35 



The magnesia content of the ash of rice was considerably increased, 

 on the calcareous plats, although the increase was not comparable 

 with that of lime. With sweet cassava :uid sugar cane the magnesia 

 in the ash was little if at all affected. With radishes, sunflowers, and 

 soy beans there was cjuite a marked depression in the magnesia con- 

 tent of the ash of the plants from Plat IV and shgiit depressions in 

 the ashes of plants from Plats II and III. Bush beans showed a 

 depression in the magnesia in the ash in Plat IV only. 



The amount of phosphoric acid in the ash did not appear to be 

 affected in any constant manner, in any of the plants tested, by the 

 carbonate of lime in the soil. Variations occurred, but they were 

 irregular, showing no correspondence with the lime content of the 

 soils. 



The same tendency to constancy and Lick of eft'ect of the carbonate 

 of lime is apparent in the figures for potash. 



In regard to the pei-centage of iron in the asii, bush beans, soy 

 beans, radishes, and rice sliowed a marked and fauiy regidar decrease 

 with increasing amounts of hme in the soil. The combined leaves, 

 stalks, and roots of sweet cassava showed a marked decrease in the 

 iron content of the ash in Plat IV only. With sugar cane and sim- 

 flower there was a tendency to a constant percentage of iron. 



The percentages of silica are iiTegular, but on the whole they were 

 little affected by the carbonate of lime. Wliere large variations 

 occurred, the percentages of sihca in tne plant were very small. 



The amounts of nitrogen in the dry substance were fairly constant 

 for all the plants, so it seems very probable that the lime had no eft'ect 

 on the nitrogen. However, in the stalks of sunflowers from Plats III 

 and IV, and in the roots and stalks of sweet cassava from Plats III 

 and IV there were noticeable decreases in the nitrogen; but the 

 leaves of both plants from these plats showed no decrease in the 

 nitrogen. 



The amount of total ash in the dry substance was slightly increased 

 in all the plants, except rice, by the calcareous soils. For the most 

 part these increases were only three or four per cent, but they occurred 

 with great regularity with bush beans, soy beans, sunflowers, radishes, 

 sugar cane, sweet cassava, and pineapples,' cane leaves from Plat III 

 being the only exception. It thus seems very probable that this is a 

 general effect of carbonate of lime on aU these plants except rice. 



Practically the same observations as were made on the quantity of 

 lime, magnesia, phosphoric acid, etc., in the ash, apply to the quanti- 

 ties of these elements in the dry substance of the plant. There were 

 some differences, however, between the relative ash compositions 

 and the relative amounts of the ash constituents in the dry substance, 



1 See Porto Rico Sta. Bui. 11, p. 35. 



