Land evaluation – towards a revised framework
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compiled in different rainfall periods. Other inputs include detailed information about
soil conditions and crop management systems. A statistical analysis identifies different
potential yield levels that could be achieved by different crop production systems. The
75 percent quartile yield represents potential yield levels that would be exceeded in
three-fourths of all years. This yield level therefore can be considered as a dependable
yield. The model has been validated for the five main crops in Botswana (maize, millet,
sorghum, groundnuts and cowpeas).
The model combines physical and socio-economic parameters in the calculation
of potential yield levels. In addition to information about physical parameters or
land characteristics in FAO terminology, a number of management-related variables
reflecting the socio-economic conditions of the farmer are included:
date of ploughing,
date of planting, number of planting opportunities used, date of weeding and percentage
weed cover.
The management variables can be adjusted to reflect differences in farmers’ socio-
economic conditions, such as the availability of household labour, draught power, tools
and
fertilizer, income levels, non-agricultural incomes, livestock-crop interactions, etc.
This facility makes CYSLAMB a flexible tool that can model crop production based
on physical and socio-economic conditions at several levels, ranging from village to
district and national scale. The results can serve as input to gross-margin calculations
to compare the performance of a range of alternative production systems and thereby
assist decision-makers in their choice between different land use options.
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