Help Interpreting a Soil Test

I just got the soil test back from the lab. From my own vague notions, it's more or less what I expected. I'm looking for a more precise analysis so that I'm able to intervene better.
The LaMotte part is the most confusing. I'm also looking for the quantities of minerals to add (kg/square meter or pound/square foot)

My own observations:
--pH is low, should be 6-7
--CEC is low, should be 15-20+, due to very low humus level (4.40% - should be 10%-40%)
--Ca is low, Mg might be okay. Adding Ca might raise pH level, which is good.


Thanks for the help.
William

Since your N, P, and K are all low, I take it you will be applying lots of organic matter to cure that problem. What type of green manures do you have available to use?

As far as the other soil nutrients, definitely add some calcium. Since you are close to the Dolomites, can you easily get some crushed dolomitic limestone? That would help on both the calcium and magnesium levels. As far as application rates, you have a long way to go to build up your soil, so one application is not going to do it. If you apply some limestone, maybe some gypsum, along with working in a lot of organic matter, then next year's soil test will show some improvement. For this year, go with a heavy application; 3 tons/acre of gypsum and 2-3 tons/acre of limestone, along with as much biomass as you can reasonably apply. How much area are we talking about here?

Then there is the issue of timing. Are you planning on tilling in your soil amendments, or are you going to layer it on and let time do the work for you? As much as permaculture is about no-till methods, when you come across a piece of new land that is depleted of nutrients, that's the one time when you can actually gain by tilling, because you are working with a practically clean slate that isn't supporting a lot of soil life already. If you till in now, then the next cycle you may plan on using less disturbance and layer on the amendments. I would plan on 3-5 cycles of soil amending to get your values up to the optimal range.

Another thing to note is that your soil boron levels are quite low. This is going to be important for actually getting some production out of the soil, as this reference describes. An application of a couple pounds/acre of borax should help to correct this.

The area is 400 square meters roughly. Planning on finding a source of finished compost nearby. We have access to rotted manure. I was planning to fork in 2 inches of compost and then mulch with 2 inches more every time I weeded this year, which is about every week or two. The soil just eats up everything I throw into it. We have small wood chips and straw, will probably add some of those on top.

I see P/K, but I don't see N in the soil test, maybe I'm missing something. I read that N isn't an important testing parameter, unless it's right before you sow.

Perhaps because this test was taken right after the summer growing season when everything was pumped out. Or I took bad samples, which is possible.

The garden was surprisingly full for such a bad test. Lots of heavy feeders (tomatoes, celery, peppers, etc). They seemed healthy but slow, but I attributed that more to a lack of water and not nutrients. It was a 4 month drought and I have water supply issues.

William

The nitrogen is contained in the nitrate and ammonium ions, at the far right of the table. You're correct that since it is so labile, what's in a soil test, unless it's right before you plant, isn't a whole lot of use.

Have you considered adding biochar? That could go a long way to help hold on to the nutrients you add to the soil. Since you say you are in Northern Italy, I was thinking it doesn't get so hot that you have stuff decomposing that fast, but maybe you do. Here in Georgia, I deal with FAST rates of decomposition of added organic matter. The only way I can possible stay ahead is to char some of that organic matter so it won't metabolize away. For 400 square meters, you could start by working in 400 kg of biochar -- which a LOT of charcoal. You may want to get yourself a 200 liter barrel (got to keep it metric!) and make your own like this guy here:



After trying numerous other methods, I have latched on to this one as the easiest way to generate your own biochar. For each barrel batch, you can get about 5kg of biochar. I've been spending the winter raking up leaves and debris, charring it, and dumping it on to all my hugelbeds. I'm looking forward to a productive spring in the garden.

The number that jumps out at me most from your test is the CEC, or Cation Exchange Capacity. You can think of this as how big of a sponge is your soil; as in, how much nutrients can your soil hold. Your CEC is quite low, so your soil's ability to hold nutrients is very limited. Even if you add a ton of P, which you need, your soil does not have a mechanism to retain that P.

