Johnny.JJ
2013-07-31, 11:27 AM
This is agriculture for worldbuilding: I'll be presenting an agricultural model; in return, all I'm asking is for you to let me know whether the proposed model makes any sense.
- - - - - -
A bit more on explaining:
The purpose of this number crunch is to discover the principles of the agricultural cycle. I'll be referring mainly to grain farming in the middle ages; still, the specific numbers of medieval "features" should serve as nothing more than some filler data to flesh out the underlying equations. The agricultural equations are the end goals here, as these might be used to model other agricultural environments (be it rice farming in the ancient China, some completely out-of-the-blue fantasy environments, etc.)
How shall we approach this? I'll be presenting some numbers and relationships I've progressed to ... and you'll object during the occasions where the presented data makes little sense.
Caloric needs
Agriculture is there to fill the empty bellies of humans, isn't it? So let's start with the calories ...
An average person (weighting some 140lbs/ 60kg) burns approx. 400 calories per 8-hour sleep and another 800 calories per 8-hours easy-going activities (sitting, walking, reading, etc.) For the other 8 hours, work activities usually take place ...
An ultimate slacker (sleeping, laying about): 1 500 calories/day
Easy work (sitting, typing, etc.): 2 000 calories/day
Standard work (shepherding, farming): 3 000 calories/day
Demanding work (digging, woodcutting): 5 000 - 8 000 calories/day
Weight is also a factor here: I'm proposing a 1.3 caloric multiplier per every 50% weight increase above 140lbs/ 60kg
As for the (reasonably active) children: 1 000 calories/2 year-old, 1 500 calories /7 year-old, 2 000 calories /11 year-old, >14 years - like an adult.
For more ideas, refer to this (http://people.eku.edu/resorc/Medieval_peasant_diet.htm).
Sources of calories
Now, where do the calories come from? From all sorts of foods, obviously ...
However, as long as we're talking in the medieval terms, "all sorts of foods" have to be reduced to "mostly grains" (not the healthiest diet - a lot of saccharides and not enough proteins - but for the time period, it'll have to do).
How balanced is the available diet?
Not quite (medieval): 75% of food are grains
Somewhat (columbian exchange (discovery of American crops), some variety): 50% of food are grains
Balanced (modern/ rich farming environment): 30% of food are grains (some farmland is assigned to non-grain food sources, as the modern farming can afford that, thanks to the strong grain yield ratios)
Using an average, reasonably busy medieval person, a need of 3 000 calories a day should be saturated, 75% by grains (2250 calories), 25% by some other sources (vegetables, fish, meat, dairy, eggs, etc.)
It just happens so that a single kilogram (2 1/4 lbs) of bread contains some 2 000 to 2 500 calories (same goes for some other bread/grain products). Source (http://www.gymeabayfitness.com.au/MemberServices/CalorieInformation/HowManyCaloriesinBread/tabid/109/Default.aspx).
As for baking, the math is quite simple here: a single kilogram of bread can be derived from a single kilogram of wheat (1kg of wheat is transformed into 0.8kg of flour (there is some material loss), but during the baking process, a 20% amount of water is added, creating a 1kg loaf of bread).
Moving on to growing the grains ...
A single person consumes a single kilogram of wheat a day (as per their medieval diet), which leads to consumption of some 350kg (780lbs) per year. That wheat has to come from somewhere - specifically, from the fields ...
A 1:3 field yield ratio is commonly known as the bare minimum to make do with farming (a lower number than that is a promise for starving). In the 21-st century, the fields give very generous yield ratios (1:50 or even higher), but these far-off numbers are caused by artificial fertilizers, mechanization and genetically engineering the crops (none of which were available in the earlier times). As for the yield ratios of the old days:
Minimum yield (inadequate land and/or a very bad year): 1:3
Bad yield (lower-grade land and/or a bad year): 1:5
Standard yield (standard farming land, a standard year): 1:8
Good yield (good land, a good year or some agricultural technology (plowing, natural fertilizers, effective crop rotation)): 1:10
Great yield (great land, a very prosperous year, or some advanced agricultural technology (very effective crop rotation, protoindustrialization)): 1:12
-A reasonable maximum for all pre-industrial societies: 1:15
Now, let's transform these abstract yield ratios into real numbers ...
Regarding sowing the grain seeds into the ground, there is an established ratio of bushels per acre (acre being about a square of 64x64 meters or 70x70 yards; a bushel (https://en.wikipedia.org/wiki/Bushel) stands for 14.5kg or 32lbs). For grains, sources (http://www.ibiblio.org/london/agriculture/general/1/msg00070.html) suggest sowing about 1-2 bushels (15 to 30kg) per acre in medieval times; some other sources (tab 4.3) (http://www.uky.edu/Ag/GrainCrops/ID125Section4.html) mention even higher amounts (3.5 bushels, i.e. 50kg), but this seems to be related to modern agriculture only.
