42 



that can be claimed is, that it is probable, whei-e marked alterations 

 in ash composition accompanied diminished growth, that the changes 

 in ash were the cause of the poor growth. For in adchtion to uncer- 

 tainty as to what changes in ash composition are injuiious, there is 

 the possibihty that differences in growth on the calcareous and non- 

 calcareous soils are conditioned simply by the reaction of the soils, 

 and that the soil reaction affects the plant in some other way than 

 through inffuenciug the absorption of mineral nutrients. If this were 

 so, the decreased growth might not be due to but accompanied by 

 modiffcations in the ash. 



Thus, because of uncertainty concerning the laws governing the ash 

 composition of plants there is considerable doubt of the accuracy of 

 the conclusion that the diminished growth of the plants on the calca- 

 reous soils is due to modifications in their ash composition induced 

 by the carbonate of hme. With these general doubts in mind, how- 

 ever, it appears that injury from the carbonate of hme, so far as it 

 concerns the ash composition of the plant, may be due to one of the 

 following modifications in the plant: 



1. An undue increase in the hme content of the plant or plant ash. 



2. A cUmunition in the iron content of the plant or plant ash. 



3. An increase in the hme combined with a decrease in the iron in 

 the plant ash. 



Judging from the ash analyses reported here it seems that the first 

 modification is the significant one, but judging from the results of 

 direct experiments with pineapples the third modification appears 

 more significant. Of course it is possible that the carbonate of hme 

 may injure different plants differently, influencing the ash ccmposi- 

 tion of one plant in one way and another species in another way. 



With respect to the assimilation of nitrogen, phosphoric acid, and 

 potash it is evident that the carbonate of hme had no depressing 

 effect. Even m the case of rice and pineapples, where the carbonate 

 of hme i^lainly caused a nutritional disturbance, the plants grown on 

 tlio hmy soils oftei^ showed liigher percentages of nitrogen, phosphoric 

 acid, and potash than the check plants. These results are plainly 

 contradictoiy of a view wluch has considerable acceptance, namely, 

 that the nutritional disturbances of some plants on calcareous soils are 

 due to a diminished potash content. The fact that fertilization with 

 potash is not a specific for such disturbances also mihtates against 

 this view. Of course, the results reported do not show whether the 

 carbonate of hme had any effect on the economical utilization of nitro- 

 gen, phosphoric acid, and potash, as those were appUed abundantly 

 and in available forms. 



