Dolomite lime questions

[RanchoDeluxe]

So I've read the first 60 or so pages of the Living Organic Soil thread. It has me convinced that I can use Oyster shell, glacial and volcanic rock dust instead of using dolomite lime. I understand that DL takes a long time to break down and become available. I'm unsure of the why.

I would like to know so I can explain to my old partner why he should stop using it. He's been recycling his soil for two years now. He adds back DL every single run. CC posted up a website for a University on the topic but nothing comes up for me. The other thing is, my old partner looked at me like I was crazy when I asked him if he ever heard of cation exchange capacity.

So basically I'm gonna need to explain the relationship between pH, CEC, microbes, nutrient uptake etc. Basically the whole fucking deal. Right now I don't even feel like I'm intelligent enough to ask the right questions. I think I can get him off the DL if I can just explain why it takes so long to break down. Or I guess I could take the angle of explaining why Oyster Shell and the rock dusts are so much better. I'm really curious if after 3-5 years when all that DL does become available, if his soil will go to shit. I really hope this makes sense to someone. If not, I need to formulate more intelligent questions on the matter.

Thanks Rancho

 

[c-ray]

some would say too much magnesium, which creates more need for nitrogen in the plant
agreed probably far too slow acting for the needs of a high energy annual like cannabis

 

[ClackamasCootz]

So I've read the first 60 or so pages of the Living Organic Soil thread. It has me convinced that I can use Oyster shell, glacial and volcanic rock dust instead of using dolomite lime. I understand that DL takes a long time to break down and become available. I'm unsure of the why.

I would like to know so I can explain to my old partner why he should stop using it. He's been recycling his soil for two years now. He adds back DL every single run. CC posted up a website for a University on the topic but nothing comes up for me. The other thing is, my old partner looked at me like I was crazy when I asked him if he ever heard of cation exchange capacity.

So basically I'm gonna need to explain the relationship between pH, CEC, microbes, nutrient uptake etc. Basically the whole fucking deal. Right now I don't even feel like I'm intelligent enough to ask the right questions. I think I can get him off the DL if I can just explain why it takes so long to break down. Or I guess I could take the angle of explaining why Oyster Shell and the rock dusts are so much better. I'm really curious if after 3-5 years when all that DL does become available, if his soil will go to shit. I really hope this makes sense to someone. If not, I need to formulate more intelligent questions on the matter.

Thanks Rancho

Cation Exchange Capacity in Soils: Simplified

 

[Sat X RB]

OK. so I'm no expert ... but how come when I add dolomite to my soil mix it takes only two weeks for the pH balance to change to where I want it?

might the proposition here be that dolomite's capacity to alter pH is NOT related to its minerals being available to the plant?

thanks!

 

[SilverSurfer_OG]

Dolomite works and is a natural product made of crushed rock so its certainly good enough for an organic fanatic. The reason to use the glacial rock and stuff is i think to add as many minerals as possible that are bio available.

I have learned my lesson with dolomite and am very careful NOT to add any more to recycled medium. I had major issues with my medium being too high around 8.5 -9ph and made calcium unavailable. This took months to come good. Now it is full steam ahead!

It is good for around 4 years once added. Your friend may have probs like i did but if using very acidic (bottled salt) nutes it may actually be of benefit.

I had to add liberal amounts of vinegar with every feed to keep my ladies green.

 

[SilverSurfer_OG]

PS. The four years refers to usual use in the ground and not the super hungry marijauna which is a calcium and magnesium hog. It may well be that a super productive harvest after harvest will need more regular topups... but i would err on the side of caution as there are plenty of liquid feeds and plants etc that contain Mg and Ca.

