554 VARIOUS FERTILITY FACTORS 



In October, 1908, Max Wagner reported 1 a similar very ex- 

 tended investigation with barley, oats, mustard, and buckwheat, 

 with various systems of fertilizing. With the barley and oats 

 more or less loss of plant food occurred before the crops reached 

 maturity, but in most cases phosphorus proved an exception to 

 the rule wherever the crops were grown without the addition of 

 a phosphorus fertilizer. 



After suggesting and rejecting the possibility of explaining the 

 loss of plant food (a) by loss of leaves or roots in harvesting the 

 plants, (b) by the decay of root parts, and (c) by volatilization 

 (except for nitrogen) , Wagner concludes that the only possible ex- 

 planation is " that during the ripening processes of the plant, a part 

 of the nutrient materials passes into the roots and from the roots 

 out into the soil." ("Fur Kali und Phosphorsaure, die ja durch 

 Veratmung nicht verloren gehen konnen bleibt nur dieMoglichkeit 

 iibrig, dass ein Teil dieser Nahrstoffe wahrend des Reifeprozesses 

 der Pflanzen in die Wurzel zuriickgewandert und aus den Wurzeln 

 zuriick in den Kulturboden getreten ist.") 



In studying the composition of solutions used for spraying, 

 Le Clerc and Breazeale of the United States Bureau of Plant 

 Industry found material in the liquid other than that put in the 

 prepared solution, and upon further investigation they deter- 

 mined with certainty that relatively large quantities of essential 

 plant-food elements may be removed from growing plants by 

 spraying with pure water, by a process similar to the action of 

 falling rain. 



On November 18, 1908, a summary of these experiments was 

 presented to the Washington meeting of the American Society of 

 Agronomy, by Doctor Le Clerc. By collecting and analyzing the 

 water used for spraying the plants and analyzing the fully mature 

 plants, it was found that of the total amounts contained in the 

 plants, the following percentages were leached out by pure water 

 (according to the author's unverified notes, taken during Doctor 

 Le Clerc's lecture) : 



In these experiments nitrogen appears to have been the limiting 

 element in plant growth, since practically all that was taken up 

 of that element was evidently required in the plant structure, 



1 Die Land-wins chafttichen Versuchs-Stationen (1908) 69, 161-233. 



