The Lounge : Growers Round Table Discussion Thread

bsgospel said:

I've started online courses for crop production through Wageningen University.

Having some difficulty understanding a linear path to calculate harvest index from start to finish. Is it cool if I throw some non-mix/nutrients type ideas and questions out here? I'm close to cracking this but I'm missing some connecting pieces. Maybe people can spot flaws in my thinking or math.

If we're keeping this thread to soils/mixes/testing, I can respect that. I'm asking more chemistry/mathematics questions on this one....

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djonkoman said:

ha nice, that's my uni (that course you're doing, does that happen to be a course with a coursecode starting with CSA? had some courses from that chairgroup dealing with stuff like this)
harvest index is just the ratio of harvested product/total biomass.

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so let's say you have a plant that produces 1 kg of dry, aboveground biomass. after trimming and throwing away fanleaves, stalk, stems etc you are left with 500 grams of buds. then your harvest index is 0.5.
I don't really understand how you would calculate it from start to finish, you can only calculate harvest index at the point of harvest(or afterwards), if a plant is in veg you would have a HI of 0 since if you cut down the plant at that point, you would have 0 usefull, harvestible product.
HI also depends on what product you harvest, for example if you would be interested in fibers instead of buds your HI is different for that same plant.
or if you would be making hash, and you only count trichomes as harvestible product instead of total buds including plant matter.

usually only aboveground biomas is included when calculating HI, but it could include underground as well. for example when the harvestible product is underground(like potatoes). so if you read a HI somewhere, you have to read the description well to see what exact formula they used.

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bsgospel said:

I've started online courses for crop production through Wageningen University.

Having some difficulty understanding a linear path to calculate harvest index from start to finish. Is it cool if I throw some non-mix/nutrients type ideas and questions out here? I'm close to cracking this but I'm missing some connecting pieces. Maybe people can spot flaws in my thinking or math.

If we're keeping this thread to soils/mixes/testing, I can respect that. I'm asking more chemistry/mathematics questions on this one....

Click to expand...

bsgospel said:

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.

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bsgospel said:

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.

Click to expand...

bsgospel said:

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.

Click to expand...

bsgospel said:

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.

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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?)

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djonkoman said:

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.

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jidoka said:

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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djonkoman said:

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.

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growingcrazy said:

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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