A source (http://www.telkoth.net/blog/?p=155) claims that to feed one person for a year on wheat required about two acres of land. Well, let's see what numbers come out of the information mentioned in the previous paragraph ...
Using the 1:8 yield ratio (the land of standard fertility), sowing 1-2 bushels (15 to 30kg) returns some 120 to 240kg of wheat. Since a single person is expected to consume 350Kg/year, these estimations seem about right (worst case scenario in here: 4 acres of wheat per person/year (including grain subtractions on possible taxes and reseed reserves); best case scenario: about 1.8 acre per yearly consumption of a single person).
Note that this calculation may seem a bit on the pessimistic side due to me taking a 3000 calories/person average as a default (including children). The real caloric consumption need average may be a bit lower, though.
Scaling to the macro-scale ...
Let's look on the countryside, the farms, the cities, the supply and demand ...
An acre (https://en.wikipedia.org/wiki/Acre) is defined as an area a single farmer can plow in a day (handling a pair of farming animals).
A source (http://www.middle-ages.org.uk/medieval-manors.htm) claims that a single farmer had about 20 to 40 acres available to themselves (and their family).
Many historical sources (http://rpg.stackexchange.com/questions/10123/pre-modern-farming-what-percent-of-the-population-is-in-agriculture) (a common knowledge) state that the agricultural:urban ratio had always been quite low in the pre-modern times (a 10:1 ratio, implying that on the average, ten farmers produced enough food for themselves with an extra surplus for a single city dweller). So, if we take a farmer working on a 30-acre field as a model example (with two acres feeding a single person a whole year), these numbers may as well add up - it's a stretch, but let's assume the following distribution:
10 to 15 acres (one third to one half) lost to crop rotation and/or pastures for domestic animals
8 to 12 acres lost due to family nutrition needs (assuming a family of three to six people)
3 to 10 acres lost on taxation (be it the feudal lord or the church)
3 acres lost to reseed needs for the next year
small, variable amounts lost due to random events and/or sold at the local market in exchange for some other goods
On a local scale, one square kilometer fits in some 250 acres; if those 250 manage to support some 125 people (using the "a person per two acres" equation), we can start thinking about cities (i.e. local clusters of concentrated population that depend on their agrarian surroundings to deliver the food). As already shown, upon taxing the farming population, every square kilometer can supply some 10 - 15 city dwellers to boot (or even a bit more (20, 30, 50?), in case of adopting more sophisticated administration and the best pre-industrial technologies). On the other hand, we have to keep in mind that not every piece of land is arable (from bogs and marshes to rock formations and mountains, etc.) - therefore, let's assume that only a half of the somewhat fertile, colonized land can be agriculturally utilized.
Some estimations on city sizes:
small scale grid: villages (a hundred to a thousand people - just the dwellings of farmers concentrated in a single location)
20x20 grid (400 square km) provides for a Small city or a Town (some 2 500 inhabitants)
40x40 grid (1 600 square km) supports a City (some 8 000 dwellers)
60x60 grid (3 600 square km) enables the city to grow to a magnificent scale (20 000 souls)
... and this is not the end of it! If the communication networks (roads, trade routes) are up for the challenge, a pre-modern city commanding a 100x100 grid is entirely possible. Moreover, marine resources and trade routes by the sea may boost grow of the city as well.
For the reference, more on demography is mentioned here (http://www222.pair.com/sjohn/blueroom/demog.htm).
Onto an even larger scale: let's consider the population potential of England (this is 130 395 square km). Let's assume that 20% of the land is arable - this gives us about 26 000 square kilometers of land. Now, using the numbers from the previous number exercises, this points to a population of about 3 250 000. According to the demography of England (https://en.wikipedia.org/wiki/Demography_of_England), this numbers correlates with the late 16th century state of the population.
Reviewing the ideas
Generally speaking:
A (human) creature requires a daily amount of calories as an input. Food sources provide that input.
Specific food sources provide specific amounts of calories and nutrients (fats, carbohydrates, proteins, etc.) - humans use these properties to assemble their own diets.
Specific food sources have their own preferences and properties (soil and climate, ripening time, expected yield, taste, restrictions on food processing, etc.) - to master and maximize these properties, humans develop an adequate agriculture.
The overall agricultural (and populational) potential is defined by technological advancement and social policies.
In terms of numbers:
Establish the nutritional values of food sources.
Establish the micro-scale agricultural potential (How many acres are needed to feed a man? (and is there a specific technology multiplier to it?) How many acres can a man manage?)
