BULLETINS OF THE U. S. DEPARTMENT OF AGRICULTURE. 



THE CHEMISTRY OF PEACH YELLOWS. 



BY EEWIN F. SMITH, SC. D., WASHINGTON, D. C. 



[Reprinted from the Proceedings of the American Pomological Society for 1891. J 



Two years ago, at the Ocala meeting, a paper on this subject was read 

 by title, and published in the proceedings of this society. Since then, 

 some new light has been shed on the peach yellows problem. This, 

 therefore, seems a fitting occasion for supplementing what was written at 

 that time. 



Those who are familiar with the question will remember that some of the 

 earlier analyses indicated a diminished quantity of K 2 0, and P 2 O s , in peach 

 branches diseased by yellows. It was only a step, albeit a rather long- 

 one, from this fact, or supposed fact, to the conclusion, that a deficiency or 

 absence of these substances in the orchard soil was a leading cause, if not 

 the only cause, of this disease. Following these analyses, and based upon 

 this theory, came a series of feeding experiments, by Dr. Charles A. 

 Goessman, then chemist of the Massachusetts Agricultural college, and 

 now director of the state experiment station, assisted by Professor S. T. 

 Maynard of the same school. These experiments were repeated and 

 extended by Professor D. P. Penhallow at the Houghton Farm experiment 

 station in New York. In both series of experiments the endeavor was to 

 add to the soil the substances supposed to be absent or deficient, particu- 

 larly K 2 O and P 2 5 , thus curing the affected trees, and preventing the 

 further progress of the disease. 



The published statements from Amherst and Houghton Farm agreed 

 substantially and lead the public to believe that the end had been accom- 

 plished, and that liberal doses of muriate of potash and superphosphates, 

 with slight addition of other substances, such as kieserite, supposed to 

 render the muriate more effective, were all that was required to cure 

 peach pellows and to keep the orchards in a healthy condition. These 

 statements were copied widely by the agricultural papers and received the 

 endorsement of several writers on horticulture, particularly A. S. Fuller, 

 J. H. Hale, and Eli Minch. 



These views were vigorously combatted by practical men equally eminent 

 in horticultural science, and the war of words ran high. The horticultural 



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