562 University of California Publications in Agricultural Sciences [Vol. 1 



tween 500 p. p. in. and 3000 p. p. m. MnSO^, but most markedly 

 at 1500 p. p. m. The root jdelds are also markedly stimulated, 

 but only at concentrations up to and including 1500 p. p. m. 

 Beyond that concentration, root yields are more or less reduced. 



In the second crop the straw yields are stimulated at from 

 4000 p. p. m. to 6000 p. p. m. MnSO^, but markedly depressed at 

 concentrations below 4000 p. p. m. The grain yields are about 

 equally depressed throughout, but not markedl}^ The root 

 yields are depressed throughout the series rather markedly, the 

 smallest depression occurring at concentrations of 2000 and 

 2500 p. p. m. MnSO,. 



In the third crop a stimulation is induced toward the pro- 

 duction of straw, grain, and roots, the medium concentrations 

 being most effective. Little or no evidence of toxic effects of 

 MnSOj was observed. 



9. In the greenhouse soil in the MnCL series the first crop is 

 markedly stimulated in straw production at concentrations vary- 

 ing from 500 to 1500 p. p. m. MnCL. Beyond the latter concen- 

 tration, MnClo becomes more and more acutely toxic, until 

 almost no straw is produced at 6000 p. p. m. MnCh. Root 

 production is affected similarly to straw production, in a general 

 way. 



In the second crop straw production is stimulated throughout 

 except at the two lowest concentrations — 500 and 1000 p. p. m. 

 respectivel^y. Grain yields, however, are depressed almost 

 throughout. The depression is relatively slight (there being 

 one case of stimulation) at concentrations varying from 500 

 p. p. m. to 3000 p. p. m. Above the latter concentration, the 

 MnClo is markedly toxic to grain production. Root production 

 is markedly depressed throughout. 



Like MnSO^, MnCl, exerts a stimulating effect on the yields 

 of straw, grain, and roots in the third crop. Again, little or no 

 evidence of a toxic effect was noted in this series. 



10. Results are given on the effect of the salts used on the 

 nitrogen content of the grain produced, on the nitrifying powers 

 of the soils concerned, on the amounts of copper and zinc taken 

 up by some of the barley plants in the different series; and 



