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SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Katem area: 20 persons/km 2 , regeneration; Sibil valley: 30 persons/km 2 , regeneration, but 
almost the whole area is in rotation. This has caused an equilibrium; Ajamaru, around the 
lakes: 35 persons/km 2 , over-cultivation, no regeneration. It seems that 30 persons/km 2 is 
about the limit, although the soil and other factors will play an important part. 
Mr. C. E. Olson (U.S.A.) asked whether the soils in New Guinea are commonly podsolic. 
Mr. Reynders answered that they are only podsolic under special conditions of microclimate, 
soil texture, organic matter, moisture, parent material etc. 
Mr. L. G. Curtis (U.K.) asked whether there was an improvement of the physical characteris 
tics (soil structure) after the soils were left for a period of time. Mr. Reynders answered that 
the physical characteristics were not examined during the cropping period. The first month 
after clearing the garden the soil becomes drier, gets a better crumb structure and it is easier 
to cultivate than the soil in the original forest. 
Mr. Sombroek (Neth.) asked whether the first sampling was done before or immediately after 
the clearing or burning of the forest. Mr. Reynders answered that the influence of burning 
plays no part in the analysis. The soil samples were taken from the A-l horizon, after the A-0 
horizon had been removed.