Soil samples

[Andymacp]

Some of the most meaningful results per £ I have had have been obtained by half filling a glass bottle with the 'soil' and topping up with water then shaking like hell and leaving it to stand for a few hours. Layers will form and give an idea of how much clay, silt and soil and organics. It's a doddle to take a pH test of the reamining water with litmus paper. The main thing then you are missig is mineral content, and particularly nitrogen. There's a simpe test for that too, but I'm not going to waste time explaining it in case its' more than you need.

 

 

Cheers , this is the sort of level I'm looking toward.

I'd be grateful if you could explain the rest.

[daltontrees]

All I can do is outline the principles. After that you'll bneed to get a soil science book.e.g. Fitzpatrick an introduction to soil sciences (I recommend you steer clear of the common Ashman and Puri essential soil science, it's not very scientific at all).

 

Plants need lots of things from soil. Support, water, minerals, gases, elements (particularly nitrogen and the metals calcium, iron, magnesium, potassium and a few others) and humus. A good soil will provide all of these in the right balance for the chosen plants.

Support - the texture of the soil will determine this. Clearly a soil composed mainly of sand won't hold up a tree in wind.

Water - this might come mainly from the sky but the soil type will determine whether it passes right through (taking all the nutrients with it) or can hold enough to allow plant uptake and to see the plant through dry spells.

Gases - mainly carbon dioxide out and oxygen in. Plant roots have to breathe, and too much water will literally drown them. Too much compaction, leaving no spaces between soil grains or routes for gases to and from the surface will asphyxiate them.

Elements (and minerals) - these wil be incorporated into the pant material after they are taken up. Plants will simply not be able to function properly or at all if some metals are missing form the soil. The mineral content of the soil also determines water retention capability and 'buffering' of elements, keeping them in steady supply when roots need them.

Nitrogen in particular is essential. Plants wouldn't be green without it and therefore couldn't makes sugars from sunshine and would die very quickly. Although air is 80% nitrogen, few plants can take in nitrogen directly from the air. They need to take it in as nitrates, which they do from degraded other plant material, from bacterial output or from fungi that co-exist with the plants. Organic material is therefore pretty much essential but the right bacteria and fungi can be immensely helpful. Organic material in the form of humus is also almost essential for soil texture for buffering and water retention.

Soil texture is hugely affected by particle size distribution. A good soil (a loam) will have sand, silt and clay particles. Any soil that is skewed towards or away from one of these 3 particle types will be compromised.

And finally pH. This is a result of most or all of the aforegoing things. Too much calcium for example will give an alkaline soil and rhododendrons will not like it at all. A lack of calcium would contribute to a soil being acidic, and the rhodies would like it. Other plants and fungi and bacteria might not, so the soil might be almost useless for anything but rhodies, ericaceous plants and the like.

So there's your potted guide to soil science.

For your client I would be very wary of trying to produce 'absolute' results, these can only be done in lab conditions. What perhaps is important for them and you is 'relative' results. Take your samples say a foot down around the rhodies. Then do the same in another part of the garden that doesn't have them and is away from their influence. Try to assess density (compaction) of all samples and presence or absence of worms and bugs. Do the glass bottle settling test for all samples. Get some litmus paper (I just bought 80 sheets on ebay for £2). Now you have some raw data to present. But what I mean by relative results is that if the soils are about the same in both locations, you can say with some certainty that the soil part of the equation is not significant and can be ruled out. You cna then concentrate on disease symptoms and abiotic factors.

Soil testing kits can be bought, but they're generally cheap and nasty. The last one I got broke on its first usage. And even if you do go for that option, you might get more precise results but you won't be able to bluff intrepreting them. It's not just a case of compensating for mineral deficiencies by adding plant food or fertiliser. Teh wrong fertiliser for the situation could be worse than doing nothing.

Welcome to the world of soil science and what Shigo calls the 'tree system'. Trees without soil are just firewood, and it's the interaction with soil and situation that makes trees truly fascinating.

[woodyguy]

How will a soil sample help if its honey fungus? Few causes of established plants dying that have anything to do with defects in the soil.

[daltontrees]

Are you asking me that or the OP?

[woodyguy]

Sorry, the OP. Seems that soil issues are probably the last reason that these plants will have died.

[jaime bray]

pm an email address and I will send you a sampling strategy that I prepared for prof dip arb revision. Not sure how to upload word docs into arbtalk

[Gary Prentice]

pm an email address and I will send you a sampling strategy that I prepared for prof dip arb revision. Not sure how to upload word docs into arbtalk

 

Can I be cheeky and request a copy, I've an assignment on selection, planting and design to do and the soil sampling part was a bit brief. -