118 ALFALFA FARMING IN AMERICA. 
anything can stand before healthy alfalfa. Almost 
any weed will conquer unhealthy alfalfa. Lime is 
its tonic, its heal-all. 
Amount of Caustic Lime.-—How much caustic lime 
will we dare use? In an acre of soil, counting the 
top foot, there are roughly about 2,000 tons. The 
sweetening of this mass of soil cannot be accom- 
plished by any handful of lime. One ton to the acre 
is one part in 2,000; two tons to the acre is one- 
tenth of one per cent. of lime. It would seem folly 
to use less than two tons to the acre of caustic lime. 
Double that, well distributed, would almost cer- 
tainly do harm. Is there a man who has harmed his 
soil by putting in it four tons of caustic lime to the 
acre, seeing that it is well distributed, and that the 
land has good store of humus, and has then sown it 
to alfalfa? 
Caustic lime must not be supposed to remain 
caustic for a long time after it is applied to the soil. 
It soon absorbs carbon again and becomes a neutral 
and harmless substance. This being true, why not 
use some form of carbonate of lime in the begin- 
ning? The only answer is that it is sometimes 
cheaper, because of freights or lack of machinery 
for grinding, to use the burned lime. 
Other Forms of Lime.—Now for some other forms 
of lime. Air-slaked lime, as has been said, has 
absorbed a lot of carbon and is not nearly so biting 
and caustic as the fresh burned lime. It is fre- 
quently for sale at a comparatively low price, be- 
cause it is a waste product about lime kilns. It is 
