing an increase in “Fusarium” diseases, and predicted that there would be an epidemic of soil diseases and a food crisis, before long. Food crops from plants badly affected by fusarium diseases can also contain the disease fungi, causing a range of health problems, or death, as happened in Mexico some years ago when tortillas made from affected corn were eaten.
Herbicides cause more problems than they solve but many people would rather believe the advertising hype put out by chemical companies because weedkillers look as though they will save the gardener some work. (See post ‘Wilting diseases’ in the Pest-free Gardening category.)

Changing soil pH

If the pH of garden beds needs adjusting, organic gardeners have a distinct advantage over “chemical” gardeners, because mature compost has a pH of about 6.5 where all the major nutrients are freely available to plants, essential trace elements are available, and aluminium is locked out. Adding mature compost to topsoil when preparing beds will help to lower pH of alkaline soils, and raise the pH of more acid soils, as well as buffering plant roots from an unsuitable pH in surrounding soil. Where the amount of mature compost is limited, green manures and well-rotted manures will break down to add nutrients, microorganisms and humus to topsoil. Worm castings and other solid organic fertilisers provide nutrients in easily absorbed form. Garden beds should be prepared a month before planting to allow soil chemistry to achieve a balance.

To raise soil pH
In all acid soils, pH can be raised by the combined use of organic matter and the addition of calcium ions in the form of dolomite or lime.
Agricultural lime – (Calcium carbonate) is finely ground limestone (chalk). Mined limestone, i.e. not chemically treated, is a safe choice to raise pH in garden beds. Although it takes several weeks to have an effect, it is longer acting than other sources of lime, and can be watered in around plants. Agricultural lime can be worked into the top 15 cm of soil when preparing garden beds. It takes less lime to raise the pH of sandy soils than it does to change clay soils. To avoid an excess amount of calcium in soil, apply as recommended in the test kit, and test soil a month later.
I must say here that I have not found the application rate recommended by Manutec for “organic soils” to be accurate, if soils contain compost. It may have been calculated for soils where only manures are added.
Dolomite – (Calcium magnesium carbonate) is limestone with a higher proportion of magnesium than agricultural lime, and is applied in the same way. It is a good way to raise soil pH on sandy soils with fairly low organic matter content because both calcium and magnesium leach easily from these soils. In soils with high magnesium content, such as in South East Queensland, agricultural lime is the preferred way to raise soil pH.
Quick lime – (Calcium oxide) is made by heating limestone in a furnace to remove carbon dioxide. It is very caustic and unsuitable for garden use.
Hydrated or slaked lime – (Calcium hydroxide) is also known as brickies or builders’ lime because it is used to harden mortar. Hydrated lime is made by soaking quick lime in water to form hydroxides. It is more soluble and faster acting than agricultural lime, but its effects do not last as long. This lime can burn roots and should not be used on beds that contain plants. It should also be applied a month before organic matter and fertilisers or nitrogen can be lost through conversion to ammonia. Gloves and a mask should be worn when applying hydrated lime because it is very drying to skin and throat. Apply hydrated lime to the soil surface, and water it in.

To lower soil pH
Adding organic matter as compost, green manures, and animal manures, without including lime or dolomite, can be enough to adjust the pH of slightly alkaline soils because organic matter produces hydrogen ions as it decomposes.
Manure from cows, horses and sheep that have grazed on herbicide-free pasture can be used more liberally on alkaline soils. It has been calculated that 2–3 kilos of manure per square metre of bed area will reduce soil pH from 8.0 to 7.0. Manures release hydrogen ions as they break down, replacing calcium ions on the charged sites.
Elemental sulphur, sometimes sold as flowers of sulphur, will assist organic matter in reducing soil pH in more alkaline soils. Elemental sulphur is available from produce stores, and some nurseries. For soils with a sandy structure, apply at 35 g per square metre, or 100g per square metre for clay soils. Test soil after one month, to see if further applications are necessary.
Please note – Lime sulphur is a fungicide, not a soil conditioner.
Acidic fertiliser can assist when alkaline topsoil contains some organic matter and herbicide-free manures are not available. Multicrop’s Ecofish liquid fertiliser is registered by NASAA as an input for organic cultivation. The concentrate is very acidic and diluting it in water should modify the acidity, somewhat. It can be watered into the soil or used as a foliar feed for plants in alkaline soils.

Manure tea

As it is Full Moon phase, later this week I will have to brew up some manure tea as a supplementary fertiliser for my lettuce, silverbeet, and spinach seedlings because they have a high nitrogen requirement. Manure tea can also be applied to flowering annuals, cabbage, celery, leeks, also Brussels sprouts that were planted out in February, or earlier.
I usually brew this up during Last Quarter phase as it only takes about a week in warm weather. As the weather has been much cooler than usual for April, the brew will take a good twelve to fourteen days to mature.
Manure tea gets its name from the fact it is applied to soil around plants at weak black tea strength, and around young seedlings as very weak black tea strength because strong fertiliser solutions can burn delicate roots. As it coats the foliage when applied to very small plants, I always water the seedlings after application because it is better to feed the soil than the plant.
Manure, and other fertiliser “teas” are easy to make. For this brew, I place a shovelful of horse manure into an old bucket, and fill the bucket with water. Then I cover the bucket with an old plastic tea tray. The cover prevents loss of nitrogen to the air, and flies laying eggs in the mixture, but a tight fitting lid will usually “pop” because of the gases formed as the manure ferments. The mixture should be stirred every couple of days, will be ready to use during New Moon phase. Sap flow in plants increases as the Moon is waxing, and New Moon and First Quarter are good phases to apply liquid fertiliser because they plants use them quickly.
I strain some of the brew through a piece of old pantihose into a watering can and add enough water to achieve the correct strength for the plants I want to fertilise. After fertilising, the bucket can be repeatedly topped up with water, and the brew can be used until it is quite pale. The residue can be added to the compost heap.
Always wear rubber gloves when handling manure fertilisers. They not only prevent smelly hands, they will prevent the manure coming into contact with any cuts or scratches on your hands.