46 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
LIME AND MAGNESIA AS CARBONATES IN SOIL CULTURES. 
To further test the influence of calcium and magnesium as carbon- 
ates on the growth of plants soil cultures were made. In this experi- 
ment a sea-island cotton soil was employed, consisting largely of sand 
with some silt and clay. The particles were finely divided, 1 kilogram 
passing through a 2=mm. sieve, leaving a residue of only 13 grams. 
Analyses showed a large amount of iron but a very small amount of 
lime and magnesia. 
To the soil there was added: 
Per cent. | Per cent. 
KH POy era ef ek ee OOM NEE eS Oe" (ce nos tsar ne Sanne 0.2 
RC) Si Dene iets Oils | ENO ssR ch a ca ie eae 0.1 
The soil was put into twenty pots, a series of nine in duplicate and 
two extra. Lime and magnesia as carbonate was incorporated, as in 
the following schedule: 
| No. pot. CaO. MgO. 
Percent. Per cent. | 
il 0.9 | 0.1 
De 0.8 | 0.2 
3 0.7 0.3 
4 0.6 0.4 
5 0.5 | 0.5 
6 0.4 0.6 
7 0.3 0.7 
8 0.2 0.8 
9 | 0.1 0.9 
i). 0.8 0.2 
rae 0.2 0.8 
EXPERIMENTS WITH OATS AND COWPEAS. 
One series of pots, Nos. 1 to 9, holding 1 kilogram each of soil, was 
planted to oats, the other to cowpeas, and were watered with distilled 
water. The seed germinated first and plants were best beginning with 
the pots containing the largest amount of lime and the smallest amount 
of magnesia, and ranging down in thriftiness to those containing the 
smallest amount of lime and the greatest amount of magnesia. Later 
the best growth of both oats and cowpeas was in the soils containing 
CaO 0.8 per cent and MgO 0.2 per cent. In all cases where the CaO 
was 0.6 per cent and less and the MgO was 0.4 per cent and more the 
plants made a very sickly growth or else died outright. In the two 
extra pots planted to tobacco, No. 10, with CaO 0.8 per cent and MgO 
0.2 per cent, the plant made a normal growth, while in No. 11, with 
CaO 0.2 per cent and MgO 0.8 per cent, the plant became atrophied 
and died. In these cases the action of the lime in counteracting the 
noxious influence of the magnesia was at most very limited. 
To further test the matter, there was added to five pots containing 
0.5, 0.7, 0.8, and 0.9 per cent of MgO 0.4 per cent of CaO as sulphate, 
