The ecological basis for the application of traditional agricultural technology in the management of tropical agroecosystems

MISSING IMAGE

Material Information

Title:
The ecological basis for the application of traditional agricultural technology in the management of tropical agroecosystems
Physical Description:
17 leaves : ill., (tables), ; 28 cm.
Language:
English
Creator:
Gliessman, Stephen R
Publisher:
Departmento de Ecología, Colegio Superior de Agricultura Tropical
Place of Publication:
Cárdenas (Tabasco, Mexico)
Publication Date:

Subjects

Subjects / Keywords:
Agricultural ecology -- Mexico -- Tabasco (State)   ( lcsh )
Sustainable agriculture -- Mexico -- Tabasco (State)   ( lcsh )
Genre:
bibliography   ( marcgt )
non-fiction   ( marcgt )
Spatial Coverage:
Mexico

Notes

Bibliography:
Includes bibliographical references.
Statement of Responsibility:
S.R. Gliessman, R. García E., and M. Amador A.
General Note:
Caption title.
General Note:
Typescript.
General Note:
"Work presented...at the second International Congress of Ecology, Israel, September, 1978..."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
oclc - 756840236
ocn756840236
Classification:
lcc - S589.7 .G5 1978
System ID:
AA00008196:00001

Full Text
IYA --oet roeccs*o =
.EWEL

The Ecological Basis for the Application of Traditional 04, O0
Agricultural Technology in the Management of Tropical
Agroecosystems.

1/ 2/
S.R. Gliessman R. Garcia E.- and M. Amador A.
Departamento de Ecologia
Colegio Superior de Agricu-ltura Tropical
H. Crrdenas, Tabasco, M'xico.


INTRODUCTION

Numerous rural development projects have been designed and
carried out in the tropics with the intention of increasing -
agricultural production. Considerable technical and economic -
resources are utilized, but the results finally achieved very
rarely approach the productive capacity originally expected ---
(Barkin, 1977). (his failure is due in large part to the lack -
of understanding of the relationship between productivity and-
ecosystem stability in the tropics, as well as the mis-applica-
tion of a technology derived in developed regions under a'dif--
feret--set-of--ecological-- imitatiorrs--nd--c ntrols- (Janzen,197-3).-

On the other hand, the rural inhabitants of tropical re---
gions (campesinos) have managed their traditional aeroecosyst--
ems for centuries, balancing outputs (yields) by various pract-
ices designed to optimize productivity on a long term basis ---
rather than maximizing it on a short term basis (Wilken, 1970;-
Ruthenberg, 1976; Soenarworo, 1975). The gaining of an underst-
anding of the ecological basis of these practices has been the-
objetive of intensive studies all of which we are applying and-
testing in modular production units managed by the campesinos -
themselves (Gliessman, 1977).

STUDY AREA

The lowlands of Tabasco, Mexico, are aptly classified as-
1/ Work presented by the first -uhot at the second International Congress of
Ecology, Israel, Septerber, 1 iS, for which the generous support of the --
Comisijn Nacional de Ciencif y Tecnologia (Conacyr) is most gratefully ---
Ac'no'..ledcod.
2/ yDto. de Fitoratologia, C.S.A.T.'




2. -


"humid tropics," with mean annual temperatures consistently -
above 25*C and annual precipitation ranging from 1500 mm clo-
se to the Gulf coast to above 5000 mm in the foothills of the
Chiapas highlands (Fig. 1). In general, precipitation is sea
sonal, there being a wet season with an early maximum in June
and an absolute maximum in September, followed by a gradual -
decrease to a minimum im'April.

Close to the coast during the drier months of March and April
approximately 40 mm of rainfall occur, increasing to a minim-
um of over 100 mm in the foothills. Climate can be classified
primarily as Am to Af, according to the K6'ppen system (Garcia,
S1973).

