February 22, 1918] 



SCIENCE 



197 



during his many years of investigation he (Hil- 

 gard) had become the best judge of the differences 

 of soils of humid and arid regions (p. 164). 



This remarkable property of arid subsoils, 

 repeatedly emphasized by Hilgard in his 

 various publications and mentioned in the 

 works of other investigators from the time of 

 the appearance in 1904 of the late Dr. F. H. 

 King's "The Soil" (p. 29), must surely have 

 excited the interest of botanists, geologists 

 and irrigation engineers as well as of agri- 

 cultural investigators, not only in California, 

 but also in arid lands on other continents. 

 Yet until the present observations of Dr. Lip- 

 man no word of criticism has appeared. 



The accepted view, in brief, has been that 

 on the freshly exposed subsoils in humid re- 

 gions inoculated legumes as well as non- 

 leguminous plants fail to make a satisfactory 

 growth, one at all comparable with that on ad- 

 jacent surface soils, while under similar con- 

 ditions in arid r^ions the subsoil may be ex- 

 pected to show practically as good a growth as 

 adjacent surface soil. The question of the 

 maintenance of productivity in the case of the 

 non-legumes on the arid subsoils has not been 

 raised, interest centering upon the initial 

 performance of the freshly exposed material. 

 With the humid subsoils the " rawness " 

 understood has not been absolute sterility, as 

 Lipman appears to assume, but a low produc- 

 tivity. Lipman recognizes and confirms by 

 his own observations the productivity of arid 

 subsoils toward inoculated legumes, but denies 

 that non-legumes make any satisfactory 

 growth on these. While recognizing the 

 characteristic sterility toward non-legumes of 

 subsoils of humid regions he doubts the exist- 

 ence of any proof that inoculated legumes will 

 not grow on humid subsoils. He uses the term 

 " grow " but, as the whole question is whether 

 the plants " thrive " and not whether they are 

 barely able to make a weakly, stunted growth, 

 it is desirable to discuss the matter as though 

 " thrive " had been employed. In short, he 

 considers " the lack of available nitrogen prob- 

 ably is suflScient to account for the rawness of 

 subsoils" of both humid and arid regions 

 toward non-leguminous plants and questions 



the existence of any rawness in the case of in- 

 oculated legumes. 



While the views current upon the subsoils 

 of arid regions may be due to Hilgard alone, 

 those upon the subsoils of humid regions are 

 founded upon the observations of numerous 

 investigators in Europe as well as in America. 

 Many of these may antedate 1886, the year in 

 which Hellriegel established the role of sym- 

 biotic bacteria in the growth of legumes, but 

 in the thirty years that have since elapsed it is 

 surprising that none from among the hun- 

 dreds of agricultural investigators in humid 

 regions has called attention to the earlier false 

 explanation, if the failure of such crop plants 

 on exposed subsoils were due only to the lack 

 of inoculation. The universally accepted idea 

 of the rawness of humid subsoils in general is 

 based not upon pot experiments or upon the 

 growth of plants upon subsoils exposed by 

 grading operations or thrown up from excava- 

 tions, but upon observations of the growth of 

 the crops in fields where the plow had un- 

 wisely been run a few inches below the usual 

 depth of cultivation, with the result that the 

 fields for years after had shown in their les- 

 ened crop returns the unproduetivity of the 

 subsoil brought to the surface. In view of the 

 almost universal distribution of red clover in 

 western Europe and in the humid states of this 

 country the necessary bacteria could rarely 

 have been missing. If the rawniess were due 

 simply to lack of inoculation such deeply 

 plowed fields might be expected to have shown, 

 when sown to small grains with the usual ac- 

 companiment of clover seed, a remarkably 

 vigorous growth of the legume accompanying 

 the failure of the cereal, a phenomenon which 

 could scarcely have escaped mention. 



In the very article by Alway, McDole and 

 Host,' which has called forth the statements 

 of Lipman, such a phenomenon has been de- 

 scribed. The field of 5 acres is in a railway cut 

 near Blair, Nebraska, where about 17 years 

 previously the surface material had been re- 

 moved to an average depth of 25 feet. It had 

 never been manured or seeded to a legume 

 crop, but for several years had been planted to 



8 "Soil Science," Vol. 3, p. 9, January, 1917. 



