Weed control by means such as cover crops or animals can

Agro-ecology >> What strategies are required for agroecological management of weeds in orchards?
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Weed control by means such as cover crops or animals can
replace herbicides, which are costly and generate pollution
Herbicide use in orchards can be reduced, if not
abandoned and the costly constraint of
mechanical weeding overcome thanks to
effective alternative methods. Weeds can be
controlled effectively by planting a herbaceous
cover comprising perennial legumes and small
grasses, or by small-scale poultry rearing, with
the birds grazing freely in the orchard.
Citrus orchard planted with Arachis pintoi
in Martinique © C. Lavigne/CIRAD
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Using cover crops (grasses or legumes) is an
interesting alternative to chemical control of
weeds.
Their functional traits must satisfy exact
specifications, notably as regards the speed with
which they cover the soil after planting so as to
compete with weeds, and also the amount of
biomass produced, regrowth capacity after
mowing, capacity to withstand trampling, and
persistence. The following factors should also be
studied: pest host status, symbiotic nitrogen
fixation capacity, tendency to creep, and degree
of competition with the cash crop for minerals. An
assessment of numerous local and introduced
species showed that no one species satisfied
every criterion. However, a herbaceous layer
comprising several genera and several species
from the two chosen families performs
satisfactorily.
In Martinique, a Neonotonia
wightii/Paspalum conjugatum mix has been used,
but the choice depends largely on plot location.
Setting up such a herbaceous layer may mean
using annual legumes.
Some weeds can be extremely difficult to control,
particularly climbers such as American rope
(Mikania micrantha). These creepers are able to
grow roots from every node and are easily
propagated from cuttings. Particular care must
therefore be taken to remove them as early as
possible, by hand.
Using perennial cover crops should be seen as a
long-term investment, given the work involved in
establishing them.
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agroecologie.cirad.fr
Annonaceae orchard, or poultry in the case of
guava. Animals significantly reduce the number
of mechanical mowing operations required to
control weeds.
Flock of grey geese grazing in a guava/longan
orchard © C. Lavigne/CIRAD
Several promising agro-pastoralism experiments,
followed by implementation of the techniques by
producers themselves, have shown how useful it
can be to keep animals in orchards. To quote two
examples, this may mean keeping sheep in an
A reduction in weed pressure can be achieved by
increasing the density of plot occupation by cash
crops. For instance, using dwarfing rootstocks
(Tahiti lime on Poncirus Flying Dragon) increases
production precocity. Intercropping species with
different fruiting dates and lifespans (mango,
guava, medicinal plants and plantain banana, for
instance) serves to manage productivity by
gradually eliminating the species that were
productive in the initial years as the definitive
species begin fruiting.
Agro-ecological weed management can be
practised on several levels of intensity and
efficacy, depending on the size of the plot or the
farm, and also on the human resources available.
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References
Some CIRAD publications
Lavigne C., Lesueur-Jannoyer M., de Lacroix S.,
Chauvet G., Lavigne A., Dufeal D. 2011, De la
production fruitière intégrée à la gestion écologique
des vergers aux Antilles Innovations Agronomiques
16, 53-62.
Lavigne C., Achard R., Tixier P., Lesueur-Jannoyer
M., 2012, How to Integrate Cover Crops to Enhance
Sustainability in Banana and Citrus Cropping
Systems, Acta Hort. 928, 351-357.
Lavigne A., Dumbardon-Martial E., Lavigne C..
2012. Les volailles pour un contrôle biologique des
adventices dans les vergers, Fruits 67 (5), 341–
351.
Devag project: Pour réduire l’utilisation des
herbicides et protéger le sol ? Intégrez des plantes
de couverture à votre verger (technical advice note:
http://devag.tropicalagroecology.org/index.php/fr/component/jdownload
s/finish/25/138
Contact
Christian Lavigne, UR Hortsys
[email protected]
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agroecologie.cirad.fr