Original vegetation consisted primarily of tropical rain-
forest, except for a rather large area of savannah in the ---
south-central part of Tabasco (see West, 1966, for detailed -
description). Marsh vegetation is quite widespread also in the
deltaic plain formed by alluvium deposited by the extensive -
river system characteristic of the region (West, et al, 1969).
It was probably the areas with forest or savannah vegetation-
in which most traditional-agriculture-occurred, and in recent
time has seen a considerable introduction of new agricultural
technology. Various forms of subsistence farming are known to
have been employed by the original indian inhabitants (Wilken,
1970) and are thought to have achieved highly productive lev-
els.Slash and burn agriculture was probably used for basic grain-
production (corn, beans, etc), whereas extensive use 6f kit--
chen gardens (huertos familiares), composed primarily of tree
crops and their associated understory herbs, shrubs, and---
vines, added great variety to the local diet. Cacao was prod-
ced as an understory element in these kitchen garden systems-
and has been expanded considerably using a plantation system-
which employs extensive use of legume shade trees.

S In recent years the emphasis in agriculture in the Tabas
can lowlands has been away from subsistence agriculture aid -
towards commercial farming and stock raising. Accompanying --
this shift towards commercial activities has been a gradual -






Page
Missing
or
Unavailable






4 -

abandonment of traditional agricultural practices and varieties,
Loss in diversity in the cropping systems is thought to lead to
detrimental effects on the diet and nutrition of the local peo- \
pie (Herndndez, et al, 1974) and a much greater dependence on--
food products of overall lower nutritional value /most often im
ported from outside the tropics (Dewey, 1978). This problem has
become especially acute in recent years due to the failure of
several modernization schemes and agricultural reform projects-
to achieve the productive levels hoped for. Instead, the emphas
is has been placed on low-risk export crops such as bananas, su
gar cane, and cattle raising. At the same time, once the origi-
nal limited productiveness of the forest soils has been quickly
depleted, large areas have been converted to very low yield ---
pasture or completely abandoned and allowed to become revegeta-
ted by weedy second growth species. The objective of this pro--
ject there-fore is to attempt to achieve once again the divers-
ity and stability of productivity originally characteristic of-
the traditional agroecosystems and natural ecosystems of the re
gion.


THE MODULAR PRODUCTION SYSTEM


As part of a program to reclaim areas that once possessed-
a much greater productivity, at various sites in the Tabascan -
lowlands we have installed production units, referred to here -
as modular systems, whose primary focus centers around the ap--
plication of ecological principles to agriculture with the in--
corporation of considerable emperical knowledge existent in the
region. Each modular production unit can be conceptualized as a
system that strives to reach an equilibrium in productive capa-
city by interrelating agricultural activities with ecological -
and socio-economic f~tr-tnr prevalent in a lowland humid tropic-
al region.

Each production unit consists of from 5 to 15 ha control-
led by several family units as part of their other agricultu--






5" -


ral activities. Depending on the social structure of the commu
nity, the families may actually live within each module, or --
they live in a nearby community and work in the module during-
the day. Many communities in Mexico are organized into a type-
of collective (ejido colectivo) and work the different agricul
tural aspects of their communities on a comminal basis (Toledo,
1977). Thus production from'each module would either be consum
ed directly by the families living there, or the products would
be distributed to the members of the ejido. Any excess in prod
4 auction would be available for commercialization or exchange.

Each production unit has as part of its basic structural-
-design (Fig. 2) an outermost band of vegetation consisting ---
primarily of second growth species present naturally in the re
gio. This band serves simultaneously as a windbreak, a sour-
ce of natural predators and.parasites for biological control,-
as well as a source of firewood and building materials. At the
same time these shelter belts serve as biological reserves or-
germplasm banks for part of the great diversity of plants and-
animals normally present in tropical ecosystems. By selective-
.species -enrichment-with-forest and fruit tree species, it is -
possible to apply agrosilvicultural management practices, inc-
reasing the long term value of the shelter belt. This activity
is consistent with the ecological basis of secondary succes---
sion and forest regeneration processes in natural forests (Go-
mez-Pompa and Ludlow Wiechers, 1976), and can contribute sign-
ificantly in achieving the successful reforestation of large--
areas in the tropics. Inicial observations of growth of some -
of the more economically important forest species in some modu
lar units demonstrate rapid initial rates of development (Ta--
ble 1).

The interior part of each modular unit is constructed on-
the basis of the topographic diversity existent at each






Page
Missing
or
Unavailable











Table 1. Height increases in four important forest species after
one yr from planting out in the second growth shelter-
belt, Modular Unit, CSAR, H. Cardenas, Tabasco, Mexico.