 

[ClackamasCootz]

From Seeds of Change - Soil Fertility Basics: Interpreting Soil Tests

Organic matter (OM)

Organic matter (OM) is a measure of all plant and animal residues, ranging from raw, undecomposed materials to stable humus. It is a source of nitrogen, the major cations (Ca,Mg,K), trace minerals, and growth hormones. OM also stimulates biological activity and enhances soil structure and water retention. It is, however, perhaps the most difficult factor to interpret on a basic soil test, as optimum OM content can vary widely depending on soil type and conditions. Furthermore, the amount of nitrogen being released by OM depends heavily on the quality of the organic matter (stable vs. unstable compounds) and the soil conditions (texture, temperature, water content). Nevertheless, testing for OM can be useful to observe general trends if it is measured every year or two.

OM levels can also indicate a soil's ability to retain nutrients. (See below in the discussion on cation exchange capacity. (CEC)) Soil #2 has a great amount of raw residues, which are useful for stimulating soil microbial activity, but do not contribute to nutrient retention. In contrast, humus and other more stable decomposed organic matter are very important nutrient sources. Note the higher CEC in soil #1, even though overall OM is considerably lower.

Soil pH

Soil pH is a measure of the hydrogen ion (an electrically charged atom) concentration in the soil solution surrounding soil particles. Pure water (H2O) has a pH of 7.0 which is neutral because it contains equal amounts of H+ (Hydrogen) ions and OH- (Hydroxyl) ions. A pH below 7.0 is acid and has a greater number of H+ ions, while a pH above 7.0 is alkaline and has a greater proportion of OH- ions. Soil pH per se has little direct effect on plant growth, provided that a plant can extract a sufficient quantity of nutrients. The most important concept regarding pH is that extreme acid or alkaline conditions affect the availability of virtually all the essential nutrients. For example, at pH 5.0 (strongly acidic) the amount of calcium, magnesium, potassium, nitrogen, and sulfur available to plants is only half as much as at pH 6.0 (moderately acidic). The availability of phosphorus begins to decline at pH 6.5. Below 6.0, most phosphorous is unavailable to plants. As pH levels drop below 5.0, iron and aluminum are released from the soil in quantities that are toxic to plants. Excessive alkalinity also leads to nutrient imbalances. Many of the trace elements, including iron, manganese, boron, copper, and zinc become gradually less available at pH levels exceeding 7.5. Soils with pH above 7.5 also show dramatic decreases in phosphorus availability.

pH also affects the activity of beneficial soil microorganisms. Although bacteria and actinomycetes prefer alkaline conditions and fungi favor acidic conditions, the optimum overall activity of beneficial microbes occurs at mid-range pH levels. Therefore, a pH that is not extremely acidic or alkaline is best for maximizing soil life and plant-available nutrients. Soil #1 has a rather alkaline pH, and the soil test report indicated low levels of several of the trace elements (not shown here). One of the recommendations was to add gypsum (calcium sulfate) because the sulfur is able to acidify the soil slightly. The pH of Soil #2 probably doesn't need to be adjusted, however, if the pH was much lower, the most effective way of raising it would be through further applications of high calcium limestone (calcium carbonate) or dolomite (calcium-magnesium carbonate).

Cation Exchange Capacity (CEC)

Cation exchange capacity is a measure of the soil's ability to retain the cation nutrients, including calcium (Ca+), magnesium (Mg+), potassium (K+), and nitrogen in the ammonium form (NH4+). These positively charged elements are attracted to the negatively charged surfaces of clay and humus particles. Once these cations are bound to these sites, they are protected from leaching away in water, yet they are still available for uptake by plant roots. As plants absorb the cations, their roots release positively charged hydrogen ions (H+), which then attach to the negatively charged sites previously occupied by the other cations. As a plant continues to take up the cation nutrients, there are more H+ ions on soil clay and humus particles and in the soil water solution surrounding the particles (i.e. more acidity). Therefore, more cation nutrients need to be added to assure an adequate future supply.

At CEC levels above 20 or 25 (milliequivalents per 100 grams of soil), the soil can hold many more nutrients than a plant would normally need in a year. If the majority of exchange sites in this soil were occupied by the nutrient cations (and not by H+), then very little or no additional amendments may be required for the next 1 to 3 years. However, once this soil is depleted of nutrient cations, it would require a large input of nutrients to restore its original fertility. On the other hand, if a soil has a low CEC, say below 10, then the nutrient reserves would be quickly depleted, and annual additions of the cation nutrients may be required (although at much lower quantities than in a high CEC soil).

