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Fearnside, P.M. 1987.  Rethinking Continuous Cultivation in Amazonia. BioScience 37(3): 209‑214.


ISSN: 0006-3568


Copyright: American Institute for Biological Sciences (AIBS)


The original publication is available at




Subhead:  The "Yurimaguas Technology" may not provide the

bountiful harvest predicted by its originators














                          Philip M. Fearnside

                          Department of Ecology

                          National Institute for Research in

                             the Amazon (INPA)

                          C.P. 478

                          69011 Manaus-Amazonas










                         Feb. 23, 1986

                Revised  July 23, 1986

                   Published: BioScience Vol 37, No. 3: 209-214.



      The land surrounding the Amazon River is often viewed as a

potential cornucopia, which could allow South American nations to

thrive despite continued population growth and poorly-distributed

resources.  A set of recommendations to increase agricultural

productivity of this region is under trial at Yurimaguas, Peru

(Nicholaides et al. 1985).  This "Yurimaguas technology" involves

continuous cultivation, with the consecutive planting of two or

more crops per year, and requires a tailored program of

fertilizer application to the acidic and nutrient-deficient

soils.  My analysis of the program indicates that previous

assessments of its long-term sustainability and profitability

were overoptimistic, and its proposed effect of reducing

deforestation is questionable.  Governments should not count on

the Yurimaguas technology for an agricultural bonanza in



      The "Yurimaguas technology" (Nicholaides et al. 1983a,b,

Sánchez et al. 1982; see also Sánchez 1977, Sánchez and Benites

1983, Valverde and Bandy 1982) refers to planting two to three

crops per year as continuous rotations of either upland rice/

maize/soybeans or upland rice/peanuts/soybeans (Sánchez et al.

1982).  A variation, called the improved Yurimaguas technology,

has rotations of maize/peanuts/maize; peanuts/rice/soybeans; or

soybeans/rice/soybeans (Nicholaides et al. 1985).  Not all of the

problems affecting the Yurimaguas technology apply to the several
other agricultural systems under testing at the Yurimaguas



      The Yurimaguas technology was developed by agronomists from

North Carolina State University (NCSU) and Peru's National

Institute for Agricultural Research and Promotion (INIPA) to

demonstrate continuous cultivation in the Amazonian uplands. 

The system's developers (Sánchez et al. 1982, p. 825) state "The

continuous production system is economically viable over a wide

range of crop and fertilizer prices, capital levels and labor

force compositions."



Soil fertility maintenance 


      Continuous cultivation cannot survive in Amazonia if

successive agronomic problems introduce costs that prevent the

strategy from being competitive with production elsewhere and

with other alternatives within Amazonia.  Over time, soil

depletion, for example, becomes increasingly expensive and

difficult to correct.  The cost of replacing all the nutrients

removed in the harvested crops or lost through such processes as

erosion, leaching must include not only the purchase and

transport of fertilizers, but also the expense of identifying for

each field, and informing the farmer, which elements are

deficient in what amounts.  The principal macronutrients
(nitrogen, phosphorus and potassium), together with lime,

account for most of the expense of purchase and transport.

Sánchez et al. (1982) state that the quantities of fertilizer

needed to supply these elements are similar to those used by

farmers in the southern United States.  Although this seems to

imply that agriculture could be as profitable in the Amazon as in

the Carolinas, the long transport distances make fertilizer cost

much higher and the prices received for the crops much lower in

Amazonia.  The substantial areas of abandoned farmland in the

southeastern United States reflect the power of soil depletion

even under economic conditions that are more favorable than those

in Amazonia for intensive use of fertilizers.


      Although correction of micronutrient depletion requires only

small amounts of fertilizer, micronutrient deficiencies add

substantially to the farmers' cost and risk.  Nutrients must be

balanced to avoid detrimental synergisms.  In the Yurimaguas

technology, soil samples are analyzed after each crop in order to

calculate the proper nutrient mix for fertilization.1  Separate

information is needed for each field in order to make the system

work.  Sánchez et al. (1982, p. 824) state that "the timing of

the appearance of soil fertility limitations and the intensity of

their expression varied among the (three test) fields, even

though they were near each other, were on the same soil mapping

unit, and had the same vegetation before clearing."


