48 HINTS ON SOILS AND FERTILIZERS 
per, and bring this in contact with some moist 
soil. If the blue color of the litmus paper 
changed to a reddish hue, then we would know 
that the soil was acid. But a weak acid soil 
would change the color of this blue litmus pa¬ 
per just as much as a strong acid soil would. 
Hence, by this method, the farmer did not know 
how much lime should be applied to correct 
the acidity. Within the last few years, how¬ 
ever, the Truog Acidity Test has become avail¬ 
able, and it is now a matter of but about five 
minutes’ time to determine accurately not only 
how acid the soil is, but a chart is also pro¬ 
vided, showing just how many tons of lime 
should be applied to the acre for that par¬ 
ticular field. Most state experiment stations 
have this test, or a similar one, and any farmer 
can either send a small sample of his soil to 
his state experiment station, or agricultural col¬ 
lege, and they will run the test off for him. 
Possibly, the county agricultural agent has 
one of these, and as he is in the county for 
such purposes every farmer who is anxious to 
determine the acidity of his soils should take 
the proper steps to obtain a reliable answer to 
his problem. 
The luxurious growth of certain weeds is al¬ 
most a sure sign of acid soils. Such weeds as 
the common plantain, sheep sorrel, corn spurry 
and horsetail all thrive best on these acid soils. 
There are many different forms of lime that 
can be applied to the soil to correct the acidity. 
Ground limestone, burnt lime, marl, marble 
dust, pulverized corals and shells are different 
forms of lime that may be used. However, the 
