highly calcareous soil: what to do?

Hi,
the soil test for field I intend to use to grow fruit trees, gives me 37% CoCO3 content in the top soil and 31% at 60 cm depth, and pH 8.

Soil conductivity is not too high in the topsoil (0,304 dS/m) altough it becomes higher at 60 cm depth (0,675 dS/m). So it looks like there is an axcess of lime.
'Ca' is also a bit high 4505 mg/Kg (the lab suggests that there can be gipsum there).
The soil texture is loamy-clayey-silty in the top soil and clayey in the subsoil at 60 cm depth.
Organic matter content is low: <2%.
Soil compaction is also an issue, mostly because the land has  been used for growing cereals for a long time: wheat/barley, so machinery may have compacted the soil
A chromatography test shows that microbial life is pretty much depressed there.
Iron seems to be low aoverall as well.

We are in mediterranean climate with mild winters and hot summers, although there we can have some precipitations all along summer time too.

So my question is what can I do to amend this soil? and what fruit trees would do best there?

I know I can remediate soil compaction by deep ripping and planting deep rootes plants, also can initially amend by bringing in microorganisms already present in other nearby places or even inoculate the soil and plants with micorrhizas. Appropriate cover crops may bring in more organic matter over time and contribute to lower the pH a bit, still I feel the lime content is what worries me most at this point, as I consider it to be a somewhat limiting factor of importance for many crops since high concentrations of lime prevent certain nutrients to be taken by fruit trees. So it is also important to determine which fruit trees can most easily grow in this type of environment. Some almond and vitis vinifera I think can do well, may be some corylus avellana too, but I'd like to consider a higher diversity.
Any help appreciated

I'd plant pomegranates, figs, cornelian cherries, plums, lemons and oranges. These will grow in 8 PH soils. Again, not knowing how cold a "mild winter" gets, I am guessing that these might do well.

Soil ammendments? Swales and mulch, mulch, mulch. Dry straw, bark mulch, compost, legumes as a living mulch.

http://www.almanac.com/content/ph-preferences

Hi Jd,
from weather, stats, in the last 30 years the lowest temperature was -16,5 ºC (and it happened just once), so I would exclude oranges and lemons, unless a very favorable microclimate is found (for just a few specimens).
But thanks for your inputs I'll consider them.
Cheers

Interesting soil you have there. Does your soil test have a Cation Exchange Capacity (CEC) number on it or was it only Electrical Conductivity? Also, does it list the magnesium and sulphur content? I think you should determine if you want to grow trees that will thrive in the soil's current pH or if you want to grow trees that thrive in a slightly acidic soil. I glanced at the link Jd provided and it does appear some fruit and nut trees may do alright with the current soil pH, but it sounds like some levels of certain elements may need adjustment. You're absolutely on the right track with wanting to plant deep rooted plants, and inoculating with mycorrhizae. Note that mycorrhizal fungi are dependent on roots to do their thing, and other bacterium (like certain strains of Bacillus for example) are not completely dependent on roots, but they do thrive well with root exudates. Jd has great advice adding straw, mulch, compost and a living legume mulch. Adding materials high in lignin like wheat straw builds humus fast with the aid of things like earthworms and a healthy population of microbes. Manures from grazing ruminants (which is basically animal composted grass), compost, straw, some hardwood mulches, and some microbial soil conditioner, and then sowing a cover crop that tolerates alkaline soil are all good things you can do to improve your soil.

Hi James,

James Freyr wrote:Interesting soil you have there. Does your soil test have a Cation Exchange Capacity (CEC) number on it or was it only Electrical Conductivity?

No I don't have it. The lab says that in very calcareous soils it is difficult to determine. Only the EC was determined.

Also, does it list the magnesium and sulphur content?

I don't have S but Mg is 199 mg/Kg

I think you should determine if you want to grow trees that will thrive in the soil's current pH or if you want to grow trees that thrive in a slightly acidic soil. I glanced at the link Jd provided and it does appear some fruit and nut trees may do alright with the current soil pH, but it sounds like some levels of certain elements may need adjustment.

Yes, I am worried that even those trees that can do well in this type of soil pH may result hindered because of high carbonates/lime content and slightly high soil conductivity at depth.
Also since the Iron seems to be low, plants can be easily affected by chlorosis.