Scientific Name


Swietania macrophylla King
Cedrela mexi ana Roem
Ceiba pentandra L.
Tabebuia pentaphylla L.


Height in meters
Local Name At Planting At 1 yr Dif


Caoba
Cedro
Ceiba
Maculi


0.30
0.35
0.45
0.25


2.57
2.11
2.57
0.88


1.27
1.76.
2.12, \.
0.63 .


* Averages of 30 individuals of each .species.






- 8


site. In cases where the lowest part of the module can be centr---
rally located as in Figure 2, we construct large tanks which serve
as catchments for all runoff from the production unit so as to ---
collect dissolved nutrients and particles of soil and organic ---
matter. Pish, ducks, and other aquatic animals are being produ
/
ced in the tanks, with the aquatic plants and sediments being --
used as fertilizer in other parts of the modulo. Depending on-
topography and the size of the unit, frequently small canals are-
built radiating out from the central tank in order to further --
aid in the capture of excessive runoff. To avoid total inunda---
tion of the site, a principal canal can frequently be built to
eliminate excess water from the site, or in some cases, serve as-
a means of adding water in times of low rainfall.


Under certain topographic conditions we have been able to--
utilize a natural water course in much the same way as the cen--
trally constructed tank (Fig.3). By constructing small earthen"-
dams and enlarging the reservoir behind each dam, areas for fish -
duck and other animal production has been possible. The ponds -
aid in the production of aquatic plants as well as-- the capture --
of sediments from the rest of the system.


Located around the central tank or along the edges of the-
water courses we construct raised platforms, often with the same-
material extracted from the catchment basins, forming a system -
of tropical chinampas (G6mez-Pompa, 1978) for intensive vegetable
production (Table 2, Part A). The soil of the chinampas is con--
stantly enriched with organic.





- 9 -


Table 2. Harvest availability on monthly basis:during the year for different
types of crops planted in the modular production units, including an
ecological classification for each one.

Scientific Name c Local Name J F M J J A S O N D Class


A. Chinanpas and Intensive Vegetables:
Lycopersicon esculentum Tomate
Capsicum annuun vars. Chile
Cucurbita Pepo vars Calabaza
Cucumis melo vars. Melon
Allium cepa Cebolla
Manihot esculenta Yuca
Colocasia esculenta Macal

Xanthosoma sagittifolium Malanga
Carica papaya Papaya
Musa ssp. and vars. Platano
Musa spp. and vars. Guineo
Cnidoscolus chayamansa Chaya
Brassica oleracea Col
Bixa orellana Achiote
Coriandrtn sativumn Cilantro
__ _pomaea batatas__ Camote
Sesamun orientale Ajonjoli
Allium sativ-n Aj',
Citrullus vulgaris Sandia
Eryngiu-n sp. Perejil
Zea mays Maiz
Cajanus cajan Chicharo
Ocimin basilicuin Albahaca
buntingia calabura Capulin
Crotalaria maypurensis Chipilin
Cucumis sativas Pepino
Raphanus sativus Rabano


xxxx


xx x
XX X


xx
xx
x x
X x
xx
xx
X-X
xx


xx
xx


XXXX
x x
XXXX
XXXX
XXXX

XXXx

xxx


x
x x x x x x x -'x
x
x


XXX


x
x


XXXXX


XXXXX


xxxxxxx


Vigna sinensis


SFrijol


B. Areas of Basic Annual Crops:


Zea nays
Oryza sativa


Maiz
Arrcz


XX XX XX
xx


XXXX


x x
x x
XXXX


x
xx


2L
2L
3M,F
3F
.1R
SR
4R
4R
6F
6F
6F
6L
1L
6F
1L
3R
2F
1R
3F
1L
2F
2F
1L
6F
2L,F
1F
1R


x
XXX


XXX
XXX
x
XXX
x x
XX X


.XX XX Xx








- 10 -


Scientific Namerc Local Name J F M A M J J AS .0 N D Classb


Phaseolus vulgaris
Vigna sinensis
Cucurbita pepo
Cnidoscolus: Chayamansa
Bixa orellana
Manihot esculenta
Stizolobium sp.
Canavalia ensiformis
Cajanus cajan
Leucaena glauca
Dioscorea alata
Sechium Bdule
Carica papaya


