Reviews 



Soil Fertility and Permanent Agriculture. By Cyril G. Hopkins. 

 8vo. Pp. 23 + 653, ill. 14. Boston: Ginn & Co., 1910. $2.75. 



This volume is a "summons and a challenge." It is dedicated to 

 "The Association of American Agricultural Colleges and Experiment 

 Stations, the rightful guardians of American soils." It is addressed to 

 farmers and students of agriculture, who "have at least as good intellects 

 as other classes of people." It is a book not written for entertainment, 

 but to be studied, and it is well worth studying. 



Part One has four chapters, largely foundation facts of chemistry; 

 three chapters on soil formation, classification, and distribution; two 

 chapters on soil survey and soil analysis by the United States Bureau of 

 Soils, an excellent summary, with instructive maps; and three chapters 

 on crop requirements in the principal soil compounds as plant foods. 

 Part Two consists of six chapters devoted to permanent agriculture, show- 

 ing the role of limestone, nitrogen, and phosphorus, the significance of 

 rotation, and theories concerning soil fertility. Part Three is an excellent 

 resume of the best soil investigations by culture experiments, as carried 

 on at Rothamstead, England, and at the leading American experiment 

 stations, Pennsylvania, Ohio, Illinois, Minnesota, and others. Part Four 

 is devoted to studies of various fertility factors; and the volume closes 

 with an appendix of valuable statistical and other data ancillary to the 

 text. 



In the introduction the author says truly: "The most important material 

 problem in the United States is to maintain the fertility of the soil, and no 

 extensive agricultural country has ever solved the problem." And again, 

 "If the art of agriculture has ruined the land, the science of agriculture 

 must restore it, and the restoration must begin while some farmers are 

 still prosperous, for poverty-stricken people are at once helpless, and soon 

 ignorant, and poverty makes no investments." 



The book is filled with the results of scientific studies, showing the 

 elements removed from the soil by the growing crops, and the quantity 

 there to be removed; showing the results of various fertilizers, and of 

 various systems of rotation; showing that the key to permanent agriculture 

 lies in phosphorus and decaying organic matter; and that good farming 

 consists in an accurate bookkeeping with the soil. 



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