166 Fertilisers [pt. hi 



wool, etc., break down more slowly. Field experiments 

 have shown that the eflfect of ammonia only lasts for one 

 season, any excess not taken by the plant being washed 

 out during winter. The easily decomposed substances 

 therefore only act for one year: they are called quick 

 acting manures. The more complex substances decom- 

 pose more slowly and last more than one year : they are 

 called slow acting or lasting manures. There is no 

 special virtue in a slow acting manure: one pound of 

 nitrogen will only jdeld the same amount of ammonia 

 whether the decomposition process takes weeks or 

 years: indeed there is the disadvantage that a slow 

 acting manure represents capital locked up while the 

 quick acting manure gives a quick return. It will be 

 seen below that all the protein substances dried blood, 

 rape cake, guano, the cake fed to animals are quick 

 acting and may last only one year, while straw and wool 

 {i.e., shoddy) last longer in the soil. 



The second great distinction between organic matter 

 and artificial fertilisers lies in their effect on the soil. 

 Artificial fertilisers have comparatively little action as 

 a rule ; organic matter, on the other hand, causes great 

 improvement in physical condition and in water-holding 

 capacity. Some of the Rothamsted plots receiving no 

 organic fertiliser have now so bad a texture that diffi- 

 culty is experienced in getting a tilth, and crops Uke 

 roots that are dependent on a fine tilth suffer accord- 

 ingly: cereals, however, are not affected. On the light 

 soils of Norfolk farmyard manure is almost indispens- 

 able, no mixture of artificial fertilisers having been 

 foimd so effective^ ; bullock feeding is therefore largely 

 practised to ensure ample supplies. On the light soils of 



> Norfolk Chamber of Agric. Expts. 



