CHAPTER VII. 



Experiments with gypsum and with the sulphates of magnesia and iron. Re- 

 sults of experiments with gypsum applied alone. Theory of the action of 

 gypsum. Why it does not produce equal effects everywhere and on all crops. 

 Suggestions for experiments with gypsum applied alone. Proportion of mag- 

 nesia contained in our usually-cultivated crops. Theory of the special action 

 of sulphate of magnesia. Suggestions for experiments with sulphate of mag- 

 nesia. Suggestions for experiments with sulphate of iron. 







1. Results of experiments with gypsum applied alone, and 

 in the different months of spring. 



IT is conceded I may say established that gypsum has a 

 remarkably fertilising effect when applied to certain crops on 

 certain soils. In Germany, its beneficial action upon clover is 

 proverbial, and in North America it is applied successfully to 

 crops of almost every kind. It is there said " to equalise the 

 value of lands, by rendering those which are naturally poor 

 almost as productive as the rich."* When its use was first 

 introduced into the United States by Dr Franklin, it was im- 

 ported by his countrymen from Paris : it is now found in the 

 State of New York, and largely in Nova Scotia, from whence 

 it is shipped in large quantities to different parts of the Union. 



The number of accurate experiments upon the effects of 

 gypsum applied alone, which I find upon record, is compara- 

 tively small. I quote nearly all that have been published of 

 late years in this country. 



1. Upon red clover. Mr Smith of Tunstal, near Sitting- 

 bourne, dressed his clover at the rate of 4 cwt. per acre, and 

 obtained of hay from the 



2d Cutting. 



5 cwt. 

 22*... 



I7f cwt.t 



Undressed, 

 Gypsumed, 



Increase, 



1st Cutting. 



20 cwt. 

 60 ... 



40 cwt. 



Seed. 



20 lb. 

 105 ... 



~85lb. 



* Nicholson's American Farmer's Assistant, p. 217. f Brit. Husb., i. p. 322. 