Establish the macro-scale agricultural potential (How many people can a square kilometer feed? what amount is the agricultural overhead?)
- - - - - -
A bit more on explaining:
The purpose of this number crunch is to discover the principles of the agricultural cycle. I'll be referring mainly to grain farming in the middle ages; still, the specific numbers of medieval "features" should serve as nothing more than some filler data to flesh out the underlying equations. The agricultural equations are the end goals here, as these might be used to model other agricultural environments (be it rice farming in the ancient China, some completely out-of-the-blue fantasy environments, etc.)
How shall we approach this? I'll be presenting some numbers and relationships I've progressed to ... and you'll object during the occasions where the presented data makes little sense.
Caloric needs
Agriculture is there to fill the empty bellies of humans, isn't it? So let's start with the calories ...
An average person (weighting some 140lbs/ 60kg) burns approx. 400 calories per 8-hour sleep and another 800 calories per 8-hours easy-going activities (sitting, walking, reading, etc.) For the other 8 hours, work activities usually take place ...
An ultimate slacker (sleeping, laying about): 1 500 calories/day
Easy work (sitting, typing, etc.): 2 000 calories/day
Standard work (shepherding, farming): 3 000 calories/day
Demanding work (digging, woodcutting): 5 000 - 8 000 calories/day
Weight is also a factor here: I'm proposing a 1.3 caloric multiplier per every 50% weight increase above 140lbs/ 60kg
As for the (reasonably active) children: 1 000 calories/2 year-old, 1 500 calories /7 year-old, 2 000 calories /11 year-old, >14 years - like an adult.
For more ideas, refer to this (http://people.eku.edu/resorc/Medieval_peasant_diet.htm).
Sources of calories
Now, where do the calories come from? From all sorts of foods, obviously ...
However, as long as we're talking in the medieval terms, "all sorts of foods" have to be reduced to "mostly grains" (not the healthiest diet - a lot of saccharides and not enough proteins - but for the time period, it'll have to do).
How balanced is the available diet?
Not quite (medieval): 75% of food are grains
Somewhat (columbian exchange (discovery of American crops), some variety): 50% of food are grains
Balanced (modern/ rich farming environment): 30% of food are grains (some farmland is assigned to non-grain food sources, as the modern farming can afford that, thanks to the strong grain yield ratios)
Using an average, reasonably busy medieval person, a need of 3 000 calories a day should be saturated, 75% by grains (2250 calories), 25% by some other sources (vegetables, fish, meat, dairy, eggs, etc.)
It just happens so that a single kilogram (2 1/4 lbs) of bread contains some 2 000 to 2 500 calories (same goes for some other bread/grain products). Source (http://www.gymeabayfitness.com.au/MemberServices/CalorieInformation/HowManyCaloriesinBread/tabid/109/Default.aspx).
As for baking, the math is quite simple here: a single kilogram of bread can be derived from a single kilogram of wheat (1kg of wheat is transformed into 0.8kg of flour (there is some material loss), but during the baking process, a 20% amount of water is added, creating a 1kg loaf of bread).
Moving on to growing the grains ...
A single person consumes a single kilogram of wheat a day (as per their medieval diet), which leads to consumption of some 350kg (780lbs) per year. That wheat has to come from somewhere - specifically, from the fields ...
A 1:3 field yield ratio is commonly known as the bare minimum to make do with farming (a lower number than that is a promise for starving). In the 21-st century, the fields give very generous yield ratios (1:50 or even higher), but these far-off numbers are caused by artificial fertilizers, mechanization and genetically engineering the crops (none of which were available in the earlier times). As for the yield ratios of the old days:
Minimum yield (inadequate land and/or a very bad year): 1:3
Bad yield (lower-grade land and/or a bad year): 1:5
Standard yield (standard farming land, a standard year): 1:8
Good yield (good land, a good year or some agricultural technology (plowing, natural fertilizers, effective crop rotation)): 1:10
Great yield (great land, a very prosperous year, or some advanced agricultural technology (very effective crop rotation, protoindustrialization)): 1:12
-A reasonable maximum for all pre-industrial societies: 1:15
Now, let's transform these abstract yield ratios into real numbers ...
Regarding sowing the grain seeds into the ground, there is an established ratio of bushels per acre (acre being about a square of 64x64 meters or 70x70 yards; a bushel (https://en.wikipedia.org/wiki/Bushel) stands for 14.5kg or 32lbs). For grains, sources (http://www.ibiblio.org/london/agriculture/general/1/msg00070.html) suggest sowing about 1-2 bushels (15 to 30kg) per acre in medieval times; some other sources (tab 4.3) (http://www.uky.edu/Ag/GrainCrops/ID125Section4.html) mention even higher amounts (3.5 bushels, i.e. 50kg), but this seems to be related to modern agriculture only.
