WATEB 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 



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Fig. 4(1. — The effect of increased water supply on the production of 



dry matter by various crops. 



Widtsoe/ tabulated on the following page, although 

 other equally valuable figures may be obtained from Von 

 Seelhorst ^ and Atterberg.^ 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., 

 BuL 116, pp. 19-25. 1912. 



2 Seelhorst, C. von, und Krzymowski, Dr. Versueh xiber 

 den Einfiuss, welclien das Wasser in dem Versohiedenem Vegeta- 

 tionsstadien des Hafers auf sein Wachstum ausubt. 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. 



