WATER OF SOIL IN ITS RELATION TO PLANTS 189 



Table XXXIV 



WATER REQUIREMENTS OF PLANTS AS DETERMINED BY DIFFER- 

 ENT INVESTIGATORS. 



1 Lawes, J. B., Experimental Investigation into the Amount of Water 

 Given off by Plants during their Growth; Jour. Hort. Soc, London, 

 Vol. 5, pp. 38-63, 1850. Pots holding 42 pounds of field soil were used. 

 Evaporation from soil was reduced to a very low degree by perforated 

 glass covers cemented on the pots. The figures quoted are from un- 

 fertilized soil. 



8 Wollny, E., Der Einfluss der Pflamendecke und Beschattung auf die 

 Physikalischen Eigenschaften und die Fruchtbarkeit des Bodens, Seite 

 125; Berlin, 1877. Wollny grew plants in sand in amounts ranging 

 from 5 to 12 kilograms. Evaporation was reduced to a very low 

 degree by perforated covers. Actual evaporation from uncropped cans 

 was observed, however. 



3 Hellriegel, H., Beitrage zur den Naturwissensehaftlichen Grundlagen 

 des Ackerbaus, Seite 663; Braunschweig, 1883. Hellriegel grew plants 

 in 4 kilograms of clean quartz sand and supplied them with nutrient 

 solutions. The loss by evaporation from uncropped pots was used in 

 determining losses by transpiration. In later experiments covers were 

 used in order to cut down evaporation. 



4 King, F. H., Physics of Agriculture, p. 139; published by author, 

 Madison, Wis., 1910. Also, The Number of Inches of Water Required 

 for a Ton of Dry Matter in Wisconsin; Wis. Agr. Exp. Sta., 11th Ann. 

 Rep., pp. 240-248, 1894; and The Importance of the Right Amount and 

 Right Distribution of Water in Crop Production; Wis. Agr. Exp. Sta., 



