154 
C. B. LIPMAN AND W. F. GERICKE 
the dry weight of the soil. The toxic salt in every case was used in 
uniform concentration throughout a given series, whereas the antago- 
nistic salt was used in varying concentrations. Except as otherwise 
stated below, all salts were mixed with the soils a few days prior to 
planting the seeds. 
Two types of soil were employed, the Oakley blow sand and the 
Berkeley clay adobe. Both of these soils have frequently been described 
in papers issued from our laboratory .^^ It should be added that dif- 
ferent lots of one and the same type of soil were used and these varied 
in producing power without treatment due to field conditions which 
need no discussion here. In any one series, however, soils from dif- 
ferent lots were never mixed. Seven series of cultures in duplicate 
were grown on each soil type. The plants were grown to maturity, 
harvested, dried at ioo° C, and weighed. The dry weights of both 
tops and roots were determined in every case, and in the case of the 
tops, separate determinations were also made of the dry weight of the 
straw and the grain. The results are given in the tables. For the 
sake of clearness, it is deemed best to consider briefly each series by 
itself. 
Series I 
CUSO4 versus Na2S04 — Adobe Soil 
Na2S04 .5 percent constant — CUSO4 varying 
Three consecutive crops were grown in this series, the second crop 
being planted shortly after the first was harvested. The salt applica- 
tions were, of course, made only once, namely, prior to the planting of 
the first crop. The results obtained with regard to yields of straw, 
grain, and roots are given in Tables I, II and III. 
Straw Production. — Straw yields are evidently not very markedly 
influenced by the antagonistic effects of CUSO4 to Na2S04. This 
seems to be true especially in the first two crops. In the third crop, 
the effect is a little more marked in the direction indicated. On the 
other hand, the lack of agreement, which is noted between some of 
the duplicate cultures, is more marked in the third crop than in the 
other two. It should be observed that the lack of toxicity manifested 
by Na2S04 alone in the second crop is doubtless due to a loss of some 
of the salt, since Na2S04 is characterized by a tendency to crystallize 
from the soil and to creep to and over the edges of the pots. Moreover, 
12 Univ. Cal. Publ. Agr. Sci. i : 495-587. 
