34 



althougli of good texture, was heavier than Plats I to III. This 

 heavier physical condition may have influenced the action of the car- 

 bonate of lime, or the lime and physical condition of the soil may have 

 affected the plant growth independently and oppositely. It seems 

 more probable, however, that the physical condition of the soil 

 influences the effect of the carbonate of lime upon the plant. 



Hilgard observed that "the gi'eater the clay percentage in a soil 

 the more lime carbonate it must contain in order to possess the 

 advantages of a calcareous soil."' And m the course of certain other 

 experiments with rice, not reported here, where rice was grown on 

 calcareous soils, we observed that on the heavier calcareous soils the 

 growth was not depressed so much as on tlie more sandy soils. 



THE EFFECT OF CARBONATE OF LIME ON THE ASH COMPOSITION OF 

 PLANTS. 



The extent to which the carbonate of lime in the soil influenced the 

 composition of the ash and the cjuantities of ash constituents in the 

 dry substance of the various plants is shown in Tables VII, X, XIII, 

 XVI, XIX, XXII, and XXV. 



In summarizing tlie effect of the carbonate of lime in the soil upon 

 the ash composition of the plant, it is assumed that the differences 

 in ash composition, which occur between the plants grown on the 

 check and calcareous soils, have been induced by the soil. This 

 assumption is justifiable in so far as other factors tending to induce 

 variations in the asli, such as differences in climate and differences 

 in maturity of the plant, have been ecjualized or eliminated. As 

 pointed out in the previous pages, it is beUeved that in growing tlie 

 plants and taking the samples these factors have. been ecjualized, 

 except in the case of the samples of rice gi-own S4, 102, and 129 days. 

 All the analyses of rice are given in Table XXV, but in the following 

 summary only the analysis of the 25-day sample is considered, for 

 the reason given on page 30. 



The carbonate of hme in the soil increased the jierceutage of lime 

 in the ash of rice very markedly. The percentage of lime in the ash 

 of sweet cassava from Plat IV was also markedly increased. Soy 

 beans, sunflowers (combined leaves and stalks), and sugar cane, 

 however, showed very slight increases in the lime of the ash. In 

 the radish plants from the plat with 5 per cent of CaCOg there was a 

 17 per cent increase of lime in the ash, while in the ashes of radish 

 plants from plats with 18 per cent and 35 per cent of CaC03 there 

 were progi-essively smaller increases of lime. This is analogous to 

 the results of Lemmerman et al. and Meyer (see p. 11) with oats. 

 The lime in the ash of bush beans slightly decreased rather than 

 increased with increasing amounts of CaCOg in the soil. 



> Hilgard, E. Soils. New York and London, 1906, p. 369. 



