10 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
Although for several reasons the burnt lime is superior to carbonate 
of lime, and even in some cases mentioned can not be replaced by the 
latter, still there are instances where finely pulverized carbonate of 
lime can be applied directly with great success, especially on sandy 
soil.*. In many other cases the sulphate of lime (gypsum) is the most 
favorable form, especially when the amount of sulphates in the soil is 
very small, it often sinking far below 0.1 per cent. 
Gypsum furthermore acts very beneficially in preventing the evapo- 
ration of ammonia as ammonium carbonate from stable manure by 
preserving the ammonia as sulphate. Its very beneficial action for 
many leguminous crops may be especially mentioned.’ 
Slaked lime is the remedy for correcting an acid reaction, while 
gypsum is the remedy for correcting an alkaline reaction of soils. 
To soils of certain arid regions of the far West which contain sodium 
carbonate, rendering them unfit for raising any crops, Hilgard has 
proposed an addition of gypsum. The gypsum acts upon the sodium 
carbonate, transforming this into the less injurious sodium sulphate, 
while the gypsum itself is transformed into calcium carbonate. 
While all these applications of lime and lime compounds’ are well 
known, a special case, the correction of the injurious effects of a high 
magnesia content, will be discussed and experiments described in the 
second part of this report by Mr. D. W. May, a subject which 
hitherto has not been taken practically into consideration. 
INJURIOUS ACTION OF MAGNESIUM SALTS. 
An excess of magnesia acts injuriously on plants, an observation 
made frequently and even long ago. The increase of lime is the only 
decisive remedy. The plants thrive best when the ratio of lime to 
magnesia does not pass certain limits. Too little magnesia in relation 
to lime may retard development, while too much magnesia in relation to 
lime may injure the crop still more. 
‘Various authors place the minimum limit of lime in a soil for good returns at 1 
per cent, although satisfactory crops have been raised on clay soils with 0.5 per cent, 
and on sandy soils with 0.1 per cent lime. 
A case may be mentioned where liming proved of immense benefit on soil that 
contained 0.55 per cent lime. ‘‘A percentage of gain of 10,000 in beets’’ was pro- 
duced as compared with the unlimed soil. Here it was certainly not the physiolog- 
ical réle of the lime, but an essential improvement of the soil (neutralization, etc. ), 
which led to this result. This case was observed in Rhode Island and described by 
Wheeler, Hartwell, and Sargent. (Journ. of Amer. Chem. Soc., 1900, p. 153). 
A too heavy application of burnt lime on certain soils might destroy not only 
noxious parasites but also the useful root bacteria of the Leguminosze. Reports retfer- 
ring, however, to different soils are still contradictory on this point. 
> The annual amount of gypsum consumed for fertilizing purposes in the United 
States is estimated by Dr. H. W. Wiley as 75,000 tons. 
’>The question of liming and of fertilizing in general is fully treated in F. H. Storer’s 
‘‘Acriculture in Some of its Relations to Chemistry,’’ New York, 1897, seventh edition. 
