Science Buddies: "Ask an Expert"

Hello,
I was thinking of doing a project on microbial remediation and was just wondering if it would be possible to do it on nitrates (from nutrient runoff from soil)? If so, I think my dependent variable would be measuring the nitrate levels after remediation, but I am a bit unsure on what my independent variable would be.

I am buying a nitrate test kit for my experiment but am unsure which one to buy as they have different limits of the concentration of nitrate they can measure. Around what values does the concentration of nitrate in soil runoff lie? I can't seem to find it online.

For my project I am incorporating different substances into soil such as compost, manure, biochar etc and testing their effectiveness. I want to make sure I apply the same amount of each substance so I can conduct a fair test, but it's quite hard since they all have different densities and particle sizes. So I was wondering if measuring each substance to the same weight would work, or would making sure they are the same volume be better?

Thanks


Moderator Note: Since your new post seems to be about the same project, I've combined them to make it easier for the experts to see the connection. Thank you for your patience in waiting for a response. I will bring your post to their attention! Thanks!

Hi, sounds like an interesting project!
Your independent variable is the one you are changing, and hoping to see an effect from. You're hoping to see differences in nitrate runoff as a result of remediation. So your remediation/additives, which you are controlling, are the independent variable.
Regarding normal levels, perhaps this will give you some ideas? https://homeguides.sfgate.com/normal-so ... 80102.html
Also, what state do you live in? Hopefully you have a 'university extension office' which might be able to tell you about nitrate levels.
Regarding your last question, I don't know for sure but my gut says you should use the same volume of each additive, to best compare them.
I'm not a soil scientist or a chemist, but hopefully this is some help. I'm also happy to help locate your university extension office if you let me know what state you're in.