98 AGRICULTURAL EXPERIMENT STATION. [Jan. 



essential articles of plant food, or to that of any particular 

 one of them. 



As the cultivation of grasses and fodder corn aifects the 

 manurial resources of the soil in a similar direction, by 

 abstracting approximately one part of phosphoric acid to 

 four parts of potash, it seemed but natural that a soil which 

 originally did not contain much more of available potash 

 than of available phosphoric acid must become unproductive, 

 as far as these crops are concerned, before the latter is 

 exhausted. It is not less evident that a system of manuring, 

 devised with reference to this circumstance alone, can pre- 

 vent an early decline of remunerative crops in the majority 

 of cases. 



The recognized importance of both — grasses and fodder 

 corn — in our present system of general farm management 

 has served as the principal inducement to begin our field 

 experiments at the Experiment Station with a practical illus- 

 tration of the particular serious changes which a close rota- 

 tion of these crops produces in the existing soil resources of 

 plant food, wherever the adopted system of manuring does 

 not provide for a periodical return of fertilizing substances, 

 with reference to the kind and to the amount of each of them 

 carried off ))y the crop. 



The land set apart for the experiment consists of ten 

 adjoining plats, one-tenth of an acre each in size. The plats 

 are five feet apart ; the grounds between them are kept free 

 from any growth, and receive no fertilizing ingredients of 

 any description. The entire field is surrounded by a tile 

 drain, and each plat has a separate one through its centre. 

 This terminates at its east end in a well, which is connected 

 with the surroundino: drain. 



The systematic treatment of the various plats began in 

 May, 1885. All were ploughed, year after year, at the 

 same time and in the same manner, — in autumn after har- 

 vesting and in spring before manuring and planting. Plats 

 1, 3, 5, 7, 9 and 10 received annually for three succeeding 

 years, 1885, 1886 and 1887, an addition of a definite amount 

 of either phosphoric acid or of a nitrogen compound or of a 

 potash compound ; while plats 2, 4, 6 and 8 received no 



