Gypsum as a Manure to Artificial Grasses. 



107 



There is perhaps no artificial manure so decided in its effects 

 upon some soils, so readily obtainable by the farmer, and so plen- 

 tiful in this country, as gypsum ; for an account of which the 

 Society's premium has been this year offered. Its mode of action, 

 too, is easily understood for it acts as a direct food for some 

 plants, is not what is sometimes called a stimulant to vegetation, 

 and has a very slight attraction for the moisture of the atmo- 

 sphere; it neither promotes the decomposition of the organic 

 matters of the soil, nor^, like those decomposing substances, 

 does it furnish the gases of putrefaction for the service of the 

 plant. There are, in fact, only four commonly cultivated crops 

 which contain gypsum in any sensible proportions ; and to which, 

 in consequence, it is a direct food : viz., lucern, sainfoin, red clo- 

 ver, rye-grass, and turnips. Now these are precisely the crops to 

 which the farmer finds, on most soils, gypsum to be a fertilizing 

 top-dressing. Wheat, barley, oats, beians, and peas, do not con- 

 tain a trace of this salt ; and the farmer tells you, that gypsum 

 is of no service to these crops, however the application may be 

 varied.* I have little doubt, therefore, whatever other imaginary 

 powers this manure has been asserted to possess, that gypsum 

 only operates as a direct food or constituent of plants. That it 

 cannot operate by its attraction for atmospheric moisture, I some 

 time since determined by my own experiments ; for 1000 parts, 

 previously dried, when exposed to air saturated with moisture for 

 three hours, only gained 9 parts ; while, under the same circum- 

 stances, a good arable soil, worth two guineas per acre, gained 14 

 parts ; and when compared with other manures, the disproportion 

 is still greater : thus, soot gained 36 parts, and horse-dung 145 

 parts. That it is not a promoter of putrefaction, I have ascer- 

 tained by mixing this salt with various animal and vegetable sub- 

 stances ; it seemed^ in every case, rather to retard than promote 



Sulphuric acid . , . , 43 parts. 

 Lime ...... 33 



Water 24 



100 



But the gypsum of commerce is usually united with a portion of silica and 

 carbonate of lime. It is thus combined in its native state. 

 According to Chaptal and Buchholz, gypsum consists of — 



Sulphuric acid . . . . 32 or 43 



Lime . . ^ . . . 3a or 33 



Water 38 or 24 



* Thus, 1 00 parts of the ashes of the complete plant of the oat, according 

 to Bergman, contain— 



Silica 55 parts. 



Phosphate of lime . . .15 



Potash 20 



Carbonate of lime ... 5 



With some oxide of iron. 



"95" 



