128 HATCH EXPERIMENT STATION. [Jan. 



regarding the best course to be adopted to determine the 

 available phosphoric acid ; in this work the writer has taken 

 some part. A compilation of the contributions to these 

 more recent experiments is to l^e i)ublished soon by the 

 United States Department of Agriculture. 



Our local observations at Amherst are briefly described in 

 a few subsequent pages upon a field which had been under 

 careful observation for five years, 1890-95. The following 

 brief abstract of the management of the field work shows the 

 condition of the soil which served for our investigation : — 



Field F. 



The field selected for this purpose is 300 feet long and 

 137 feet wide, running on a level from east to west. Pre- 

 vious to 1887 it was used as a meadow, which was well 

 worn out at that time, yielding but a scanty crop of Eng- 

 lish hay. During the autumn of 1887 the sod was turned 

 under and left in that state over winter. It was decided to 

 prepare the field for special experiments with phosphoric 

 acid by a systematic exhaustion of its inherent resources of 

 plant food. For this reason no manurial matter of any de- 

 scription was applied during the years 1887, 1888 and 1889. 



The soil, a fair sandy loam, was carefully prepared every 

 year by ploughing during the fall and in the spring, to 

 improve its mechanical condition to the full extent of exist- 

 ing circumstances. During the same period a crop was 

 raised every year. These crops were selected, as far as 

 practicable, with a view to exhaust the supply of phosphoric 

 acid in particular. Corn, Hungarian grass and leguminous 

 crops (cow-pea, vetch and serradella) followed each other 

 in the order stated. 



'1890. — The field was subdivided into five plats, running 

 from east to west, each twenty-one feet wide, with a space 

 of eight feet between adjoining plats. 



The manurial material applied to each of these five plats 

 contained, in every instance, the same form and the same 

 quantity of potassium oxide and of nitrogen, while the 

 phosphoric acid was furnished in each case in the form 

 of a different commercial phosphoric-acid-containing article, 



