6 1 4 Journal of Agricultural Research vol. vi, NO. 16 



The difference in the medium in which the plants were grown caused 

 different effects upon the plants. Brown silt loam was a better medium 

 than sand when treated with chemically pure magnesium carbonate, even 

 though it already contained 25 times as much calcium and magnesium 

 as did the sand. Still sand would have an ameliorating effect when com- 

 pared with solution cultures. Jensen (10) found that in quartz sand a 

 much higher concentration of salts was required to cause death than in 

 water cultures. 



As previously shown under literature studies it is quite generally 

 believed that plants have to some extent a selective absorption. The 

 results here seem to indicate such a condition, for the dolomites used 

 tend to go into solution in a molecular ratio, but the plants failed to take 

 them up in this ratio. The tendency of the plants under these conditions 

 was to take up relatively larger molecular proportions of magnesium than 

 of calcium. Analysis of the plants show that they do not necessarily 

 take up calcium and magnesium in the same ratio as applied, as, for 

 example, in dolomite 3 the ratio of calcium to magnesium is 5:5.2, 

 whilg the plants may and do take it up in a ratio of 5 : 7 or 5 :3-95. 



In the case of the addition of 25 per cent of magnesite the ratio of cal- 

 cium to magnesium was 5 : 125, while in some of the plants grown in such 

 treatment the ratio varied from 5:15 to 5:21. Wheat grown in soil 

 treated with 6 per cent of dolomite showed in the tops a ratio of 5:9.1 

 and in the roots a ratio of 5 : 4. 3 5, or for the whole plant a ratio of 5 :6.3, 

 while in dolomite Ci it was 5:4.8. Alfalfa grown in the same treatment 

 showed for the entire plant a ratio of 5:4.2, but when grown in soil 

 treated with dolomite 3 the ratio for the total alfalfa plant was 5: 

 3.95, while in the dolomite the ratio of the calcium to the magnesium 

 was 5: 5. 2. 



The chlorids of calcium and magnesium were more detrimental to 

 wheat and soybeans than were the sulphates at concentrations up to 

 o.i per cent of magnesium. This amount of magnesium in the prepared 

 carbonate entirely inhibited growth, whereas lower concentration gave 

 better growth than either the sulphates or chlorids. 



Wheat 65 days old showed smaller percentages of calcium and mag- 

 nesium than did similarly treated wheat at 53 days of growth, but the 

 total amount of these two elements in the plants increased with the 

 duration of growth. 



Soybeans at maturity, or 80 days after planting, showed for the hay 

 higher calcium and magnesium contents than at 53 days of growth, 

 except in the case of the checks and those treated with extremely small 

 quantities. Some of the samples showed as much as 73 pounds of cal- 

 cium and 25.2 pounds of magnesium per ton when grown in a mixture 

 of one-half sand and one-half calcareous soil, but when grown in soil 

 containing 35 per cent of magnesite there were 22.9 pounds of calcium 



