CHAPTER XV 



WATER REQUIREMENTS FOR PLANT GROWTH 

 Water Requirements of Plants. — It is vary evident from the 

 preceding studies that plant growth necessitates a large amount 

 of water and that the water requirements vary greatly for differ- 

 ent plants, for different parts of the same plants and for plants 

 at different se^asons of the year. It has been estimated that an 

 average of about 300 pounds of water are necessary for the pro- 

 duction of one pound of dry matter. This is an average and, 

 of course, varies for different species of plants and for plants 

 grown under different conditions. In the following table the 

 figures represent the number of pounds of water used in the pro- 

 duction of one pound of dry matter. The two columns represent 

 the results of different workers. 



Mustard 843 774 



Barley 262 274 



Oats 402 665 



Buckwheat 664 3.71 



Red clover 249 453 



Pear 235 479 



Potatoes 423 



Eye 377 



Wheat 225 359 



Bean 214 262 



Corn 233 



The variation in the figures in these two columns may be 

 accounted for by the fact that the tests were made in different 

 parts of the world and therefore the plants were subjected to 

 different temperature, humidity, soil aud other important 

 environmental factors which would influence their growth. 



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