618 



SCIENCE 



[N. S. Vol. XXXIII. No. 851 



annual importation of the three plant-food 

 elements, including that in 150,000 tons of 

 Thomas slag, would be: 



N p K 



tons tons tons 



In oil cakes 16,977 2,660 4,244 



In bones and fish 2,575 5,472 



In guano 884 2,147 



In mineral phosphates . 29,821 



In Thomas slag 12,000 



In grains 73,987 11,838 17,757 



Total 947423 63,938 22700i 



To these amounts should be added the heavy 

 importations of nitrate of soda and of potash 

 salts. 



The phosphorus content of these importa- 

 tions is sufficient to apply 6.54 pounds to each 

 acre of arable land in the United Kingdom 

 and this amount is all that is carried in the 

 grain and straw of 20 bushels of wheat. Dur- 

 ing the twelve years preceding 1906 there was 

 an importation of potash salts sufficient to 

 carry 99,426 tons of potassium, which, added 

 to the above, aggregates enough for 13 pounds 

 per acre of the arable land. Through more 

 than a century increasingly larger importa- 

 tions of fertilizers and feeding stuffs have 

 been going into all of the countries of western 

 Europe. These annual additions of soluble 

 plant food elements to the film moisture and 

 to the interior of the soil granules can not fail 

 to exert cumulative effects upon both micro- 

 scopic and higher plant life, which together 

 must react upon yields continuing their in- 

 crease until available soil moisture and then 

 standing room become the limiting factors. 



The increase in yield in the United States 

 to which attention has been called is certainly 

 associated with the importation of feeding 

 stuffs and fertilizers, and while better cultural 

 methods, better seed, better strains and fuller 

 control of fungus diseases are responsible for 

 some of these increases, the addition of plant 

 food must play a large part now in the older 

 states, especially in the North and South 

 Atlantic groups where fertilization has been 

 so long and so extensively practised. In the 

 northern group, $15,641,995 and in the south- 

 em, $22,732,670 were paid for fertilizers in 



1899 and applied to less than 24,683,365 and 

 29,194,361 acres, respectively, the amount of 

 land in all crops that year. To give expres- 

 sion to these figures in terms of plant-food 

 elements and crop yields, the mean value and 

 composition of twelve " complete " * fertilizers 

 may be used, worth $23 per ton and containing 

 33 pounds of N and K and 88 pounds of P. 

 On this basis the fertilizer purchased would 

 contain sufficient phosphorus for 2.42 pounds 

 for every acre under crop in the North At- 

 lantic states and for 2.98 pounds in the South 

 Atlantic states. These are the amounts of 

 phosphorus contained in the grain and straw 

 of 7.5 bushels of wheat and 10.5 bushels of 

 corn in the first case and in the second case, 

 9.31 bushels of wheat and 13.0 bushels of corn. 

 But in the most thickly settled states the 

 amounts of fertilizer used are much above the 

 average, Rhode Island using sufficient to carry 

 10.2 pounds of phosphorus to each acre in 

 crop; Connecticut, sufficient for 6.5 pounds; 

 New Jersey, for 6.39 pounds; Massachusetts, 

 for 6.37 pounds, while the District of Columbia 

 is credited with fertilizers sufficient for 26 

 pounds of phosphorus and of 10 pounds of 

 potassium per acre in crop, added to her culti- 

 vated soils each year. 



There never has been doubt regarding the 

 truth embodied in the statement, " that there- 

 fore there must be some efficient natural 

 process for the maintenance of soils," but 

 because of its association with other state- 

 ments there is danger that it may be taken 

 explicitly to mean, that therefore there must 

 be some efficient natural process for the main- 

 tenance of soil productivity capable of sus- 

 taining, in the United States, 2,000 million 

 people with relatively little greater effort at 

 curtailment of waste or of return of essentials 

 to the soil than is now practised here. If all 

 that the Chinese and Japanese farmers are 

 doing, and for centuries have felt compelled 

 to do, are to be included in the " some efficient 

 process," then all danger of misleading will be 

 removed, for there has long been more applied 

 science in the agriculture of " oriental experi • 



' Hopkins, ' ' Soil Fertility and Permanent Agri- 

 culture," p. 157. 