      An awesome expansion of laboratory and extension services

would be necessary if the Yurimaguas technology were widely

implemented.  While these services have been provided free of

charge (i.e., as a subsidy) by NCSU for the farmers collaborating

with the Yurimaguas experiment station, either the farmers,

taxpayers or consumers in the Amazonian countries would have to

bear these expenses in an expanded system.


      The capital required to assure adequate fertilizer

application is more than all but a few Amazonian farmers have.

Not only must the requisite doses be purchased and applied for

each crop, but the farmer must be capable of making the outlay a

second time should an application be lost to heavy rains.

Torrential rainstorms that can sometimes drop several hundred

millimeters of precipitation in a 24-hour period occur every few

years in Amazonia.  This happened in Yurimaguas in 1975, washing

away an application of lime and lowering yields (NCSU Soil

Science Department 1975).  In 1983 a similar event eliminated

recently applied nitrogen.  In both cases the experiment station

was able to obtain and reapply the chemical inputs (Weischet



      When the Yurimaguas results were obtained (Sánchez et al.

1982; see also Nicholaides et al. 1985), the eight-year-old

experimental plots required--in addition to nitrogen, phosphorus

and potassium--replacement of five other nutrients: magnesium,
copper, zinc, boron and molybdenum.  Three years later, two more

nutrients were deficient: sulfur and manganese.2  The research

group complains about the difficulty of obtaining adequate purity

in the soil samples and sufficient precision in the laboratory

analyses: with micronutrients, a difference of only a few parts

per million can have a large impact on crop yields.  The

difficulty of obtaining such precision would be much greater for

farmers handicapped by geographical isolation, little education,

and a tenuous link to laboratory facilities through a chain of

often poorly trained and poorly motivated extension personnel.


      The Yurimaguas authors admit: "In the complete treatment,

fertilizers and lime were added according to recommendations

based on soil analysis.  During the second or third year,

however, yields began to decline rapidly.  Soil analysis

identified two possible factors ... lime and ... magnesium."

(Sánchez et al. 1982, p. 824).  If yields can suffer from

misassessment of nutrient needs in an experimental plot  closely

monitored by a highly-qualified team of research agronomists,

such declines would be much more frequent in the fields of

Amazonian farmers--particularly the "shifting cultivators"

identified as the system's intended beneficiaries.




Erosion also impedes widespread use of the Yurimaguas

technology.  The Yurimaguas experiment station is almost totally

flat, but signs of erosion are apparent at Yurimaguas wherever

slight slopes occur.  Only a small portion of Amazonia is flat at

a scale of a few tens of meters.  Sá ánchez et al. (1982) indicate

that 50% of the Amazon region is well drained and has slopes less

than 8%, the maximum slope the group suggests for the system.

The survey on which the information is based (Cochrane and

Sá ánchez 1982) used the side-looking airborne radar (SLAR) imagery

of the RADAM Project (Brazil, Ministério das Minas e Energia,

Departamento Nacional de Produçăo Mineral, Projeto RADAMBRASIL

1973-1982) mapped at a scale of 1:1,000,000.  When specific

localities are examined that are within the less-than-eight-percent slope areas, much of the land is found to have steeper

slopes.  In a 23,600 ha area on Brazil's Transamazon Highway

shown by Cochrane and Sánchez (1982) as all having less than 8%

slope, a map of 1180 20-ha quadrats based on measurements at 225

locations showed 49.3% of the land to have slopes at least 10%,

and some to have slopes as high as 89% (Fearnside 1984, 1986).


      According to Sánchez et al. (1982, p. 822), "Only about six

percent of the Amazon has soils with no major limitations to

agriculture.  Nevertheless they represent a total of 32 million

hectares.  They are classified mainly as Alfisols, Mollisols,

Vertisols, and well-drained alluvial soils, and where they occur

permanent agriculture has a good chance of success".  Alfisols
and Vertisols, which are among the more fertile soils, normally