Frijol
-Frijol
Calabaza
Chaya
Achiote
Yuca
Nescafe
Costilla
Chicharo
Leucaena
Name
Chayote
Papaya


x
x
xx
xx x


. xx x
x x
xxxxx


x
xx
xx
x
X


xxxxxxxxx


xxxxxx xx


xx
xx
xx
xx
xx
xx
xx
XX


C. Areas of Perennial Crops.

Theobroma cacao
Annona muricata
SMangifera indica
Coffea arabica
Ananas sativas
Citrus auranteum vars.
Citrus limonia vars.
Citrus grandis
Psidium guayava
Cocus nucifera
Achras zapota
Chryssophyllum cainito
Talisis olivaeformis
Persea americana
Persea sp.
Tamarindus indica
Passiflora edulis
Artocarpus comunis
Annona scuamosa
Spondias purpurea
Calocarpui m-Tnaosumn


Cacao
Guanabana
SMango
Caf6e"
Pifia
Naranj a
Lim6n
Toronja
Guayaba
Coco
Zapote
Caimito
Guaya
Aguacate
Chinin
Tamarindo
Granadilla
Castafia
Anona
Ciruelo
Zapote


x x
xx
xxx


xx


xx .


XXX


xxxxxx


xx x xx


x
x
X


xx
xx


xx
XXX'X


x


x



x
x
X


xxxxxxx
XX


XXX


xx
x


2F
2F
3M,F
6L
6F
SR
3M, F
3M,F
6M,F
6M,F,L
9R
9F
6F


XXX


XXX


6F
7F
7F
6F
4F
6F
6F
6F
6F
7F
7F
7F
7F
7F
7F
6F
9F
7F
7F
6F
7F








- 11 -


a


Scientific Namec


Anacardium occidentale
Inga quinicuil
Byrsonima crassifolia
Hibiscus sabdariffa
Muntingia calabura
Theobroma bicolor
Pimienta officials
Hevea braziliensis
Cymbopogon citratus
Additionally many of the species
classification of 3, 4, 5, 6 and


Local Name J .FMAM J JA S ON D Class


Marafion xx
Quinicuil x x
Nanche x x
Jamaica xxx
Capulin xx x x x
Pataste x x xx x x x x x x xx
Pimienta xx
Hule xxxxxxxxxxxx
Zacate Lim6nx x x x x x x x xx x x
from A and B, but especially those with
9.


a) x = available for harvest

b) Classification of crops according to the ecological states of each plant
plant in the cropping systems:

(1) Annual, low growing (R=root, F=fruit or seed, L=leaf, S=sap, M=green -
manure)

(2) Annual, upright
(3) Ground cover
(4) Perennial, low growing
(5) Perennial, medium height, entire plant harvested completely usually in
less than one year.
(6) Perennial, medium height, leaves or fruits harvested only
(7) Perennial, tall, fruit crop
(8) Perennial, tall, leaf, wood, or sap crop
(9) Climber, usually perennial

c) Nomenclature after Bailey, L.H. 1975. Manual of Cultivated Plants. New -
York.






- 12 -


matter produced by the abundaift aquatic plant growth as well as -
the sediments fron the bottom of the'reservoirs, Animals kept :in
small corrals, such as pigs, chickens, or ducks, are fed the exc-
ess or waste produce from the chinampas, as well as from other --
parts of the module, in order that manures can be incorporated --
back into the platforms for added productivity.

Around the areas of chinampas we concentrate the major part-
of the production of basic food crops traditional in the region -
(Table 2, part B, C). According to the distribution of soil types,
drainage, topography, and other physical characteristics of each-
site, a wide variety of annual and perennial crops are planted --
following the planting methods and combinations recommended by --
the campesinos. This includes such systems as the traditional -.-r
cornibean/squash polyculture, cassava/corn/papaya, and fruit ----
trees associated with various cover crops, shrubs, or vines. A --
concept that we never lose sight of is the need to make our modu-
lar units productive on a sustained basis. Thus much of our expe-
rimentation is focused towards understanding the best crop combi-
nations and rotational schemes, especially in developing the best
--means of managing--the_large_ organic matter inputs necessary for -
the maintenance of productive potential, and their importance in-
the overall functioning of tke agroecosystem. /

-- ECOLOGICAL PROCESSES.


