WATER OF SOIL IN ITS RELATION TO PLANTS 255 



the vegetative parts. As available water increases this 

 dry matter ascends until a maximum is reached. The 

 general relationships are well exemplified by data from 



/6 



L 

 1 



I* 



r 



 



so eo 30 4o so 6om. fi a O 



Fig. 40. — The effect of increased water supply on the production of 

 dry matter by various crops. 



Widtsoe, 1 tabulated on the following page, although 

 other equally valuable figures may be obtained from Von 

 Seelhorst 2 and Atterberg. 2 The curves above (Fig. 40) 

 illustrate Widtsoe's data and the general trend in the 

 dry matter produced as the moisture is increased. 



1 Widtsoe, J. A. The Production of Dry Matter with Dif- 

 ferent Quantities of Irrigation Water. Utah Agr. Exp. Sta., 

 Bui. 116, pp. 19-25. 1912. 



2 Seelhorst, C. von, und Krzymowski, Dr. Versuch iiber 

 den Einfluss, welchen das W T asser in dem Versehiedenem Vegeta- 

 tionsstadien des Hafers auf sein Wachstum ausiibt. Jour. f. 

 Landw., Band 53, Seite 357-370. 1905. Also, Atterberg, A. 

 Die Variationen der Nahrstoffgehalte bei dem Hafer. Jour. f. 

 Landw., Band 49, Seite 97-113. 1901. 



