Is this a supersack type bag?

A few questions may help narrow the possibilities ...

1. color of the product, and is the color uniform (all particles the same)?

2. Is it water soluble ?

3. Why did you think it might be plant food/fertilizer ?

There are a lot of materials moved in supersacks, including wastes headed for landfill or hazmat incineration. If it were me, until I had it narrowed down a good bit I would be very cautious and suspect of what it is.

What kind of an auction was this? Is there any chance of learning more from the auctioneers or the previous owners?

Tx,are you thinking it might be possiable to identify the material by observation making lab analysis unnessary?
It is in a supersack type bag.
1. Various earth tone colors
2. Not completly
3. (A) It was in a warehouse which had been occupied by a landscaper. (B) The smell is consistant with that in a feed and seed store. (C) I reasoned it was left behind because unlike the truck which delivered it ,they didn't have a fork lift . The gambler in me said the odds were favorable at the price.

Caution is why I don't plan using it until analized. Actually,if I knew for 100% certain it is plant food,I would still want it analized for nutrent %. I figure to kill two birds with a single stone with lab results. Knowing based on it having high nutrent or lack of nutrent if it is plant food and if so,if it is 1-3-0 , 3-2-1 or such and such.
While anything is always possible,I would expect the container to be far more resistant to puncture if it contained hazardous material. My primary concurn is how much of what nutrents it has and wherther it has pesticide or herbicide in it.

Tox,the previous owner skipped on the lease and the landlord who acted as auctioneer only knew what business they were in for 3+ years while in the building.

No, I don't think it's possible to ID the stuff short of analysis. But, it may be possible to narrow it down or exclude some things. As a chemist I would be looking to narrow down the possibilities with some simple qualitative testing, and go from there.

Supersacks are used widely for handling all kinds of materials, including a wide range of things you would consider potentially hazardous.

klem - look anything {{gwi:310141}}?

Any chance you can post a pic of the material similar to that one ?

Tx,it differs from your image in that (A,) the random size pieces are more "ragged" as if coming from being crushed,like tea and coffee (B) in addition,there are a few small flakes and even fewer 3/16ths diameter pellets. The pellets are definantly a processed material as in having been pressed from slurry into pellet form then baked/dried and broken into short pieces. The remainder would appear to have been ground from larger pieces.
I can't seem to get all my devices talking to one another so pictures have to wait until one of the grandkids gets things combobulated.

That image was of a K-Mag product (aka Sul-Po-Mag or langbeinite). What you're describing sounds like a traditional multi-component fertilizer, with a lot of components, perhaps including secondary and micronutrients.

Do you know if this landscaper did regular lawn service?

Do let us know what the analysis finds. You may have found a good deal.

It could be a great thing, unless it has weed killers in it and you're planning on using it on your vegetables!

This will be an interesting Sherlock Holmes project.

Anxiously awaiting pics.

When you say 'not completely water soluble', which parts are not? Keep in mind it may take awhile to dissolve in cold water. You might try a spoonful in hot water.

If it's a mixture of fertilizers and gypsum or lime, the soluble fertilizer pellets should dissolve while lime or gypsum or sulfur would not.

What's the typical soil pH where you are, and do people typically add lime to raise pH or sulfur to lower it?

It is pretty simple to conduct a DIY bioassay to determine the potential for herbicide residue. I would certainly have a lab analysis of the product done to determine composition and NPK and then you can test it yourself for any further pesticide contamination.

I'd try a variety of plants, including beans, greens (lettuce), radishes, tomatoes and sunflowers - these all germinate quickly and are sensitive to various herbicides. The link explains how to go about this process quite thoroughly.

Here is a link that might be useful: plant bioassay

gardengal,thanks for the link,that is exactly what I need plus I added bioassay to my vocabulary.

TX,I think he did installations because I didn't see worn out mow and blow equipment parts.

Tox, even if gardengal's bioassay indicates herbiside,9 chances out of ten it would be pre-emerge and suitable for many applications. I am hopeing for nothing weird so I can barter some of it. I agree it will be fun figuring it out since not much happens from now until seed starting time.
Soil ph runs high in our black clay so it's common to use sulfur or other means from time to time.