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Old 09-25-2018, 04:53 AM #711
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Same I'm wrapping my weekend at a bar. I'm going to start a new thread for this. I'll synthesize the lectures and slideshows and if anyone wants to chime in, please do. It'll be here in the advanced section. All told, I think they do provide the elements needed to solve these problems/graded questions but there are no lectures on how to apply it. In which, I'm lost. 🙁
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Old 09-25-2018, 03:08 PM #712
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It's through a certificate platform called edX.org- The three part program is called Sustainable Food Security. In order, I'm taking crop production, systems analysis, and security & access.



I believe I've mis-worded my objective. You're correct, though. What I mean to ask or investigate are the steps, beginning to end/ gigajoule to yield. The program is very detailed but also condensed where math steps are necessary. And I don't think the math is hard but I can't visualize or connect certain steps:

600 joule per m2 per second (Clear day, middle of summer)
+
40 kg Co2 per HA per Hour (C3 plant, single leaf at normal temperature. 80 kg CO2 per HA per hour assimilated by a closed canopy)
=
Gross Assimilation Maximum (Amax) (best possible outcome without greenhouse influence or assistance)

Next remove energy spent on respiration
-maintenance respiration
-growth respiration
-photorespiration

[hazy on this- respiration coefficient .01-.03 kg of assimiliates per kg of standing phytomass. What do I even do with that?]

=
Net assimilation in kg CO2 per HA per hour


[hazy again- use the assimilation here to drive growth and quantify biomass, I think? But now we've gone from joules to gigajoules per HA per Day...]

It's between net assimilation and yield that I can't wrap my brain around. So when a question like this:

"Tree biomass contains a considerable amount of core wood, that is no longer metabolically active and therefore does not require maintenance respiration. So this implies all other organs require maintenance respiration. The maintenance coefficient of the remaining active tree components amounts to 0.1 ton (CH2O or assimilates)per ton-1 (dry matter) per year. Information collected from a Douglas fir plantation in 1924 and 1983 is given in Table 1. [table given] Q. Express the maintenance coefficient in ton CH2O per ton dry matter per day.
answer with 6 decimals, e.g. 1.234567"

Is posed, my hair blows back.
ok, so first that last question. I looked up the specific question so I could also see the table given with it.

the thing here is that the table lists FM(fresh matter), and a water content. while you need DM(dry matter). so this excercise is mostly just calculating between fresh/dry matter, and reading the question well enough to know you have to ignore the core wood. other than that it's just multiplying by the given maintenance respiration.

the first question after the info given, the one you copied, is actually really, really simple. you don't need the table at all for that. it's just a step to make the next question easier, it's asking you to convert the given maintenance respiration, which is per year, to a value per day.

so it's just 0.1/365

after that you have to calculate the maintenance respiration of that specific douglas fir plantation from values given in the table.

so for 1924:
33.3 tons needles, 70% moisture content, 0.3*33.3=9.99 ton dry matter per ha
+
42.0 ton branches, 50% moisture, 0.5*42=21 ton DM
+
(core wood, not relevant since it doesn't require maintenance respiration)
+
200.0 tons sap wood, 40% moisture, 0.6*200=120 tons DM
+
40 t roots, 60% moisture, 0.4*40=16 t DM

so together: 9.99+21+120+16=166.99 ton DM per ha

maintenance respiration given= 0.1 ton (CH2O or assimilates) ton-1 (dry matter) per year.

so 166.99*0.1=16.699 ton assimilate per ha per year.

but, you have to answer per day, not per year.

so:
16.699/365=0.04575068493 ton assimilate per ha per day, for 1924.


for the other comments:
I think you need to look into respiration a bit more.
the step between gross assimilation and net assimilation is using respiration.

so gross assimilation is your total production by photosynthesis. it's a certain amount of energy from the sun, which assimilates a certain amount of CO2, which is converted into sugars(assimilates).

