Environmental Engineering Reference
In-Depth Information
than orchard. However, when the cocoa canopy closes the intercrops can no longer
survive, and the field type evolves into a cocoa-dominated plantation interspersed
with the original trees left in place during land preparation. This evolution brings
into question whether this final land-use stage should be called agroforest or orchard
within the context of the BAG definitions (Zarin, Huijin, and Enu-Kwesi, 1999).
At the closure of the canopy, the floor of the cocoa plantation is almost always
covered by a mat of mulch made up mainly of senesced cocoa leaves. This, in
addition to the reduced insolation by the closed canopy, effectively controls the
growth of weeds. The management of the field at the early stages of establishment
consists of frequent weeding, which turns into occasional brushing once the
cocoa canopy is closed. The weed biomass is left to augment the mulch on the
floor, which decomposes to enhance soil organic matter content.
The current practice of
proka
in this land-use stage, as in others, consists of an
initial land clearing followed by the burning of the biomass. This reduces the tree
density and permits the recent introduction of the light-demanding maize as an
intercrop in addition to food crops. The field is, therefore, deprived of the benefits
of the biomass at the establishment stage. With the intervention of cocoa extension
by the Ministry of Food and Agriculture (MOFA), line planting of raised cocoa
seedlings is increasingly replacing seeding at stake. This, according to the PLEC
collaborating farmers, reduces wastage of planting material and facilitates weeding
and systematic spraying to control pests and diseases in the cocoa plantation.
Annual cropping
Annual cropping is a land-use stage often practised in fields with short fallow
periods. At the PLEC sites in central Ghana, the fallow vegetation often consists
of
Chromolaena odorata
,
Panicum maximum
,
Aspilia africana
,
Sida acuta
,
Griffonia simplicifolia
, other herbaceous plants, and shrubs.
Generally land preparation consists of total land clearance and burning of the
biomass followed by planting on the flat, mounds, or ridges. However, because of
the short fallow period, biomass regrowth is limited. This has made it possible for a
few of the PLEC farmers to practise
proka
in this land-use stage with maize/cassava
intercrop as the sole field type. Land management after the initial establishment
consists of weeding as and when necessary, leaving the weed biomass in place to rot.
In most cases no mineral or organic fertilizer is applied. The maize is harvested
within three months. Thereafter the cassava remains as the field type till its harvest.
Other field types under this land-use stage, but without
proka
, include
monocrops/maize and vegetables (tomato, okra, garden egg, pepper, and cabbage).
Among all the field types, maize/cassava intercrop is the most common.
Monocrops of vegetables are popular among younger farmers who practise market
gardening for the nearby urban market in the city of Kumasi. The vegetables are
often cultivated in valley bottoms with or without the application of mineral or
organic fertilizers. Supplementary irrigation cultivation of vegetables is often char-
acterized by indiscriminate use of pesticides.
