Interest in determining soil nitrogen concentrations?

[Est]

I've always been interested in taking the superstition and mystery out of the cultivation of CPs. In the past I've had the opportunity to do so from a cultivation angle, now I have more-quantitative tools available.

I'll often see discussions of old media coming up. Many repot religiously to avoid problems associated with nitrogen buildup in their soil. Many blame nitrogen buildup for poor performance of their plants or the plants of another grower. We've heard about N accumulation from a worm in the media, undrained pots, bad water -- you name it, we've heard it.

I currently find myself in a position where I will be for the next foreseeable future be running soil samples for their total carbon and nitrogen levels. In the process of doing so I need what are called "dummies." These are samples which are used as an instrument check at the start of a run so make sure that it is functioning correctly and not drifting. For these dummies I can run whatever soils I'd like. If I can save my samples for analysis rather than being run as dummies, that's great. If I find a soil which is very homogenous and gives me really consistent numbers, that's super great. I need to run these dummies anyway, so no additional resources would be spent running these samples (lest anyone reading this think I'm essentially stealing from work).

So I'd like to simply poll you for now: If any of you have old CP media (no fertilized soil please!) that you think may have accumulated N over time, would you be interested in finding out how much nitrogen is actually in those soils? I suspect that the problem is often not N buildup, but I'd certainly like to quantify it.

Notes: This would be analysis for total nitrogen and would not provide us information on which nitrogen species are present (that would cost cash and I'd probably need to buy instrument time and reagents, so I'm not really looking into that at the moment). I'll need to do some reading on how well bulk soil N corresponds with available N for peat. I'd need the samples to be largely free of roots. I'd only need a few tablespoons to be able to run the soils many times. These would be run on an as-needed (by me) basis with no guarantee that they will ever be run.

Let me know if you're interested or have any questions.

 

[pappydew]

I'll need to do some reading on how well bulk soil N corresponds with available N for peat.

Most N in highly organic soils is relatively unavailable, as a general rule, because it's likely organically "bound" versus being more available in porewater as an inorganic species (i.e. NH4+, NO3-, etc.)

However, as someone with a background in wetland biogeochemistry, I'm coming from a more "natural" view on things...what happens to the peat after X years of cultivation would be pretty interesting to see. Lots of potential chemical and physical changes could happen depending on how the grower "manages" the soil...always cool to see actual numbers!

 

[Not a Number]

This sounds like an interesting and worthwhile project. It would be of value to test samples from CP sites as a comparison.

Given state agriculture quarantine restrictions transporting or mailing unsterilized outdoor soil across state lines without permits would technically be a no-no.

 

[Est]

Most N in highly organic soils is relatively unavailable, as a general rule, because it's likely organically "bound" versus being more available in porewater as an inorganic species (i.e. NH4+, NO3-, etc.)

However, as someone with a background in wetland biogeochemistry, I'm coming from a more "natural" view on things...what happens to the peat after X years of cultivation would be pretty interesting to see. Lots of potential chemical and physical changes could happen depending on how the grower "manages" the soil...always cool to see actual numbers!

Right, I figure much of our N is not readily available, but it would be interesting to at least compare a few things. If someone had a bag of peat that they'd been drawing from for a few years, it'd be fun to see a comparison of the media from each pot over time. It'd be fun to be able to compare the total N with nitrate/nitrite/ammonium, but that's beyond the scope of what I can accomplish for free right now. I'd love to chat with you some more about your background; I've been working in biogeochemistry for a few years now and I'm still contemplating grad school at some point...

Given state agriculture quarantine restrictions transporting or mailing unsterilized outdoor soil across state lines without permits would technically be a no-no.

I run a USDA certified quarantine containment facility and have an APHIS permit to receive soil. The permit allows me to receive soil from most non-embargoed/sanctioned locations globally. All soil that is not rendered sterile by analysis is sterilized before it can be removed from lab. It'd require a few extra hoops to manage though, so sticking with things that don't require permits is always easier.

 

[Steve Booth]

A very interesting test, I have no formal training or background in soil chemistry, but I certainly would like to know the results. I have some CP media that I have used for well over 12 years, by 'revitalising' it periodically with pine bark, perlite and a small amount of new peat with some some sulphur mixed in. it seems to work OK but whether thats just because it breaks up the compaction and adds oxygen, I dont know, but you would be welcome to a sample if you think it is of any use.

cheers
steve