Topic: Shelf life of compost?

[caroline7758]

I need to buy some compost and as it's always cheaper to buy multiple bag, I was wondering if I buy it now will it still be ok to use in the spring or will it have lost anything by then?

[grannyjanny]

I think the recommendation is not to store. Having said that this year I bought some JAB compost which was not fit for purpose so in desperation I used a bag of last years compost which had been outside throughout the Winter ::). Brilliant germination so I shan't  worry in the future. The same thing happened with grow bags.

[goodlife]

We had this question raised by some of our members (those who are never happy for what you are trying to do ::))..as we had to buy big bulk order to qualify for decent discount..some grumpies were trying to say.."it will go old"..
Anyway we contacted for few companies to raise the issue and answer was...
generally composts will last fine for few years..providing that they are stored in dry conditions, if not, fertilizers will eventually leach out...this compost is still usable but will not have enough nutrient for proper plant growth.
However..if the compost contain special treatments eg. insecticides the shelf life should be stated on packaging.
"Old" compost can be 'revitalized' by adding some BFB fertilizer..but if it is used for seed sowing or just general addition into soil, it's fine as it is... ;)
Problem with 'old' compost that has been stored away from weather is, that it may become dry. Re-wetting the stuff will take some doing..mixing with 'fresh' moist stuff is easiest way of using it..but the nutrients should have not disappeared anywhere during storage. If the compost is made with peat...peat itself is 1000's yrs old..so no worries 'going' old ::) ;D
The recommendation for '"not to store" is because if stored 'badly'.."the what it says on the bag" doesn't apply anymore..and then folks start complaining ::)

[caroline7758]

Thanks, goodlife, that's very helpful.

[lincsyokel2]

Years.

When was the last time you heard of a peat bog going off ?

[grannyjanny]

Will we go gff before it then ;) ;D.

[Robert_Brenchley]

When was the last time you heard of a peat bog going off ?

They go off when drained.

[Tee Gee]

The recommendation for '"not to store" is because if stored 'badly'.."the what it says on the bag" doesn't apply anymore..and then folks start complaining ::)

I generally agree with what ' Goodlife' says apart from the bit about what ' it says on the bag'

There is nothing on the bag!!

I raised this matter a few years ago with the gardening press I.e. All other products containing fertilizer had to have the NPK values printed on the packaging,this is not the case with compost!!

The reasoning that was given was ' storage' could alter the ratios.

I agreed with this but pointed out on the same packaging it usually says; this bag contained x litres at time of package intimating this might not be the case at point of sale.

Why can' t they do the same with NPK values?

I tend to buy multi- purpose compost when it is cheap but not potting compost,which I like to buy 'fresh' but how fresh is fresh??

I use the MP diluted with sand as seed compost and add ' potting base' fertilizer to turn it into potting compost.

I just assume that there is no fertilizer in the MP  which is fine for seed sowing! Adding my own quantities of base fertilizer!! gives me the compost that I want.

Next season I plan on making all my own compost,in fact I ordered all the ingredients today.

I am sick of this stuff that is being put out as ' compost' these days so to h*ll with the Eurocrats,I' m doing it my way!!

[lincsyokel2]

When was the last time you heard of a peat bog going off ?

They go off when drained.

They dry out when there drained, they dont go off though..............peat bogs do not have a Sell By date.......

[lincsyokel2]

The recommendation for '"not to store" is because if stored 'badly'.."the what it says on the bag" doesn't apply anymore..and then folks start complaining ::)

I generally agree with what ' Goodlife' says apart from the bit about what ' it says on the bag'

There is nothing on the bag!!

I raised this matter a few years ago with the gardening press I.e. All other products containing fertilizer had to have the NPK values printed on the packaging,this is not the case with compost!!

The reasoning that was given was ' storage' could alter the ratios.

I agreed with this but pointed out on the same packaging it usually says; this bag contained x litres at time of package intimating this might not be the case at point of sale.

Why can' t they do the same with NPK values?

I tend to buy multi- purpose compost when it is cheap but not potting compost,which I like to buy 'fresh' but how fresh is fresh??

I use the MP diluted with sand as seed compost and add ' potting base' fertilizer to turn it into potting compost.

I just assume that there is no fertilizer in the MP  which is fine for seed sowing! Adding my own quantities of base fertilizer!! gives me the compost that I want.

Next season I plan on making all my own compost,in fact I ordered all the ingredients today.

