MODEL TESTS OF VAPOUR MOVEMENT IN SOIL 8i 



test plants and controls wilted (e.g. Fig. 4), the wilting percentage in the 

 control soils was higher than in the test containers, i.e. the soil could be 

 dried out much more within the test containers before the plants began to 

 wilt. It may be supposed that the roots or root hairs of the test plants are 

 points of condensation for the ascending water vapour, which in this way- 

 need not be bound to the soil colloids, but is at once made available to the 

 plants. Trenel (1950) believes that vapour will be taken up 'in statu nascendi' 

 of condensation by the roots. 



Trenel (1949, 1950), citing papers of other authors, in particular Lebedeff 

 (U.S.S.R.), Kekkonen (Finland), Beskow (Sweden), Chaptal (France)- 

 Literature, see Trenel, 1949, summarised by Trenel et ah, 1958 -pointed 

 out that vapour movement and condensation in soil may even affect the 

 ground water level. Water is supposed to move from subsoil to topsoil in 

 winter, in the opposite direction in summer. Keilhack (19 12) considers 

 vapour condensation in soil to be responsible for the fact that the ground 

 water level may rise if gloomy weather with high air humidity has pre- 

 vailed for a long period without precipitation. In the end, the drained 

 water volume of a certain catchment area may be greater than the total 

 amount of precipitation. In 1888 a total precipitation of 762,300 m^ was 

 registered for the area of the Remscheid dam (Germany) compared with a 

 total drain of 800,630 m^. It must be doubted that this surplus of nearly 

 40,000 m^ was only due to vapour condensation in soil, nevertheless this 

 kind of water translocation seems to be of greater ecological importance 

 than hitherto considered. 



This opinion is supported by observations recently made at different 

 field stations by the MeHoration Department of the Agricultural Faculty, 

 University of Rostock* (E. Germany). Measurements conducted there over 

 several years, on different soil types below different crops, showed that 

 soil moisture was usually higher than expectations, calculated from the 

 amount of precipitation. 



Most importance, however, must be attributed to water movement due 

 to temperature gradients in winter. The ice shield within the frozen soil 

 surface is steadily increasing by condensation and freezing of water vapour 

 ascending from deeper layers in the soil. The result is a considerably higher 

 humidity in soil being available to the crops in spring. 



From the results of our model tests it may be summarised that vapour 

 movement and condensation in soil due to temperature gradients may be of 

 considerable ecological importance under suitable conditions. A rough 



* The authors are indebted to Prof. Dr. M. Olberts, Institut iir Meliorationswesen 

 der Universitat, Rostok, for kindly supplying this information. 



