14 HATCH EXPERIMENT STATION. [Jan. 



Natural Phosphates compared with Each Other and 

 WITH Acid Phosphate. (Field F.) 



This series of experiments was begun by Dr. Goessmann 

 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. A full account 

 of the experiment and the results obtained up to the end of 

 1896 is given by Dr. Goessmann in our ninth annual report. 

 It is only necessary to restate the following points : — 



The field was at first divided into five plots, containing 

 about 6,600 square feet each. These plots received equal 

 money's worth (on the basis of prices in 1890) of the phos- 

 phates used, as follows: Plot 1, phosphatic slag; Plot 2, 

 Mona guano ; Plot 3, at first, apatite; later, Florida phos- 

 phate ; Plot 4, South Carolina phosphate ; Plot 5, dissolved 

 bone-black. Plot 3, as above stated, received an applica- 

 tion of ground apatite in 1890. In 1891 it was found im- 

 possible to obtain this material, and no phosphate of any 

 kind was applied to this 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 application of nitrate of soda and potash-magnesia 

 sulphate. The quantities of these applied per plot during 

 the first four years were about 44 pounds of the former and 

 6Q pounds of the latter.* 



Since 1894 no phosphate of any kind has been applied 

 to these plots, but the quantity of nitrate of soda and of 

 potash-magnesia sulphate has been used in one-half greater 

 quantities. 



At first Dr. Goessmann included no plot on which phos- 

 phate was not used for comparison with others. Later such 

 a plot was added, but it was left entirely unmanured until 

 189j6. Durino; 1896 and 1897 it has received the nitrate of 



* The plots in this experiment differ from each other by a few square feet in size, 

 and the fertilizers have from the beginning varied in proportion as the size varied. 



