394 



Journal of Agriculture, Yictoria. [lo July, 1912. 



Besides hot and mild lime, a number of other substances have alsa 

 been tried to find their effect upon nitrification. These include gypsum 

 (sulphate of lime) and superphosphate (phosphate of lime), both of which 

 are generally available for application to land. Then magnesium car- 

 bonate, which often occurs as impurity in limestone, has been tested. Ferric 

 hydrate or iron rust is present more or less in practically all soils, and it 

 has been tried as to its effect upon nitrification. It can neutralize some 

 acids as lime does, but is altogether less active. Common salt, excess of 

 which is injurious to crops, has been included. Citric acid was used in 

 order to imitate the acidity of sour land, which lime can be applied to 

 sweeten. Finally, sugar and starch were used to find the effect of too 

 much fresh humus in soil, and also when the soil is badly aerated. 



The scheme of experiments is set forth in Table I, 



The first ten tests supply equivalent amounts of lime, magnesia, or iron 

 in large or moderate doses. Regarding the use of magnesia, which in 

 amount here is about one-sixth too little, reference is made later on. The 

 amount of citric acid in 13 was estimated from the combined carbonic 

 acid found on an analysis of the soil, and to 14 was applied o.i per cent, 

 over and above the amount required for neutralizing. Each of the mate- 

 rials was used in a finely powdered condition. 



