Environmental Engineering Reference
In-Depth Information
Crop yield assessment
Yield has been defined as the amount of product available and useful for
collection or harvest at a given point in time, i.e. that which can be used com-
mercially (FAO, 2001). It can also be interpreted as the total biological poten-
tial of a species. Traditional assessment of yield is dependent on the type
of crop. In the case of fruits, the assessment is based on fruit colour, and
cutting and tasting of the fruit. In the case of other crops such as plantain,
cassava, cocoyam, and maize, it is dependent on the type of crop variety and
maturation period.
Maturation period
Table 3.4 summarizes how communities assess maturity of crops locally. This
knowledge, combined with physical characteristics such as size and colour, is
used to determine yield per crop. Total crop yield estimation is speculative. By
contrast, the scientific approach uses a variety of methods for yield assessment.
Some of them are indicated in Table 3.5.
Species diversity
Farmers' assessment of species diversity is based on three parameters, namely
leaf type, colour of the tree stem, and branching of the tree.
Yield/maturity assessment
Farmers contend that no two trees have the same type of leaves, colour of
the tree stem, and branching of the tree. On the other hand evenness of
species is determined by counting species in various farms or, alternatively, by
the amount of fuelwood collected by the farmer. The scientific method of
measuring richness and diversity, e.g. that by Shannon-Weaver (1949) and
Simpson (1949), is more systematic.
Table 3.4 Indicators used traditionally by communities to assess maturity of crops
Food crop
Indicator
Plantain
Tip of the finger becomes black, and/or browning of leaves around the
pseudostem
Cassava
Cracking of the soil beneath and around the base of the stem/the
bulging of the tubers
Maize
Development of black layer of the maize caryopsis or browning of
the silk
Cocoyam
Browning of the leaves
