soil test results - sodic, clay, ph 8

jojomojo(6b)May 21, 2013

I had a soil test done in March. My soil is sodic, clay, has a ph of 8, and very little OM (2%). Nitrogen is low too, but that seems easy enough to fix. Everything else was high/adequate.

I'm confused by the results though. Under "Sodium Absorption Ratio" it says that the soil can be reclaimed by leaching the site with "good quality water" and that gypsum/sulfur may be added. Yet under gypsum, it says gypsum is NOT needed.

What exactly is good quality water? Is it about sodium content? Ph? I only have access to tap & ditch water (from the San Juan River). Ditch water is going to be tricky though - haven't managed to figure out how to use the pump yet, or set up a way to get it to the garden site.

Our plans were for a 40' x 40' garden area (although, about half of that will be cover crops until next Spring to improve for next year).

I don't have access to large quantities of leaves, grass clippings, etc. I have maybe 2-3 yards of compost (never saw it really heat up, but its been sitting around since last summer - mainly horse manure, chicken manure, kitchen scraps, shredded newspaper & sawdust). And about 10-11 yards of horse manure (not a "ball" in sight, not much smell at all, very fluffy). I've called around and can't find bulk compost anywhere. Buying it bagged is so expensive, but I might consider it.

Here's the report. What would you do with this info?

pH: 8.0
pH is high, but native and introduced plant species that are adapted to this pH should not be negatively affected.

Electrical Conductivity or Salts: 8.1
Salts are very high with may cause poor plant growth. Salts may be reduced by leaching the site with 6-12 inches of
water to help push salts deeper into the soil profile to dilute their effect. Leaching depends on the availability of good
quality water and good drainage.

Lime: High
High: Lime is 2%-5% in the soil. Plants can still grow quite well in soil with this lime content.

Texture Estimate: Clay
This soil may drain at a very low rate. Watering schedules may have to be increased to allow for better water
infiltration into the soil profile.

Sodium Absorption Ratio: 23.1
High: This soil has high sodium and is considered to be sodic. Sodic soils can be reclaimed by leaching the site with
good quality water. Gypsum or sulfur can be added to the soil along with water to help remove sodium from the root

Organic Material: 2.0
Organic Matter is Low. Gradually increase the OM content to about 5% over a period of years. For 2-3 years in the
spring or fall, apply 2-3 inches depth of plant-based compost, or 1 inch depth of animal-based compost, and
incorporate into the top 6-8 inches of the soil in flower beds. When planting trees and shrubs mix the backfill soil
with low salt OM such as peat moss at a rate of 15-20%. For established trees and shrubs add OM to the soil surface
at a depth of 0.5 inch.

Nitrate: 13
N is low: Apply 0.3 lb N/100 sq ft to the soil. For each 0.1 lb of N needed, apply about 1/4 lb urea, or 1/2 lb
mmhos/cm ppm ammonium sulfate, or 3/4 lb bloodmeal, or 1 lb corn gluten meal, or 5 lb alfalfa meal pellets per 100 sq.ft. Other
fertilizers can be used as well. Check with your local garden center or home improvement store to determine what
fertilizers are available in your area. When calculating fertilizer rates take the amount of N needed and divide by the
% N in the fertilizer. For example, if your fertilizer contains 30% N, take 0.30 lbs (N needed) divided by 0.30 (N in the
fertilizer) to get 1 lb of the 30% N fertilizer that is needed to apply per 100 sq.ft. For rates per 1000 sq. ft multiply the
quantities by 10.

Phosphorus: 17
Phosphorus is High; No additional Phosphorus is needed.

Potassium: 563.3
Potassium is High; No additional K20 is needed.

Zinc: 15.5
Zinc is Adequate; No additional Zn is needed.

Iron: 18.8
Iron is Adequate; No additional Iron (Fe) is needed

Manganese: 7.4
Manganese is Adequate; No additional Mn is needed.