Soil #2 has a low CEC and may need to be monitored more closely than soil #1, which has a moderate CEC level. CEC levels are largely dependent on the amount of clay (fine texture) and humus in the soil. Silty (medium texture) and sandy (coarse texture) soils contribute almost no exchange sites, and hence must be fertilized more often. Soil #2 is interesting in that it has a relatively low CEC but a large amount of organic matter (humus). The humus contributes a large number of exchange sites, yet the texture is silty (few exchange sites), so that the combined exchange site contribution of the humus and mineral portions of the soil is still relatively modest. Since the humus is contributing the lion's share of exchange sites, an increase in the pH will increase the CEC. In most soils, however, the CEC remains fairly constant, yet knowing what it is will help us determine the amount and frequency of fertilizer applications.

The cation nutrients (Ca, Mg, K) are expressed in parts per million (ppm). If you multiply ppm by 2, you will get the approximate number of pounds/acre of the nutrient (in the top 6 inches of soil). Soil labs usually report the level of each of these cations from very high to very low, relative to the CEC of each particular soil. This explains why, although the calcium level of soil #1( higher CEC) is greater than soil #2 (lower CEC), the Nutrient Level Rating of soil #1 is lower. Considering this, the total amounts of the cation nutrients are not as important as the proportion of exchange sites that each of these cations occupies. This is expressed as the "% Base Saturation." Calcium dominates the exchange sites, and for best crop performance, should occupy 65 to 85 percent of the sites . Magnesium is best between 10 and 20 percent, while potassium should be about 3 to 5 percent. The remaining sites are occupied by hydrogen, sodium (high alkaline soils), ammonium, and trace elements. Even these ranges are not necessarily the best in all cases, but they can be used as guides for balancing your nutrients.

Soil #1 is rated very high in potassium, which could lead to nitrogen deficiency. If your plants are not exhibiting N-deficient symptoms (yellowing of leaves, slow growth), then you probably have nothing to worry about. The calcium level of soil #1 is rated medium and the lab recommendation was to add gypsum (Calcium sulfate), which can be helpful in several ways. First, it raises the calcium level. Second, the calcium in the gypsum replaces some of the potassium on the exchange sites, allowing excess to leach away. Third, the sulfur in the gypsum decreases the pH, which increases the availability of several trace minerals. Soil #2 has high or very high levels of the major cations and their ratio appears to be ideal, therefore no major adjustments are needed.

Phosphorus, like the cations, is also expressed in parts per million. Two tests are performed on this element. The P1 (weak Bray extraction) measures the amount of phosphorus immediately available to the plant. P2 (strong Bray extraction) measures the readily available P plus the active reserves, which usually are available later in the season. The P2 levels should be 2 or 3 times the P1 levels. Soil #1 had no P1 reported because this test is unreliable in soils above pH 7.5. P2 levels were very high in soil #1, so presumably no additional P is required. If phosphorus deficiency symptoms show up (purpling of leaves, poor root growth, poor flower/fruit set), the best strategy would be to lower the pH and increase biological activity through the addition of compost and green manure crops. Soil #2 had high P1 and P2 levels, and their ratio indicates no problems for supplying the crop throughout the season. If phosphorus levels are low, a colloidal, soft rock phosphate is best because it can supply adequate P over a relatively long period.

 

[RanchoDeluxe]

Dolomite works and is a natural product made of crushed rock so its certainly good enough for an organic fanatic. The reason to use the glacial rock and stuff is i think to add as many minerals as possible that are bio available.

I have learned my lesson with dolomite and am very careful NOT to add any more to recycled medium. I had major issues with my medium being too high around 8.5 -9ph and made calcium unavailable. This took months to come good. Now it is full steam ahead!

It is good for around 4 years once added. Your friend may have probs like i did but if using very acidic (bottled salt) nutes it may actually be of benefit.

