116 ALFALFA FARMING IN AMERICA. 
will attack vegetable matter or humus in the soil. 
Applied in excess it will destroy bacterial life, so 
caustic lime is not so safe to use as the raw rock 
ground, the true carbonate of lime. On the other 
hand one can use less of it and get effect sooner, be- 
cause of its energy. The difficulty in its use to pro- 
mote alfalfa growing is that one ought to use more 
than lime enough to correct acidity when he is lay- 
ing land down to alfalfa; he ought to correct the 
acidity and leave a goodly store of lime carbonate 
lying in the soil, so that alfalfa roots will be in actual 
contact as the plants grow. This one can hardly 
do with safety with caustic lime. 
Use of Caustic Lime—How much caustic lime 
can be safely used and how can it best be applied? 
Soils differ in their power to absorb lime safely. 
Strong clays and soils full of sour humus can take 
most; sandy, poor soils must be’ limed with care if 
caustic lime is used. There is some danger of ‘‘lime 
burn,’’ that is, of making soil temporarily barren 
by giving it an excess of caustic lime. The poorer 
the soils in humus the more danger of this. Yet I 
have seen alfalfa fields in Maryland where the only 
good alfalfa present was where the piles of lime had 
been slaked, and where probably the lime had been 
applied at the rate of ten tons to the acre or more. 
How much caustic lime can we use? No one 
knows just at present. I saw this experiment tried 
in Tennessee: On Idlehour Farm, near Knoxville, 
Tenn., James P. MeDonald had tried to grow alfalfa 
on Tennessee River lands. It had miserably failed. 
