168 MAINE STATE COLLEGE. 



All who have given especial attention to the subject of plant 

 nutrition will, undoubtedly, agree that the foraging powers of 

 plants for the elements contained in the ash, vary greatly. This 

 fact is recognized by the majority of observing farmers, as is 

 shown by the following common sayings : "Wheat requires a rich 

 soil." "Corn is a gross feeder." "Oats are an exhaustive crop." 



Notwithstanding that these views regarding the variation in 

 foraging powers of different crops have been held by many for 

 years, no one is prepared to say just how it is exerted. We are 

 hardly ready to express an opinion whether the greater vigor of 

 certain plants as compared to other species grown on the same soil 

 is due to their superior foraging powers for all of the elements con- 

 tained in their ash, or for one or more particular elements. 



It seems quite as likely, however, that some plants are able to 

 use certain soil compounds of potash or phosphoric acid, which 

 are not available to other plants, as it did that the legumes were 

 able to obtain nitrogen from sources that were not available to the 

 grasses. 



Believing that a study of the foraging powers of different agri- 

 cultural plants would reveal facts of scientific interest, and at the 

 same time of practical value to agriculture, the writer commenced 

 a series of experiments, in the fall of 1892, designed to test the 

 readiness with which different plants obtain their phosphoric acid 

 from insoluble phosphates. 



The reason why phosphoric acid was selected on which to make 

 these first studies, in preference to any other substance was, that 

 in practical manuring with crude phosphates, and also in their use 

 in experimental work, different crops had apparently showed 

 decided differences in their abilities to gather phosphoric acid from 

 such a source. 



EXPERIMENTAL METHODS. 



In order to have the work as much as possible under control the 

 experiments were conducted in boxes in the college forcing house. 

 These boxes were of wood, fifteen inches square and twelve inches 

 deep. For soil a fine sand was used, taken from a sand bank 

 about three feet below the surface. This sand was drawn to the 

 forcing house, screened and thoroughly mixed by repeatedly shov- 

 eling it over, after which a sample was taken and the contents of 

 potash and phosphoric acid determined, with the following result : 

 Potash, 0.096 ; phosphoric acid, 0.012 per cent. 