so you then have this amount of sugar, but it can't be all used for growth. the are a few different kinds of respiration, which are things that cost energy, so to provide that energy sugars/assimilates produced by photosynthesis are used.

first you have the loss from photorespiration(only aplicable with C3 plants). this is the loss from the chemical that binds CO2 from the leaf pores to bring it into the leaf, this chemical also binds O2, which has to be split off again before it can be re-used for CO2, but with O2 it doesn't give a CO2, so it's a loss in energy.

then you get maintenance respiration. this is the sugars used just to maintain all the plant matter that's already there. this is also what was calculated in that question above. it's expressed as a amount of assimilates per total DM(but in the specific question above it was about a douglas fir plantation, so a tree, so therefor you have to deal with corewood which is dead, so doesn't require maintenance respiration. with annual crops that's irrelevant)

what you have leftover after the 2 respirations above is what can be used for new growth. however, new growth is not directly equal to the weight of the assimilates. your assimilates are sugars, but new growth also contains other compounds(more complex carbohydrates like starches, proteins, fats). converting assimilates into those compounds also costs some energy, so that's growth respiration.

if you know a conversion factor for how much new growth you get per amount(kg or ton or whatever) of assimilates, you can calculate how much new growth you get. and that conversion factor also depends on what is grown, for example a plant setting seed with oily seeds will have a different conversion factor from a plant with starchy seed.

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Old 09-25-2018, 04:22 PM #713
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So, the class is revolving around core principles of ecology.

First tier is Potential Yield: If you have ideal climate and ideal genetics, these represent the absolute best you can do. You can't have a crop without assimilation of CO2- and your environment has everything to do with this. Maximums and efficiencies have been gathered across all main crops, across the globe. If you aren't fixing CO2 or assimilates to the best of your genetics ability, then you're leaving potential on the table and no water or nutrition can make up for that. In parts of the world where greenhouses, nutrition, and water are no issue and the yield gap between real harvest indexes and projections is small, the next step is to continue breeding for varieties which make the most of storage organs or sinks and use all light and assimilates even more efficiently.

Second tier is then limiting factors, Water and Nutrition: Doesn't really apply to many of us but in parts of the world where yield gaps are high, the breeding takes a backseat to amending the land and providing nutrition.

Third tier is then weeds, pests, human factors/errors, molds, preventing loss and overcoming incidental packaging wear and tear.

So where I'm at to begin is setting a baseline- if everything were perfect, what is the net result of best possible gigajoules and best possible CO2 at the optimum temperature. And there is a way, they have answers for "What was the annual growth rate of the plantation in both years if the gross assimilation rate was 43 tons (CH20) ha-1 y-1 (dry matter per ha per year) in 1924 and 31 tons (CH20) ha-1 y-1 (dry matter per ha per year) in 1983, assuming CVF equals 0.7 g (prod) g-1 (CH20).
answer with 1 decimal" - I'm just not in the groove, yet/I need to re-write all my notes and figure it out. I swear I watched each lecture 4 times and I wasn't prepared to answer these. Must dig deeper....

It's funny you say decades of measurements- they have a crop simulator which contains data from like 10 different crops in seven different countries over the last 25 years or something. You input the country, the crop, the year and the planting date and it shows you the tonnage of potatoes in Poland from 2010, planting on day 105- and broken down by storage organs, stems, leaves, and roots. It's really damn cool.

growing anything is simply about bottlenecks, any one significant limiting factor holds back all others (light, water, Co2, Temp, minerals etc), the slow kid on the relay team screws it all......

The first tier is situational and based on where you are, you might as well toss it. Gee, I wonder what their baseline is for ideal (how many different ones do they have for regions?), and where this is, growing what? ridiculous if you ask me!! inside a GH, haha, I'd bet 98% of the worlds crops are NOT grown under cover, toss it...

