Testing Farmyard Manure to Make Sure it's Weedkiller Free

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We have a ready supply of horse and cow manure from the farm next door. However, I've read that nowadays there's always a risk of it containing weedkiller.

Is there a reliable way to test for this?

We've had a huge bin full rotting down since last summer. I'm toying with the idea of mixing some with compost and using it to grow a very early crop of peas. If I start now I figure I'll know by early April if it's safe to use?
 
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The way that manure is contaminated is through the hay/straw that the animal eats. Many of todays farmers use herbicides such as Picloram but there are many others as well. This chemical is applied to the hay fields to stop weeds which it does very well but this same chemical is also on the hay. The animal eats the hay and the chemical goes through the cow and contaminates its manure. This residue can last for years in some cases even after the manure has decomposed so it is imperative to test the manure/compost before composting it or applying it to your soil. It is an easy test. Just fill a bucket half full of the manure and then fill it up with water. Let it sit for 3 or 4 days occasionally stirring it. Then find a broadleaf weed such as a dandelion and pour the liquid from the bucket over the plant and saturate the soil. Come back in 3 or 4 days and if the weed shows ANYTHING abnormal then the manure is contaminated and should be removed from your property.
 
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Another way is to fill a couple of pots one with the suspect manure, the other as a control, and plant bean seeds in them. I have heard that some of those weed killers that are used in the US are not authorised here, and those that are are don't pass through the animal unchanged, but best not to rely on that, even if it were true once it may not be now the way the present govt. is rescinding controls.
 
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Another way is to fill a couple of pots one with the suspect manure, the other as a control, and plant bean seeds in them. I have heard that some of those weed killers that are used in the US are not authorised here, and those that are are don't pass through the animal unchanged, but best not to rely on that, even if it were true once it may not be now the way the present govt. is rescinding controls.
From what I can gather, there was a problem in the UK with whole allotments being wiped out in the early 2000's. The weedkillers in question were temporarily banned here and then came back with tighter restrictions. Bottom line is (from the RHS) is that the problem is unlikely to occur nowadays, but unless you are 100% certain of your source best to play it safe and test.

I used manure from our farm the past two years without any testing (or any problem) so it's probably safe. However, with things being tight due to the economy I imagine farmers will be under pressure to find new sources for animal feed/bedding. They grow their own hay - clearly haven't used these weed killers in the past. But they buy in bedding for the horses. So to be 100% sure I'm going to start up a little routine for making sure it's safe.

 
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I am gonna suggest my experience takes a little more time. There is a growth stage, that takes 2 or 3 weeks to arrive at, where the chemistry begins to impact plants. I have had hot compost (Black Kow brand) and it was not until the plants began that stage where they were trying to grow to maturity from the inititial pop up seedling stages that they began to show. Give it that extra week to be sure.
 
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We have a ready supply of horse and cow manure from the farm next door. However, I've read that nowadays there's always a risk of it containing weedkiller.

Is there a reliable way to test for this?

We've had a huge bin full rotting down since last summer. I'm toying with the idea of mixing some with compost and using it to grow a very early crop of peas. If I start now I figure I'll know by early April if it's safe to use?
These hormone weedkillers are perhaps not as strong here as in US & they break down in a year, especially if you turn the compost once or twice to make certain ground microbes get access to it.
 
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Your garden is calcium deficient.
Chicken manure pellets at 3handfuls p.sq.yd
I've heard that's the case. However, I'm not sure I buy it.

If you sow dandelion seeds in pretty much any soil they will grow. If you or your near neighbours allow dandelions to go to seed there will be lots of seeds falling on your garden.

I think it more likely if few things but dandelions grow in your garden then it's likely to be due to deficiency. But mere presence of a weed that seeds prolifically doesn't really tell you much?
 
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I have also seen it said that deep rooted plants, like dandelion and dock, are indicators of compacted soil, my feeling is that they don't make it where I cultivate because I cultivate, they try.
 
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Am I missing something here? Is it being said that if one has multitudes of dandelions his soil is deficient in calcium? If so, my soil must not have any calcium although it tests out to have too much. The bedrock here is limestone and very close to the soil surface and I have been waging war against dandelions and thistles for almost 25 years. But perhaps it is because I have so much calcium that it is not available as uptake for plants which could be the reason I struggle with Blossom End Rot and have bumper crops of dandelions.
 
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Am I missing something here? Is it being said that if one has multitudes of dandelions his soil is deficient in calcium? If so, my soil must not have any calcium although it tests out to have too much. The bedrock here is limestone and very close to the soil surface and I have been waging war against dandelions and thistles for almost 25 years. But perhaps it is because I have so much calcium that it is not available as uptake for plants which could be the reason I struggle with Blossom End Rot and have bumper crops of dandelions.
There is a theory that weeds that are needed to improve the soil will grow in abundance.

Dandelion's deep roots will pull nutrients (including calcium) from the soil and this will improve the health of your soil. So, if the top layer of soil is low in calcium *according to the theory* dandelions will grow in abundance to improve the soil.

However, it's possible that what's really happening is that with very poor soil ONLY plants able to thrive in that soil will grow. Those plants will decay, die and over time improve the soil allowing a wider variety of plants to grow. So - if the calcium is locked deep down in the bedrock those dandelions (if allowed to break down in the soil) will improve the top soil over time.
 

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