685 



Nitrification will not commence it" the alkalinity of the 

 ammonia solution exceeds four hundred parts ot nitrogen per 

 million, and an alkalinity tar below this figure retards nitrification. 



Nitrification is more vigorous in the autumn than in the spring. 

 If the land is allowed to be bare in the autumn there is liable to be 

 a threat loss of nitrogenous matter. It would be best to put in a 

 catch crop and plough it in as it begins to {lower. 



Denitritication is the reverse of nitrification. It is the result 

 of the action of a micro-organism or bacterium on the nitrates, 

 which it decomposes and sets the nitrogen free, which escapes into 

 the air, causing a loss of nitrogen. 



It occurs in soils that are water-logged, or in soils with a large 

 amount of organic matter, such as peaty soils, that oxygen cannot 

 enter. There not being enough oxygen in the soil to allow 

 nitrification to take place, the denitrifying bacteria become active. 

 It cannot take place in free open soils. A plant not only requires 

 nitrogen, potash, phosphoric acid, and the other constituents that 

 are found in the ash for its maintenance ; it requires water just as 

 much as any of the other parts of its food, and in greater proportions. 

 If the plant cannot get enough for its requirements, it sickens and 

 shrivels up. Different soils have different powers of absorbing and 

 retaining water. Soils with a large amount of humus, or decayed 

 vegetable matter, have the power in the highest degree ; light sandy 

 soils possess it in the lowest degree ; clay, not much less than 

 those with a large amount of vegetable matter. 



Schubler gives the following table as the absorptive power of 

 the different soils at 60 deg. Fahr. : 



Per cent, of water absorbed 



by loo parts of earth. 



Siliciqus sand ... 25 



Gypsum ... ... 27 



Calcareous sand ... ... 29 



Sanely clay ... ... ... 40 



Strong clay ... ... ... 50 



Arable soil ... ... ... 52 



Fine calcareous earth ... ... 85 



Garden earth... ... ... 89 



Humus ... ... ... 190 



Schubler in the following table gives the rate of evaporation in 

 different soils at 60 deg. Fahr. : 



In four hours. Time required to evaporate 

 Per cent. <,<> per cent. 



Quart/ ... ... ScS 4hrs. 4inin. 



Limestone ... 76 4 ,, 44 ,, 



Sandy clay... ... 52 5 ,, i ,, 



Stiff ish clay ... 40 6 55 ,, 



Loamy clay ... 46 7 ,, 52 ,, 



