132 Report of Farmers' Iivstitutes 



The magnesia in silicate form has some value to keep the soil 

 sweet and promote the growth of lime-loving plants. 



New York soils pretty generally contain more magnesium than 

 calcium in total. Strongly magnesian lime is, therefore, not 

 desirable on the soil. However, the use of a lime containing not 

 over 15 per cent of magnesia is not seriously objectionable. 



FINENESS OF LIMESTONE 



Bearing on the relation of fineness to solubility, the Tennessee 

 investigations show that ground limestone passing a one-hundred- 

 mesh screen, and in which the average length of crystals was .005 

 millimeter (.0002 inch), was only 7.7 per cent as soluble in car- 

 bonated water in four hours as precipitated chalk in which the 

 average length of crystals was .0003 mm. (.000012 inch). This 

 difference in solubility may be attributed to difference in surface 

 exposed by the particles to solution. 



No conclusion as to the proper fineness can be drawn from field 

 tests where limestone containing particles of a wide range of 

 fineness is used. 



The possibilities of distributions may readily be calculated. 

 Assuming that one ton of ground limestone is uniformly distrib- 

 uted in the surface six inches of soil of one acre, the number of 

 particles in each cubic inch of soil for different degrees of fine- 

 ness would be as follows: 



Diameter of Particles per 



limestone particles cubic inch of soil 



1/10 inch:=2. millimeters 2. 



1/50 inch=0.5 millimeters 137. 



1/100 inch=0.25 millimeters 1200. 



Since the diffusion of soluble material through the soil is known 

 to be exceedingly slow, the inference is that large particles of 

 lime would form a thin shell of neutral or slightly alkaline soil, 

 and the remainder of the mass would be influenced only as the 

 capillary movement of water carried the lime carbonate beyond 

 this shell. The probabilities of the tenth-inch materials reaching 

 the entire cubic inch of soil within five years is small. 



