196 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
In dem Vortrag werden enige Beispiele gegeben werden, bei denen verschiedene externe 
Faktoren ausschlaggebend sind für eine lohnende Urbarmachung bestimmter Gebiete. 
The picture of the agricultural land use in the third quarter of the 20th 
century is one of all easily reclaimable soils already in more or less intensive 
use. Probably only a few exceptions can be made to this. The soils not in agri 
cultural use at the moment can be divided roughly into two groups: 
1. Soils of such low (potential) quality, that it is economically impossible to 
reclaim them. 
2. Soils with potentialities for development, but with such difficult attendant 
technical aspects, that the local or regional community is unable to tackle 
the problems. 
To meet the increasing requirements for food and industrial crops, it is 
necessary to reclaim land. In development projects, because all “easily reclaim- 
able soils” are already in cultivation, we have to deal mainly with soils of the 
above mentioned group 2. This means that areas have to be studied, which in 
their natural state are unsuitable for agricultural production, either because they 
are too dry, or because they are too wet. In both cases a comprehensive inves 
tigation will be necessary, in order to draw up a well-balanced plan, which gives 
proper credit to the technical and economical aspects. 
Soil surveys and soil investigations play a very important role. The soil 
scientist of the investigating team has to determine the potential possibilities of 
the soil. Without considering other aspects, it can be stated that a potentially 
bad soil, with low agricultural production capacity, has to be considered as 
unsuitable for development. When we have to deal with soils with medium or 
high potentialities, economical reclamation depends on factors which are 
beyond the scope of the soil scientist. A justified conclusion on this point can 
be drawn only by intensive cooperation between the different experts of the 
investigating team. 
The external factors which have an important influence are the costs of 
drainage and the costs of irrigation. With drainage, as well as with irrigation, we 
have to deal with problems and costs of earth movement, construction of dykes, 
structures, pumping stations and so on. These costs mainly determine the econ 
omy of a project, and influence the cost-benefit ratio in an important way. 
Individual specialists are only interested in, and concerned with, the prob 
lems in their own field; important problems in other fields concerning the 
same project, they cannot evaluate. It is necessary to work with a rational 
cooperating team of experts, to consider all aspects of the development plan 
and to see all parts of the study in their correct proportions. 
Indeed it can be stated that in an agricultural development plan the soil 
investigations play a principal role. The soil scientist is able to give the location 
and differences in quality of the soils. However he is unable to evaluate all 
reclamation problems which can lead to a land classification of the soils for 
reclamation purposes. He is able to give - and he has to give - a classification 
on a purely pedological basis, indicating which soils will be more or less suitable