occur on more steeply sloping terrain than do the less fertile

soil types (Falesi 1972, Fearnside 1984).  In selecting sites for

continuous cultivation in the Amazonian uplands, a tradeoff will

be faced between soil fertility and suitable topography.  In

Brazil there has been a tendency to resolve this kind of tradeoff

by ignoring long-term restrictions from unfavorable topography in

order to exploit higher-fertility soils.  The choice of sloping

Alfisols for siting the sugarcane production area of the

Transamazon Highway (Smith 1981, 1982) and the Gmelina

plantations at Jari (Fearnside and Rankin 1985) illustrate this

tendency.  The same temptation will apply to the Yurimaguas



Crop pests and weeds


      The number and severity of pest and disease organisms

generally increase formidably as the cultivated area expands.3 

Using pesticides to counter such problems is expensive.  In

addition, insects typically develop resistance to pesticides,

leading to escalating dosages and costs.4  Heavy insecticide

dosages are already being applied at Yurimaguas.  Tropical

agriculture generally is plagued by higher insect populations

than is agriculture in temperate locations because no winter ever

reduces insect populations (Janzen 1970, 1973).


Weed populations are already a major problem.  Some weeds,

such as the grass Rottboelia exaltada in upland rice fields, have

not been controlled with herbicide spraying.5  Intensive hand

labor is used to control this weed at Yurimaguas--otherwise it

takes over the rice fields and seriously reduces yields.

Herbicides, like the other agricultural chemicals required by the

system, must be available at critical times.  The herbicide

preferred at Yurimaguas for rice weeds (other than Rottboelia) is

metolachlor (tradename, Dual) which had been unavailable

commercially in Peru for at least four months as of June 1985.

While the experiment station has an adequate stockpile of this

and other chemicals, irregular market availabilities of inputs

would be a serious impediment for Amazonian farmers.



Economic Problems


      The preliminary results at Yurimaguas are poor indicators of

the system's performance under more representative circumstances.

In addition to subsidizing extension and soil analyses, NCSU and

the Peruvian government underwrite the true costs in a number of

indirect ways.  Fifty percent of the cost of transportation for

fertilizer is provided by the Peruvian government, lowering the

Lima-to-Yurimaguas rate to US$1.20/kg.  A special agreement

between the experiment station and the Peruvian Air Force

provides free transportation for many lighter items and for items
needed when roads are impassable during the rainiest months.

Transportation to and from the Yurimaguas area is also subsidized

through government price supports.  Fertilizers available in

commercial outlets in the town of Yurimaguas are sold at

essentially the same prices as those in Lima, even though

phosphates, potassium and nitrogen fertilizers come to Yurimaguas

from the coast.  Lime, fortunately, is available from limestone

outcrops along the Upper Huallaga River, to which the Yurimaguas

River is an affluent.  The government buys products such as rice

at the same fixed prices whether in Amazonian locations or in the

irrigated rice areas along the northern part of Peru's Pacific

coast with paved highways to the major consumer markets.  Thus,

in effect, the costs of transporting Yurimaguas rice to market

are being paid by urban consumers, taxpayers and Peru's

international creditors.  The cost of providing these subsidies

to the increased number of farmers if the Yurimaguas technology

became widespread in Amazonia would be prohibitive to any of the

financially pressed governments of the Amazonian countries.


      The collaborating farmers at Yurimaguas have received many

free inputs from the experiment station, including seeds,

fertilizers, lime, pesticides, and herbicides.  In addition, the

roughly 25% of the participating farmers who live along a road

near the experiment station have received an important subsidy in

the form of the station's agricultural machinery.  The farmers

pay rent for the machinery use, but rental equipment would be
more expensive elsewhere.  The farmers would need to assume the

debt service costs for the capital necessary to buy tractors and

other equipment used only during a small portion of the

agricultural year.  Farmers would also have to maintain the

equipment--an extremely expensive enterprise in the Amazon.  Not

only does machinery deteroriate more quickly than in temperate

zones, but parts and the services of skilled mechanics are much

less readily obtainable.


      Those collaborating farmers in locations too isolated to

have access to tractors have been subsidized more directly.

Digging and turning the soil using hand tools is a particularly

onerous task as the soil becomes progressively more compacted

under continuous cultivation.  The amount of labor required

became prohibitive in the absence of tractors, and NCSU paid

outside laborers to go to the more remote properties and turn the

soil for the collaborating farmers.  The Yurimaguas technology is

unlikely to spread if the work of turning the soil by hand is too

heavy for the collaborating farmers to do themselves and too

expensive for the agricultural production to justify their paying

others to do.


