70 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



of these potash fertilizers has to be considered, and eventually liming 

 has to be carried on in conjunction with it. 



A question, then, of considerable importance for agriculture is the 

 judicial regulation of the lime and magnesia content of the soil, espe- 

 cially when mineral fertilizers are employed. This regulation must 

 be based on the knowledge of the readily assimilated amounts of these 

 bases. Hence only the liner soil particles should serve for analysis. 

 When a soil is much richer in magnesia than in lime extensive liming 

 is necessary. The liming should be clone chiefly with the carbonate 

 and only in part with slaked lime and the sulphate. On the other 

 hand, when the magnesia content is much less than that of lime the 

 addition of a powdered magnesian limestone or magnesite is necessary. 

 Burned magnesite and artificially precipitated magnesium carbonate 

 must be avoided under all circumstances, since they are too hnely 

 divided and too easily absorbed. 



Experiments to determine the most favorable ratio of lime to mag- 

 nesia have recently been made by D. W. May (1900), in Washington,* 

 and by K. Aso and F. Furuta (1901), in Tokyo. 6 The results of these 

 experiments show that cereals thrive best when the lime content of 

 the soil only slightly exceeds that of magnesia. Crops having more 

 abundant foliage, however, require considerably more lime. For the 

 most luxuriant development cabbage needs twice as much lime as mag- 

 nesia, while buckwheat requires three times as much lime as magnesia. 



a Bull. 1, Bureau of Plant Industry, U. S. Dept. of Agriculture, The Relation of 

 Lime and Magnesia to Plant Growth, Washington, 1901. [On page 34 read 0.05 cm. 

 and 0.02 cm. instead of 0.5 cm. and 0.2 cm.] 



&Bull. College of Agriculture, Tokyo, 1901, Vol. IV, No. 5. 



o 