Copper: 9.0
Copper is Adequate; No additional Cu is needed.

Boron: 0.30
Boron is High. No additional boron is needed.

Gypsum is NOT Needed.

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First a question - did they test for calcium (Ca)?

For sodic soils a common amendment is gypsum, but the results state gypsum is not needed. That has me wondering what the Ca level is, because gypsum is a hydrated form of calcium sulfate. The Ca will help displace sodium, and then the sodium will leach, over time, with irrigation. However, on clay it will probably be very slow. In this case good quality water would be low in sodium, and maybe Ca too. Do you know what your water is like for hardness or salt?

pH - you can use garden sulfur. The pelletized stuff is easier to use. To lower pH about 1 unit in clay soil will take ~ 4-5 lbs per 100 sq. ft, so 65-80 lbs over the whole area, tilled in. With regular irrigation it will take several months for the effect to be realized. Check with local feed or farm supply houses (check the yellow pages).

For a 40'x40' bed, a 2" layer of organic stuff will take about 10 yards. The problem with manures is they tend to be high in soluble salts, especially sodium. So while they are desirable for OM, they probably will, in quantity, make your sodium / salts problem worse.

Do you have access to anything like shredded wood or good sawdust? If so, and option might be to use some of that along with ammonium sulfate (common 21-0-0 fertilizer) as a nitrogen source to balance the high carbon of the wood as a soil amendment. The ammonium sulfate will also help a bit with pH.

Use what compost you have and go ahead with your plan for green manure cover cropping. while you keep looking for other non-animal compost or OM possibilities.

    Bookmark   May 21, 2013 at 2:55PM
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All of the information I got for that particular soil test is posted above, there was no mention of calcium.

I'm not sure about the river water, but the water from our house is VERY hard (not based on analysis, just based on mineral deposits left on glasses, etc).

I'll look around for sulfur. Home Depot has it with free shipping, so that's an option. Is it okay to apply that after the garden is growing? Does it need to be tilled in?

I do have access to coarse saw dust, a LOT of it. I use pine pellets for the bedding in our chicken coop (I've put probably 8-10 40-lb bags in there over time). It's time to shovel it all out and replace it too. Obviously, that means there's some fresh manure mixed in (most of it is caught under the roost and removed though, not mixed in with the bedding). Should that get tilled straight into the garden with the extra bit of nitrogen? I planned on using alfalfa pellets to add the nitrogen suggested on the report (prefer to go as natural/organic as possible). How much extra would be needed for 320-400 lbs of saw dust? I'm afraid to find out.

Thanks for your reply!

    Bookmark   May 21, 2013 at 3:25PM
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Link below is the form I used for the soil test. I chose the 'Routine Garden & Landscape soil test' and 'Routine + Sodium Evaluation (SAR)' (already suspected sodium problem), neither of which mentions calcium.

Here is a link that might be useful: colorado state soil testing form

    Bookmark   May 21, 2013 at 3:38PM
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Also thought I should mention I had soil sampled in a field that is only a couple hundred feet away and the suggestion for gypsum was very different (2.1 tons per acre), but the results didn't seem that different. It was sent in a very different format too, not sure why.

Here is a link that might be useful:

This post was edited by jojomojo on Tue, May 21, 13 at 16:25

    Bookmark   May 21, 2013 at 4:15PM
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Sulfur should be tilled in to ~ 4-6" depth.

Not sure where you are, but Peaceful Valley (CA) sells pelletized sulfur in 50 lb bags. It is probably available locally near you from a farm supply house. Ask for ag sulfur, and see if the have pelletized stuff.

