PHOSPHATES IN MASSACHUSETTS AGRICULTURE. 135 



Some of the more essential among the reasons which Dr. Hopkins 

 here advances in support of his system of dependence upon apphcation 

 of fine-ground rock phosphate are the following: — 



1. Phosphorus is already dangerously deficient in the soils of our older 

 States, and is rapidly becoming more so. 



2. There are, on the other hand, in the most common soils of the United 

 States, "immense supplies of potassium" (and other essential elements), 

 — enough, "supplemented by the amounts returned in manures and crop 

 residues," for the production of "large crops at least for thousands of 

 years." 



3. If limestone be first applied to neutralize existing acidity, and fine- 

 ground rock phosphate thereafter abundantly applied, the soil will be- 

 come fitted for the growth of clover (or other legumes) . 



4. The gro\\i,h of clover makes possible the acquisition of nitrogen 

 from the air, so that this element need not be purchased. 



5. If organic matter in the residues of clover and other crops, and in 

 manure made largely from clover hay and pasture, be abundant in the 

 soil, the phosphoric acid of the natural rock phosphates will be rendered 

 available with sufficient rapidity for large crop production. 



6. The use of rock phosphate instead of acid phosphate or (by fair 

 implication I think) other sources of phosphoric acid means a large saving 

 in money outlay. 



7. The results of numerous experiments which it is held prove the 

 soundness of these conclusions are presented in the book above referred 

 to, in bulletins of the Illinois Experiment Station, as well as in other 

 writings by Dr. Hopkins, who in the book and to some extent elsewhere 

 also quotes results obtained in several other experiment stations. 



It is proposed to consider these propositions, as to the degree of their 

 applicability to the conditions of our agriculture, in the light of such 

 experimental work bearing upon them as has been done in this experi- 

 ment station. The writer would call particular attention to the fact that 

 this study is not entered upon because of any doubt of the validity and 

 soundness of Dr. Hopkins's conclusions and advice in so far as they 

 relate to the conditions of the corn-belt. He is at the same time an able 

 investigator and a tireless worker. His work has been of enormous value 

 to the farmers of the corn-belt. . 



Among the reasons enumerated the first and second, both of which 

 relate to the composition of the soil, are most conveniently considered 

 together. 



RELATION OF MASSACHUSETTS AGRICULTURE TO SOIL 

 COMPOSITION, AND RESULTS OF CHEMICAL ANALYSES. 



Under the system of agriculture most common in the corn-belt States 

 phosphoric acid is largely carried away from the farm in products sold. 

 Wheat, corn, oats, beef, mutton, pork and milk are all rich in this com- 

 pound. Id view of this fact it is not surprising that, as Dr. Hopkins points 



