The Lounge : Growers Round Table Discussion Thread
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cannabisforjoe
New member
I have a sample from a pH 6.5 soil with:
1500 ppm Ca from 8.2 test and
2500 ppm Ca from mehlich test
no history of lime/gypsum/rock dust on this mineral soil
what is causing the difference in numbers and which should I use for the base saturation?
I have another mineral soil with a 6.8 pH and the mehlich calcium is twice as high as the 8.2. 4000 vs 2000. once again no history of calcium ammendments
same question. what is causing the huge difference in numbers? and which should i use for the base saturation?
the potassium numbers are almost identical so the mehlich doesnt dissolve any more potassium minerals than the AA @ 8.2 test. Which calcium minerals are getting dissolved in such greater numbers?
Joe
Lower the pH to around 3 with Pacid and it will keep for 12 months if stored in a cool dark place. I use it within two weeks if I don't add the Pacid and that is still opening and closing it every couple days over that time period.
I don't count on a 1:1 addition of Ca into a soil mix. If using something like bone meal or calphos/srp the calculated Ca addition doesn't match on soil test. Sometimes they are 50% less. Each soil is different.
In something like DTE liquid bone meal, they guarantee 7% Ca in that bottle. If you make a solution and 100% of it makes it to the soil, you hit your target ppm whether its a salt/chem or organic. That still doesn't mean the organic form is as available to the plant.
Because your N comes from bone meal you have a much slower release rate than that of other forms. Biology and moisture dictate that rate. Properly watering with very little to no run off you will be able to grow a number of cycles without any additional N. I wouldn't add any additional chem ferts to a soil with that much N. They are an even quicker pathway to root uptake and subsequent N overload. You are correct on the binding.
I will explain what I mean by "put N in a class by it's own".
Nitrogen is the easiest element to read in a plant. Light green leaves and yellowing in the lowers and you are on the low end. Dark green and tip burn and you over did it. Your goal is to keep that light green from top to bottom through correct timing and quantity of feeds. If the plant is given the ability to pickup N or P, it will take the N. Your job is to limit the N available so it has a greater change to absorb the available P.
This is the exact same situation that happens between Ca,Mg and K. You want bare minimum Mg and K so the plant doesn't show a deficiency in either of those elements and it will be able to uptake as much Ca as possible.
50-60ppm N is a much better starting point if you plan to feed at some point in the cycle. I would put in some serious veg time at higher rates or limit container size to use all the N by mid flower.
Don't get set on needing to feed. You have everything you need in the soil. Keep it on the dryer side and only make corrective actions if needed.
What about using bone char in that mix would It still need cooking?
Not sure on that one. With a really fine powdered bone meal the heating and boiling allows for smaller particles that are easier to suspend in the solution.
paradoxlost
Member
Wouldn't that be a result of the calcium tests being done at pH's that favor the net mineralization of the calphos. I know, for instance, calphos is not soluble at pH 7 and has a very narrow range of solubility, mostly in the alkaline spectrum of the pH scale. In a case with a lot of added calphos (and i suspect a lot of other tests that "miss" added calcium) if you take slow's advice at pay the extra for the calcium test at pH 8.2, you will find more calcium in those test results.
Arnold.
Active member
Thanks for the elaborate answer GC.
I did indeed notice I didn't had to feed my previous mix as well, just water went fine. It's a shame I did it bad, I guess I'll be mixing again soon. Good thing bonemeal is fairly slow release.
I also noticed another flaw today: I always assumed that this convention:
The top 6 to 7 inches of 1 acre of average soil= 2 000 000 lbs/ 1 acre = 43 560 ft2
The top 15 to 17cm of 1 hectare of average soil is assumed to weigh 2 000 000 kg
used the dry content of the soil. But apparently it is not, it is a soil with 20% water by weight. (https://www.fairbankssoilwater.org/user-files//ChemistrySoil.pdf) That means I have to weigh my peat mix when moist as well.
That explains a lot on the bulk density. I'll have to bend over it again and see where this caused mistakes in my fertilizing.
Learning by mistakes huh
I did indeed notice I didn't had to feed my previous mix as well, just water went fine. It's a shame I did it bad, I guess I'll be mixing again soon. Good thing bonemeal is fairly slow release.
