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Hi, While viewing a certain compost distributors website I came across a compost analysis that they had performed for them by a soil lab. The results were in the form of a %, not ppm or lbs/acre that I have seen for soil tests.
Example: Phosphorus (as P2O5).23%
Potassium (asK2O) .45%
I contacted the lab and asked if those results could be converted into something that I could understand that would show the balance of those nutrients. The person I spoke with wasn't 100% familiar with compost analysis as opposed to soil analysis, but she did believe it could be done by moving the decimal point four places to the right. In the above example that would result in a Phosphorus level of 2300 and Potassium of 4500. That seems extremely high. Do any of you soil experts have an answer to this question? Thankyou, Tony

12/20/2006 12:10:15 PM

Cornwall UK.(50N 5W)300ft.

No expert but it sounds right,that would be a normal level for manure.

12/21/2006 3:26:51 AM

Ctpumpkin@optonline.net

Compost is usually tested a little differently with an eye toward insuring that the composting operation is finished. IE the original C:N ratio is being considered by the composter to determine when it's done cooking. To convert to pounds per acre you need to consider the bulk density of the compost. Since organic compost contains no mineral soil (essentially crushed rock or sand & clay) the material weighs much less. Hence the unusual values you're seeing when moving the decimal.

12/21/2006 7:47:46 AM

This is also why "a little goes a long way" when adding to the patch, I cringe when I see how much some growers are dumping on thinking once again "if a little is good, more is better"

Don't forget to add some good bacteria to replace those lost in the composting process this can be done in a number or ways,,,pick the one that works for you.

12/21/2006 8:33:17 AM

southwest MO

1% would be 10,000 ppm. So the conversion is correct. They are reporting in % because the concentration of nutrients are ALOT higher then soil. There is also many different ways to digest or extract soils or composts for analysis. Depending on how it is preped the results can vary greatly. The best thing to do is reacearch the method that is being used to run the samples. Keep in mind the reporting also. Results as P2O5 are alot different than results as P ect...

12/21/2006 9:46:46 AM

Caution. The test results may or may not be accurate for the material you get. Depending on how much you are getting, I would try to get a sample from the actual pile and get it tested prior to purchase or have it tested before applying. Ask if they use lime. If so, the ph may be higher than you like (or advertised/indicated in the test results) and the compost may have excess lime.

1/2/2007 9:39:54 AM