      Subsidies are only one reason that the interpretation the

Yurimaguas authors give to their results is probably

overoptimistic.  The farmers participating in the Yurimaguas

trials are not typical of the rural Amazonian population.
Nicholaides et al. (1984) leave no doubt that these model

farmers, described as "respected community leaders" (Nicholaides

et al. 1985), are some of the best in the Yurimaguas area.

Certainly the farmers who have volunteered to collaborate with

the experiment station are a select set who have more money,

initiative, and contact with urban society than the "shifting

cultivators" indicated by Sánchez et al. (1982) as the target

population for the Yurimaguas technology.


      The agricultural extension portion of the program is also

atypical of Amazonian conditions.  It has trained a team of local

extension agents, who have not yet been entrusted with the task

of serving as intermediaries between the station and the

collaborating farmers.  Even such fundamental concepts as the

difference between linear and square measures are not easily

grasped by the local extension agents.  The head of the

experiment station's extension sector has therefore retained

personal responsibility for communicating with the collaborating

farmers.  Only the small number of farmers allows such a highly

qualified person to advise them directly.


      The results presented in 1982 were overoptimistic because

the collaborating farmer program had been underway onlt three

years (Sánchez et al. 1982), and only two years of production

data were available.  Even with traditional methods, yields in

tropical farmers' fields are usually reasonably high in the first
two years after clearing, only thereafter declining rapidly (Nye

and Greenland 1960).  The early results presented for

collaborating farmers are therefore a poor indicator of long©term

sustainability.  Heavy fertilization, of course, allowed much

higher yields and more crops per year than would otherwise have

been possible in the first two years.  The claim that "the first

eight farmers averaged 3 tons of rice per hectare, 4.5 tons of

corn, 2.6 tons of soybeans and 1.8 tons of peanuts--similar

yields to those obtained at the station" (Sánchez et al. 1982, p.

825) does not demonstrate that high yields will be maintained in

the collaborating farmer plots over the nine-year period the

experiment station plots had run at that time, much less over the

long term.


      The most telling evidence that the "technology validation in

farmer fields" (Sánchez et al. 1982) was premature in claiming

commercial success is the later history of the program.  In 1982

the Yurimaguas researchers were able to state that "the tests

have expanded, and farmers are attracted by the prospects of

increasing their yields" (Sánchez et al. 1982, p. 825).  The

picture has changed markedly in the years since.  In 1985,

according to researchers at the experiment station, no farmers in

the Yurimaguas area were employing the Yurimaguas technology of

high-input continuous cultivation on a commercial basis.  Even

the farmers in the special program, with inputs given or

subsidized by NCSU, had switched to lower-input options
introduced under the program.  The Yurimaguas researchers'

calculation that the system would be highly profitable using

input and product prices prevailing in Yurimaguas (i.e., without

direct subsidies, but still including the indirect ones through

price supports, free extension, etc.) is contradicted by this

lack of response on the part of the area's farmers.


Limits to the technology


      Large-scale expansion of the Yurimaguas technology is likely

to encounter limits.  One is the inherent difference in

production efficiency between upland and irrigated rice.

Irrigated rice plantations in Peru's coastal lowlands, for

example, apparently can produce this cereal more cheaply than can

upland farming in the Amazon.  Another constraint to high-input

agriculture is the availability of phosphate rock.  Amazonia has

virtually no phosphate rock (de Lima 1976, Fenster and León

1979).  Brazil's major phosphate deposits are in the south

central state of Minas Gerais, and Peru's are in the Pacific

coast state of Piura.  On a global scale, most of the world's

phosphates are located in Africa (Sheldon 1982).  The earth's

phosphate deposits are finite, and use has been increasing

exponentially since the end of World War II (Smith et al. 1972,

United States, Council of Environmental Quality and Department of

State 1980).  As phosphate supplies dwindle in Amazonian

countries and in the world, the price of this input can be
expected to increase dramatically, shifting the economic balance

even further away from high-input systems like the Yurimaguas



Policy implications


      The Yurimaguas technology was presented as a practical means

of combatting deforestation. The systems developers imply that

Amazonia's high deforestation rates are caused by shifting

cultivators clearing land in order to grow food for their

subsistence needs: "We believe that the continuous cropping

technology can have a positive ecological impact where it is

practiced appropriately, because for every hectare that is

cleared and put into such production, many hectares of forest may

be spared from the shifting cultivator's ax in his search to grow

the same amount of food.  People do not cut tropical rainforests

because they like to, but because they need food or fiber"

(Sánchez et al. 1982, p. 827; see also Nicholaides et al. 1985).


