No. 85.J 73 



Gypsum, 30 lbs. 



Epsom salts, 200 " 



Alum, 83 " 



Bone dust, c 210 " 



The importance of any particular earth or salt to the growth of 

 plants, and the influence which even a minute quantity can exert, is 

 perhaps best shown by the action of plaster on clover. According to 

 Prof. Johnston, " half a grain of gypsum in a pound of soil, indicates 

 the presence of nearly two cwt. in an acre, where the soil is a foot 

 deep, — a quantity much greater than need be added to a soil in which 

 gypsum is almost entirely wanting, in order to produce a remarkable 

 luxuriance of the red clover crop. In 100 grains of this soil, this 

 quantity of gypsum amounts to only seven thousandths of a grain 

 (__'^_ or 0.007 grs.) — a proportion, which only a very carefully con- 

 ducted analysis would be able to detect, and yet the detecting of which 

 may alone be able to explain the unlike effects which are seen to fol- 

 low the application of gypsum to different soils." Now every farmer 

 is aware, that half the above quantity of gypsum, or 100 lbs. per acre, 

 constitutes a sufficient dressing in most cases, and that a greater quan- 

 tity on vegetables, or soils favorable to its action, would injure rather 

 than benefit, by causing an overgrowth. We are aware of only two 

 cases in which the addition of plaster appears to produce no effect ; 

 one of these is where the soils are near the sea, and consequently ex- 

 posed to the effects of a sea atmosphere ; and the other is, where the 

 land is wholly or partially irrigated by surface waters holding in solu- 

 tion considerable quantities of lime or its sulphates, and which will 

 be more or less of it left as a deposit annually. All hard waters are 

 of this class, though in some the proportion of gypsum is much greater 

 than in that of others. 



We may remark here, that as a general rule, (and the exceptions 

 are yet to be discovered,) whenever a substance is always present in 

 soils, it is essential to the formation of plants, and they cannot suc- 

 ceed without it. Lime furnishes an instance of this substance. No 

 soil, moderately fertile, is found destitute of lime, and there is no plant 

 in the ashes of which lime may not be detected, and which of course 

 it must have derived from the earth. This we think determines the 

 utility, or rather the necessity of the presence of lime in all cultivat- 

 ed soils. Much has been written and said on the use of lime as an 

 application to the soil, which might have been spared, had this law 



