Decembeb is, 190S] 



SCIENCE 



865 



are uow prosperous and capable of in- 

 augurating and supporting sj'stems of 

 profitable improvement leading to perma- 

 nent prosperity, would, under fifty j-ears' 

 struggle to practise this tlieorj^ become too 

 completely impoverished ever to redeem 

 themselves from iiltimate land ruin? 



Surely we should consider the inadequate 

 foundation of this widely promulgated 

 hj-pothesis, that praciicaUy all soils contain 

 sufficient plant food for good crop yields, 

 that this supply icill he indefinitely main- 

 tain-ed, that crop rotation alone ivill main- 

 tain the fertility of the soil, and that it is 

 not necessary ever at any time to introduce 

 fertilizing material into any soil for the 

 purpose of increasing the amount of plant 

 food in that soil. 



The one theory advanced in support of 

 this remarkable doctrine is based upon the 

 assumption that sufficient amounts of solu- 

 ble plant food are brought up from the 

 lower subsoils by the rise of capillary water 

 to constantly replace the plant food re- 

 moved by the largest crops, and thus to 

 permanently maintain the fertility of the 

 surface soil. (See heai'ings before the 

 Committee on Agriculture, January 28, 

 1908.) 



It is ■well known that soluble materials 

 are brought from the subsoil to the surface 

 by capillary moisture in semi-arid coun- 

 tries where the water leaves the soil, not 

 by drainage, but onlj' by evapoi-ation, and 

 also that there is some little tendency in 

 this direction in humid countries, especially 

 in times of partial drouth, but for all nor- 

 mal agricultural conditions this movement 

 is insignificant compared with the actual 

 losses of plant food in drainage water and 

 in crops removed. 



This truth is already fully established, 

 not only by the fact that underground 

 drainage waters always carry off some 

 soluble plant food, but also bj' the fact that 



in humid regions the surface soils are not 

 richer, but much poorer, than the lower sub- 

 soils — in potassium, in magnesium, in lime, 

 and in all other constituents that dissolve • 

 in the soil waters and that do not accumu- 

 late in the humus from plant residues. 

 Indeed, the surface even of normal virgin 

 soils is almost invariablj' markedly poorer 

 in such mineral constituents than are the 

 corresponding lower subsoils ; so that in all 

 countries the common method employed by 

 geologists for ascertaining the relative age 

 of different soils is to determine the depth 

 of soil to which some mineral constituent, 

 as lime, has been leached out. It is every- 

 where recognized, both in science and in 

 practise, that more or less of the plant food 

 applied to soils is lost by leaching. 



One of the most potent factors in the 

 formation of all residual soils is the process 

 of leaching. Thus, from the leaching of 

 disintegrated rock have soils been formed. 

 Limestone soils were originally impure 

 limestone rock from which a very large 

 percentage of the original rock material 

 has been removed by leaching. No geolog- 

 ical fact is better established or more uni- 

 versally recognized. From 75 to 90 per 

 cent, of the original rock formation is not 

 infrequently removed by leaching in the 

 making of I'esidual soils. 



Under ordinary circumstances, I would 

 no more think of taking up the valuable 

 time of this society by citing proofs of the 

 marked and continuous losses of plant food 

 by leaching from the surface soil, than I 

 would to cite the proofs that the earth is 

 round, for the one fact is as well established 

 as the other; but under the extraordinary 

 circumstances of the confident promulga- 

 tion from the position of highest agricul- 

 tural authority of the theory that the fer- 

 tility of American soils will be permanently 

 maintained by the rise of plant food in 

 capillary moisture, I feel justified in bur- 



