Do you recommend professional soil testing?

redwolfdoc_z5(5)December 30, 2013

Hello All! Happy New Year!

Any thoughts on the efficacy of home testing kits? I tested my soil in 2012 with a home kit and got low/adequate to depleted results for both phosphorous and nitrogen in most of my beds. I've since added lots of leaf compost to my soil but haven't done much else. This year I'd like to put more care into my amendments and start things off right... does that mean sending samples to a lab?


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anntn6b(z6b TN)

If your bedrock is uniform and if your soil profiles (vertical) are well developed, a soil test could be a wonder and really important.


In my part of the world, that works for some but not for others.

Over in North Carolina in the mountains, there are complexes of igneous and metamorphic rocks and the basis of the soils can vary significantly from one end of a fifty foot long bed to the other.

In my gardens, spread over about three acres, in some parts there are sandy soils left from river meanders, there's an area with one kind of acidic red clay. On the hillside there are different red clays, some covered with top soils of variable thickness and back by the barn there are soils developed on deeply weathered sandy-silty near vertical strata some of which have been improved by been a cattle feeding lot for many decades.

One test doesn't tell me anything that is generally useful; averaging soils is worthless for my uses as well.

If I were out in the middle of the US where the rocks are flat lying and the soils are uniform developed on them, then yes to tests. Unless you're in the middle of glaciated areas, again where generalizations fly out the window.

The only easy answer is that most soils need Nitrogen.

    Bookmark   December 30, 2013 at 2:22PM
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michaelg(7a NC Mts)

Home test kits are generally a waste of money, except for pH checks with litmus paper or a meter.

Available nitrogen is transient in the soil, so there is not much point in testing for it. Roses need N added every year. Rotted leaves can actually deplete nitrogen unless the compost is at least two years old.

If the test was accurate (no telling) you could add superphosphate. Phosphate does persist in the soil.

Most states (not California) offer cheap professional tests through your county extension office,

    Bookmark   December 30, 2013 at 2:54PM
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Also try the state university. I know nothing about CA, I'm in MA and UMass Amherst has a lab for this. Prices were lower than professional labs because they are training students to do the work. Results were very detailed, and both emailed and mailed.

    Bookmark   December 30, 2013 at 6:32PM
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My state Ag Dept. does it very inexpensively and is local. Since I test regularly for my pastures anyway, I generally check my gardens too.

Low in Nitrogen is expected and predictable. Low in Phosphorus is not. Rarely is non-agriculturally used soil (think "crops") low in phosphorus. A home test that came back with that result would make me suspicious of the tests' accuracy, particularly if I had pretty normal/common soil.

Additionally, applying phosphorus in excess can be damaging--which I realize is contrary to the "conventional wisdom" of many rosarians. I would be very hesitant to add it without a reliable/professional soil test.

Here is a link that might be useful: Dr. Linda Chalker-Scott/research

This post was edited by subk3 on Tue, Dec 31, 13 at 10:47

    Bookmark   December 30, 2013 at 7:46PM
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cecily(7 VA)

How does your foliage look? Roses communicate their needs pretty well.

    Bookmark   December 31, 2013 at 12:36PM
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I had mine done to our local county extension office but its run by KState university. There several different tests, depending on what you want to know.

    Bookmark   December 31, 2013 at 2:37PM
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toolbelt68 (7)(7)

What would one look for to determine what to add? Yellow, meaning to add _________? Dark green to add/not add .....etc??? Thanks Give me a list as I've just started learning about roses .....even though I've been growing them for 15 or more years.....
Happy New Year

    Bookmark   December 31, 2013 at 3:53PM
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anntn: thank you for your comprehensive answer! I'm in Ontario, Canada (not California) and we're on Canadian Shield bedrock. Pretty uniform! According to soil maps of the region, I should expect clay till soil, and that's pretty much been my experience.

michealg: yes, I expect that the kit wasn't particularly reliable.

LynnT: Thank you for the tip about universities. An excellent idea! There's a service through the University of Guelph, which is a big aggie school not too far from here.

subk3: Thank you so much for the great information about phosphorous and the link to that wonderful essay. I also navigated to the Dr Chalker-Scott's website and am looking forward to reading up on soils and other gardening practicalities in more detail.

Cecily: I assume that was a rhetorical question, but even so I'm going to answer it! lol. Julia Child looked great all season last year - plentiful, healthy green foliage and great repeat on her blooms. She's truly a star. Wild Blue Yonder also grew well, though was stingy with blooms and hardly repeated at all. The rest (Blue Girl HT cl., Bolero, Carefree Beauty are a few) were pretty leggy and sparse, though they're all young plants (1 - 2 years, 3 for BG) so that's not necessarily indicative of anything.

In any case, I really appreciate all the help! Please, keep it coming! :)
Happy New Year,

    Bookmark   December 31, 2013 at 4:01PM
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cecily(7 VA)

If you Google 'rose foliage nutrient deficiency' you will have a multitude of sites to choose among. Various deficiencies manifest as discolorations on the new-ish foliage. Rose mosaic virus can also resemble a nutrient deficiency but a smart rosarian like michaelg can tell you which is which.

    Bookmark   December 31, 2013 at 7:57PM
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toolbelt68 (7)(7)

Thanks bunches Cecily. By the time I get through reading all of that info we will wishing everyone Happy New Year.....again!!!

    Bookmark   December 31, 2013 at 8:56PM
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My recommendation is, if you have never tested your soils, you should at least once take a soil sample & send it off to a professional lab for testing. Have them test for N-P-K & pH (usually the basic test) and add on the secondary nutrients Ca-Mg-S. I think the main thing you should pay attention to is pH since pH imbalance can cause certain nutrients to be unavailable in your soil even if they are present. A too high or low pH causes some nutrients to be in insoluble in water & therefore unavailable to your roses (see chart scan below). I'm not a fan of home test kits because the reagents (test chemicals) in them are easily degraded by many environmental conditions...aging, high & low temps, sunlight, humidity. I remember a "Fine Gardening" article & "The Victory Garden" TV show both gave them a thumbs down. I'm also adding a scan of an "chlorosis" chart that will help you look at your plants to see if they are showing signs of a nutrient deficiency.

This post was edited by wirosarian on Tue, Dec 31, 13 at 22:38

    Bookmark   December 31, 2013 at 9:58PM
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redwolfdoc, I'm going to add one other thing that makes me suspicious of the results from your home test kit. You said the results showed you were "low to adequate" in phosphorous (P). Most of the info I have come across says that northern soils (since you are in z5, I would consider you on the lower end of northern) have high to excessive levels of P. My own professional soil tests in z4b show high to excessive levels of P.

    Bookmark   December 31, 2013 at 10:28PM
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