I also noticed another flaw today: I always assumed that this convention:
The top 6 to 7 inches of 1 acre of average soil= 2 000 000 lbs/ 1 acre = 43 560 ft2
The top 15 to 17cm of 1 hectare of average soil is assumed to weigh 2 000 000 kg
used the dry content of the soil. But apparently it is not, it is a soil with 20% water by weight. (https://www.fairbankssoilwater.org/user-files//ChemistrySoil.pdf) That means I have to weigh my peat mix when moist as well.
That explains a lot on the bulk density. I'll have to bend over it again and see where this caused mistakes in my fertilizing.
Learning by mistakes huh
Last edited:
ledo
Chasing the Present
this post here is filled with little nuggets of great information, worth reading more than once ! thanks GC
ledo
Chasing the Present
Thanks for the elaborate answer GC.
I did indeed notice I didn't had to feed my previous mix as well, just water went fine. It's a shame I did it bad, I guess I'll be mixing again soon. Good thing bonemeal is fairly slow release.
I also noticed another flaw today: I always assumed that this convention:
The top 6 to 7 inches of 1 acre of average soil= 2 000 000 lbs/ 1 acre = 43 560 ft2
The top 15 to 17cm of 1 hectare of average soil is assumed to weigh 2 000 000 kg
used the dry content of the soil. But apparently it is not, it is a soil with 20% water by weight. (https://www.fairbankssoilwater.org/user-files//ChemistrySoil.pdf) That means I have to weigh my peat mix when moist as well.
That explains a lot on the bulk density. I'll have to bend over it again and see where this caused mistakes in my fertilizing.
I firmly believe the biggest factor people overlook is proper watering & moisture levels which heavily drive how a plant absorbs varying minerals. The presence of H also sways things. You can have perfect soil, if you water wrong your screwed. You can have average soil but if you water right you'll be just fine, happy.
It seems to this simple farmer that people put the cart before the horse far too often. What GC is trying to do is for GC, own your own space(s), circumstances and yourself (one of the largest variables) all the while trying to learn from others but knowing you're unique and so is your situation(s)...
Arnold.
Active member
Yes indeed, I noticed you mentioned that a few times Led.
I am more aware on my watering since starting this journey and my plants are happier. But I still do not got the hang of it entirely. For example when I take the plants out of their pots I notice dry spots and moist spots in there. The bottom tend to be dry.
Putting a wooden skewer in from top to bottom in my pots has been a valuable monitoring tool as well.
Can I ask what constitutes 'proper watering & moisture levels' in your eyes Led?
I am more aware on my watering since starting this journey and my plants are happier. But I still do not got the hang of it entirely. For example when I take the plants out of their pots I notice dry spots and moist spots in there. The bottom tend to be dry.
Putting a wooden skewer in from top to bottom in my pots has been a valuable monitoring tool as well.
Can I ask what constitutes 'proper watering & moisture levels' in your eyes Led?
I would say that in a good bit of cases, yes that could be the cause. I have noticed this same thing happen on soils with a pH from 5.7-7.3 though, So I don't have a concrete answer. My thoughts were binding and solubilty are the culprit but it happens with more than just Calphos and Bone meal.
How many of you have pulled samples at greather than 7 pH that show identical numbers on M3 and [email protected]? I have multiple times now on highly biologically active soils. My answer to this is to take samples at 30,60,90 days after amending and watch the numbers.
Arnold, wet some medium to what you consider perfect moisture (squeeze a handful and barely a drop come out) and fill a pot like normal. Weight the soil to see exactly what the weight is. Now dry the soil and take a weight. You will now know how many grams(ml) you need to add to get that pot back to that same point.
Example:
Moisten gallon of soil and squeeze out moisture
zero scale with container, fill with soil to desired level and compaction and record Grams
Dry the soil and weigh container and soil again, record the grams
Subtract the wet number from dry, IE 350-275 = 75 grams of H20 to hit your target moisture level in that container.
This works well on smaller plants that you can weigh each time before watering to learn how to water correctly. If you have a group of 12 plants, each will require a different water amount to hit the target number...its a great way to learn.
(What is up with the double spacing on posts? Why did they turn on double spacing? lol)
Soil weight is taken at field capacity. Essentially a 48 hour air dried sample.
Like LED said, "what gc is doing is for gc" can be used for multiple things...
IF you take your samples all on dry medium, you created that data set for your situation. If you amend that dry soil, you are creating your own curves for soil quantities. You can dial that in just fine as long as you know what your doing and keep your methods the same. Test, amend, retest. Make changes to amending based on what the test numbers show happened in the soil.
Create a method that works for YOU and YOUR space.