Calcium will improve your CEC. Humus is not the issue. 4% humus is not bad at all, I understand that 7-8% is the max you want, so humus is by no means your weakest link. I would not use dolomite, because proportionally speaking, you need calcium much more than magnesium. Add calcium lime, realizing that calcium takes a year or two to fully assimilate into the soil and show up in a future soil test. Don't over do it. Slow and steady wins the race.

The other thing to improve your CEC is to get more clay into the soil. I might think that some fertile, dark clay would be the most valuable amendment you could add to start. Clay and calcium will increase your CEC, giving your soil a much greater nutrient holding capacity. Then add your P, N, etc as needed. Until your CEC improves, you can only hope to feed the plants, as your soil simply cannot hold much nutrient.

Hmm. I have heavy clay, so I think I have my fair share of clay.

I saw that low CEC is usually found in sandy soils, and I have the opposite. I thought it might be the high negative ions in clay that might be tying up nutrients.
William

I see, then certainly no need for more clay. I'll also change my other suggestion, and agree with John on the dolomitic lime. Your magnesium is just as low as your calcium, sorry I overlooked that previously. Dolomitic lime is the ticket, for sure. Magnesium increases CEC faster than any other soil mineral.

There are soils like yours in the Deep South of the US. Heavy clay with low fertility. Fortunately you are only trying to remedy a small area, as these soils are among the most expensive to enrich. I dont mean to sound like a broken record, but Steve Solomon talks about this specific soil type in Intelligent Gardiner. Always a good resource for balancing your soil.

Have you done a soil separation jar test? If so what percent of sand, silt, and clay are present?

Haven't done a jar separation test. I had planned to do it but other things came up. I'll do it in spring and take a pic and do it again in summer to see if I'm making any gains in OM levels.
W

William James wrote:The area is 400 square meters roughly. Planning on finding a source of finished compost nearby. We have access to rotted manure. I was planning to fork in 2 inches of compost and then mulch with 2 inches more every time I weeded this year, which is about every week or two. The soil just eats up everything I throw into it. We have small wood chips and straw, will probably add some of those on top.

I see P/K, but I don't see N in the soil test, maybe I'm missing something. I read that N isn't an important testing parameter, unless it's right before you sow.

Perhaps because this test was taken right after the summer growing season when everything was pumped out. Or I took bad samples, which is possible.

The garden was surprisingly full for such a bad test. Lots of heavy feeders (tomatoes, celery, peppers, etc). They seemed healthy but slow, but I attributed that more to a lack of water and not nutrients. It was a 4 month drought and I have water supply issues.

William

I have noticed this too, my soil test labs ignore the N, but I can get that test at any garden center for cheap. I think the lab assumes we already have too much NPK, because perhaps they assume we have been applying the fake fertilizers for years already. Not so in MY sand. Have you looked at www.soilminerals.com? and any William Albrecht, or Neil Kinsey work already? Another additional great I would recommend would be Alan Savory's article 40,000 elephants; http://articles.mercola.com/sites/articles/archive/2013/03/30/grazing-livestock.aspx
He came from the generation of wildland management that told us all grazing animals increased the desertification of the lands, and he personally took part in killing 40,000 elephants from Africa, only to discover desertification worsened. He has converted from that experience to real science and is now an advocate for grazing animals improving the soils. Thier fertilizer pellets help spread organic matter and any minerals they may have eaten- add this to Pat Coleby's natural livestock books, and in a desolate sandy land where minerals are all deficient, she deliberately allows free choice mineral selection for her cattle, horses, sheep and goats, and they Assist in the mineral dispersal. my system is incorporating these methods. I too have a sandy infertile base.

I wouldn't worry about N beyond maybe planting/innoculating some legumes. Maybe even perennials if you can find good ones for your climate.

Some things I do note, your calcium is low (should be 65% of CEC), and so is your magnesium (should be 15%). Dolomite has too much magnesium vs calcium, and should be used primarily for magnesium and use regular lime for caclium. Your K level is fine.

Your sodium is a little low (should be 1-1.5% of CEC) and boron is way low (should be 4ppm). Copper is fine, but your zinc is way low (should be 25ppm). Your manganese levels are pretty high, but that's fine.

Phosphorus is not a cation, and has no relationship to CEC. Your P is pretty low for an M3 reading, rock phosphate or manure can fix that. Sulfur also isn't a cation, and your sulfur is really low. S should be 100ppm or so, and yours reads 10. Gypsum is in order.

