© T. M. Whitmore TODAY Questions about ecological management? Today: Issues beyond the purely...

© T. M. Whitmore

TODAY•Questions about ecological

management?

•Today: Issues beyond the purely ecologicalMethods to increase agricultural

outputAgricultural Change TheoryClassifying Agriculture

© T. M. Whitmore

Agricultural Output• How to increase output: two ways to do so

Extensification (expansion): bringing new areas not previously used under cultivation (often this is the easiest way)

Intensification: Increased output per area per unit of time (or reduced decline)

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Methods to intensify• Most commonly all (good) land is already

used so expansion is not an option => 5 ways to intensify that frequently interact: Inputs Frequency of cultivationChange in cropsCapital investment (landesque capitol)Techniques/technology

• These are interrelated – usually impossible to do one without one or more of the others

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Methods to intensify I: Input intensity

• Addition of soil amendmentsTraditional or modern

• Addition of other chemical inputsPesticides, herbicides, etc

• Addition of water through irrigationAlso adds nutrients via silt & fixed N2 in

water • Addition of labor (e.g., weeding)• May result in increased output but may also

just accommodate loss of natural fertility(AKA treadmill)

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Methods to intensify II: Frequency intensification

• Typical mid to high latitude systems1 annual harvest per plot and at least a

seasonal fallow due to coldAdditional 1 + years (i.e., seasonal) fallow

to allow soil to recover through natural processes

fallowing may involve a “cover” crop Most farms have multiple plots in various

stages of fallow or cropping

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Frequency intensification II• Tropical systems

In many places there is no “cold” season to stop cultivation => Multiple harvests in a single solar year

on a single plotDry season is a limit in many more

placesStorage is a problem in tropical systems

so multiple harvests annually may be necessary

Soil recovery fallow an issue

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Methods to intensify III: Different Crops

• Changing from a low-yield grain crop to a high yield root crop effectively increases output per area

• Changing the genetics of the crop itself Modern (or ancient) hybrid varietiesGenetically “engineered” varieties

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Methods to intensify IV: Landesque Capital

• Changes to cultivated landscapes that are enduring – over multiple years

• They represent the embodiment of labor and other resources so are equivalent to capital goods in an industrial context

• Universally require large investments of labor and goods and especially labor in maintenance (may be at the “state” level; local level (village) or even farm scale level

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Methods to intensify IV: Landesque Capital continued

•ExamplesCanals, dams, weirs, etc. for

irrigationRaised fields in wet environmentsTerraces or other alternations in

slopeField-scale modifications

New raised fields in Llanos de Mojos, Bolivia (© C. Erickson)

Cajetes, N. MexicoB.L. Turner

Hill slope temporal cultivation

(with ridges) in Mexico

© B.L. Turner II

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Methods to intensify V: Techniques/Technology

•Crop rotations

•Multiple cropping

• Intercropping

•Technological/mechanical advances

•Food preservation and prep advances

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Crop Rotations• Earliest “rotations” were annual fallow to

allow soils to recover some lost fertilityA “2 field” system

• Value of legumes known in antiquity (e.g., De Agri Cultura [On Agriculture], written around 150 BC by Roman Cato the Elder

• Some key “rotation” revolutions/introductionsIntro of moldboard plough in N Europe =>

3 -field system with legumes (fodder such as alfalfa)-grain-fallow

Adoption of 4-field system in NW Europe by lat 1700s/early 1800s

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Multiple cropping:• Intensification in time and space =>

multiple harvests per year (not necessarily of the same species) on a given plot Relies on non-competitive crop

relationships or circumvents problems

• Intercropping – more than 1 species growing together in any plot

• Sequential cropping – here there are 2 or more crops grown in a year in the same soil but one after another

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Crop-crop relationships• Competitive

Plants may interfere with each other’s ability to be properly nourished (the rationale for weeding!)

• Non-competitiveNo real competition – enough nutrients for

both

• ComplementaryOne plant species actually helps the other

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Intercropping

•Typically out-produces monocrops

• In many tropical locations problem is shortage of water and soil nutrients – there is plenty of solar radiationThus, works only if there is no

major shortage (or it can be remedied – irrigation, fertilization)

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Complementary Intercropping – two or more species planted

together• Grain + legume + root are a common strategyEach has a different development cycle

over time => less competitionSome species act as ground covers to

reduce erosion and lower evapotranspiration

Some species provide structural support for others

Mimics natural succession

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Row intercropping - typically with tall and short plants in alternate

rows•height mixture => better capture of

solar energy

•plants with different growth schedules

•protects soil from wind and accelerated erosion

•a common type of this is to plant an annual crop beneath and between a perennial one

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Phased or relay intercropping – 2nd crop planted after the 1st enters the reproductive phase

•Less time together minimizes potential competition

•Root development slows after flowering and nutrient uptake is slowed in 1st species

•Classic example of this is maize and beans in many LA systems

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Sequential Cropping

•There are 2 or more crops grown in a solar year in the same soil but one after anotherEasier management than

intercropping but with many of the same benefits

A special type of this is the use of seed beds

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Advantages of Multiple Cropping

