CHAPTER II 



RELATIONS OF SOIL TO WATER 



Water required by Crops Deposition of Dew Hygroscopic Water -^ 

 Maximum Water Capacity of Soils Optimum Proportion of Water 

 Power of retaining Water Percolation. 



To supply water to the plant is one of the proper functions 

 of the soil. A plant is not constructed with a view to its ab- 

 sorbing water by means of its leaves, or indeed by means of 

 any of its above-ground parts ; water is only absorbed from 

 dew or rain by these parts when the plant is in a wilted 

 condition. With this limited exception the whole of the 

 water required by a plant is taken up from the soil through 

 the roots. The amount of water supplied by the soil is one 

 of the most important factors in determining the luxuriance 

 of plant growth. It is seldom that there is a sufficient supply 

 of water during the whole time of the growth of a crop. In 

 localities receiving an ample amount of sunshine the supply 

 of water from the soil becomes the circumstance which more 

 than any other determines the quantity of the produce. The 

 large increase of produce which results from artificial irriga- 

 tion is well known. 



Water required by Crops. A large supply of water is 



