Titre : L'Agronomie tropicale
Auteur : Centre de coopération internationale en recherche agronomique pour le développement (France). Département des cultures annuelles. Auteur du texte
Auteur : Institut de recherches agronomiques tropicales et des cultures vivrières (France). Auteur du texte
Éditeur : Institut de recherches agronomiques tropicales et des cultures vivières (Paris)
Date d'édition : 1975-04-06
Notice du catalogue : http://catalogue.bnf.fr/ark:/12148/cb34398560g
Type : texte texte
Type : publication en série imprimée publication en série imprimée
Langue : français
Description : 06 avril 1975 06 avril 1975
Description : 1975/04/06 (VOL30,N2). 1975/04/06 (VOL30,N2).
Description : Collection numérique : Numba, la bibliothèque... Collection numérique : Numba, la bibliothèque numérique du Cirad
Droits : conditions spécifiques d'utilisation (sous convention BnF-ADM-2025-035729-01)
Identifiant : ark:/12148/bpt6k1100499x
Source : CIRAD, BH_PEHIST 5290
Conservation numérique : Bibliothèque nationale de France
Date de mise en ligne : 04/12/2022
Summaries
I) LAND USE CAPABILITIES
A multidisciplinary approach in which soil scientists and agro-
nomists are closely associated is necessary to determine land
use capability in a natural environment. This includes:
1) Environment knowledge: this stage is based on mapping. Me-
thods were developed by IRAT in cooperation with the “Centre
de géographie appliquée of Strasbourg” to analyse the components
the natural environment considered as a system the interactions
of which defining “environment types” which are areas with
common structure, evolution and constraints. To protect the resour-
ces of each environment type more or less specific development
Methods are required.
These studies fall within the competence of both scientists and
geomorphologists.
2) Plant behaviour knowledge: in order to study this behaviour
the plant responses to the various constraints are assessed,
analysed and measured with a view to finding means of improving
production.
Many studies related to development projects were carried out
according to these concepts.
II) WATER-SOIL-PLANT RELATIONSHIP - BIOCLIMATOLOGY
IRRIGATION
The water-soil-plant complex is studied to define the methods and
systems which can make the best use of water resources both
under natural and artificial conditions (irrigation) along the following
– agroclimatology: determination of natural water potential, plant
needs for water, by species and variety, and the limiting climatic
– agropedology: characterization of the water reserves of the soil
and determination of the possible limiting effect of the soil on
the suitable water supply of the crop,
crop science: choice of species and varieties adapted to water
Sources, development of methods and cropping calendars,
– water management: methods of water distribution at the field
and plot level or drainage.
1) For the main rainfed crops, definition of the useful rainy season
and thereby appropriate growth duration and dates when cultural
practices are possible; these are definite selection criteria for the
breeder. It was also shown that it would be interesting to improve
by all means soil water storage and conservation both during the
crop season and from one rainy season to the other.
2) For the irrigated crops: cropping and irrigation norms were
established.
good management of the large water amounts required is
related to the use of improved varieties.
From an agropedological point of view, several irrigated areas
with development problems were studied and based on the results
mods were devised to diagnose how suitable soils are for
irrigation. For this, advanced technics were used such as neutron,
gammametry, tensiometer technics for example. Thus the existing
maps of land use capabilities could be corrected and soil mana-
gement operations such as subsoiling and drainage suggested.
Continuation of work on the irrigation methods.
III) SOIL WORKING - SOIL PHYSICS
Particular attention was paid to the problems of porosity evolution
which governs root development and thereby their resistance to
drough.
The results obtained in the various ecologies show a very marked
effect of soil working for exundated crops. Ploughing, more
particularly, seems in most cases the best method to increase
yields significanthy; in the soils with a slight slope it can limit
1) In the dry tropics, for all the exundated soils of this zone,
except th vertisols, ploughing which provides better water supply
for the plants is necessary to improve the cultural profile and
crop yields.
Ploughing effects are best in a wet environment. This is more
particularly the case with the turning under of organic matter
which must be made, whenever possible, at the end of the rainy
THE MAIN CONCLUSIONS OF THE IRAT AGRONOMY PROGRAM (1969-1974)
season; if not, (too short rainy season), dry ploughing is used
when the soil permits it.
Lastly, when ploughing is not possible, there are intermediary
though less interesting solutions such as tine working.
As regards vertisols, it is not yet possible to say whether soil
working is required. Without having a negative effect ploughing
gives not sufficiently superior results to be extended.
2) In the humid tropics, in all the soil types found, except
vertisols ploughing still appears as the best method of soil
preparation; its action is more effective in case of drought.
Here the conditions of ploughing are more important than in the
dry tropics, particular attention must be paid to them.
3) In the equatorial zone, the same conclusions are found for
the ferruginous tropical, ferallitic and hydromorphic soils.
