128 FOOD FOR PLANTS 



is exceptionally high and the physical condition of 

 the soil is good, applications of inoculated sulphur 

 might be more economical and satisfactory. 



A mixture of inoculated sulphur and lime in the 

 right proportion, however, will have somewhat the 

 same effect as gypsum. If sulphur and calcium are 

 both needed, cost ought to be the big factor in de- 

 termining whether to use gypsum or lime and 

 sulphur. 



Functions of Gypsum. 



1. Gypsum neutralizes black alkali. 



2. Gypsum supplies both calcium and sulphur. 



3. Improves the mechanical condition of the soil, 

 etc. 



4. Promotes the development of beneficial bac- 

 teria through the calcium it supplies. 



5. Helps in the decay of organic matter. 



By comparing the functions of lime with gypsum, 

 the following main differences should be noted: 



1. Whereas lime corrects acidity, gypsum does not. 



2. Whereas gypsum neutralizes black alkali, lime 

 does not. 



A further discussion of the value and use of gyp- 

 sum is given later. 



Ground Sulphur. 



Ground sulphur, 97 per cent to 100 per cent pure, is 

 in an unavailable form until bacteria change it to a 

 sulphate, hence it may remain useless in the soil for 

 years. There is now an inoculated sulphur on the 

 market which contains sulphating bacteria and thus 



