NPK probe meters? : LUSENET : Countryside : One Thread

I do a fair amount of composting but it seems like its all guess work when using the finished product. Guesswork in the sense of actual macronutrient content.

I'd like to know if there is such a thing as a easy-to-use NPK meter similar in design to the moisture and ph meters used in a garden?

I know they sell soil testing kits but would prefer to use a meter if they have such a thing. It seems to me I've seen them but don't remember where.

-- john (, March 02, 2002


Yes, they exist, a scientific instrument company would be the place to look for one, about $40.00 and up if I remember correctly.

-- mitch hearn (, March 02, 2002.

I know that the lab I work for used to recommend a soil testing kit that used the Cardy line of nitrate and potassium meters. Check out, and search for "Cardy". They ain't cheap! Phosphorus is usually done by wet chemistry, even in home kits, although I have seen specific ion probes for P. However, you can get a lot of P analysis done by a lab for the cost of a specific ion probe and the meter needed to read it. Good luck!

-- Paul D. (, March 02, 2002.

I agree, if they are of any value at all, they are several hundred dollars, need calibration (balance, volumetric, reagent) , some need additional chemicals and they are fragile with expensive replacement parts, plus bench space. I have done the wet chemistry and it needs some kind of colorimeter or, in my case, a spectrophotometer. A lot of work and expense if you want a go-no-go type indicator.

Some soil-test kits have a little capsule of chemicals you mix with water from a soil extract and then you compare the resulting color against a chart. Others have a strip of paper that you dip into the water (best if filtered and using constant proportions of water and soil). The paper route is much cheaper. I bought a vial of 100 strips at 1-800-SID-WATER or www.sid-water for $10-12 or so. I wouldn't rely on it for court testimony, but it seems to work OK.

-- MartyB (, March 02, 2002.

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