52 CHEMISTRY, GEOLOGY 



Hay is returned to the land in the form of 

 the dung of the animals by which it has been 

 used as food. Straw is sometimes cut and mixed 

 in feed, and thus becomes manure ; but it is 

 generally returned to the soil trodden amongst 

 the litter. Where few cattle are kept, straw is 

 rotted with water and a little cow-dung, and put 

 into the land in a half-fermented state. For 

 light lands, the straw, etc., should be well rot- 

 ted ; but for heavy lands the manures are best 

 applied half-fermented, because then they help 

 to keep the soil light and porous. 



Rape-cake and rape-dust are also applied as 

 manures to turnips and potatoes, thereby saving 

 the whole or a part of the common farm-dung. 

 It is also sometimes applied advantageously as a 

 top-dressing to spring wheat. Rape-cake is the 

 substance that remains when the oil is squeezed 

 out of the seed ; and when the cake is dried and 

 crushed it becomes rape-dust. 



The most important animal manures are blood, 



Questions. How is hay returned to the soil as a ma- 

 nure ? How is straw used for the same purpose ? What 

 difference should there be in vegetable manures for light 

 and heavy soils ? Is rape-cake useful as a manure ? Hov 

 is it made ? How is it applied as a manure ? 



