Decomposition rates of organic fertilizers for full outdoor season?

[weedlover_89]

Hello to everyone. I've been looking to calculate application rates of organic fertilizers for an outdoor legal cbd grow of 10.000 square feet (1000 m2).

Take nitrogen for example. According to Berger's suggestions (1969) as they are mentioned in McPartland's et Al Hemp Pests and Diseases, nitrogen needs of cannabis is calculated at 20 kg N /1000 m2 for a full growing outdoor season.

The issue is that many organic sources of N are fully decomposed ~75-100 days after application and I want to grow for the full season of 6-7 months. What I understand by the term "full decomposition" is that all the nitrogen ions of the organic fert will have been available to the plants by the time the organic source has decomposed completely, correct?

If I apply the whole amount of N fertilizers/amendments from the beginning to reach 20 kg N/1000 m2 will this be ok to cover the needs of the plants in nitrogen? What happens with the excess nitrogen ions that will have been produced by days 75-100 and aren't used by plants then? Are they being lost to lower parts of the soil by repeated irrigation?

This is something I haven't fully understood,thanks for any clarifications on the issue.

 

[dank.frank]

Read the first 40 pages of my current grow thread...link is in the signature.



dank.Frank

 

[weedlover_89]

Hell yeah, I can easily tell that there is a wealth of info in your thread,just by looking quickly through the first 5 pages!! Amazing, I think I am gonna find a lot more than what I was looking for!
Hope I can find ways to contribute to this wonderful forum in the future

 

[CrushnYuba]

For N, Something like feather meal will last the whole growing season. It is very difficult for bacteria to break down keratin. 6 mon later, it's still there.
Something like blood meal or manure or guano, will be broken down pretty fast and will become available as roots grow into it. Outdoor growers try to use these large volumes of soil to keep nutrients available for long periods off time.

I usually top dress mid season. Its hard to get around it. But feather for n, calphos and bone meal For p and ca, greensand for k, other rock dusts for micros really take some time to break down.

I would rather top dress faster working amendments mid season though.

 

[dank.frank]

I suppose to give a more direct answer, there are at least the major factors in play: Biological activity of the soil, hardness of the object in use, and particle size. Things like soil acidity change how an object breaks down as well. There are many factors, but generically, look at what it's really made of - ie egg shell = calcium carbonate and the above example, feather meal = made of keratin, crab shell = chitin, calcium carbonate, etc, etc, etc.

This is from a sticky in the Stank Bros sub-forum. If you are trying to grow in lbs/acre over a specific square footage, this will help you.

I've gotten asked countless times over the years for the weight of various amendments. It would have come in handy for myself years ago if this type of information had been made available. With that in mind, this chart, expresses the weight (in grams) of various amendments in different volumes, per cup. Keeping in mind, the brand or formulation of the material can change the weight, but this chart is certainly better than not having the information at all.

These weights can be converted to pounds (lbs), dividing them by 454 and then plugged into these equations, for figuring out NPK values in pounds per acre.

The first formula, will tell us how much of any given amendment to apply to achieve a desired nutrient level within a known planting area.

[(pounds per acre needed/square foot in an acre) x sq ft to be fertilized] / elemental percentage of fertilizer being applied

Example: A soil test says you need to apply 120 lbs per acre of P. You decide to use steamed bone meal. 2-14-0. Let's assume you have a 2' x 5' soil bed, so 10 sq ft.

[(120 lb/acre / 43,560 sq ft/acre) x 10 sq ft] / 0.14 = 0.1968 lbs of 2-14-0 steamed bone meal to provide 120 lbs of P to the 10 sq ft bed.

However, notice we also applied nitrogen in the bone meal. So that brings us to the second necessary formula, which is a simple 3 part process.

A. weight of fertilizer applied x percent of elemental nutrition
B. Square Foot per acre / square foot fertilized
C. A x B

To continue with the example above, in the process of applying the bone meal to get 120 lbs of P, we also added:

A. 0.1968 lbs bone meal x 0.02 (nitrogen) = 0.0004
B. 43,560 sq ft per acre / 10 sq ft = 4,356
C. 0.004 x 4,356 = 17.424 lbs of N applied

Chart is weight in grams per volume of a given amendment.

This should help anyone who is actually getting soil tests done and trying to adjust accordingly.

It's especially helpful if you actually know what NPK values you are trying to achieve.



dank.Frank

 

[weedlover_89]

Thanks a lot about your contributions gentlemen!

@ CrushnYuba: Nice tip about the feather meal! Yeah, I guess feather meal would be a nice addition in order to make sure that plants with 4+ months of veg don't start yellowing mid-flowering or earlier, something I have faced in the past. I guess top-dressing before flowering would involve smaller amounts of blood meal or something with similar decomposition rates.

You talked about manure. I guess you are talking about the ammonium (inorganic) form of N being released rapidly.
According to this link: http://cceonondaga.org/resources/nitrogen-credits-from-manure we could estimate that ~35% of organic N (dry matter 18%) from manure is released gradually over the whole first season of application?