Pine sawdust is good, but you do want stuff free of chicken manure. The US Forest Service did quite a study on composting pine sawdust, and there have been other studies also. According to the Forest Service, you need 5 pounds of elemental nitrogen for each ton of ponderosa pine sawdust. That's an amount lower than you would initially think, but that's because only a fraction of the ca. 40-50% total carbon is readily degradable. So for 400 lbs of pine sawdust, that's 0.2 ton, which means 1 lb of nitrogen. I like the alfalfa idea too. Alfalfa is typically about 5% nitrogen, so that leads to 20 lbs alfalfa meal or pellet added in with the sawdust. Again, till those in together. You could easily and safely double or triple that amount with the extra feeding your soil (1.5 lbs of N per 1000 sq ft over 1600 sq ft would take about 48 pounds of alfalfa - add that to the 20 lbs for the sawdust).

Funny that they report SAR but don't give Ca and Mg results, which are usually reported and are needed to determine SAR. You might give the lab a call and see if they can help you zero in on the Ca and Mg levels.

    Bookmark   May 21, 2013 at 4:34PM
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I'll call the lab, hopefully they hold onto the reports for a while.

I'm in NW New Mexico, pretty big on agriculture. I'm sure I'll find some sulfur after looking around a bit.

The coop bedding has very little manure in it. I'd say 99% of the manure is caught under the roost. Still not good to till in? Does it matter that I don't plan on putting any root crops or greens in this garden? I have a few raised beds that I plan on using for that. The closest any food is going to come to the soil is probably melons or winter squash sprawling out. Other than melons/squash, I was planning on tomatoes, peppers, okra, corn, etc. I could always adjust what I put there too if it helps. I also plan on a good layer of straw between the soil & plants. If it's just not worth the risk, I'll drop it. I guess I could always use unused bedding (usually less than $5 for a 40 lb bag).

This post was edited by jojomojo on Tue, May 21, 13 at 16:55

    Bookmark   May 21, 2013 at 4:52PM
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nil13(z21 L.A., CA (Mt. Washington))

I remember someone in CO running into trouble for collecting rainwater for a garden due to the prior appropriations water rights we have out here in the West. You might want to look into that before pulling too much water out of the river.

    Bookmark   May 21, 2013 at 5:10PM
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With those kinds of local soils I would expect agricultural S would be readily available. If you know any other growers in your immediate area you might ask them about Ca and gypsum and what they do.

I doubt anyone but you can judge the bedding. If it's pretty much manure free, then it probably is fine to use. The point is you just don't want to add to a problem that you're trying to fix.

As far as crops and nutrients go (not soil texture or moisture), most do well on about the same kind of soil with amounts of nitrogen being the major swing. I doubt that different crops would give much mileage except for something that might be especially salt/sodium sensitive.

    Bookmark   May 21, 2013 at 5:36PM
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Technically you are not allowed to collect rainwater in CO, but most residents can get away with it unless/until a neighbor rats you out...or you do something stupid like use it commercially (such as a car wash).

Groundwater recharging is a very big deal in some areas...CO takes it a bit more seriously than some other areas.

You can divert it for immediate use, but storing it in tanks/cisterns/etc isn't legal.

There's no one going around playing "police" but all it takes is one neighbor that doesn't like your tanks reporting you.

    Bookmark   May 21, 2013 at 5:40PM
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For your reference, here is a secondary reference to the work that was done on using sawdust as a soil amendment. The original work was done by W.B. Bollen in 1953, but is not freely publically accessible (ref is Agr. & Food Chem. Vol 1, pp 379-381, 1953). The pertinent section on using sawdust immediately before the growing season appears on the bottom of page 2. The recommendation is 50-100 lbs of ammonium sulfate per ton of sawdust. Ammonium sulfate is 21% N, alfalfa is 5% N, so about 4X as much alfalfa meal or pellet as ammonium sulfate. For ammonium sulfate half now / half later approach is suggested. Ammonium sulfate is a fast N source, where as alfalfa would be a good bit slower, so adding all at once should be fine.

