ix-x. Agronomic and biophysical research programme

Land evaluation – towards a revised framework
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In this stage, confrontation with the local knowledge on the natural resources is 
essential, so the need arises for participatory methods for land resource analysis and 
for methods and guidelines for integration of participatory methods and biophysical 
survey. Land users might also possess valuable knowledge on land use requirements 
and limitations. Over time they may have developed their own local land suitability 
classes.
Research loop R1 was introduced by Young (1985 ). An important implication is 
that it takes at least two to three years even for annual cropping systems, and thus 
prevents the immediate completion of the evaluation. A realistic way to overcome this 
problem, according to Young (1985), is:
¾Complete the evaluation, using best available estimates of performance where 
knowledge is insufficient;
¾Note those land utilization types that have potential for improvement through 
research and also those for which performance data are relatively uncertain;
¾Set up a programme of research into the improvement of land utilization types 
and assessment of their performance. Results from this research will be fed into 
the land use planning process in due course.
The dual function of the research may be noted. First, it seeks to improve and 
optimize land utilization types, e.g. through selection of crop and tree varieties, 
fertilizers or other aspects of management. Secondly, it determines the performance of 
the improved systems, thus providing data for revision of the land evaluation.
Research loop R2 is related to biophysical research activities. Information collected 
in the land resource survey feeds other disciplines. An example of a specialized 
study might be carbon sequestration assessment in soils. The assessment of carbon 
sequestration involves two phases: measurement of soil carbon stocks and evaluation of 
changes in carbon storage. Total organic carbon has to be determined at different depths 
or for one or more horizons, and these data should be transformed into mass of soil 
organic carbon per unit land area, taking into account the bulk density and stoniness 
of the soil. The data are then stratified by soil and terrain unit and extrapolated using 
digitized soil and terrain maps and land-use information (FAO 2001). Changes in 
carbon storage are estimated on the basis of historical examples and models.
Research activities related to local knowledge on the biophysical environment such 
as soil resources and water conservation also fit in research loop R2.

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