1917] Lipman-GericJce: Smelter Wastes and Barley Growth 525 



which would of course react deleteriously on the development of 

 the barley plant. Again, the washing out of the salt by irri- 

 gation may have caused physical conditions in the soil which 

 are inimical to the proper air and water supply for both plants 

 and the soil bacteria. The first conception is the one employed 

 to a considerable extent by the "old-line soil chemist" to explain 

 the depressing effects on soil fertility of the large and continued 

 use of gypsum. The second is a condition demonstrated in this 

 laboratory' recently" to be of considerable importance. Further 

 discussion will be accorded this subject in a general comparison 

 given below of our results with those of others. In general it 

 may be added that the results of the third crop in the potash 

 alum series are more in keeping with those of the ZnSO^ series 

 than with those of any other series discussed. 



Manganese Sulfate 



After our work on the effects of the compounds mentioned 

 on barley plants had been under wa^' for one season, it was 

 deemed advisable to inaugurate some new experiments, using 

 manganese salts. The latter it will be remembered were rep- 

 resented by MnSO^ in preliminary experiments by F. H. Wilson 

 and the senior author, which are cited above. Owing to the 

 fact that the preliminary experiments with manganese had 

 shown the latter to be comparatively innocuous, and even stim- 

 ulating at considerable concentrations, for barley and vetch, 

 larger amounts of manganese than of copper and zinc were em- 

 ploj^ed. Both MnSO^ and MnClg were tested. Each of these 

 salts will be considered separately, and tables IXa, IX&, and 

 IXc, which follow, give the plan and the results of the experi- 

 ments with MnS04. In the case of both manganese salts, only 

 one application was made, and that was prior to the first crop. 



First Crop 

 It becomes at once clear from an examination of table IXa 

 that we can find in the first crop no indubitable evidence of 



Univ. Calif. Publ. Agri. Sci., vol. 1, no. 10, p. 291. 