• More efficient use of solar & other nutrients

• Fewer weeds and other pests

• Evens out peaks in labor demand

• Improves diet

• Reduces risks overall

• Wildlife is favored

• Reduction in the outlay for fertilizers

• Availability of harvest over a much longer period of time

• Can occupy much more labor

• Produce a large variety of useful products

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Disadvantages of Multiple Cropping

• Harder to manage and likely takes more labor especially hand labor

• Competition between plants for light; for soil nutrients; for water

• Possibility for allelopathic influences• Harvesting of one crop component may

cause damage to the others• Difficult to incorporate a fallow period• Difficult to mechanize • Increase in evapotranspiration • Possible over-extraction of nutrients• The systems are more complex and little

understood

Eric Guinther

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Technological/mechanical advances

• Moldboard plough• Cast-steel plow• Seeding machines• Harvesting and threshing machines• Steam and later internal combustion power

sources• Precision farming or precision agriculture

Tull’s seed drill (1701)

Modern seed drillModern steel plough

McCormick’s Reaper: 1834 patent illustration

Charles C. Rhode

A 1923, J. I. Case; 65-horsepower agricultural steam traction engine

Charles C. Rhode

Threshing with steam tractor

Modern harvester

Modern combine harvester

Precision farming software

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Food preservation and preparation

•Canning

•Freezing and chilling

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Drivers of intensification - i.e., Agricultural Change Theory

• Basic idea is G.K. Zipf’s principle of least effort In traditional, non-commercial systemsSimplest ag has greatest return to labor

– more intensity => diminishing returns• General Demand Principle of intensification

- 4 major parts (people would not intensify unless faced with one of these)Population pressureOther demands (above subsistence)Changes of stateEnvironmental necessity

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•Changes in population change or interact somehow with agricultural managementMalthus late 1700s/early 1800sBoserup late 1960s – 1990sChayanov 1920s

Drivers of intensification I: Population pressure

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Rev. Thomas Malthus• Late 1700s – early 1800s English cleric• Writing to counter arguments for greater

support for the poor (it only encourages them to breed)

• Pop grows geometrically food supply only arithmetically => “positive” checks

• Idea of “carrying capacity” • Modern neo-Malthusianism• Naïve idea (increased local pops =>

famines) NOT empirically verified• Malthus missed the ag revolution going on

in early 1800s England

Ester Boserup 1910 - 1999 Thomas Malthus (1766-1834)

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Ester Boserup (Danish Ag economist)

• Increasing population density => agriculture changes from very low intensity, long fallow to more intensive forms (shortening fallow) (frequency intensification)

• Essentially refutes Malthus (for her, as pop goes up so does output)

• Pop growth exogenous to the system

• Farmers already know more intensive forms

• Aim is to maximize leisure since more intensive forms => less marginal return to labor therefore intensification only if necessary

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Alexander Chayanov (1888–ca.1938)

• Rural sociologist (purged by Stalin)

• “The volume of the family’s [ag] activity depends entirely on the number of consumers and not at all on the number of workers.”

• Agricultural techniques/crops etc. are chosen to avoid “drudgery”

• Note different scales of analysis: Malthus vs Boserup vs Chayanov – all argue re population but in different contexts

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Drivers of intensification II: ‘Other’ demands

• People need output from ag for more than family foodTaxes Markets for cash for other goodsCultural needs “Usual” surplus (next year’s seed,

surplus against loss in storage)

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Drivers of intensification III: Changes of state

• Changes in relative amounts of land/capita independent of population change per seLand seizure

less land per capita => Boserupian or Malthusian issues

The reverse - more land per capita => Can lead to de-intensification

Land degradation that effectively reduces amount of land

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Drivers of intensification IV: Environmental necessity

• In some environments it is necessary to do landesque or input intensification to get even a minimum outpute.g., arid regions need irrigation or hills

need terraces Poor soils need amendments

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Classifying Agriculture – a series of ways to view

agriculture expressed as continua

•Production Goals

•Production Means/Technology

•Social-cultural traits

•Output intensity (e.g., kg/ha/yr)

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Production Goals• Consumption/Subsistence

Main goal is family food production Risk aversion Goal is optimum output (family

survival)• Market/Commodity

Food sold and processed/consumed away from farm (family food is purchased) Main goal is profit (innovation and

change frequently) Goal is max output per unit of land,

labor, and cost

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Production Means/Technology

• Paleo-technic (traditional)Origin/Type of inputsServicesDiversity of crops

• Neo-technic (with fossil fuels)Origin/Type of inputsServicesCrop specialization

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Social-cultural Continuum I• Traditional

Customs and rulesLand tenureInstitutional frameworks“Smallholder” agriculture

Poverty Field fragmentation Risk averse Polyculture & intraspecies diversity Role of off-farm income

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Output intensity

• TraditionalUsually lower per area / yr May also be low per labor unit but not

always

• CommercialHigh per labor unitUsually high per area

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Paleo-technic/Consumption agriculture

•Long-fallow cultivation (AKA swidden or slash and burn or shifting or brush/forest fallow)

© T. M. Whitmore TODAY Questions about ecological management? Today: Issues beyond the purely...

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