28 EXrERlMENT STATION. [Jan. 



CoMPAKisox OF J)iffej;e.\t riiosniATEs. 

 This is the sixteenth year of the experiment, the |)hin and 

 ohjeet of ^\■hi<•h is (juoted from the twentv-third annual re- 

 port : — 



Ten of the leading- materials whicli may be used as a source of phos- 

 jihoric acid have been under comparison in one of our fields since 1(S97. 

 The ditTerent materials are ai)plied to the sejiarate plots in such quan- 

 tities as to furnish equal amounts of actual phosphoric acid to each. 

 There are three check plots to wliich no phosphate whatever has been 

 applied during the entire period of the experiment. All the plots receive 

 annually equal and liberal quantities of materials supplying nitrogen 

 and potash in highly available forms. The field has been used for a 

 large variety of crops, the succession having been as follows: corn, 

 cabbages, corn, oats and Hungarian grass (followed by rye plowed 

 under), onions, onions, corn, mixed grass and clover three years, cab- 

 bages and soy beans and potatoes. 



In view of the fact that the results of similar experiments 

 (comparison of different materials as sources of ])hos})]ioric 

 acid) in other States have not shown the marked differences 

 between the ground rock phosphates and the more soluble 

 phosphates that our results show, and in view of the fact that 

 the hnnius content of the different soils is claimed by some 

 authorities to be the cause of the differences in the showing of 

 the rock phosphates, it has been our aim in the treatment of 

 the field for the last few years to get as much humus into the 

 soil as possible. 



In 1011 the field was seeded in IMay with oats and alfalfa. 

 Two crops were harvested, one in July and one in September. 

 In 1012 the field was plowed and Japanese Buckwheat sown, 

 which was jdowed under in Jidy. In August rye was sown, 

 to be plowed under in the spring. 