Like LED said, "what gc is doing is for gc" can be used for multiple things...
IF you take your samples all on dry medium, you created that data set for your situation. If you amend that dry soil, you are creating your own curves for soil quantities. You can dial that in just fine as long as you know what your doing and keep your methods the same. Test, amend, retest. Make changes to amending based on what the test numbers show happened in the soil.
Create a method that works for YOU and YOUR space.
Arnold.
Active member
Yes I do understand that. But now it just makes more sense why my mixed dry media was so much lighter than the field soil convention. Plus I like to minimize the need for soil testing over and over again since I think it is quiet expensive for a hobby grower.
Thanks a lot for all the insight GC, I do appreciate it a lot.
Good tip on the scale method for watering. I did it by feel, lifting the pots, but this sure is a better way to get my 'hand scale' tuned in
Thanks a lot for all the insight GC, I do appreciate it a lot.
Good tip on the scale method for watering. I did it by feel, lifting the pots, but this sure is a better way to get my 'hand scale' tuned in
To me I would say you have not given me enough info to decide. At a minimum I would want m3 numbers for k, mg and p. N if you have them.
If those are adequate gypsum is the answer. If P is short then part of the ca added might be bone meal. If k/mg are short then you gotta think
The test itself shows you not all of your Ca is gonna be available this yr. it would behoove you to get some more soluble forms in there for this next run
ledo
Chasing the Present
I would say that in a good bit of cases, yes that could be the cause. I have noticed this same thing happen on soils with a pH from 5.7-7.3 though, So I don't have a concrete answer. My thoughts were binding and solubilty are the culprit but it happens with more than just Calphos and Bone meal.
How many of you have pulled samples at greather than 7 pH that show identical numbers on M3 and [email protected]? I have multiple times now on highly biologically active soils. My answer to this is to take samples at 30,60,90 days after amending and watch the numbers.
Arnold, wet some medium to what you consider perfect moisture (squeeze a handful and barely a drop come out) and fill a pot like normal. Weight the soil to see exactly what the weight is. Now dry the soil and take a weight. You will now know how many grams(ml) you need to add to get that pot back to that same point.
Example:
Moisten gallon of soil and squeeze out moisture
zero scale with container, fill with soil to desired level and compaction and record Grams
Dry the soil and weigh container and soil again, record the grams
Subtract the wet number from dry, IE 350-275 = 75 grams of H20 to hit your target moisture level in that container.
This works well on smaller plants that you can weigh each time before watering to learn how to water correctly. If you have a group of 12 plants, each will require a different water amount to hit the target number...its a great way to learn.
(What is up with the double spacing on posts? Why did they turn on double spacing? lol)
no kidding on the double space, I have to fix every time.
Arnold, GC gave a great answer on watering but I also think pulse watering a little bit at a time for a number of plants, and then returning to the first plant feeling its weight each time and so forth goes a long way. A scale helps takes away some of the human error, always good....
When I water a container, it's very rare to ever see anything come out the bottom, trickle /pulse watering helps ensure this. It also gets better uniformity and avoids dry spots in my opinion. Also think about what your plants roots are doing, where they like to be, how they grow; was the plant just transplanted into a larger container where there are no roots in spots, etc.. listen to them buddy. When you kill plants for whatever reason, inspect that root-ball every time until you are very comfortable watering that type and size container.
I know poor watering 9/10 times are the root of ones issues and leads to other wrongly identified problems of which they then chase themselves trying to fix and create more and more and then are unhappy. Ca for example, greatly depends on moisture levels and their flux.
Sometimes you just can't water but when you have that control to be able to do so, people are normally overdoing it and drowning their plants which ends bad normally.
Big containers aren't all they are cracked up to be sometimes, necessary during others though too...
Arnold, are you factoring in compaction for the field soil vs. your dry mix appropriately in your calculations?
This is a great point on the watering. Break your watering amount into at least 4 rounds between all of your plants per watering. If you need 60ml of water in a pot, add it at 15ml per time until you get your desired run off.
You have to make calcium available to see a change in the soil. Without moisture and biology the Ca will sit unavailable for a very long time.
Give us an idea of your climate, soil type and past history on the fields. That will tell us much more than additional soil numbers.
ledo
Chasing the Present
that plant from the looks of it is as near perfectly fed as any I have ever seen you post, nor anyone else for that matter... well done
Seriously. Those are a thing of beauty.
You drying in the school bus?
You drying in the school bus?
