1892.] PUBLIC ^DOCUMENT — No. 33. 173 



in that state, to study the effect of an entire exclusion of 

 nitrogen-containing manurial substances on the crop under 

 cultivation, while the remaining ones received as before a 

 definite amount of nitrogen in the same form in which they 

 had received it in preceding years : namely, either as sodium 

 nitrate or as ammonium sulphate, or as organic nitrogenous 

 matter in form of dried blood. A corresponding amount of 

 available nitrogen was applied in all these cases. 



Aside from the difference regarding the nitrogen supply, 

 all plats were treated alike. They each received without an 

 exception a corresponding amount of available phosphoric 

 acid and of potassium oxide. The phosphoric acid was sup- 

 plied, in form of dissolved bone-black, and the potassium 

 oxide either in form of muriate of potash or of potash-mag- 

 nesia sulphate. From 120 to 130 pounds of potassium 

 oxide, from 80 to 85 pounds of available phosphoric acid 

 and from 40 to 50 pounds of available nitrogen were supplied 

 per acre. 



One plat marked received its main supply of phosphoric 

 acid, potassium oxide and nitrogen in form of barn-yard 

 manure ; the latter was carefully analyzed before being 

 applied, to determine the amount required to secure, as far 

 as practicable, the desired corresponding proportion of 

 essential fertilizing constituents. The deficiency in potas- 

 sium oxide and phosphoric acid was supplied by potash- 

 magnesia sulphate and dissolved bone-black. The fertilizer 

 for this plat consisted of 800 pounds of barn-yard manure, 

 32 pounds of potash-magnesia sulphate and 18 pounds of 

 dissolved bone-black. * 



The mechanical preparation of the soil, the incorporation 

 of the manurial substances, — the general character of the 

 latter being the same, — the seeding, cultivating and harvest- 

 ing were carried on year after year in a like manner, and as 

 far as practicable on the same day in case of every plat 

 during the same year. 



This course in the general management of the experiment 

 has been followed thus far forthree successive years — 1889, 

 1890 and 1891 — in connection with different crops : — 



Corn (maize), in 1889 (see seventh annual report) ; oats, 



