126 MASSACHUSETTS HORTICULTURAL SOCIETY. 



Dr. Sturtevant stated that Prof. Stockbridge claims that by sup- 

 plying to our fields the chemicals representing, in kind and amount, 

 the materials removed b}" our crop, we can invariably produce the 

 crop. That is to say, if we apply the potash, phosphoric acid, and 

 nitrogen, which anal3'sis shows fifty bushels of corn and its stover 

 to contain, then we shall expect to obtain a crop of fifty bushels. 

 He added that the mere mention of this claim brings into promi- 

 nence the enthusiasm which is possessed by its originator ; that his 

 claims are supported by too few facts to receive universal credence ; 

 but still, in the present state of American knowledge, the verdict 

 must be given " not proven,", only. He said American, because 

 the most of our experimental knowledge on the subject is from 

 English sources, and Americans have been always too ready to 

 use these for inferences, forgetting the differences in climate. 

 Thus, in old England, the winters are mild, and the rainfall, which 

 is large, passes down through the soil, and carries with it fertile 

 elements. In New England, as a rule, the winters are severe, the 

 ground is frozen deeply and the rain and snowfall passes off mostly 

 by flowing over the surface of the land. English experiments 

 justify the belief, for instance, that of the applied nitrogen, one- 

 third is taken up by the crop, one-third passes away in the drain- 

 age, and one-third remains in the land in an inert form. With our 

 different climatic conditions, does the same rule apply here? The 

 Doctor said that we have no evidence for or against, and conse- 

 quently cannot decide. 



Dr. Sturtevant continued : Prof. Stockbridge fui'ther claims that 

 his yield is intended to be above the natural yield of the soil, and 

 defines the natural yield as being the product of an unmanured por- 

 tion of the field. Here he has made an evident miscalculation. For 

 instance, to a field which last year was excessively manured, I 

 apply his formula on one half, and no manure on the other half. 

 It is probable that there will be little difference between the two 

 yields to represent the efficacy of the fertilizer. What then is the 

 natural fertility ? 



Every agricultural field on any farm contains two kinds of fer- 

 tility. The one is the surplus of the manure which has been ap- 

 plied in previous years, and which has not been removed either by 

 crops or other agencies ; the other is the natural fertility, or that 

 amount of fertility which is food to the plant by natural agencies 

 each year. We may measure this last fertility by a fallow yield. 



