WATER-CULTURE METHOD HOAGLAND AND ARNON 



465 



washing the seedling, he fastened it into a perforated cork, with the 

 roots dipping into the solution. The complete assembly is shown in 

 figure 1, which is a reproduction of Sachs' illustration. 



Since the publication of Sachs' standard solution formula (table 1) 

 for growing plants in water culture, many other formulas have been 

 suggested and widely used with success by many investigators in 

 different countries. Knop, who undertook water-culture experiments 

 at the same time as Sachs, proposed in 1865 a nutrient solution, which 

 became one of the most widely employed in studies of plant nutrition. 

 Other formulas for nutrient solutions have been proposed by Tollens 

 in 1882, by Schimper in 1890, by Pfeffer in 1900, by Crone in 1902, by 

 Tottingham in 1914, by Shive in 1915, by Hoagland in 1920, and 

 many others. 



Table 1. — Composition of nutrient solutions employed by early investigators x 



i These and other formulas are given in: Miller, E. C, Plant physiology, pp. 195-197, McGraw-Hill Book 

 Co., New York, N. Y., 1931. For best results, these solutions should be supplemented with boron, man- 

 ganese, zinc, copper, and molybdenum, as described in the text, p. 487, if distilled water is used in the prepa- 

 ration of the nutrient solution. 



At the very inception of the water-culture work, investigators clearly 

 recognized that there can be no one composition of a nutrient solution 

 which is always superior to every other composition, but that within 

 certain ranges of composition and total concentration, fairly wide 

 latitude exists in the nutrient solutions suitable for plant growth. 

 Thus Sachs wrote: 



I mention the quantities (of chemicals) I am accustomed to use generally in 

 water cultures, with the remark, however, that a somewhat wide margin may be 

 permitted with respect to the quantities of the individual salts and the con- 

 centration of the whole solution — it does not matter if a little more or less of the 

 one or the other salt is taken — if only the nutritive mixture is kept within certain 

 limits as to quality and quantity, which are established by experience. 



Until recently, the water-culture technique was employed exclusively 

 in small-scale, controlled laboratory experiments intended to elucidate 

 fundamental problems of plant nutrition and general physiology. 

 These experiments have led to the determination of the list of chemical 

 elements essential for plant life and have thus profoundly influenced 

 the practice of soil management and fertilization for purposes of crop 