Now that brings other questions to mind: Is the release of organic N something that is being done at the same rates with every month after application? I.e ~3 percent of N being released every month over 12 months? I guess this is not the case. I am really interested in finding a way of calculating something like this. Application of manure could cover a good deal of potentially bioavailable N, P, K , Ca etc.

Thanks for the tip about calphos! Through searching in this wonderful forum I saw that aragonite is a really good source of calcium as well!

@dank.frank: Thanks for taking the time to explain it further! That will simplify a lot things for me after making the conversion from imperial to the metric system! Concerning ppm results of soil analysis: I remember I had seen a post by Michael Astera (if I am not mistaken, could be someone else as well) here in IcMag explaining how to convert ppm concentrations nutrients of soil analysis -> kg/acre based on bulk density of soil. Besides that, after calculating bulk density, we could estimate how many kgs of a fertilizer to add to achieve desired ppms. Really useful advice which I have translated in my language but I am unable to find the link.

Except nitrogen, calcium is another element that has put me into much thought. I am trying to figure out how much CaO is being provided by liming and how much extra is nescessary by other sources. Let's take a source of calcitic lime for example with CCE (calcium carbonate equivalent) of 100% CaCO3.

According to this handful conversion tool: https://www.yara.co.uk/crop-nutrition/farmers-toolbox/conversion-calculator/ 100% CaCO3 equals 40% elemental calcium. And 40% elemental calcium equals ~55% CaO, the bioavailable form of calcium. Am I right to guess that 100 kg of this lime would provide gradually ~55 kg of CaO? Something I am missing here?

 

[CrushnYuba]

In manure, i think the p and k is pretty water soluble. Manures like chicken and guano have a portion of the N content as amonical. That's water soluble and instant but even the organic N portion of manures does not take a very long time to break down in a very biologically active soil. Partical size and hardness of the partical makes it break down faster then something like feather.

I wouldn't use lime to add calcium unless i had an acidic soil. There are other choices that dont mess with ph.

 

[dank.frank]

Lime itself is pH netural and can only push a soil to about 7.4, on it's own, but when you add other things that push it out of balance.

I prefer to add more calcium in general than is necessary in many different forms and offset that with elemental sulfur. That gives the soil the full range of ions it needs to fluctuate and swing as necessary. Root exudates control the pH range so a plant can get what it needs at maximum efficiency during different hormonal phases.

I use a mixture of dolomite, aragonite, gypsum, and elemental sulfur as my primary pH buffer. I use dolomite because it is much faster acting. Aragonite because it supports bacterial colonies and stays in the soil for a long time contributing to tilth. Gypsum because it is a faster acting calcium source that doesn't alter pH. Everything has a purpose and when in proper balance, you'll get great results. Balance meaning I like to have a 7:1 - 8:1 Ca:Mg ratio in my soils. A Mg heavy soil faces compaction and is subject to cracking in drought. A soil heavy in Ca stays soft and loamy.

Sorry, I'm not much help when it comes to converting things to metric.



dank.Frank

 

[troutman]

It's better to feed smaller amounts more often than trying to figure this out.
There's too many variables in the outdoors and each situation will be a little different.

 

[dank.frank]

Guess you aren't much in favor of guerilla patches then...



dank.Frank

 

[troutman]

Guess you aren't much in favor of guerilla patches then...



dank.Frank

Who me? I do guerilla patches don't kid yourself.

 

[growingcrazy]

Using Berger's numbers:


20 kilo x 2.20 lb = 44lb / 1000m2

1000 m2 = .25 acres


44 x 4 = 196lbs / acre or ~100ppm.


I normally stick to soil Organic Matter percentage (OM%) x 7-9 ppm for N holding capacity of the soil. So that is 14-18lbs of N per point of OM in the soil per acre.



Example:
OM% of 10= 70-90 PPM or 140 to 180 lbs N per acre,roughly.


I normally apply 30-60 ppm (60-120lb) N when applying mid season depending on how much has been removed.


30 ppm of N at plant also helps.


Everything depends on what your soil is like and the weather conditions in that area.


I would recommend not following any guidelines designed for indoor cannabis. You will waste a lot of money.

 

[CrushnYuba]

Frank: i feel like you are pretty dialed and probably know a bit more then me. Why do u choose lime over something like calphos? Most of the wells i use have carbonates or bicarbonates and i usually have to avoid adding more.

I have had varying success with elemental sulfur. I don't really have the buffer balancing act dialed. I also don't really know how to predict when elemental sulfur will break down to sulfuric acid... Do you think it's possible to have too much sulfur in a mix? I use langbeinite and potash for most of my k and mg. I use a little gypsum also. I wonder if there is such thing as too much sulfur

 

[growingcrazy]

CrushnYuba: Most of the amendments you list would be added either in the fall or very early in the spring. By doing that a good amount of the S that isn't bound to another element is going to be washed out of the root zone.


