500 University of Calif omia PuiUcati<yns in Agricultural Sciences [Vol. 1 



Color of Leaves 



In the first crop on the greenliouse soil the color of the blade 

 was a much deeper green in the treated pots, no matter what salt 

 was used, than in the untreated ones. This was true despite the 

 fact that the leaves were dark green in the plants of the control 

 pots, which had a plentiful supply of available nitrogen at their 

 disposal. The plants of the pots treated with copper sulfate 

 showed, however, a darker green color than those in the pots 

 treated with other salts. That excessive nitrogen feeding was 

 probably the cause of the very deep green color of the leaves 

 referred to was further indicated by the tendency to lodge mani- 

 fested by the plants in the copper and lead series and to some 

 extent in the other series. In the second crop, prior to the plant- 

 ing of which the salt content of all series in the greenhouse soil, 

 except the lead and the manganese, was doubled, manifestations 

 as to color similar to those above described were observed. These 

 were not so marked, however, even though the contrast between 

 the plants on the treated and those on the untreated soils was 

 easily discernible. As a result of the smaller amount of stimula- 

 tion in the crop under consideration, no tendency to lodging was 

 noted, and the plants were erect and rigid. In the third crop 

 on the same soil without further salt treatment, there was only 

 a slightly deeper green color in the leaves of plants on the 

 treated than in those on the untreated soil. Again, the plants 

 were erect and vigorous in appearance throughout. 



On the Oakley blow-sand soil, in which only copper was 

 tested, was discerned a similarlv striking effect on the color of 

 the barley blade exercised by the salt treatment of the soil. In 

 the clay adobe soil similar observations were made. We are 

 therefore led to believe that the effect of the salts in question 

 seems to be general in at least one direction for all soils, namely, 

 for the production of a deeper green color in the leaves of plants 

 growing on the treated soil. The stimulating effect in that 

 direction shows a tendency to diminish at first rapidly, then 

 slowly, in the succeeding crops. The probable causes of this 

 manifestation, as briefly referred to above, will be mentioned 

 later in connection with the studies of the treated soils them- 