The focus of the modular production units represents in many
ways a reversion to the diversity of cropping systems that were -
traditional among the campesinos and makes use of ancient practi-
ces still observable in mainy parts of the Tabascan Lowlands. At -
the same time each of these practices has a distinct basis in eco
logical theory.

The high species diversity in many tropical ecosystems is --
well known in ecological literature (Whittaker, 1965, 1972).This-
same concept is managed in each module, first in considering the -
overall diversity of each entire production unit, and secondarily






- 13 -


in each particular crop subsystem within the unit (Table 2).This
varies from the chinampas (e.g.a platano/chaya/tomate/cilantro/-
rabano mixture), to the annual cropping areas (e.g. the tradition
nal maiz/frijol/calabaza polyculture), to the perennial crop sys
teams with diverse mixtures of fruit trees and their associated
understory herbs, shrubs, and climbing vines. Greatest diversity
is seen in the second-growth shelter belts around each production
unit. Following the tradition of the local campesinos, every uti
lizable area is occupied by vegetative cover, both in time and -
space. The classification of growth forms and habits presented -
in Table 2 gives idea of the structural diversity possible with-
in each subsystem. Crops with different canopy configurations -
give better light interception and ultimately lead to better uti
lization of solar radiation (Allen, et al, 1976), as well as ---
higher biomass accumulation within the system. Therefore, spe---
cies diversity on an area basis is increased even more through -
an increase in spatial arrangement and crop architecture (Horn,-
1971).


A further characteristic of tropical ecosystems, as well as
the traditional agroecosystems-, is-the _high rate of biomass accu
mulation within the system in relation to harvest output. This -
can vary from 16 to 22 t/ha dry weight of organic matter (Whitta
ker, 1975), and is thought to play an important part in the long
term productive stability of each system (Sanchez, 1976b).With -
higher crop diversity, it appears that the need to produce an in
creased harvestable food portion can be better combined with the
need to maintain greater organic biomass content in the system as
a whole (Trenbath, 1974). Without this organic matter input, it-
soon becomes necessary to constantly import larger and more ex--
pensive amounts of inorganic fertilizers whose effective-ness in
the face of high temperatures and heavy rainfall is questionable
(Gliessman, 1978). In the chinampas, for example, the major ----
source of organic matter input is the water hyacinth (Eichornia-
crassipes), capable of producing up to 900 kg/ha dry matter dai-
ly (N.A.S., 1976). Supplemented with relatively small amounts of
animal manure high in nitrogen, the chinampas can be made essen-






* 34 -


tially self-sustaining (Gonfez-Pompa, 1978), Other aquatic plants--
are being tested, especially those with nitrogen fixing potential.


In the annual crop areas the main sources of organic matter -
input come from a rotation with various species of legume cover --
crops, other crop residues, and the incorporation of any other as-
sociated herbaceous species present. The importance of the legume-
cover crops in the elimination of undesirable herbaceous species,-
soil borne diseases and nematodes, as well as increasing soil fer-
tility, is presently being studied (Garcia and Gliessman, in prepa
ration). The same cover crop concept is being employed in the ----
areas of perennial cropping, but we are finding that the biomass -
input in the perennial systems in relation to output is very simi-
lar to that reported for natural ecosystems of similar structure,-
and thus are much more stable in obtainable yields.The nutrient --
flow in each system is presently being intensevely studied in seven
ral modular units in order to gain a better understanding of the -
relationship between biomass accumulation and yield output, espe--
cially in relation to diversity and its management.