If they are in containers that don't get enough runoff, and S numbers are very high, the flowers will burn poorly and taste like burnt matches aka S.


Lime to hit a certain pH. After that a soluble(gypsum) and a slow release (bone meal) Ca source to fill CEC sites. Test regularly to dial your application rates until your comfortable and can test less.

 

[CrushnYuba]

So Frank, it's there a reason to use lime and sulfur to balance it out? Or is it just something u do that works? I hope im phrasing this correctly. Like is there another benefit to it? Do u think the medium is more ph stable with the different buffers? Is there something else that I'm missing doing it the way i do?
I really run high calcium levels, but i really like cal-phos and other none carbonate forms of calcium. Do u think i would do better doing it the way you do with lime and elemental sulfur?

The compost portion of the soil can change in ph as it ages. Do you think that the way you do it holds better? My compost is usually alkaline and it gets balanced with acidic peat or fir bark. As it ages it changes though. The only carbonate i use comes from my water. If there is a better way, I would like to try it this year.

 

[dank.frank]

Lime is faster acting. ELEMENTAL sulfur, not so much. It's all about buffer capacity...except...sulfur is used by the plant for terpenes as well.

Fertoz is just mined at a different location. It's calcium phosphate, but also has silica. I have CalPhos and Tennessee Brown Rock Phosphate on hand as well...I prefer the Fertoz product.

My liming mix is 3 part - aragonite (or oyster shell flour), dolomite, gypsum - but calcium comes from all sorts of places. I know my exchange sites are generally 75-80% Ca, and 10-13% Mg, which I feel seems to be the sweet spot.

Outside of what is in the soil itself, if it is in balance, plant exudates can gradually shift and alter pH to allow for better uptake of whatever it is they need. I'm a firm believer if it is present in the soil in a variety of inputs, the plant can and will pick and choose from what and when it takes it's nutrition.

Diversity of inputs also allows you to foster diversity in bacterial and fungal colonies.

I actually charted this in the beginning of my thread:

Rock Phosphate in this chart is referencing Fertoz, fwiw.

Aged soil has more hummus. Humates - humic and fulvic acid attract positive ions and effectively increase nutrient holding capacity because of the bonds they form. This is why you kick start that process in dead soils by adding those very things back to the soil either in a granular form or as part of the nutrient tea/compost tea scenario.



dank.Frank

 

[weedlover_89]

Hello guys! Glad to be seeing that more and more good info is provided!

@growingcrazy: Nice info man! Excellent explanation about the soil OM and N. What do you mean when you say "not to follow any guidelines designed for indoor cannabis"? Could you be a little bit more specific?
Your explanation about sulfur nutrients was very good! Considering gypsum, this one has relatively large amounts of S and it is recommended at relatively large quantities instead of lime. What's going on in this case? I guess your explanation about applying it in early spring or fall covers it...Really nice explanation about filling of CEC sites.

Bart Hall has explained it nicely in Hemp Pests and Diseases but part of his recommendations is based on chemical ferts. For example, in order to increase K saturations level it is suggested that 50 kg of potassium muriate (0-0-60, inorganic fert) and 50 kg of potassium sulfate (0-0-50, organic fert) are added per hectare (ha) at K saturation 3%. What would be the alternative of potassium muriate in this case? More potassium sulfate? .

@dank.frank: I had read some interesting info about calcium phosphate. Supposedly applying ~180 lbs of soft rock phosphate + 600 - 1100 lbs of calcitic lime / 10,000 square feet (in that order) many harmful microorganisms + insects etc are killed. Applying fertilizers after 10-14 days means that soil will be holding those ions much better. Gotta find the source, with all that stuff i've been checking out...About compost tea, I found this one interesting:https://www.gardenmyths.com/compost-tea/. Of course you talked about dead soil ( custom soil mixes made by us) and that article talks about adding compost tea to a "default" natural soil.

Guys, considering fertilizer recommendations for big outdoors projects...Combining McEno's and Berger's recommendations (from Hemp Pests and Diseases book)...For 1200 kg / ha of flowers (Sorry about the kg info but I am a little bit bored to convert them to lbs):

N: 200 kg/ha
P2O5: 65 kg / ha
K2O: 191 kg/ha
CaO: 202 kg/ha
MgO: 39 kg /ha
S: 18 kg/ha

 

[Charles Dankens]

CrushnYuba: Most of the amendments you list would be added either in the fall or very early in the spring. By doing that a good amount of the S that isn't bound to another element is going to be washed out of the root zone.


If they are in containers that don't get enough runoff, and S numbers are very high, the flowers will burn poorly and taste like burnt matches aka S.


Lime to hit a certain pH. After that a soluble(gypsum) and a slow release (bone meal) Ca source to fill CEC sites. Test regularly to dial your application rates until your comfortable and can test less.

Are you recommending to soil test regularly? Also what range of S numbers would you consider "very high"?

Thanks for sharing.