Early Experiments on Wheat at Rodmersham. 15 



Generally, the results obtained during the four years that 

 the manures were applied showed that mineral manures 

 increased the wheat crop but little, ammonia- salts much 

 more, mineral manures and ammonia-salts used together 

 more than either, or both, used separately; that Peruvian 

 guano, containing both mineral and nitrogenous constituents, 

 gave a considerable amount of increase, but that carbona- 

 ceous manures had no perceptible effect. They further 

 showed that the condition of the land was higher than was 

 desirable for the purposes of the experiments, the result of 

 which was, not only that the seasons set a limit to the 

 amount of crop, and therefore to that of the increase 

 produced, below that which the manures might otherwise 

 have yielded, but that the increase consisted of a very 

 undue proportion of straw. 



Passing now to the fifth and sixth years, in which all 

 applications of manures were withheld, the results corrobo- 

 rated the conclusion already arrived at, that the condition 

 of the land was too high for the full action of the manures 

 in the years of their application. They likewise showed 

 that their influence was not even then exhausted, and this 

 is further proved by the fact that calculation shows there 

 was a less proportion of the nitrogen supplied in the 

 manures in the four years recovered in the increase of the 

 six years, and in some cases much less, than is sometimes 

 recovered in the crop immediately succeeding the application 

 of a nitrogenous manure. Under favourable circumstances, 

 from 40 to 50 per cent, of the nitrogen supplied in an 

 artificial manure for wheat may be recovered in the increase 

 of a first crop. But it is estimated that, in the cases of 

 the rape cake and of the ammonia-salts alone, there was 

 only about one-fourth, and in those of the mineral manure 

 and ammonia-salts, and of the guano, under 40 per cent, of 

 the nitrogen supplied in the manure of the four years 

 recovered in the increase of the six years. 



A comparison of the value of the increase of crop with 



