3o8 Journal of Agricultural Research voi. xv. no. $ 



resistance was found at the highest moisture content consistent with good 

 growth. In the second series, in which the theoretical concentration of 

 the soil solution was the same, different results were observed. In the 

 case of the chlorids and sulphates the toxicity was nearly proportional to 

 the strength of the solution, the best growth otherwise being with the opti- 

 mum moisture content. In the case of the carbonates, however, the 



HaCL in pf>. m of dry soil 



400 ipoo ipOO ipOO 4,000 



moisture V^^rxr?X>"^:>^!_^A^!^^^^ 

 mo/sture 



jor. 

 moisture 



moisture 



• • an* plant ^"mm ^ o i grn tfr> matter 



t)ai COs in a Dm of dry soil 



300 1000 3.000 iplfo IPOO lOBOO 



iov. 

 moisture 



Z3t. 



moiSTure 



J0% 



moisture 



J5 7. 



moisture 



I ml One plant 



i0 7a 



moisture 



^5 7. 

 moisture 



JOT. , 

 rr.vsture 



JJ7. 



moisture 



HoiSOt in p m of dry ioil 

 iOO 1.000 J.ooo 5poo ipoo lopoo 



©^©©©©OOOCOO 



t plant ^^mm ■»» * igm. dry motttr 



Fig. 20. — Diagram showing the number of wheat plants up and the dry matter produced in 21 days in 

 loam and clay maintained at different moisture contents and containing sodium chlorid, sodium car- 

 bonate, and sodium sulphate added in various concentrations. 



greatest growth was where the least amount of solution, and conse- 

 quently of salt, had been applied. This shows that in the case of the 

 carbonates at least the concentration of the soil solution does not depend 

 directly on the proportion of salt to soil, or on the proportion of salt to 

 water, but on a combination of all these factors probably, depending on 

 the relative absorptive powers of the soil for the salt and for water. 



