50 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
with MgO 0.2 per cent, CaO 0.7 per cent, MgO 0.3 per cent, and 
CaO 0.6 per cent made a better growth and were of normal propor- 
‘tions and of good color. 
_ The figures for the best proportions of lime to magnesia in soils for 
the early germination and quick development of plants refer, of course, 
to the soluble amounts—that is, to that portion directly available to 
the immediate needs of the plant. These figures are therefore arhi- 
trary in agricultural practice, owing to the variation of the solubility 
of these elements in the soil. It will also be noticed that soluble mag- 
nesia in excess of soluble lime in small amounts may have a deterrent 
action upon plant growth while not becoming noxious to the extent of 
killing the plant. Also, lime may be in a great excess over magnesia, 
and yet there may be enough of the latter element available to respond 
to all the requirements of the plant. 
LIME AS SULPHATE AND MAGNESIA AS CARBONATE IN SOIL 
CULTURES. 
From the preceding experiments the favorable action of gypsum in 
counteracting the toxic action of magnesia is apparent. From an 
agricultural standpoint it is, besides, the most available form for liming 
because of its cheapness as compared with other of the more soluble 
forms of lime. 
To further test the action of gypsum in combination with an excess 
of magnesia, cultures were made up in iron pots holding 30 kilograms 
each. The soil had the following ¢omposition: 
Per cent. | Per cent. 
WMinteyoraiel? ete ese pee Bete 0. 65 | Die Sera Sey oye ee eee 279 
Coarse: sand U5 Aa oN 2 ee eee 420 | Clays sis sti sistas eae Ne tags eee ee 9. 80 
Wediunntsamaaeeae a mem ta ei ee 9) 40)s| Iloss*onsienttion ss 59s an ene 3 (i/ 
IPimessanGhy 268 25 wae Soe ee Se 30. 55 | 
Nery, tine) sands) eps aah esas are 20.14 | Mo tally s sso Rees Sok An aoe 100. 20 
Soluble in 1.115 per cent hydrochloric acid: CaO, 0.14 per cent; MgO, 0.144 per 
cent. 
Four pots were made up as follows, using magnesia where applied 
as carbonate and lime as sulphate: 
No. pot.) Solution. | Per cent.| 
| | 
Clieoks un. ties ae eae eae 
23) CAO ts aoe ee Bees as 0.8 
(MioOs ot eu we bee 02 
| Pion) calc ees Ousion| 
(MeOs isc s- . meee |? 70.68 