A source (http://www.telkoth.net/blog/?p=155) claims that to feed one person for a year on wheat required about two acres of land. Well, let's see what numbers come out of the information mentioned in the previous paragraph ...
Using the 1:8 yield ratio (the land of standard fertility), sowing 1-2 bushels (15 to 30kg) returns some 120 to 240kg of wheat. Since a single person is expected to consume 350Kg/year, these estimations seem about right (worst case scenario in here: 4 acres of wheat per person/year (including grain subtractions on possible taxes and reseed reserves); best case scenario: about 1.8 acre per yearly consumption of a single person).
Note that this calculation may seem a bit on the pessimistic side due to me taking a 3000 calories/person average as a default (including children). The real caloric consumption need average may be a bit lower, though.
Scaling to the macro-scale ...
Let's look on the countryside, the farms, the cities, the supply and demand ...
An acre (https://en.wikipedia.org/wiki/Acre) is defined as an area a single farmer can plow in a day (handling a pair of farming animals).
A source (http://www.middle-ages.org.uk/medieval-manors.htm) claims that a single farmer had about 20 to 40 acres available to themselves (and their family).
Many historical sources (http://rpg.stackexchange.com/questions/10123/pre-modern-farming-what-percent-of-the-population-is-in-agriculture) (a common knowledge) state that the agricultural:urban ratio had always been quite low in the pre-modern times (a 10:1 ratio, implying that on the average, ten farmers produced enough food for themselves with an extra surplus for a single city dweller). So, if we take a farmer working on a 30-acre field as a model example (with two acres feeding a single person a whole year), these numbers may as well add up - it's a stretch, but let's assume the following distribution:
10 to 15 acres (one third to one half) lost to crop rotation and/or pastures for domestic animals
8 to 12 acres lost due to family nutrition needs (assuming a family of three to six people)
3 to 10 acres lost on taxation (be it the feudal lord or the church)
3 acres lost to reseed needs for the next year
small, variable amounts lost due to random events and/or sold at the local market in exchange for some other goods
On a local scale, one square kilometer fits in some 250 acres; if those 250 manage to support some 125 people (using the "a person per two acres" equation), we can start thinking about cities (i.e. local clusters of concentrated population that depend on their agrarian surroundings to deliver the food). As already shown, upon taxing the farming population, every square kilometer can supply some 10 - 15 city dwellers to boot (or even a bit more (20, 30, 50?), in case of adopting more sophisticated administration and the best pre-industrial technologies). On the other hand, we have to keep in mind that not every piece of land is arable (from bogs and marshes to rock formations and mountains, etc.) - therefore, let's assume that only a half of the somewhat fertile, colonized land can be agriculturally utilized.
Some estimations on city sizes:
small scale grid: villages (a hundred to a thousand people - just the dwellings of farmers concentrated in a single location)
20x20 grid (400 square km) provides for a Small city or a Town (some 2 500 inhabitants)
40x40 grid (1 600 square km) supports a City (some 8 000 dwellers)
60x60 grid (3 600 square km) enables the city to grow to a magnificent scale (20 000 souls)
... and this is not the end of it! If the communication networks (roads, trade routes) are up for the challenge, a pre-modern city commanding a 100x100 grid is entirely possible. Moreover, marine resources and trade routes by the sea may boost grow of the city as well.
For the reference, more on demography is mentioned here (http://www222.pair.com/sjohn/blueroom/demog.htm).
Onto an even larger scale: let's consider the population potential of England (this is 130 395 square km). Let's assume that 20% of the land is arable - this gives us about 26 000 square kilometers of land. Now, using the numbers from the previous number exercises, this points to a population of about 3 250 000. According to the demography of England (https://en.wikipedia.org/wiki/Demography_of_England), this numbers correlates with the late 16th century state of the population.
Reviewing the ideas
Generally speaking:
A (human) creature requires a daily amount of calories as an input. Food sources provide that input.
Specific food sources provide specific amounts of calories and nutrients (fats, carbohydrates, proteins, etc.) - humans use these properties to assemble their own diets.
Specific food sources have their own preferences and properties (soil and climate, ripening time, expected yield, taste, restrictions on food processing, etc.) - to master and maximize these properties, humans develop an adequate agriculture.
The overall agricultural (and populational) potential is defined by technological advancement and social policies.
In terms of numbers:
Establish the nutritional values of food sources.
Establish the micro-scale agricultural potential (How many acres are needed to feed a man? (and is there a specific technology multiplier to it?) How many acres can a man manage?)
Establish the macro-scale agricultural potential (How many people can a square kilometer feed? what amount is the agricultural overhead?)