      This view of the deforestation problem is incorrect.

Especially in Brazil, large ranching operations account for most

deforestation (Fearnside 1983).  Even in parts of Amazonia where

small farmers are of greater relative importance, the farmers do

not fit the mold of traditional subsistence farmers who limit the

areas they cultivate once the production satisfies the

nutritional needs of themselves and their families, plus a margin
to protect against shortfalls in lean years.  Brazilian colonists

in government settlement programs, for example, have a virtually

insatiable demand for goods: the areas cleared and planted are

limited not by humble ambitions but rather by the amount of labor

and capital available to the farmers for expanding their

agricultural activities (Fearnside 1980).  Increasing yields

would have little negative effect on clearing rates.  Profits

from the intensive farming would probably be invested in rapid

deforestation for extensive land uses such as cattle pasture.


      This scenario has often been the response of beneficiaries

of another cropping system promoted as an antidote to

deforestation: cacao.  In Rondônia, Brazil, cacao planters who

have ready cash from a good cacao harvest frequently invest these

profits in cattle--an understandable strategy to insure against

low cacao prices or increased losses of cacao to fungal diseases.

Similarly, should farmers find the Yurimaguas technology

profitable, the earnings might well be invested in deforestation

for cattle pasture.


      This is not to imply that farmers should be kept poor to

avoid deforestation.  In considering the pros and cons of the

Yurimaguas technology, however, impact on deforestation is likely

to be a con rather than a pro.  A correct understanding of the

deforestation process is essential both to formulating effective
policies to slow clearing and to developing sustainable land



      The illusion that new technologies are about to transform

Amazonia into an agricultural breadbasket is inherently alluring

to government planners, who have in the past often promoted the

region as an El Dorado that will someday solve national problems

of every description.  The El Dorado myth diminishes planners'

incentive to find solutions to such problems as the underlying

causes of the rapid spread of cattle pasture in Amazonia today

and the land tenure concentration and population growth in the

non-Amazonian areas from which a rising flood of migrants is

being expelled.


      The Yurimaguas technology points to a persistent dilemma in

the search for ways to improve Amazonian agricultural systems.

Research and extension efforts to improve agricultural technology

are vitally important for the future of the area.  At the same

time, their development must not be presented in a way that feeds

false hopes of an agricultural bonanza in Amazonia capable of

freeing national policymakers from facing the politically riskier

issues of population growth and resource concentration.






1.)  Soil analyses and fertilizer dosage adjustments after every

crop in the "technology validation in farmer fields" described by

Sánchez et al. (1982) strongly suggest that this frequency of

sampling is integral to commercial application of the Yurimaguas

technology.  Elsewhere in the Peruvian Amazon a commercial system

with only one sample per year for every five to ten hectares is

reported to be successful so far (J.H. Villachica, personal

communication, 1985, INIPA, Iquitos).  Reduction of the sampling

rate is a logical cost-reducing step, but would probably result

in lower yields than those reported for the Yurimaguas



2.)  D.E. Bandy, personal communication, 1985, NCSU/INIPA, Lima.


3.)  This pattern accords with the theoretial expectations of

MacArthur and Wilson (1967); for an example with sugarcane, see

Strong et al. (1977).


4.)  For an example from coastal Peru see Barducci (1972).


5.)  J. Mt. Pleasant, personal communication, 1985, NCSU/INIPA,





      I thank the Yurimaguas station staff for their patience with

my questions, and G. Budowski, R. Buschbacker, J.G. Gunn, C.

Jordan, C.A. Palm, J.M. Rankin, J.M. Robinson, A.B. Rylands, and

J.H. Villachica for their comments.



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26-28 May 1986, Blaubeuren, FRG.