I'm sure there's some cool things and you do need a lot of data for value, if you grow in one place say for a decade, you begin to realize very clearly each year is quite different but with obvious significant similarities. The problem with things like this is they are esoteric and hardly the reality for a single site / farm....

To me it sounds like a clear cut case of farmer vs science, one realizes the practicalities of farming, the other likes to hear themselves talk and hypothesize what may or "could be" ideal.....

I know who I'd want helping me in my fields. I have GH's, I use Co2, I grow indoors and out, what you mention above I've been studying for years in a true and practical sense for over 25 species of plants across fruit and veggies on a single acre....

if you actually want to ever grow something and proper, listen to the farmers. If you want to dream about ideal scenarios, send off soil samples weekly, hope for peace etc.... sit in the classroom...

It's nothing personal toward you, but this class makes me laugh. Like most classes (I have a couple degrees, one advanced btw) they have done nothing for me in comparison from learning and doing oneself.

Everyone in here seems to like / value Jidoka, I'm pretty sure that boy is self taught, perhaps some schooling but me thinks he learns on the fly, as one should, it sticks around forever that way vs just retaining it for the next exam....
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Old 09-25-2018, 06:55 PM #714
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I disagree, I think you're too quick to throw out science like that(but of course, I have my stake in the science...)
I think it's not either the farmer or the scientist, the farmer and scientist need eachother and work together.

you also need to see this specific course and excercises in the right context. ofcourse science is aware of all those pitfalls and details that make these kind of calculations hard to get 100% accurate. but for most practical purposes, 90% accurate works fine too. and after following this course you won't be able to exactly calculate all those things, but you will be able to give a rough estimate which can help you with making farming-decisions. it's an intro course, introducing the core concepts which can be build upon later, and leaving out a lot of the detail, since if you would get everything thrown at you at once you wouldn't understand a iota of it.

but where this course has for example helped me is to make better guesses how often I have to visit my guerilla-plants, since I can make a good guess how long the water in the soil wil last, based on when it last rained and what kind of soil my spot has. I can also keep an eye on the weather forecast, and look at predicted mm of rain and based on that decide if it's needed to visit or not. ofcourse you would arrive at the same point with experience, but understanding the science gives me a good start from where I can continue on experience, and escape some beginner mistakes.

Quote:
The first tier is situational and based on where you are, you might as well toss it. Gee, I wonder what their baseline is for ideal (how many different ones do they have for regions?)
that's the point. the first tier establishes an upper limit to your production. those tiers are not one specific number, so there are not 'different ones' all over the world. potential yield is just a theoretic maximum yield you'll never actually achieve, but by calculating it you have an idea how much you can improve. for example if you're already performing at 95% of optimal yield, it would be wiser to buy more land instead of trying to push even more out of your existing land. if you're at 10% of optimal yield, you can still do a lot to improve your existing land.


and a lot of things you could indeed arrive at trough experience too, but often science is cheaper and faster. you don't need to trial and error for 10 seasons before you have the right values, because you can make a computer simulation and get a good guess what's optimal, then trial and error with that value you found in the simulation, and you only need a few seasons to get it right.

as an example of possible practical uses for this kind of stuff:
-decisions to fight a pest. if you can model crop growth, and you spot a pest, you can model what the decrease in yield will be due to the pest, what value of money that equals, then if the cost of the pesticide needed is more as the loss in yield, you don't fight the pest.

-similar for fertilizer. often there's a break even point for fertilizer, more fertilizer will still give more yield, but the increase in yield is simply not worth the cost of fertilizer above a certain point.

