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



111 the third crop both root and top production are stimulated 

 up to and including concentrations of CuSO^ equivalent to 2200 

 p. p. m. Grain production is almost similarly stimulated. 



2. In tlie clay adobe soil in the first crop straw, grain, and 

 root production are all stimulated up to and including concen- 

 trations of CuSO^ equivalent to 800 p. p. m. 



In the second crop no stimulation takes place in the 100 and 

 200 p. p. m. concentrations, but in all higher concentrations, at 

 least including that equivalent to 900 p. p. m. This holds for 

 both straw and root production. 



3. In the Oakley blow sand, only one crop being grown, 

 CUSO4 stimulates markedly grain production and slightly straw 

 and root production at concentrations up to and including 300 

 p. p. m. CuSO^. 



4. In the greenhouse soil in the ZnSO^ series the first crop 

 is stimulated both as to root and straw yields throughout at 

 concentrations varying from 100 p. p. m. to 2000 p. p. m. ZnSO^. 



In the second crop stimulation to straw and root yields occurs 

 at 200 p. p. m. ZnSO^, and marked stimulation to root yield 

 without effect on straw yields up to 600 p. p. m. ZnSO^. Beyond 

 that point slight toxicity sets in and is maintained almost 

 uniformly throughout. 



In the third crop neither stimulation nor toxicity is apparent 

 at concentrations of 200 p. p. m. ZnSO^, but concentrations in 

 excess of the latter are distinctly toxic. 



5. In the greenhouse soil in the FeSO^ series, the first crop 

 shows the stimulating effects of FeSO^ throughout in concentra- 

 tions varying from 0.1 per cent to 1 per cent. The straw yields 

 are increased throughout and the root yields slightly so up to 

 and including the concentration 0.7 per cent FeSOi. 



In the second crop FeSO^ stimulates straw production in 

 concentrations varying from 0.2 per cent to 1 per cent inclusive. 

 Grain production is only slightly and irregularly stimulated at 

 the same concentration. Root production is affected similarly 

 to the grain production. 



In the third crop concentrations from 1 per cent FeSO^ up 

 to and including 2 per cent are markedly stimulating to straw 

 and grain yields and very slightly effective in both directions in 



