32 BULLETIN 169, U. S. DEPAETMENT OF AGEICULTUEE. 



That acid solutions, in fact, are much more toxic just after applica- 

 tion is clearly shown by the experiments at Halsey. That the 

 rapidity with which disinfectants are rendered inactive in the soil 

 should vary greatly in different soils is to be expected, in view of the 

 great differences which exist in both their physical and chemical 

 constitution. However, examinations of soils by the usual methods 

 of chemical and physical analyses and lime requirement and wilting- 

 coefncient determination do not give much indication as to how sul- 

 phuric acid may be expected to behave in different soils. A soil with 

 a low wilting coefficient may be expected to have a rather low aver- 

 age water content under field conditions and therefore to require 

 small amounts of disinfectants to raise the soil solution to a killing 

 concentration. Coarse texture indicates low absorptive power and 

 a consequent small capacity for disinfectants without injury to roots. 

 A high lime requirement may indicate soil acidity, but it may also 

 be found in a nonacid soil which has high absorptive capacity. 1 Both 

 on theoretical grounds and from the results obtained at Halsey with 

 sulphuric acid and mercuric chlorid treatments followed by lime, 

 the carbonates present should have a decided influence in preventing 

 injury by acids, and probably by many toxic salts as well. Experi- 

 ments are under way at several nurseries at which preliminary re- 

 sults indicated a distinct relation between determinable chemical 

 and physical characters and the behavior of disinfectants. But 

 between soils as much alike as those on which the foregoing experi- 

 ments were conducted, the physical and chemical exam in ation made 

 gives no clue to any difference which can explain the different be- 

 havior of sulphuric acid on the two. Xeither soil yielded C0 2 by 

 the method employed in the examination by the Bureau of Soils. 

 The surface soil at Morrisville contains more CaO, has a higher igni- 

 tion loss, a higher wilting coefficient, and a lower lime requirement 

 than the Halsey soil, all of which would seem to indicate a greater 

 capacity for acid at Morrisville. The experiments show throughout 

 that the reverse is the case. While the tests made at the two nur- 

 series are not absolutely comparable, comparison of the plats of 

 series 501 (Table VI), which received from 0.125 to 0.25 ounce per 

 square foot, with series 631 to 637 inclusive (Table VII), in which 

 from 0.031 to 0.083 ounce was used, indicates that at Halsey the 

 amount of acid required to cause injury is three times that required 

 at Morrisville. It seems probable, in view of the semiarid conditions 

 at Halsey, that the Morrisville soil was more acid or less alkaline than 

 the Halsey soil. 



An attempt to get an indication of different reaction between the 

 two soils a year after the samples were taken failed, both soils giving 



1 Cameron, F. K. The Soil Solution, the Nutrient Medium for Plant Growth, p. 65, footnote 1 . Easton, 

 Pa., 1911. 



