50 ACTION OF FARMYARD MANURE ON SOILS. 



whose friability and openness are already too great, 

 and which do not require to be increased, the manure 

 will be best applied in a rotten condition. It adds, 

 further, greatly to the heat of the soils by its decom- 

 position. Thus on cold damp soils it effects one very 

 marked benefit. The influence it exerts in its decom- 

 position upon the fertilising ingredients present in 

 the soil is also by no means inconsiderable. In the 

 process of its fermentation large quantities of carbonic 

 acid gas are generated. This carbonic acid probably 

 acts in a double capacity. It will, in the first place, 

 greatly increase the solvent power of the soil-water, 

 and thus enable it to set free an increased amount of 

 mineral plant-food ; and secondly, it will help to con- 

 serve a certain quantity of the soil-nitrogen, by pre- 

 venting its conversion into nitrates. 



As its indirect and mechanical properties are greatest 

 when in its fresh condition, it will be better to apply 

 it in that condition to soils most lacking in these 

 mechanical properties. We may therefore say that 

 farmyard manure is best applied in a rotted condition 

 to light sandy soils, and to soils in a high state of 

 cultivation, where its mechanical properties are not 

 so much required. 



An important point still remains to be discussed 

 viz., the rate at which the farmyard manure should be 

 applied. This, of course, should naturally depend on 

 a variety of circumstances the amount of artificial 

 manures used as supplementary to the farmyard 