You're absolutely on the right track with wanting to plant deep rooted plants, and inoculating with mycorrhizae. Note that mycorrhizal fungi are dependent on roots to do their thing, and other bacterium (like certain strains of Bacillus for example) are not completely dependent on roots, but they do thrive well with root exudates. Jd has great advice adding straw, mulch, compost and a living legume mulch. Adding materials high in lignin like wheat straw builds humus fast with the aid of things like earthworms and a healthy population of microbes. Manures from grazing ruminants (which is basically animal composted grass), compost, straw, some hardwood mulches, and some microbial soil conditioner, and then sowing a cover crop that tolerates alkaline soil are all good things you can do to improve your soil.

One thing I am not sure about is how well do micorrhizas cope in this kind of soil even if they have roots to attach to.

I am not sure on whether it can be wiser to wait for a couple of years (and observing the evolution) before really planting any productive tree in order to give the them a better situation to start with, while I 'work' the soil with cover crop sequeces/rotations, soil biota etc. or to plant the trees next fall already, having used the time untill then to grow some good cover crop, subsoil at 90 cm depth right after the cover crop has done his job (to relieve compaction and aerate it), inoculate, spread compost etc.  so the trees will evolve with the soil.

Other than that, I am interested in strategies to improve this kind of soil that has high lime content.
Regards

I believe a good approach is to absolutely add organic matter such as compost, it will have an pH balancing effect from microbial activity. Also pine bark mulch and pine needles have a pH lowering quality. Often times, sulfur is used to adjust soil pH's and even though you don't currently have a known value from your soil test, it may be a good idea to take this approach. There are several kinds of sulfur methods to adjust your pH, and in your case, I would recommend iron sulfate since your iron appears to be low according to the soil test. Your current Ca:Mg ratio is a bit excessive to say the least, being about 20:1. Ideally that number should be about 10:1. The acidifying process will help strip some of the excessive calcium cations off the soil colloids, and help bring your numbers into balance. Adding amendments like iron sulfate are much more effective if you can work it into the soil instead of it being broadcasted onto the surface. Be careful not to bring your iron levels too high, as iron becomes more available to plants as the pH lowers. You may be able to apply some iron sulfate to achieve part of the desired acidification, then perhaps switch to some elemental sulphur so iron doesn't get too high, if you choose to use sulphurs. Using sulphurs to lower your soil pH can take up to a year for the amount applied to have its full affect, and that can take longer with drought. I fully subscribe to and believe in organic methods of cultivating crops, but I personally believe that sometimes if an extreme case presents itself, the use of a non-organic approved amendment such as iron sulfate at the beginning warrants use to bring a soil into balance so food crops can actually grow in it. I would seek advice from a professional in Spain as far what quantity of sulphur to add. In America, each state university has an agriculture extension and they are to help with advice such as this, and many more things I might add. Perhaps Spain has a similar program.

I think if your going to subsoil, I would have compost and sulphurs (if you choose that route) in place before you subsoil, that way when you go over it some of the material will work its way deep, and the next rain will aid in that process also. May I also recommend getting another soil test done in 6-12 months (perhaps from a different lab that will offer CEC and sulfur values). This way you see the progress being made. Cheers!

I've been fighting high pH, high Calcium soil for a decade in one of my gardens. I finally stopped growing trees in that garden, except that one tree has survived, but it doesn't thrive, and the cost of the continuous amendments are way higher than the value of the apricots that it produces. I only grow annuals in that garden now, and only those species that can deal with the existing conditions.  

Hi James,
thanks for all your advice. I was also considering adding sulphur and/or some iron + all the organic matter I can. I'll ask the lab that did the soil test for advice on amounts of these minerals. We have quite a few pine trees there so getting mulch out of pine needles shouldn't be an issue. Not sure though if I can collect enough to spread in the whole field since it is big (almost an acre). I would also spread those needles in the compost so that I can get a more acidic compost as well, I would probably make enough compost to spread it around each tree, not everywhere.
Interesting what you say about the Ca:Mg ratio. The soil analyst told me that in this case the info given by this ratio would not be significative, because if I divide Ca/Mg just by using the (ex)change cations the number will only be useful if I have an acidic soil with a % of base saturation < 100% (not sure if the technical terms I used are the correct ones in English)

As for what Joseph says, in Spain most soils, apart in a few specific areas, have high pH and lime, so most farmers need to cope with these conditions and I guess that since most of them are into  conventional agriculture and they are heavily subsidized by EU they don'y mind spending money on amendments.
But surely in my situation I need to take your advise into consideration too. Most probably I will only able to use fruit trees that can naturally cope with these conditions.
What have you done in the last 10 years to try to improve it, by the way? Is your soil also somewhat saline or with high sodium content as well?
Regards

Adding a lot of organic matter/compost tends to lower PH over time.  You could also add sulfur at the rate of about 10oz per 100ft sq to lower ph one number.  Yearly testing and readjustment would be in order until you get the ph where you need or want it.  A ph too high is as bad as one that is too low.  Either extreme tends to tie up nutrients and cause imbalance in the soil.  Most plants, in general, like the ph somewhere between 6 and 7.  There are always plants that thrive outside this, but as a general rule you can't go too wrong with a ph of 6.5ish.