Your CEC is rather low, but not too low to be fertile. 40% organic matter is unreasonable, 7-12% is more realistic, but if you try to force feed manure to those levels you'll probably end up with problems (and it's expensive). Your pH isn't all that low and would quickly be corrected if you add Ca and Mg, which leaves me wondering what your soil type is like. That's a low CEC for a soil that isn't even very acidic.

EDIT: Just read sand. That explains everything.

Your CEC is rather low, but not too low to be fertile. 40% organic matter is unreasonable, 7-12% is more realistic, but if you try to force feed manure to those levels you'll probably end up with problems (and it's expensive). Your pH isn't all that low and would quickly be corrected if you add Ca and Mg, which leaves me wondering what your soil type is like. That's a low CEC for a soil that isn't even very acidic.

EDIT: Just read sand. That explains everything.

I have heavy clay, not sand. I would not be surprised by low CEC if I had sand, which is not the case.

I also thought the pH test was pretty acidic (5.50). I assume you mean "adding logs of OM" when you talk about force feeding, which is sort of what I was planning to do (compost not manure). The low CEC would suggest adding OM, but the low-ish pH suggests not adding OM (humic acids raise acidity, lowers pH).

So I'm thinking: raise CEC via Gypsum + compost, add borax. Sulfur/Mg might go up with a better CEC. Add again and again and again on a low but regular basis. It's not so difficult if I include it with the weeding strategy with is a regular thing and water with the minerals as I water.

Compost levels I can control via a Jar test to check OM levels. Should I go with the 3 tons/acre of gypsum = 740g/m2 ?

The other curiosity is the LaMotte test. Do the numbers correspond to the CEC/Nutrient test? I'm wondering why I even got that test.
edit: with all the LaMotte testing kits out there you would think someone would have a guide to the results.

Thanks again. Trudging through a little confusion here.
William

I found this interesting:
http://cals.arizona.edu/pubs/garden/az1413.pdf

Gypsum: Will not change soil pH
Dolomite Lime (Ca+Mg): Raises soil pH; not soluble in higher pH soils

So, I guess I'll go with Dolomite Lime, unless anyone objects. Need a higher pH and need a Ca/Mg-induced CEC raise.
Or perhaps a mix of Dolomite (low %) and regular lime (higher %) to ease up on the Mg.

William

William James wrote:
Gypsum: Will not change soil pH
Dolomite Lime (Ca+Mg): Raises soil pH; not soluble in higher pH soils

Highly oversimplified, and not really true. This oversimplification might work in Arizona, an arid and alkaline place. But it is not scientifically true, and not universally applicable. Definitely not relavent for your soil and enviornment.

The key consideration and objective is your cation saturation ratios. In your case, anything that displaces Hydrogen will raise your pH. So Ca, Mg, or even K would raise your pH by displacing H. Mg is the most powerful cation, then Ca, then K. So molecule for molecule, Mg would raise your soil the most.

The caveat is that pH doesnt really matter. It is the cation balance that does. You want a balanced cation ratio. Something like 70-80% Calcium, 15-20% Magnesium, 5% Potassium. Then your pH will be allright, but it isnt really the pH that matters. You could say that pH is just one indicator of things, and not itself the thing that matters most.

Thanks for shaing your soil numbers here, it's given me some interesting food for thought. Worlds apart from my soil type, but definitely a good mind excercise.

Thanks for shaing your soil numbers here

Thank you for bearing my lack of knowledge and confusion! I'll be buying a book soon to help myself out.

So, to get (eventually) a balanced cation ratio, which of these should I use and how much? compost, manure, gypsum, Lime, Dolomite, Calcium sulfate, Potassium fertilizer, borax
I'd dealing with 2-300 square meters.

Thanks,
W

William James wrote: compost, manure, gypsum, Lime, Dolomite, Calcium sulfate, Potassium fertilizer, borax
I'd dealing with 2-300 square meters.

Thanks,
W

Let's take these in turn. I can appreciate 2-300 square meters, because that is the size of the plot I am trying to improve.

