278 SYSTEMS OF PERMANENT AGRICULTURE 



These data show that the first two years after application the 

 acid phosphate gave about the same results as the raw phosphate, 

 but the last two crops gave better results from the raw phosphate, 

 even when compared with the original apparent difference in the 

 productive power of the two plots, a difference which may or 

 may not hold for other crops in other years. 



In commenting on these experiments, Director Jordan said 

 (Maine Report, 1894, page 31): 



"With the exception of the oat crop of 1891 the production of plot two has 

 largely exceeded that of plot three. Especially is this true of the 1894 crop 

 after the exhausting effect of three years of cropping. . . . This is certainly 

 one instance of the unmistakable persistent influence of a crude phosphate 

 in increasing the growth of a field crop." 



According to Doctor Jordan, the 20 loads of stable manure con- 

 tained 172 pounds of nitrogen, 50 pounds of phosphorus, and 146 

 pounds of potassium. 



The Massachusetts Experiment Station has reported, with the 

 following explanations, an experiment with different kinds of 

 phosphates, extending over n years, 1890 to 1900 (see 9th, loth, 

 and i3th Annual Reports) : 



"This series of experiments was begun by Doctor Goessman in 1890, with 

 a view of determining whether it is not more profitable to employ one of the 

 cheaper natural phosphates than to use the more costly acid phosphate." 



"The field was first divided into five plots, containing about 6600 square feet 

 each. These plots received equal money's worth (on the basis of prices in 1890) 

 of the phosphates used, as follows: 



Plot i. Phosphatic slag. 



Plot 2. Mona guano. 



Plot 3. Apatite at first; later Florida phosphate. 



Plot 4. South Carolina phosphate. 



Plot 5. Dissolved bone black. 



"Plot 3, as above stated, received an application of ground apatite in 1890. 

 In 1891 it was found impossible to obtain this material, and no phosphate of 

 any kind was applied to the plot. In 1892 and 1893 ground hard Florida 

 phosphate was applied to this plot. It is not believed, however, that it is fair 

 to this phosphate to compare it with the others, since it has been used only 

 two years, while the others have been applied for four years. 



"From the beginning, each of these five plots has received the same applica- 

 tion of nitrate of soda and potash-magnesia sulfate. The quantities of these 

 applied per plot during the first four years were about 44 pounds of the former 

 and 66 pounds of the latter. 



