WATER IN SOILS 



19 



In an experiment with five species of plants growing in 

 six different soils, the plants were allowed to wilt excessively 

 under very dry conditions for two consecutive days. The 

 amount of water in each soil was determined at the time of 

 wilting and at the close of the second day of wilting. Tha 

 average of the results from five species is as follows: 



Water in Wilting Plants arid in the Soils. 



The plants used were Helianthus annuus^ a cultivated va- 

 riety, Hordeum vulgare, Phaseolus vulgaris, Ricinus communis, 

 and Zea mays. Although the limit of non -available water 

 was not quite reached by these plants, the amount of water 

 that they were getting was below the amount requisite for 

 growth. If we arrange the soils in order of the per cents of 

 water they contained at the time of wilting the series is as 

 follows: saline, humus, loam, loess, clay, and sand, the 

 last being the lowest. 



The following table gives the average amount of physio- 

 logical water used by the plants, and evaporated from the 

 soil during the period of drought, and the corresponding 

 loss of water from the tissues of the plant : 



Water Loss in Plants and Soil during Drought. 