-determine optimal interval/doses for pesticides, to again save money. for example I had to make a simple model for a course(I think it was a followup course to the intro-course that included this edx module), where we had to model fighting armyworms with a bacteria(a form of biological control). you can spray this bacteria on the leaves, the worms eat it and die. however, the bacteria are broken down by light, and you get growth of new leaves not covered in bacteria, and shedding of old leaves that are covered.

there's a certain tresshold concentration of bacteria needed for the worms to be controlled. so you can make a model of this, including parameters for how the worm population grows, how fast the bacteria is rendered ineffective, and by playing around with different numbers for the interval between sprays and the concentration of the spray used you can find out what the optimal interval+concentration is to control the worms but use the least possible of the bacteria, so you limit the costs for aplication.
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Old 09-25-2018, 07:18 PM #715
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I disagree, I think you're too quick to throw out science like that(but of course, I have my stake in the science...)
I think it's not either the farmer or the scientist, the farmer and scientist need eachother and work together.

you also need to see this specific course and excercises in the right context. ofcourse science is aware of all those pitfalls and details that make these kind of calculations hard to get 100% accurate. but for most practical purposes, 90% accurate works fine too. and after following this course you won't be able to exactly calculate all those things, but you will be able to give a rough estimate which can help you with making farming-decisions. it's an intro course, introducing the core concepts which can be build upon later, and leaving out a lot of the detail, since if you would get everything thrown at you at once you wouldn't understand a iota of it.

but where this course has for example helped me is to make better guesses how often I have to visit my guerilla-plants, since I can make a good guess how long the water in the soil wil last, based on when it last rained and what kind of soil my spot has. I can also keep an eye on the weather forecast, and look at predicted mm of rain and based on that decide if it's needed to visit or not. ofcourse you would arrive at the same point with experience, but understanding the science gives me a good start from where I can continue on experience, and escape some beginner mistakes.


that's the point. the first tier establishes an upper limit to your production. those tiers are not one specific number, so there are not 'different ones' all over the world. potential yield is just a theoretic maximum yield you'll never actually achieve, but by calculating it you have an idea how much you can improve. for example if you're already performing at 95% of optimal yield, it would be wiser to buy more land instead of trying to push even more out of your existing land. if you're at 10% of optimal yield, you can still do a lot to improve your existing land.


and a lot of things you could indeed arrive at trough experience too, but often science is cheaper and faster. you don't need to trial and error for 10 seasons before you have the right values, because you can make a computer simulation and get a good guess what's optimal, then trial and error with that value you found in the simulation, and you only need a few seasons to get it right.

as an example of possible practical uses for this kind of stuff:
-decisions to fight a pest. if you can model crop growth, and you spot a pest, you can model what the decrease in yield will be due to the pest, what value of money that equals, then if the cost of the pesticide needed is more as the loss in yield, you don't fight the pest.

-similar for fertilizer. often there's a break even point for fertilizer, more fertilizer will still give more yield, but the increase in yield is simply not worth the cost of fertilizer above a certain point.

-determine optimal interval/doses for pesticides, to again save money. for example I had to make a simple model for a course(I think it was a followup course to the intro-course that included this edx module), where we had to model fighting armyworms with a bacteria(a form of biological control). you can spray this bacteria on the leaves, the worms eat it and die. however, the bacteria are broken down by light, and you get growth of new leaves not covered in bacteria, and shedding of old leaves that are covered.

there's a certain tresshold concentration of bacteria needed for the worms to be controlled. so you can make a model of this, including parameters for how the worm population grows, how fast the bacteria is rendered ineffective, and by playing around with different numbers for the interval between sprays and the concentration of the spray used you can find out what the optimal interval+concentration is to control the worms but use the least possible of the bacteria, so you limit the costs for aplication.

farmers are scientist friend, in the truest and purest form, classroom teachers and theorist are just that, in the classroom, they rarely apply what they spew in real world "actual" scenarios....
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Old 09-26-2018, 04:35 AM #716
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Led...I am really not self taught. This community taught me. Avenger, Tom Hill, BYF, Orechron, Don Juan Mattaus, gmophree, Slow plus Bob Wilt and Gary. Probably dozens of others...root wise, my son on microbes, the Taino organization...ride or die with all of them

But yea, lot of trial and error, lot of shit we just learned what not to do.