Compost/manure: A dump truck load is roughly 10 tons. It spreads out pretty thin over that amount of area. A truckload of each right now would be a start, but only a start. You will be wanting a couple of truckloads for each amending cycle.

Gypsum/calcium sulfate (same thing): 1kg/sq. meter? You can't really overdose on this stuff, as there are places that have natural gypsum soils and plants grow just fine there. Of more concern is where to get it at low cost (like the manure and compost). I like to use drywall. Get scraps of it from a building site and cut it into pieces and scatter it all over the field. Rains will rot the paper off of it and in time it will crumble and incorporate into the soil. Any crushing or grinding that you do just speeds up the process. There is a lot of drywall that has bits of fiberglass added to it (for strength), and I haven't noticed any detrimental effects of the added fiberglass in my gardening.

Lime/dolomite: Depends on how soon you want to plant. The more you apply, the longer you should wait to plant. If you intend to plant this area in April or so, you would be safe applying 100 kg now and letting that work in.

Potassium fertilizer: Since you are just at the low level of the range, I don't think you have to go out of your way to apply this. Compost and other organic matter is a good enough source that working some of that in will bring your potassium level up. If you come across any wood ashes, just scatter them all over and let the rain soak that in.

Borax: Rather than a field application, I would add small amounts every time you water. I like to add a gram or so (yes, just 1g) to a 20 liter bucket of compost tea and use that for foliar applications. Boron doesn't move very well in plant tissues, so foliar applications are the best way to get it to where it needs to be.

In order:

Compost/manure: Wow! Amazed that it's going to take that much. But it does make sense.

Gypsum/calcium sulfate / drywall: I just found out I live really close to a drywall recycling factory. It might be possible to get some from them - already granulated.

Lime/dolomite: I usually always have the beds planted, so I imagine I'm going to have to go with lower concentrations more frequently.

Potassium fertilizer: Ok. Ashes in small quantities scattered widely.

Borax: Ok. Foliar feeding was something I was interested in doing anyway.

Thank you!
William

How well does your soil drain? If you add have clay, it likely doesn't drain well. If you add magnesium, it will tighten up and drain even less well. If your soil doesn't drain well, you are going to have lots of problems. Around here, you can get wood chips for free. Can you get them or other OM free? I agree with earlier poster that you need to think long term. Adding OM will help you have better TCEC, a bigger sponge/pantry to be able to hold onto or accept nutrients. Right now you need to be careful not to add too many minerals to shock the plants. I second the recommendation of Steve Solomon's the Intelligent Gardener. Answers exactly the questions you are asking.
John S
PDX OR

How well does your soil drain? If you add have clay, it likely doesn't drain well.

The soil remains wet or inundated for 8 months a year. Then for the 4 summer months it has zero water in the top few inches.

Perhaps I'll start with heavy compost and wood chips and gypsum, then start with a little dolomite later on when things open up a bit.

This week I'm going to the local compost/wood chip factory and seeing how much it's going to cost to use their materials.
W

If you talk to someone who boards horses (for tourists, maybe?) or other animals, they will surely give you their manure for free, even if you can't find a tree company to give you chips. Any other multi animal owners will likely do the same. That could also be a great start. I would start on the drainage/ OM issue first.
John S
PDX OR

Just bought the Intelligent Gardener. This thread was the push I needed to do that. Thanks.
William

I found drywall! And it is granulated and costs only 15 euros a Ton.
And they sent me an analysis of the material.

Here it is. The only strange thing I see is Pb at 19 mg/kilo. Is that too high to use?

edit: now that I look at it, it's seems to have a lot of Mg. Only 68% CaSo4....or 86% with water....?

William

It looks fine. If only the food coming out of China had only 19 ppm of lead in it. And that's not a lot of Mg either. In dolomite, you can have equal parts Mg to Ca, and that would be perfectly fine to apply to your garden.

You've got it right that the different ways of expressing the calcium percentage depends on whether or not you count the 2 waters of hydration. Apparently this lab gives you both values, in case you have trouble figuring out how to convert from one to the other. Since you are going to be using it for soil amendment and not making plaster or drywall, it really doesn't matter. In the soil, any anhydrous molecules will quickly pick up the two additional water molecules.