I am sick of this stuff that is being put out as ' compost' these days so to h*ll with the Eurocrats,I' m doing it my way!!

most retail multipurpose composts have an EC of about 500. soil is about 300. Professional potting and bedding is about 800, thats why plants grow better in professional growing media. I keep trying to convey this to people, there a HUGE difference between retail and professional growing medias.

If i have to use a retail media, i will usually add more ferts to it, depending what i want to use it for.

'fresh'  is peat that was harvested this year, ie after january 1st but before last week.

The reason they dont print NPK values on is because you cant g'tee every bag is identical, and at £50 a lab  test, its not really economic to test every bag.......Even most professional growing medias only get an EC, moisture and Bulk Density test and thats all, and you're talking about a 72 cubic metre load thats selling at £50 a cubic metre.....

Also, the formulations of most composts is a trade secret, including the nutrient balance, pH and other properties.

[Tee Gee]

Very interesting that Lincs

Excuse my ignorance but what does EC stand for?

I have considered the professional mixes,Levington M series comes to mind,but the cost puts me off a bit!

I find that making my own compost meets the need of the type of stuff I grow but I understand the need for the commercial people wanting  a better quality mix. They want a better % germination rate than  perhaps I would accept.

I can recall visiting a nursery and watched the mechanical seed handlers sowing one seed per cell,even dust sized seed they are amazing.

I had it pointed out to me that for instance begonia semperfloren seed was gram for gram more expensive than pure gold.

So a few % drop in germination can be quite expensive to them.

I see your point about the testing, but I thought that batch testing would suffice us amateurs.

Like you say the mixes/ formula are secret but the cynic in me sees this as an excuse to keep the fertiliser ( the expensive bit of the mix) to a minimum therefore keeping the cost of a bag down.

When you think the sand/ peat content in all brands are similar then the cheap stuff you buy is likely to have less fertiliser in it making the NPK content variable.

I know from my working days that this is how it works in the food industry. 

Expensive brands usually have higher levels of the main ingredient in them for example M&S yoghurt has the highest fruit content of all the yoghurt brands.

As I said it is the cynic me that makes me think as I do ;D

 

[GodfreyRob]

Generally its not poor germination that is the problem for me, its the seedlings running out of food too soon.

I would have thought the germination success is more dependant on the compost structure/drainage (assuming you provide the right heat/water) - seeds have their own in built food store after all.

For several years I have used New Horizon multi-purpose peat-free compost but every now and then a sowing would fail, not at germination but a week or 2 later - the seedlings would just stop growing turn yellow and die - and I am almost certain its because there was little or no food in the batch of compost. Also even a good batch would run out of food within 4/5 weeks - so not great for potting on.

I've almost got to the point of giving up on the peat free because of these problems.

Does anyone know of a better compost that is not based on peat?

[shirlton]

We have allways used homebase MP until last year when we used Eden. We had great results from both.
This year we were on homebase and thought we would get our supply of theirs as it was more convenient.One had an ants nest in (which they said was quite common and the rest was used for sowing and potting. The stuff was useless it wouldn't hold water at all. Will definitely go back to Eden.

[Digeroo]

I have been mixing my potting compost on a 50 50 basic with recycled compost.  If the seeds are very small I put a layer of the potting only on top.  Have had brilliant results, no running out of food.

I have left compost over the winter in poor conditions and the result in the spring was a slimey mess and a crop of toadstools.   I now use mine up and buy fresh.

Peat bogs are anaerobic so I would think that the addition of air may have a detrimental effect.  But with the advent of peat free you don't know what is in it.

[earlypea]

Does anyone know of a better compost that is not based on peat?

Not really, but I had very poor results with the New Horizon and others and feel bad buying peat so I went for this stuff this year.
Moorland Gold - Reclaimed peat, soil association approved.
http://www.wrorganics.co.uk/moorland.html
Trouble is if you get it through retail suppliers by the bag it's really expensive.  I ended up clubbing together and getting a pallet delivered which made it reasonable, but not the cheapest.  Very good results.

[lincsyokel2]

Very interesting that Lincs

Excuse my ignorance but what does EC stand for?