Contrarily, ploughing does not appear to be necessary in andosols,
and it does not seem advisable to recommand it when the slope
reaches 10 to 15 %. Particular attention must be paid to erosion-
control. We must notice that in any case, when the slope is
slight, ploughing under rational conditions limits erosion and
run-off.
In flooded soils, the results are still very divergent.
IV) POTENTIALITIES
In case all the technical and environmental conditions would
permit potential production, cereal yields could be up to 100 qx
by hectare and cycle in the climatically most favorable zone and
35 to 30 qx in the less favorables zones.
In the field of minerals others than nitrogen, it was shown that
phosphorus was the most limiting factor, and often the only one,
for the most part of the exundated soils. This deficiency can
be corrected by applications ranging from 50 to 150 kg of P2O5
by hectare (under various forms) except for some soils with a
high fixation capacity where they must reach 300 kg.
The other limiting factors of yield are non existent, except the
very desaturated soils of Madagascar in which potassium and
magnesium deficiencies have been observed.
The phenomena of toxicity and salinity in some low lying lands
must also be noted.
Lastly the use of depleted soils, such as the degraded “terres
de barre” is difficult and raises microbiological problems. Farm-
yard manure and soil working are recommanded.
V) MAINTAINING FERTILITY WITHIN THE FRAMEWORK OF A
CROPPING SYSTEM
When a soil was made fertile again (by reducing P deficiencies
more particularly) there was the problem of maintaining this new
fertility. This was studied along three lines:
— direct experiments,
— evaluation of the element amounts removed by the crops,
— evaluation of leaching losses.
The results obtained were:
• simple compensation of the phosphorus, amounts removed by
the crops ;
• for potash, this nutrient can be applied only when the first
deficiency symptoms appear ;
• as regards trace-elements highly significant responses can be
obtained with minimum applications (boron, molybdenum).
• A risk of acidification appears in the soils exhausted by conti-
nuous cultivation without sufficient resting periods and rain
leaching. This acidification releases toxic elements in the soil,
more particularly aluminium, which can significantly reduce yields,
especially legume yields (groundnut, soyabean). This situation can
be corrected and prevented.
• A very high proportion of some of the elements removed by
the plants (nitrogen, potassium) is found in crop residues, whence
the interest of residue recycling.
VI) NITROGEN FERTILIZATION OF TROPICAL FOOD CROPS
Nitrogen fertilizer is a production expense and its use is difficult.
I) LAND USE CAPABILITIES
A multidisciplinary approach in which soil scientists and agro-
nomists are closely associated is necessary to determine land
use capability in a natural environment. This includes:
1) Environment knowledge: this stage is based on mapping. Me-
thods were developed by IRAT in cooperation with the “Centre
de géographie appliquée of Strasbourg” to analyse the components
the natural environment considered as a system the interactions
of which defining “environment types” which are areas with
common structure, evolution and constraints. To protect the resour-
ces of each environment type more or less specific development
Methods are required.
These studies fall within the competence of both scientists and
geomorphologists.
2) Plant behaviour knowledge: in order to study this behaviour
the plant responses to the various constraints are assessed,
analysed and measured with a view to finding means of improving
production.
Many studies related to development projects were carried out
according to these concepts.
II) WATER-SOIL-PLANT RELATIONSHIP - BIOCLIMATOLOGY
IRRIGATION
The water-soil-plant complex is studied to define the methods and
systems which can make the best use of water resources both
under natural and artificial conditions (irrigation) along the following
– agroclimatology: determination of natural water potential, plant
needs for water, by species and variety, and the limiting climatic
– agropedology: characterization of the water reserves of the soil
and determination of the possible limiting effect of the soil on
the suitable water supply of the crop,
crop science: choice of species and varieties adapted to water
Sources, development of methods and cropping calendars,
– water management: methods of water distribution at the field
and plot level or drainage.
1) For the main rainfed crops, definition of the useful rainy season
and thereby appropriate growth duration and dates when cultural
practices are possible; these are definite selection criteria for the
breeder. It was also shown that it would be interesting to improve
by all means soil water storage and conservation both during the
crop season and from one rainy season to the other.
2) For the irrigated crops: cropping and irrigation norms were
established.
good management of the large water amounts required is
related to the use of improved varieties.
From an agropedological point of view, several irrigated areas
with development problems were studied and based on the results
mods were devised to diagnose how suitable soils are for
irrigation. For this, advanced technics were used such as neutron,
gammametry, tensiometer technics for example. Thus the existing
maps of land use capabilities could be corrected and soil mana-
gement operations such as subsoiling and drainage suggested.
Continuation of work on the irrigation methods.
III) SOIL WORKING - SOIL PHYSICS
Particular attention was paid to the problems of porosity evolution
which governs root development and thereby their resistance to
drough.
