Newly Registered
Posts: 2
Joined: Tue Dec 27, 2005 4:24 pm
Location: Westchester, New York



I am a high school student performing a two-year science research project. I'm investigating the impact that invasive earthworms are having on the forests where I live.

Why am I on The Helpful Gardener? The main portion of my project relies on testing the soil nutrient content (NPK, and pH) in the forests, and I'm having a little trouble. Hopefully someone on the Helpful Gardener can help...

My school purchased a Hach "NPK-1 Soil Test Kit." It seems to be very advanced, and I'm sure it will work very well once I get the hang of it. The problem isn't that it's too complicated. The kit comes with an extremely detailed, step-by-step guide describing how to use the kit. I'm just worried about how accurate the tests are.
-Has anyone ever used this kit, or one like it before? Do you have any tips?
-Today, I began testing a soil sample. It was pouring rain when I collected the sample. I dried it overnight and came back to test today... The results indicated that there were 0ppm Nitrate-Nitrogen in the soil. I know that can't be true. My question-- Is this due to leaching (did the rain wash away the nitrogen)? Or is there something wrong with how I'm doing the tests? Once again, if anyone has used soil tests kits like this and knows what I'm talking about, please help.

I appreciate any response and any other tips you have.


Super Green Thumb
Posts: 4659
Joined: Thu Oct 21, 2004 5:58 pm
Location: Victoria, BC

Any nitrogen that may be in the soil would have been in the form of nitrates (NO3-), Ammonia or bound up in some sort of organic chemical. So, the rain would most likely have not washed them all away. The nitrates are more or less ionically bound to positively charged particles in the soil and therefore, depending on the pH of the rain that fell, they would most likely stay put. Ammonia can get washed away in a simmilar manner but, it's not as easy as all the ammonia being washed away after one rain.

If the soil in your forest is healthy it should have an abundance of nitrogen locked up in caron compounds or chelated by carbon compounds and that definately wouldn't get washed away.

I have never used a soil test kit because for my purposes they are rather redundant. Hopefully someone else can offer you some advice. You know a great place to ask about your kit would be a local nursery

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