Antonio Scotti wrote:What have you done in the last 10 years to try to improve it, by the way? Is your soil also somewhat saline or with high sodium content as well?

I've tried all the commonly recommended pH modification methods: Adding organic matter, sulfur, aluminum/iron/magnesium/ammonium sulfate, etc... The garden frequently receives organic matter in the form of grass clippings, leaves, and plant debris. I see temporary modifications sometimes. The cost is too high to maintain consistently. I don't have problems with salinity. We have abundant low sodium irrigation water. Which is   saturated with limestone. Therefore, irrigation tends to undo any pH lowering applications I might make.

Joseph Lofthouse wrote:
... Which is   saturated with limestone. Therefore, irrigation tends to undo any pH lowering applications I might make.

Are you saying that if it wasn't for the type of irrigation water you have the measures you took might have been (more) successful?
Cheers

Walt Chase wrote: You could also add sulfur at the rate of about 10oz per 100ft sq to lower ph one number.

Hi Walt,
is this some kind of general rule/recipe for applying sulphur to a landscape (of the type I have) anywhere?

Also James talked about "sulphurs"...does that mean that there are different types or fomulations of sulphur to consider? You mentioned two of them iron sulphate and (plain I assume) sulphur, are there others that might be worth researching?

By the way I found articles suggesting that it is not worth trying to use pine needle for acidifying a soil: http://gardening.stackexchange.com/questions/13789/does-a-pine-needle-mulch-make-your-soil-acidic although they can be a good and cheap mulching material.
Cheers

Yes there are a few different sulfurs that I am aware of for adjusting soil pH. There's plain elemental sulfur, iron sulfate, magnesium sulfate and aluminum sulfate, and I believe there are a couple more. Elemental sulfur will have the greatest acidifying effect. I suggested iron sulfate if your soil is low in iron. Magnesium sulfate is just epsom salts, useable if you have a magnesium deficiency. There is also ammonium sulfate, but from what I understand it is not so good at lowering a soils pH, but is good at providing available sulfur if there is a sulfur deficiency. All should raise the amount of sulfur in the soil, but only sulfates (SO4) are available for plant uptake, and the elemental sulfur will eventually be available for plants use after microbes convert it into sulfate.

Antonio Scotti wrote:Are you saying that if it wasn't for the type of irrigation water you have the measures you took might have been (more) successful?

I live in limestone country. The dust that blows in from the desert contains limestone. The water contains limestone. Everything that washes into my garden from the surrounding areas contains limestone. The organic matter around here was grown in limestone soil. There are hundreds of feet of limestone derived dirt under my gardens. My budget can't afford to modify the soil in any sort of significant, long lasting way. Mother Natures economy is much larger than mine.  I can modify the top few inches of soil to grow some annual vegetables, but any sort of deep rooted perennial or fruit tree is not viable in my kitchen garden.

Sure, there is a farmer in my village that grows blueberries which love acid soil. He brought in special soil. Not just a little. One dump truck load after another. And he installed a special irrigation system that applies acid to the soil every time it is irrigated.  That doesn't strike me as a permanent solution to growing fruit in my area.

Antonio Scotti wrote:

Walt Chase wrote: You could also add sulfur at the rate of about 10oz per 100ft sq to lower ph one number.

Hi Walt,
is this some kind of general rule/recipe for applying sulphur to a landscape (of the type I have) anywhere?

Also James talked about "sulphurs"...does that mean that there are different types or fomulations of sulphur to consider? You mentioned two of them iron sulphate and (plain I assume) sulphur, are there others that might be worth researching?

By the way I found articles suggesting that it is not worth trying to use pine needle for acidifying a soil: http://gardening.stackexchange.com/questions/13789/does-a-pine-needle-mulch-make-your-soil-acidic although they can be a good and cheap mulching material.
Cheers

There are "different" sulfurs as has already been mentioned.  I think some of the confusion is in the different acceptable spellings for the same thing.  The 10oz per 100 sq ft is a general rule of thumb.  It is actually a bit on the conservative side, but better to be a bit conservative.  If I need to change my ph without adding other minerals (iron, magnesium etc) I use elemental sulfur and dig in to the top 6-8 inches of the soil.  I am not familar with your particular soil type though.