86 RESULTS WITH GRASS 



permanent value as a manure, unless phosphates and alkalies 

 were supplied with them. 



The best return from the application of ammonia salts to 

 the grass is that given by plot 13. Here the same quantities 

 of manure are applied as on plot 9, and in addition 2,000 Ibs. 

 of chopped wheat straw per acre. The average produce of the 

 first twenty years is 57^5 cwts, and of the second twenty years 

 69*9 cwts. of hay. Thus, including the second crop, the manure 

 gives an annual increase of 44*1 cwts. of hay over that given 

 by the unmanured plot. The quality of the hay has been 

 much superior to that on plot 9. 



Return for Ammonia applied. There are great diffi- 

 culties in expressing by figures the return given by ammonia 

 salts in these grass experiments. We can calculate the return 

 on the inferior plots, but materials are wanting for a calculation 

 of the return obtained on such plots as 9 and 13. 



When ammonia salts are applied alone, we have in the first 

 ten years an increase over the unmanured plot of 8 cwts. of 

 hay, which is at the rate of 2-2 cwts. of hay for i cwt. of sulphate 

 of ammonia applied. As the experiment progresses even this 

 small return entirely disappears. 



When the ammonia salts are applied with superphosphate, 

 the increase over the crop given by superphosphate alone 

 represents a return of 2-8 cwts. of hay for i cwt. of sulphate 

 of ammonia during the first twenty years of the experiment, 

 and a return of 3*6 cwts. of hay during the second twenty years, 

 when the second crop of hay is included. 



When we come to the much larger crop obtained when 

 ammonia salts are used with alkalies and superphosphate 

 we are no longer able to calculate satisfactorily the return given 

 by the ammonia. We cannot deduct the produce of plot 7 

 from that of plot 9 to obtain the wished for result, because, as 

 we have already seen, the produce on plot 7 is not the produce 

 of cinereal manures alone, but the produce of cinereal manures 

 plus nitrogen obtained from the air. On plot 9 there is no 

 corresponding assimilation of atmospheric nitrogen, as there 

 are no clovers or vetches on this plot. The nearest result to 

 the truth we can obtain is got by taking the produce by 