The results obtained in the various ecologies show a very marked
effect of soil working for exundated crops. Ploughing, more
particularly, seems in most cases the best method to increase
yields significanthy; in the soils with a slight slope it can limit
1) In the dry tropics, for all the exundated soils of this zone,
except th vertisols, ploughing which provides better water supply
for the plants is necessary to improve the cultural profile and
crop yields.
Ploughing effects are best in a wet environment. This is more
particularly the case with the turning under of organic matter
which must be made, whenever possible, at the end of the rainy
THE MAIN CONCLUSIONS OF THE IRAT AGRONOMY PROGRAM (1969-1974)
season; if not, (too short rainy season), dry ploughing is used
when the soil permits it.
Lastly, when ploughing is not possible, there are intermediary
though less interesting solutions such as tine working.
As regards vertisols, it is not yet possible to say whether soil
working is required. Without having a negative effect ploughing
gives not sufficiently superior results to be extended.
2) In the humid tropics, in all the soil types found, except
vertisols ploughing still appears as the best method of soil
preparation; its action is more effective in case of drought.
Here the conditions of ploughing are more important than in the
dry tropics, particular attention must be paid to them.
3) In the equatorial zone, the same conclusions are found for
the ferruginous tropical, ferallitic and hydromorphic soils.
Contrarily, ploughing does not appear to be necessary in andosols,
and it does not seem advisable to recommand it when the slope
reaches 10 to 15 %. Particular attention must be paid to erosion-
control. We must notice that in any case, when the slope is
slight, ploughing under rational conditions limits erosion and
run-off.
In flooded soils, the results are still very divergent.
IV) POTENTIALITIES
In case all the technical and environmental conditions would
permit potential production, cereal yields could be up to 100 qx
by hectare and cycle in the climatically most favorable zone and
35 to 30 qx in the less favorables zones.
In the field of minerals others than nitrogen, it was shown that
phosphorus was the most limiting factor, and often the only one,
for the most part of the exundated soils. This deficiency can
be corrected by applications ranging from 50 to 150 kg of P2O5
by hectare (under various forms) except for some soils with a
high fixation capacity where they must reach 300 kg.
The other limiting factors of yield are non existent, except the
very desaturated soils of Madagascar in which potassium and
magnesium deficiencies have been observed.
The phenomena of toxicity and salinity in some low lying lands
must also be noted.
Lastly the use of depleted soils, such as the degraded “terres
de barre” is difficult and raises microbiological problems. Farm-
yard manure and soil working are recommanded.
V) MAINTAINING FERTILITY WITHIN THE FRAMEWORK OF A
CROPPING SYSTEM
When a soil was made fertile again (by reducing P deficiencies
more particularly) there was the problem of maintaining this new
fertility. This was studied along three lines:
— direct experiments,
— evaluation of the element amounts removed by the crops,
— evaluation of leaching losses.
The results obtained were:
• simple compensation of the phosphorus, amounts removed by
the crops ;
• for potash, this nutrient can be applied only when the first
deficiency symptoms appear ;
• as regards trace-elements highly significant responses can be
obtained with minimum applications (boron, molybdenum).
• A risk of acidification appears in the soils exhausted by conti-
nuous cultivation without sufficient resting periods and rain
leaching. This acidification releases toxic elements in the soil,
more particularly aluminium, which can significantly reduce yields,
especially legume yields (groundnut, soyabean). This situation can
be corrected and prevented.
• A very high proportion of some of the elements removed by
the plants (nitrogen, potassium) is found in crop residues, whence
the interest of residue recycling.
VI) NITROGEN FERTILIZATION OF TROPICAL FOOD CROPS
Nitrogen fertilizer is a production expense and its use is difficult.
Le taux de reconnaissance estimé pour ce document est de 99.8%.
En savoir plus sur l'OCR
En savoir plus sur l'OCR
Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour ce document est de 99.8%.
- Auteurs similaires Bibliothèque Francophone Numérique Bibliothèque Francophone Numérique /services/engine/search/sru?operation=searchRetrieve&version=1.2&maximumRecords=50&collapsing=true&exactSearch=true&query=colnum adj "RfnEns0"Numba, la bibliothèque numérique du Cirad Numba, la bibliothèque numérique du Cirad /services/engine/search/sru?operation=searchRetrieve&version=1.2&maximumRecords=50&collapsing=true&exactSearch=true&query=colnum adj "NmBA001" Bibliothèque Diplomatique Numérique Bibliothèque Diplomatique Numérique /services/engine/search/sru?operation=searchRetrieve&version=1.2&maximumRecords=50&collapsing=true&exactSearch=true&query=colnum adj "MAEDIGen0"
-
-
Page
chiffre de pagination vue 1/100
- Recherche dans le document Recherche dans le document https://numba.cirad.fr/services/ajax/action/search/ark:/12148/bpt6k1100499x/f1.image ×
Recherche dans le document
- Acheter le livre complet Acheter le livre complet https://numba.cirad.fr/services/ajax/action/indisponible/achat/ark:/12148/bpt6k1100499x