18!)7.j PUBLIC DOCUMENT — No. 33. 173 



deservedly of late engaged the most careful attention of 

 agricultural investigators. 



The systematic treatment of the field here under consider- 

 ation (Field A), as far as suitable modes of cultivation and 

 of manuring are concerned, was introduced during the season 

 of 1883 to 1884. 



The subdivision of the entire area into eleven plats ' ' one- 

 tenth of an acre each," of a uniform size and shape, 132 feet 

 long and 33 feet wide, with an unoccupied and unmanured 

 space of 5 feet in width between adjoining plats, has been 

 retained unaltered since 1884. 



A detailed statement of the temporary aim and general 

 management of the experiments, as well as of the results 

 obtained in that connection from year to year, forms a 

 prominent part of my contemporary printed annual reports, 

 to which I have to refer for further details, 1884-96. 



Our observations upon Field A are divided into three 

 periods : — 



(a) Study of the existing soil resources of plant food, 

 1884 to 1889. 



(b) Study of the eflect of excluding nitrogen plant food 

 from outside sources and of adding nitrogen plant food in 

 various available forms, 1889 to 1892. 



(c) Studying the eflect of the cultivation of leguminous 

 crops on the resources of available nitrogen plant food in 

 the soil under treatment, 1892 to 1897. 



The first four years of the stated period 1884 to 1889 

 were principally devoted to an investigation into the general 

 character and condition of the soil under cultivation as tar 

 as its natural and inherent resources of available phosphoric 

 acid, nitrogen and potash were concerned. 



The soil proved to be in particular deficient in potash. 

 Diflerent varieties of corn (maize) were raised in succession 

 to assist in the investigation. 



Since 1889 the main object of observation upon the same 

 field has been to study the influence of an entire exclusion 

 of any additional nitrogen-containing manurial substance 

 from the soil under cultivation, as well as of a definite addi- 

 tional suppl}" of nitrogen in different forms of combination 

 on the character and yield of the crop selected for the trial. 



