LIMING OF SOILS FROM A PHYSIOLOGICAL STANDPOINT. 11 
In drawing inferences from agricultural experiments much atten- 
tion should be paid to all conditions that might possibly have an 
influence. For example, while one author reports that a deficiency of 
lime will cause yellow spots to develop on the leaves of the sugar beet. 
and consequently decrease the yield of sugar, another asserts that 
beets richest in lime are poorest in sugar.’ In such cases it is neces- 
sary to ascertain also the amount of the other nutrients, since too 
much magnesia may influence the results just as certainly as a reduced 
amount of potash. 
In another instance it is reported that calcium nitrate is a less favor- 
able source of nitrogen than sodium nitrate, an observation which 
may have been made on soils rich in lime and too poor in magnesia, 
otherwise it would be difficult to understand, since experiments with 
water cultures have shown calcium nitrate to be an excellent nutrient. 
As early as 1814 Davy discussed the question why magnesia some- 
times acts injuriously on crops. He wrote: **It has long been known 
to farmers in the neighborhood of Duncaster that lime made from cer- 
tain limestone applied to the land often injures the crop considerably. 
This lime contained magnesia. On mixing some calcined magnesia with 
soil in which different seeds are sown, it is found that they either die 
or vegetate in a very imperfect manner.” He also states that ** lime 
from magnesian limestone may be applied in large quantities to peats, 
and where lands have been injured by the application of too large a 
quantity of magnesian lime peat will be a proper and efficient remedy.” ” 
An injurious action was observed with the limestone from quarries 
near Belvidere, N. J.. while other limestones from near Oxford, some 
distance off, showed very beneficial effects on the same field. The 
difference between the effects was so striking that it was considered of 
some importance to investigate the cause. Samples of the two lime- 
stones were therefore sent to the U. 8S. Department of Agriculture, 
where they were analyzed, with the result that the /njurious limestones 
were found to contain 38 to 42 per cent of magnesium carbonate, while 
the beneficial limestone contained not quite 1 per cent of this substance.* 
The explanation, however, that the injurious effects of burnt magnesian 
limestone are due mainly to the fact that the caustic magnesia turns 
much more slowly into carbonate than the caustic lime can not be the 
correct one, neither can the hypothesis be accepted that the injurious 
effect is due to the formation of hydraulic cement in the soil. since the 
effect is less noxious on clay soil than on sandy soil, while just the 
reverse should be expected if that hypothesis were correct. 
Very injurious effects have been reported from manuring with pre- 
cipitated magnisium carbonate, these being ascribed, however, to the 
‘Hollrung, Die Zuckerindustrie, 1898. 
* Elements of Agricultural Chemistry, 2d ed., p. 322. 
* Report of the Commissioner of Agriculture, Washington, D. C., 1876, p. 142. 