Here is a link that might be useful: Sawdust Mulches for Larger Crops, Better Soils (1955)

    Bookmark   May 21, 2013 at 6:06PM
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Thanks for that link TXEB. I'll have to think about using the bedding. Maybe I can compromise and use the bedding on the cover crop half only, and spend money on the veggie half. Next time I clean out the coop, I'll have to plan on timing it just right so it can sit and mellow a bit.

nil13, we have water rights to the lateral ditch that runs through our property. Thank goodness NM allows rain barrels too, that's one of our summer projects :)

    Bookmark   May 21, 2013 at 6:45PM
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toxcrusadr Clay Soil(Zone 6a - MO)

I wonder if the two reports looked different because one was for a 'field' and the other for a 'garden'? My ag extension lab asks for the type of use on the request form so they can make recommendations accordingly.

Really odd that they didn't analyze for calcium.

    Bookmark   May 21, 2013 at 6:47PM
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Some late thoughts ...

In addition to being 5% N, alfalfa is also 2% P. Your P level is already high. If it were me I would go with ammonium sulfate, which should also help with pH and may help mediate the sodium levels and pH as well.

I just read through CO's Soil Test Explanation Fact Sheet, and I now better understand what the report is indicating. The fact that is the soil shows sodic (SAR >15) leads them to consider and evaluate if there is sufficient gypsum content for the soil to be reclaimed and leached. According to your results the answer is yes.

What stands out to me now is that your Ca levels should be high (high lime) along with high enough sodium to push SAR to very high levels, all in an alkaline soil, suggesting very high carbonate levels. Sounds to me like a very challenging combination.

A couple remaining important questions are how well does the soil/site drain, and what is the sodium level in the water you will use for irrigation?

nc- I believe he's in NM not CO.

Here is a link that might be useful: CO Soil Test Explanation

    Bookmark   May 21, 2013 at 6:51PM
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toxcrusadr - That's what I was assuming too. The pasture soil report looked like it was for someone who might have a clue what it all means. The report for the garden looked "dumbed down" (as it should be, I don't know anything about soil science).

Speaking of not understanding soil science...
"What stands out to me now is that your Ca levels should be high (high lime) along with high enough sodium to push SAR to very high levels, all in an alkaline soil, suggesting very high carbonate levels. Sounds to me like a very challenging combination."

I don't really understand how it all works together and just what the challenge is. I have a lot more reading to do.

I really don't want to use chemicals on the garden, but I may have to consider it just to get things where they need to be and maintain it organically. What problems can you run into if P is too high?

About draining....we really don't get enough rain here to necessitate draining or ever observe it. We did do a percolation test last year - but I completely forget what the results were. I vaguely remember coming away from that test thinking the results weren't good, but it could be worse. I'll have to do it again.

Is there an easy way to test water for sodium content at home, or do I have to send it off? We'll be using tap water until we get the pump/irrigation worked out this summer.

    Bookmark   May 21, 2013 at 7:32PM
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P exists in soils primarily as phosphates, which themselves act as bases and can increase alkalinity. That's one of the things your are trying to overcome. At high levels P can reduce the availability of a number of metal ion nutrients, such as zinc and copper. Your levels are high, which shouldn't be a problem. You just don't want to be adding and pushing them to very high levels.

When I said "drain" I meant percolate. The question is can excess sodium be leached from the soil with good quality water? That requires that if the soil were soaked or saturated it would drain down, leaching sodium as it does.

The water question is critical to your long-term success at that site. There is no home test for amounts of Na or Ca. But if you know a well driller with good local knowledge he may be able to tell you what kind of water exists in your area, and how deep the natural water table lays. Those would be good first clues.

One of the interesting things that some clays can do is to transport water and dissolved minerals upwards towards the surface from below by capillary action. It is most pronounced when the water table is closer to the surface. I see this very frequently in my neighborhood, where water will ooze up and out of cracks in our concrete streets. I have no idea if your clay soils are susceptible to that kind of action, but if they are then the potential for restoring the soil becomes somewhat questionable. A good well driller who knows your area may be able to clue you in.

