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IOWA ACADEMY OP SCIENCE 
c. Time of Sowing. 
The time of sowing is another factor that enters in. From the cultural 
experiments that have been outlined, it is apparent that the temperature has 
considerable influence. Prom this fact it is at once evident that barley placed 
in the soil at a time when the temperature is 15 degrees C., will not offer the 
conditions when it is 24 degrees C. It is therefore advisable to get the seed 
into the ground when the temperature is sufficient for complete germination 
of the seed, and where the growth of the fungus is held in check. 
d. Volunteer Groioth. 
The remaining stubble and the volunteer growth play a part in the trans- 
mission of the disease from one season to another. These young plants con- 
tinue to propagate the conidia, while the straw harbors the pycnidia and 
sclerotia. Where a field has been in bad shape it is advisable to burn over 
the stubble before plowing. 
e. Soil Sanitation. 
The question of soil sanitation is one that has an important bearing on the 
transmission of the spores of HelmmtJiosporium species. Serious damage can 
be imparted to our cereal crops when the soil in which these crops are grown 
is filled with spores of various parasitic fungi. As a result the tender seed- 
lings must undergo a struggle for existence that is possibly not equaled at 
any later period. In Germany, this fact was long ago established for certain 
crops like the sugar beet and clover. It was shown that these crops were not 
remunerative because the soil was inoculated with numberless parasites like 
Rhizoctonia. Pammel found the same thing to be true in the case of the root 
rot of the cotton {Ozonium auricomum=0. omnivorum^) . 
Professor Bolley of North Dakota has recently brought this matter of sani- 
tation to the attention of agriculturists. In his work on flax raising, he found'^ 
that the farmers of that state were putting flax growing aside for the reason 
that it was not profitable. These “flax sick” soils were found to possess all. 
the chemical constituents and compounds that go to make up good soil. In an 
address before the Fifth International Dry Farming Congress at Spokane, 
Bolley adds: “But I may state that the three most destructive - parasites 
taken in their order are one or more species of Helminthosporium, one or more 
species of Fusariuin, the type of fungus which produces the wheat scab and 
flax wilt, and one or more species of Colletotrichum. These are universal and 
effective on roots and leaves, stems and seeds, and various species of Macro- 
sporium and Alternaria are great blighters of seed and destructive both on 
straw and on grain especially at germination time. If you declare for careful 
seed selection in all cases, careful seed disinfection at all times, the formation 
of a well aerated but compacted seed bed, and for an extensive rotation of 
crops of as wide spread a character as possible, you of the new dry land region 
of the West, have the greatest possible opportunity to prove to the world that it 
is not necessary to lose a crop of such importance as linseed from among your 
rotations nor is it necessary that your wheat fields yields should fall from the 
now promising ones of thirty to sixty bushels to the general average of twelve 
to fifteen.” 
la. Agr. Exp. Sta. 15:242-251. 1891. 
Bull. Texas Agr. Exp. Sta. 4 :1-18. 1889. 