EC - Electrical Conductivity.  The crude way to measure the total nutrients in a medium. The point here is that nutrients exist as free radicals, ie part molecules with  an electrical charge (because they are either short or have an excess of electrons). This means in theory if you stick two copper rods into a bag of compost you can measure the potential difference created by the flow of ionised nutrients. So the higher the EC, the more nutrients. Soil is about 300 on the scale (its measured in a really obscure metric called Microesiemens per cubic centimetre  - uS), retail compst is about 500, good prof medium is 800-1000. The stuff thats been sat in your compost bin at home for two years is around 2500. If you know that, you can calculate how to mix it, eg 1 part home compost at 2000uS and 4 parts soil at 300 us will give you a medium with an EC of (2000 + 4x300) = 640, which will rock the socks of any retail compost.

I have considered the professional mixes,Levington M series comes to mind,but the cost puts me off a bit!

Thats why professionals use them, there good. Also, bear in mind professional growers sometimes have various agrochemicals added as well as slow release fertilizers, but in the end that why they manage to produce thousands of identical plants for places like B&Q

I find that making my own compost meets the need of the type of stuff I grow but I understand the need for the commercial people wanting  a better quality mix. They want a better % germination rate than  perhaps I would accept.

I can recall visiting a nursery and watched the mechanical seed handlers sowing one seed per cell,even dust sized seed they are amazing.

I had it pointed out to me that for instance begonia semperfloren seed was gram for gram more expensive than pure gold.

So a few % drop in germination can be quite expensive to them.

absolutely. Most growers would not tolerate lower than 96% or so germination rate. When your growing 75,000 poinsettias for Tesco (not an unusual contract) , 4% germination fail is 3000 plants.

I see your point about the testing, but I thought that batch testing would suffice us amateurs.

Like you say the mixes/ formula are secret but the cynic in me sees this as an excuse to keep the fertiliser ( the expensive bit of the mix) to a minimum therefore keeping the cost of a bag down.

When you think the sand/ peat content in all brands are similar then the cheap stuff you buy is likely to have less fertiliser in it making the NPK content variable.

exactly correct. Peat is cheap - its cost about £12 a cubic metre to harvest and move it, its the agrochemicals that bang the cost up. Some slow release ferts can cost £10 a kilo, which if your mixing in at 2.5kg per cubic metre is expensive. The average person will never use enough different composts to really be able to tell the difference, but its still there. Its when you have 1000 plants all in 4 different composts you can see the effect. For this reason, just like the drugs industry, growing trials are usually secret until the results are known.

I know from my working days that this is how it works in the food industry. 

Expensive brands usually have higher levels of the main ingredient in them for example M&S yoghurt has the highest fruit content of all the yoghurt brands.

As I said it is the cynic me that makes me think as I do ;D

 

Another point is, believe it of r not, some growers have no idea whats in the compost there using. This is because they left it to the compost makers and there technical guys to come up with there special formulation, which they keep secret. So if you want to move to a rival compost supplier, then you have to reformulate it from scratch. If it works ok already , no sane  grower is going to take that risk by fiddling with the status quo.  Another point is that prof media is generally better sterilised - the worst thing a grower can get is weeds, because they have to be handed weeded, and thats seriously expensive to do. Weeds in 75,000 2 Litre poisettias pots woudl basically wipe the crop out, the cost of weeding woudl be prohibitive.

Another dread problem is stones.  Stones in compost will wreck potting up machines (you mention earlier), and even worse, some compost comes in 3 cum compressed bales, which are reconstituted into usable compost by a big machine called a Bale Ripper, stones in a bale ripper is on par with a flock of birds flying into a Airbus 320 engine.

Growing media is a huge subject, the minuatae of it is endless.

[lincsyokel2]

Does anyone know of a better compost that is not based on peat?

Look for coir based peats. PM me, i might be able to help you.

[kypfer]

Look for coir based peats.

but be careful ... I bought some early this year, in compressed blocks, advertised as making up to a specific volume when mixed with water ... seemed like a reasonable price.

I managed to "misinterpret" the fine print. The advertised volume of compost is only achieved when mixed 50/50 with sand, the compressed block itself only made up to half of the advertised volume.

It is mentioned, in the fine print, that the compost "works better" (or words to that effect) when mixed with an equal volume of sand. It doesn't mention that the advertised volume is only achieved with the sand added. This made it rather more expensive  >:(

[grannyjanny]

I bought some of those from Poundland Kyper, 2 in a pack for £1. I must read it carefully then when I use them. I mininterpret things very easily in instuctions so thanks for the warning ;).

[Digeroo]

It doesn't mention that the advertised volume

Suggest that you take it back and ask for a refund.  I would not expect to have to add saind to compost to get the stated volume, in fact I would not expect to have to add it at all.