I had to add liberal amounts of vinegar with every feed to keep my ladies green.

A rising pH makes alot of sense to me. I think he still has a pH meter from when he tried to use an aerocloner. (epic fail) Pretty sure he is still rocking fish hydroslate and kelp teas. I have no clue what the pH would be. Our water supply is 7.8-8.3 262ppm 60ppm Ca forget what Mg is. Anyhow thanks man.

 

[RanchoDeluxe]

CC- Thanks again man. Looks like I'm gonna have to make him read. He's got an English degree so it's not gonna be easy.

 

[SilverSurfer_OG]

Yeah no worries. If you start seeing yellowing and smaller leaves on new growth and an overall loss of vigour then this would be my guess. I used to add 2 or 3 tablespoons of cider vinegar per litre to get some balance.

Also an acidic medium like peat would benefit more from dolomite than say a coco based medium (as i use indoors)

 

[RanchoDeluxe]

I remember Gas posting up a quote from Jeff Lowenfells (sp) the Teaming with Microbes author. It basically said that a healthy microherd will maintain the proper pH in soil. So, since the microbes are maintaining the proper pH the only benefits we are getting from DL is the Ca and Mg...which take a long time to become available and are in the wrong ratios. Still, if for some reason, one feels like they need a pH buffer Oyster Shell accomplishes this?? The rock dusts are immediately available for the microbes to consume should be considered another way to maintain pH?? Also the Ca and Mg are available and in the right ratios. CEC comes into play because without a relatively high CEC it won't matter how much Ca,Mg, or K is added to the soil?? Mostly thinking while I type....but I think I've got the basics down. Tell me if I'm on the right track here???

 

[SilverSurfer_OG]

Sounds good to me except dolomite is a rock dust. Not sure which rocks are consumed faster by microbes.

A good thing to remember is maintaing a healthy microherd and tapping into fungi and really growing a plant as nature intended is much easier outdoors in soil vs under lights. I am however very impressed with my 18" deep indoor bed and it certainly is coming good after a heavy handed top dress of dolomite about a year or so ago. Outdoors i would expect a similar dosage would be less likely to cause issues and indeed that is just for me because i have a heavy clay soil.

 

[VerdantGreen]

i did a test with powdered dolomite lime and it neutralized acidic water in a matter of hours so i dont agree that it takes ages to work, but i would agree that you dont need to add it every time in recycling and you need to take note of the lime content of your water and other soil amendments when mixing or recycling soil.

i use it at 5g per litre of soil and it does the job for me.

VG

 

[Scrappy4]

i did a test with powdered dolomite lime and it neutralized acidic water in a matter of hours so i dont agree that it takes ages to work, but i would agree that you dont need to add it every time in recycling and you need to take note of the lime content of your water and other soil amendments when mixing or recycling soil.

i use it at 5g per litre of soil and it does the job for me.

VG

How right you are VG!

In winemaking there is a way to neutralize acids, it's powdered calcium carbonate (aka lime or chalk) It does work very quickly, but it can be tricky to get the amount just right because time does change things. So although it works fast, it might not stop working on your schedule. But in our field most lime is not always powdered or soft like chalk and it does vary on it's break down time, and the amount of neutralization probably involves the total acidity of the medium rather than just the PH. So IOW there could be some gotchas when using lime.

And from my own personal experience adding lime to previously limed soils is asking for problems. And i have found you really do not need to use lime, even in peat mixes, as long as you have your calcium covered in other ways. Those other ways might be oyster shells, crab shells, good compost, gypsum, most botanical inputs, neem meal and so on.

And once again the PH of the soil is not only a chemical process, it also involves biology and the interactions of plants and soil microbes. Anyone with a PH soil probe can tell you when you feed a low PH input the soil's PH goes down, then bounces right back up in a day or three.....that's biology in action......scrappy

 

[SeaMaiden]

i did a test with powdered dolomite lime and it neutralized acidic water in a matter of hours so i dont agree that it takes ages to work, but i would agree that you dont need to add it every time in recycling and you need to take note of the lime content of your water and other soil amendments when mixing or recycling soil.

i use it at 5g per litre of soil and it does the job for me.