.Asin traditional agroecosystems, the modular production units
are managed without the use of commercial chemical insecticides or-
fungicides. By maintaining as high a structural diversity in each-
unit as possible, aided by surrounding shelter belts of natural ve
getation, we hope to attain the optimum equilibrium between pest -.
populations and corresponding predator and parasite populations --
proposed by Price (1976). Extensive evidence ha/'been accumulated-
which demonstrates that many traditional intercropping patterns --
are in fact pest suppressant (Litsinger & Moody, 1976). At the same ti-
me, by utilyzing native stock in all of our plantings, the probabi
lity that the crop species still retain a high degree of natural -
chemical defenses is much higher (Janzen, 1973) These types of--
biological control mechanisms can function for insects, fungi, bac
teria, and nematodes, above as well as below ground. It is much --
less probable that population size of any one pest will reach epi-
demic (and thus economic ) levels due to the specific and structu-
ral diversity present in the production units.








-15 i

Biological control of pests can be extended to include the -
control of weeds. The campesino employs a wide variety of crop --
combinations (mixture and cover) and rotational rest periods in -
order to help keep his cropping areas free of undesirable herbace
ous plants. By maintaining a continual crop cove{, combined with-
other cultural practices, the opportunity for weed invasion and -
growth is minimized. Recently it has been proposed that the allel
opathic potential of the crops (Putnam and Duke, 1974) could be a
definite mechanism of weed control, especially since the tradition
nal crop varieties could still possess a greater toxic potential-
due to their continual association with weed populations in the -
traditional agroecosystems. The fact that the campesino rarely --
practices "clean" cultivation, rather'selectively leaves some and
eliminates others, suggests a potential for managing certain crop
weed mixtures so that biomass accumulation in the system can be -
increased, yet the harmful effects of interference from certain -
weeds avoided.

Further enrichment of the cropping diversity in the modular-
units is being attempted through the introduction of other varie---
ties of crops already utilized in the various regions of the Ta--
bascan lowlands, as well as other parts of tropical Mexico. Thoro
ugh ethnobotanical studies from this region are still lacking,and
the ecotipic variation available in most of the crops very little
explored. The location of this variability into the ecological di
versity of each modular unit could aid in approaching productive-
stability as well as further complement the dietetic needs of the
compesino. Introductions from other tropical regions of the world
could even be attempted, provided that a thorough knowledge of --
the ecological relationships of each potential component within
the modular system was understood. By complementing the system --
that the campesino already recognizes, the acceptance of the new
species would be more plausible. At present, for example, we are-
studying the problems involved in the'addition of the winged bean
(Psophocarpus tetrogonolobus (L) DC.) into the traditional nai:/
frijol/calabaza polyculture of the region. The potential of the -
winged bean for improving dietetic diversity and qualitY is Ce!l-





S316 -


recognized (N.A.S., 1975),


PERSPECTIVES


A thorough understanding of the ecological processes function
ning in the traditional agroecosystems in the tropics, coupled --
with the development of a productive system with which the campe-
sino can identify and understand, holds out the possibility that
we can develop a technology that provides once again better diver
sity in diet, stability of production, reduced pest and disease -
problems, more efficient use of family labor, and the potential -
for intensive production even when there exist the various limi--
ting factors well recognized in tropical environments. The need -
to focus research efforts towards the further development of cro-
pping systems with high structural and specific diversity has re-
cently been proposed (Sanchez, 1976a), and how to do this at lea
st in the selection of proper varieties has been outlined (Francis,
et al,-1976). As of yet very little information has been gathered
and tested within the context of production oriented systems, es-
pecially as related to the understanding of the ecological rela--
tionships between the many and varied components of the agroeco--
system.


In the lowland tropical regions of southeastern Mexico there
exists a considerable body of emperical knowledge concerning the-
structure and management of traditional agroecosystems, as well -
as the original germplasm to utilize as the basis for the organi-
zation of productive units. Utilizing the modular unit concept, -
the potential for restoring a more productive capacity to tropi--
cal ecosystems can be achieved. The imposition of a new technolo-
gy has been shown to be of very limited potential in increasing -
productivity, especially when that technology comes from extra---
tropical regions. The acceptance of a technology with which the -
campesino can readily identify is an obvious advantage to the pro
posal. At the same time, the collective ejido structure can poten
tially satisfy the socio-economic limitations posed by any kind -
of organized agricultural enterprise. In order to insure that each










S modular unit can sustain its productive capacity is dependent on
the thoroughness of our understanding of the ecological relation
ships functioning within.the structural diversity that we design.































/