But I will never knock education. Learn every single thing you can from where ever you can. And pass us old fucks by
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Old 09-26-2018, 05:01 AM #717
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Led...I am really not self taught. This community taught me. Avenger, Tom Hill, BYF, Orechron, Don Juan Mattaus, gmophree, Slow plus Bob Wilt and Gary. Probably dozens of others...root wise, my son on microbes, the Taino organization...ride or die with all of them

But yea, lot of trial and error, lot of shit we just learned what not to do.

But I will never knock education. Learn every single thing you can from where ever you can. And pass us old fucks by
Taught by real world hands on farmers, growers etc but I completely agree, grasp at knowledge wherever it comes from with both hands for sure !
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Old 09-26-2018, 03:16 PM #718
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Originally Posted by djonkoman View Post

after that you have to calculate the maintenance respiration of that specific douglas fir plantation from values given in the table.

so for 1924:
33.3 tons needles, 70% moisture content, 0.3*33.3=9.99 ton dry matter per ha
+
42.0 ton branches, 50% moisture, 0.5*42=21 ton DM
+
(core wood, not relevant since it doesn't require maintenance respiration)
+
200.0 tons sap wood, 40% moisture, 0.6*200=120 tons DM
+
40 t roots, 60% moisture, 0.4*40=16 t DM

so together: 9.99+21+120+16=166.99 ton DM per ha

maintenance respiration given= 0.1 ton (CH2O or assimilates) ton-1 (dry matter) per year.

so 166.99*0.1=16.699 ton assimilate per ha per year.

but, you have to answer per day, not per year.

so:
16.699/365=0.04575068493 ton assimilate per ha per day, for 1924.


[sic]
if you know a conversion factor for how much new growth you get per amount(kg or ton or whatever) of assimilates, you can calculate how much new growth you get. and that conversion factor also depends on what is grown, for example a plant setting seed with oily seeds will have a different conversion factor from a plant with starchy seed.
Thank you for giving me a frame to see how that works. I'm not sure where I took a left turn but I was even at that 16.69 number and kept doing something until I was off course and got it wrong. And the definition of the conversion factor is much simpler and useful to me. Sometimes it helps to see those things explained casually rather than clinically. Really this helps- I think I could answer questions/scenarios like that with a whole lot more confidence now.
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Old 09-26-2018, 06:36 PM #719
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Excellent conversation starter BSG... Knowledge is numero uno.


Still in my early 30's I am looking to further my education on this subject... A degree in marketing and web design doesn't help much in this industry.


Anyone care to elaborate on what education path they would choose if they had the ability to do so again? Specialized area of interest, general horti, no degree and just weasel in?... Where we are heading in the future I see a degree being beneficial unless your "old as fuck" and already know your shit.


What helped with your choice BSG?
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Old 09-27-2018, 02:28 AM #720
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Excellent conversation starter BSG... Knowledge is numero uno.


Still in my early 30's I am looking to further my education on this subject... A degree in marketing and web design doesn't help much in this industry.


Anyone care to elaborate on what education path they would choose if they had the ability to do so again? Specialized area of interest, general horti, no degree and just weasel in?... Where we are heading in the future I see a degree being beneficial unless your "old as fuck" and already know your shit.


What helped with your choice BSG?
it is a good subject and I mentioned my degrees for a reason, I'm by no means against learning of any forms. being a wee bit older than you (btw, I thought we were closer in age, upper 30's) I've learned that learning to learn is as important as anything, the drive, zest for it, continual desire not to ever stop...

I was speaking specifically about this class mentioned. it seems to be, like the "ideal" scenario, pun intended, to really screw with someones learning process to actually grow, way, way, way over-complicating the reality of farming, especially as an intro course for what seems like part-time schooling or just a block of it....? Is this part of a full time BS program or advanced degree? This class seems more applicable for Master's or Phd level to me....

then again, chasing ones tail in pursuit of perfection is a blast
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