    Bookmark   May 21, 2013 at 8:05PM
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Ca can also "lock up" P availability to plants (as well as Fe and Al...and HCl-P which is extremely stable and hard to access) in alkaline/calcareous soils.

High alkaline, calcareous soils can have high P that don't negatively effect plant life in these cases. It can, however, hog exchange sites on clay/silt that other nutrients would like to well as having a pesky habit of complexing other nutrients such as Fe and Mn when it does cleave off into the soil solution, making them plant unavailable or subject to leeching out of the soil solution because of a lack of place to hang around.

All these effects working together makes for a highly buffered solution in the soil of Ca and P even when you're adjusting the pH to a more plant desirable range. It usually takes an extremely harsh acid to break some of these bonds/relationships in a "scale tipping" manner, such as hydrochloric acid. far as amending goes...I'd mix/till in sulfur (or another pH lowering substance) + organic matter that's not manure heavy at least 6 inches. It's not a fast fix, though. There may need to be a micronutrient amendment needed for best plant growth, too. Iron is a special consideration in these soils, especially with the high P because of availability issues.

This post was edited by nc-crn on Tue, May 21, 13 at 20:39

    Bookmark   May 21, 2013 at 8:37PM
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You may find this tidbit helpful in better understanding the complex relationships you're dealing with. I just found it looking for something fairly straightforward but with enough depth that may help you understand what you have. It's from a commercial producer of soil amendments, but it seems fairly commercial free. Hope it helps.

Here is a link that might be useful: Biogro - Alkaline, Saline & Sodic Soils

    Bookmark   May 21, 2013 at 9:33PM
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Thanks for the info & suggestions (that Biogro article was very helpful, I'll pass that onto my husband too who is much better with chemistry than I am). I think my soil may be a lost cause, so I won't be sinking much money into this project, but I'm not giving up either.

We dug a 2ft hole last night and hit water. I knew the water table was artificially high (everyone in the area is on septic), but I thought it was a little farther down than that. So, we filled the hole anyway around 7pm last night. I just checked and it has dropped maybe 2-3 inches. I'd say that could be considered a drainage problem.

Raised beds it is (or mounds anyway). My original idea was to create raised beds (without the expense of walls) and at the end of the season till everything in and plant a cover crop and do it again in the spring (bring in material for raised bed, till in at end of season). I'll get a soil test again next Spring to see if much changes.

    Bookmark   May 22, 2013 at 1:31PM
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Two feet, huh? That sounds a bit ominous to me, but then I know nothing about your soils or environment, other than what's been discussed here.

Have you talked with your County Cooperative Extension folks? I've found in the past the local the ag/soil guys are usually very knowledgeable about local soils, what works, what doesn't, etc. With the info you have on your soil and water table they may be able to tell you what's possible, or at least what's been tried by others. Here's a link to the NM Coop Extension directory - click on your county, get the contact info and give 'em a call. They are usually very helpful.

Here is a link that might be useful: NMSU Cooperative Extension Service

    Bookmark   May 22, 2013 at 2:23PM
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Last time I talked to them was long before I got a soil test done, so there wasn't much to discuss. Not sure why I didn't think to talk to them since I got it.

Just gave them a call and they already had my soil report, kind of surprised me. Basically, reclaiming my soil is a lost cause. The water from the river is good, not high in salts (Animas River, oops, said San Juan earlier, not sure what I was thinking), so maybe I'll still do what I can (irrigate to flush salt, add OM, clay busting crops) to improve the area without spending money on it.

Wish me luck! It sounds like I'm going to need it.

    Bookmark   May 22, 2013 at 5:08PM
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Sounds like a good call to me. Not only the $ saved, but the potential for wasted labor as well as heartache when it doesn't work.

I was concerned about the water table. Not sure your clay will wick upwards, but if it does and you have a high water table (you do), it's about impossible to restore the soil to what you want for good gardening. You would just be fighting nature. Raised beds sound like a very good idea.


    Bookmark   May 22, 2013 at 6:44PM
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