bushels ; and that when 195 lbs. of sulphate of ammonia were re- 

 placed by 345 lbs. of muriate of potash the increase was 4s 

 bushels. 



The three groups show that the greatest yield comes from 

 phosphoric acid and potash, (Plot 3) ; the next best from nitro- 

 gen and potash, (Plot 5) ; the next from phosphoric acid alone, 

 (Plot 20), and from potash alone, (Plot 19) ; the next from phos- 

 phoric acid and nitrogen, (Plot 4) ; and the poorest from nitro- 

 gen alone, (Plot 18). 



(Series 3.) complete chemicals. 

 In this series three elements of plant food are combined in 

 rarious ways, the object being to form some idea of the " crop 

 ration " best suited to the conditions of this soil for the potato 

 crop ; to this end the method suggested in Bulletin No. 6 of this 

 Station, p. 15, was practiced, and in plots 2, 9, 10, 13, 15, and 

 «6, we have combinations of the three fertilizing chemicals which 

 cost the same per acre, but which differ very materially in the 

 proportion of their parts as the per cent of phosphoric acid, pot- 

 ash and nitrogen, given in Table 1, will show. 



Group (e) differs from (a*) by decreasing the per cent of 

 phosphoric acid and increasing the per cent of potash. So far 

 as the average is concerned the yield was slightly decreased by the 

 exchange, but it will be observed that there is a wide difference 

 in the yield of the plots ro and 13. The cause of this is un- 

 known to me, and while I feel sure that there was some local 

 circumstance which seriously affected plot 13, yet I have aver- 

 aged it with its dunlicate. As a matter of fact, however, I have 

 no doubt but that the yield from group (e) should have been 

 much nearer that of plot 10. 



On Plot 16, however, where still further reduction of phos- 



*P 2 05 means phosphoric acid; K 2 means potash; N 

 means nitrogen. 



9 