VG

I have performed similar tests simply using RO/DI water and it took minutes to change the parameters of hardness (dKH, carbonate hardness) as well as shift pH upward. If carbonate hardness is measurably changed, then I think that nails it. I would further suggest that if someone is using a very hard (carbonate especially) source water without filtering, then they should avoid DL, or be certain to counter-balance it with something such as peat.

 

[VerdantGreen]

really we have to look at soil holistically - as the sum of it's parts.
Its hard to pick out one amendment and say do/dont use this, as it depends on what your other inputs are (including water hardness/alkalinity)
im sure many great grows have been done with DL and just as many great ones using oyster or whatever else...
i think where problems can arise is buying a ready made 'complete' soil and then trying to further amend it, because unless you now what is already in it you could be inviting problems. most peat based potting composts will already have been limed.
i use straight peat, and all the other separate components so i know what is in my soil.
VG

 

[SupraSPL]

+1 verdant. Pulverized dolomite is immediately available and will neutralize acids, releasing calcium and magnesium. From what I understand the cal/mag ratio in dolomite lime is near ideal. I always add a bit when recycling soil (.5ml/L)

 

[RanchoDeluxe]

Hey Supra, Take a look at the first 7 or 8 pages of the Living Organic Soil thread. It may change your mind. I used to believe exactly what you just stated. That is until I read that thread. Especially if you've read and trust the main players of that thread - Gascanastan- CC. I've spent a little time Googling as well and the 2:1 Ca:Mg ratio is not ideal. I believe we are looking for at least a 3:1 ratio if not more. Any takers on what the proper ratio is??

Verdant- My buddy has been using 60% Roots soil 20%compost 20%perlite. He adds back 11/2tbs per gal of DL every run as well as some dry amendments and some compost and/or perlite. Water source is 262ppm 62ppm of which is Ca.

 

[SeaMaiden]

I'm landing squarely in the 3:1 and up (5:1, anyone? At least this is what I'm experiencing in my native soils in terms of best amending practices sans soil testing) crowd. That said, this year I began playing around with this Sea-90 stuff and it arrested completely all blossom end rot issues I was seeing in tomatoes and squashes, three applications and no additional Ca this year. I can't say why this is, just that it is what I observed.

Also, my (deep well) water column is extremely high in both general and carbonate hardness, and I use unfiltered water for my OD irrigation. Given that it's something like 9-10* dKH, I would think that if Ca or Mg bound with CO3 were so readily available for uptake I'd not see the problems I consistently have every year with these plants.

RD, Ca in what form? I'm thinking also that if his soil has a high peat content that will, if I haven't said it previously, help a good bit to essentially counterbalance the effects of the CO3 portion of the bound molecules present in the DL.

 

[VerdantGreen]

Hey Supra, Take a look at the first 7 or 8 pages of the Living Organic Soil thread. It may change your mind. I used to believe exactly what you just stated. That is until I read that thread. Especially if you've read and trust the main players of that thread - Gascanastan- CC. I've spent a little time Googling as well and the 2:1 Ca:Mg ratio is not ideal. I believe we are looking for at least a 3:1 ratio if not more. Any takers on what the proper ratio is??

Verdant- My buddy has been using 60% Roots soil 20%compost 20%perlite. He adds back 11/2tbs per gal of DL every run as well as some dry amendments and some compost and/or perlite. Water source is 262ppm 62ppm of which is Ca.

but this is my point, perhaps 3:1 is the ideal ratio but there is calcium in many of the other amendments you add.

EWC has lots of calcium. bone meal, P guano, rock phosphate are also all liming agents... so perhaps with the DL they bump it up to the ideal ratio?
there are many ways to get it right, DL isnt perhaps the most fashionable or cutting edge source of calmag but it works very well in my mix (i dont re-amend with it when i re-use soil)
i seldom see pictures of plants on here that i regard as looking healthier than mine.

VG