25 
a large amount of organic matter, but that when the proportion of 
organic matter to calcium carbonate falls below a certain point chlo- 
rosis is produced in spite of the large amount of humus. 
Results of experiment in which calcium carbonate was added to a soil rich in humus. 


Average 
green 
onto cu. Appearance of plants during growth. | nee pia 
end of 10 
| months. 
Grams. 
Colits a All plants dark green throughout the experiment.......................--- 1,137 
10 per cent. ....| All plants equal to check in color throughout the experiment...............-- | 812 
20 per cent. ..-..|..-.-- (as poy OS Ae AEA A cn he) ot Se Rs oe a ee oe Re po ee aE 1, 048 
30 per cent. ....|.---. Oe ee ae te ee eee eye ars miele are mene ateraps alate ci afele= nis Si cuaesooueeMON a Se rod isly 
40 per cent. ....| At fourth month color of all plants equal to check; at sixth month 2 plants 1,006 
chlorotic and 1 slightly chlorotic; at ninth month 1 plant slightly chlorotic, 
others equal to check. ; 
50 per cent. ....| At fourth month color of all plants equal to check at sixth month all plants 1,070 
strongly chlorotic; at ninth month 1 plant chlorotic, 4 very slightly chlo- 
rotic. 




Experiment IV is the same as experiment I throughout, except 
that the magnesia limestone (No. 211) was used, instead of No. 216, 
As but 75 pounds of this limestone was available, only the effect of 
soils containing 10 and 30 per cent of the combined carbonates (of 
lime and magnesia) was tried. The results are given in the table 
below. 
The object of this experiment was to see if increasing the available 
magnesium in the soil would lessen the chlorosis. The results were: 
The check plants maintained a good green growth; the plants in all 
the pots with the magnesium limestone became chlorotic; the chlo- 
rosis was fully as intense as in the parallel experiment with the lime- 
stone low in magnesia (experiment I). It is apparent that increasing 
the ratio of magnesium carbonate to calcium carbonate from 1:51 to 
1:9 has no beneficial effect in diminishing the chlorosis or increasing 
the growth of the plants. 
Results of experiment in which limestone containing 10 per cent of magnesium carbonate 
was added to sandy soil. 


Amount of Average 
combined car- ae ae £5 
bonates (lime Appearance of plants during growth. = t *t 
and magnesia) Pp “7 " 
in soil. dee 
months. 
Grams 
Ci ee oe All pout dark green throughout the experiment.-...............----..----- 653 
10 per cent. .-...| At fourth month color of all plants poorer than the check; at sixth month 1 508 
pit seat 2 plants slightly chlorotic; at ninth month all plants slightly 
chlorotic. 
30 percent. .-.. At fourth month 1 plant chlorotic, 4 plants color inferior to check; at sixth 358 
month 1 plant strongly chlorotic, 4 plants very slightly chlorotic; at ninth 
month all intensely chlorotic. 


{Bull. 114 
