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Nitrogen deficient compost

Posted by GWTaz 7a (My Page) on
Wed, Feb 12, 14 at 7:59

Am researching the nitrogen content of my various compost piles using my cool LaMotte soil tester. I was astonished to find that all of my manure compost piles as well as my leaf mulch compost pile had no nitrogen or just a trace. It was my understanding that horse manure (no lime, very little bedding) is rich in nitrogen.. Anyone??


Follow-Up Postings:

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RE: Nitrogen deficient compost

Horse manure is considered a hot source of Nitrogen because it is fairly readily available, however composting it changes that. The Nitrogen in compost is not very readily available but it is there, just not very soluble and your test looks for soluble Nitrogen. The same with the N in leaves, it is there just not very soluble so tests do not show much.
The test I have had done on my compost, most often made with horse manure and shredded leaves, show an N content in the 1 to 2 percent range, but the plants growing in soil amended with that compost grow quite well. The soil bacteria release the Nitrogen as the plants need it.


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RE: Nitrogen deficient compost

It is your tester that is at fault :-) Nitrogen is the most mobile and unstable of all the soil nutrients and unless using rather sophisticated labs and apparatus, virtually impossible to measure to any degree of accuracy. Certainly with any home testing kit. Heck, even many professional soil labs do not test for nitrogen because its levels can vary from day to day, hour to hour and even in sun versus shade so they are unable to report with any accuracy!

Any reasonably decent organic matter that is not wood based - compost, manures, leaves, grass clippings, etc. - should provide very adequate levels of N for at least one growing season.


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RE: Nitrogen deficient compost

What is the LaMotte actually measuring? Ammonium, nitrate...? Just curious. And how is it calibrated or checked?


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RE: Nitrogen deficient compost

good question. I have no clue so researched. This is what I found when google LaMotte soil nitrogen
"This Nitrate Nitrogen Test Kit tests for nitrate nitrogen levels using cadmium reduction which undergoes diazotization/coupling to form a pink color. Levels are determined using the Octa-Slide 2 comparator. Range and sensitivity is 0.25, 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 10.0 ppm NO3--N."

I have absolutely no idea what it means. Shades of pink I could figure out.


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RE: Nitrogen deficient compost

I read elsewhere that Nitrogen is really hard to test for so decided that I shouldn't worry about it. Don't seem to have problems associated with nitrogen deficiency so am cool with that.

Thanks everyone.


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RE: Nitrogen deficient compost

It should be easy to add anyway, right? Urine, blood meal, bunny food pellets with Alfalfa. Manure tea.


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RE: Nitrogen deficient compost

It is very easy to add too much Nitrogen too, which then would promote lush green growth that would be more attractive to insect pests and plant diseases. Excess N can also interfere with the plants ability to utilize both major and minor nutrients.


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