soil testing labs

Discussion in 'Pesticide & Herbicide Application' started by grassmasterswilson, Apr 22, 2012.

  1. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    FYI Skip, A&L Labs West does not use the same methods as A&L Labs East, so it is unlikely they all use the same methodology.

    You can accurately measure N in a lab however it requires special sample handling. A more appropriate value of N to lab measure would be total N, if you measure it at all. Also nitrogen contained in organic matter is far less transient than nitrate or ammonium, and a lab estimate with respect to organic-N would be more reliable. All that said, real time N availability (in particular nitrate) is best measured in the field.
  2. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,076

    I'm trying to keep it simple here, Kiril. I understand that different exractants adn different methods will be used in different parts of the country. If you're in North Carolina (as the OP was), I don't think you would send your sample to A&L West. The point I was making was that the private labs don't have any method or extractant that is any better than what the state labs do. Maybe the point I shoudl have made was that your state lab will use the method and extractant that gives the best representation of the nutrient profile for your state's soil conditions. If your state uses a different extractant or method than a private lab, its probably for a good reason.

    I never said that N can't be measured, but N is used so quickly by plants and changes so quickly (nitrate leaching, nitrification, denitrification, volatilization, etc) that the actual amount has changed by the time you get the test results back.

    You could certainly test the OM for N content, but mineralization rates are usually too slow to incorporate meaningfully into a North Carolina program, with OM naturally ranging in the 1 to 2% range. I don't think you're going to see much value in adjusting your N program by 0.05#N/M/yr to account for mineralization.

    You're not stumbling across anything new or revolutionary here. There's a reason (the ones I described here) why N isn't tested in standard soil test reports.
  3. v6rs97

    v6rs97 LawnSite Member
    Messages: 234

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  4. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    All potential N inputs should be considered when determining your N budget. It would be inappropriate to disregard these inputs or to think you are only going to get 0.05 lbs/M of N per year from mineralization of OM.

    FYI, A&L West includes both nitrate and an estimated nitrogen release from organic matter in their standard complete analysis package (S3C).
  5. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,076

    I agree. However, I also need to be mindful of what is environmentally meaningful and what is meaningful to the target plant.

    When my soil test report determines that my mean N mineralization rate is 0.05#N/M/yr, I think following that figure is entirely appropriate. Anyone who thinks he can adjust a standard lawn care program for 0.05#N/M/yr and apply it to that level of accuracy is fooling himself.

    I'm not here to get in a urinating contest about soil tests. You can get whatever number you want from your analysis. I'm just not sure what benefit you're looking for in a nitrate test (no ammoniacal N -- as I stated) in lawn care, since nitrate levels change by the hour in most soils.
  6. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    You and I both know net mineralization rates can vary highly due to many different factors over a growing season. That said, ENR from SOM (and other inputs) are estimates which need to be considered. For example, I have a soil test that reports 2.3% SOM with an ENR of 76 lbs/acre (~ 1.74 lbs/M) which is hardly insignificant and not difficult to adjust for.
    Last edited: Apr 24, 2012
  7. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,076

    OK, this brings up a couple of discussion points.

    1) How do you use ENR in a route-based lawn care business (of which most of us on this forum are a part)?

    2) Because ENR is an estimate derived from several assumptions, have you tested the validity of those assumptions on each of your customers' properties? If not, you're shooting blindfolded.

    3) Have you used this info to reduce your N inputs and not reduced turf quality? If so, congratulations!

    Understand, I'm not arguing against your method. I only wanted to convey to the OP that N usually isn't tested or reported b/c it changes forms and presence very quickly -- in a matter of hours, while samples generally take days or weeks to get back.

    Also, b/c mineralization rates can change radically with the weather and can vary tremendously across different areas of a single property, most of us in route-based businesses can't operationalize a program that is dependent on mineralization rate at the time of application. If you can determine the mineralization rate for each individual microclimate of a lawn and customize several different fert rates for several different areas of each lawn you treat, more power to you.

    But, in states where I have to file a nutrition plan with the Dept. of Ag that mandates equal fert amounts at each app and that plan can't be changed from lawn to lawn or microclimate to microclimate, I might find your method difficult to operationalize.
  8. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    Skip, you are losing sight of the bigger picture. Most people here are residential/commercial landscapes, not sports turf.

    To answer you questions.

    1) Don't even understand this question. A yearly budget is a yearly budget.

    2) Yes via performance evaluations.

    3) Yes

    And with regard to a states Dept. of Ag mandating every property gets the same amount of nutrients/fert per app ..... I would like to see that mandate because it is nothing short of stupid. Talk about shooting blindfolded .... damn.
  9. Skipster

    Skipster LawnSite Bronze Member
    Messages: 1,076

    OK, so what I'm hearing you say is that you're using ENR to adjust your fert to match some yearly budget number. Sounds good.

    If you're using a yearly N budget that was developed from university research, you're using a number that was developed using correlation/calibration studies that applied particular amounts of N to research plots WITHOUT regard to ENR on the plots, meaning that ENR was not accounted for in the university research (b/c of its variability). Thus, you're trying to use ENR to hit a number that was arrived at with fert on top of ENR. Subtracting ENR from your total budget # doesn't put right on the plant needs, but puts you a little short, according to university research data.

    1) If you don't understand Q #1, you're asking us to account for ENR without testing to see how much we should account. Why bother going through the extra step of ENR if you're going ot use it wrong anyhow?

    2) So, if you haven't tested OM mineralization in each microclimate of each lawn, you've shot blind, which is what you're accusing everyone else of doing. Performance eval doesn't test the assumptions. Thus, there are conditions outside of ENR that impact lawn performance more than ENR.

    3) Congratulations!

    Remember, this thread isn't a battle between us. The OP wanted to know what lab was better to test soil N than the NC state lab. I don't think knowing soil N status at any one point in time is particularly useful for route-based lawn care, but the NC state lab is just as good a lab to use as any other and is FREE to NC residents.
  10. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    You are not hearing correctly. What I am saying is I take into account all potential nitrogen (and nutrient) inputs, including ENR, in order to develop as best a management plan as possible. This is what any good land steward worth his/her salt would do.

    I use published research as a guide for what I might expect under the conditions of the study at the performance level measured. I am curious however, do you speak for all research (University or otherwise) when stating ENR and/or nitrogen inputs other than applied fertilizers has never been taken into consideration?

    Make a reasonable estimate of N inputs into the system and develop a yearly N budget based on available data, observations and management goals. Seems pretty cut and dry to me, so why the question? How accurate does your N budget (or overall fertilizer budget) need to be for residential/commercial turf/landscapes, which BTW revolve around aesthetics, not performance? The university N budgets for turf I have seen are a range of values not an absolute number as you are suggesting, and certainly not an absolute number that can be applied to all possible scenarios. Now if you have references for this hypothetical all encompassing absolute number by all means please post them.

    Where have I accused anyone of shooting blind in this thread? Perhaps in other threads I have accused people of shooting blind for not soil testing before developing a management plan, but then I believe you have as well. Further, the ENR is an estimate, even the lab doesn't "measure" mineralization rates, or at least A&L West doesn't for the test noted. What would you have, year round real time in situ measurements of plant available N for residential/comm landscapes in order to make a reasonable estimate for N inputs outside of your applied fertilizer? You are being absurd. One can make reasonable assumptions to estimate all N inputs using published research/data, soil/plant tissue analysis and observed plant performance in order to develop a relatively informed N budget. But it would appear you would rather ignore those inputs .... or perhaps we should all just follow the back of the Scott's bag?

    Gee, thanks.

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