40 GARDENING FOR THE SOUTH. 



It is by putrefaction that all animal and vegetable re- 

 mains are rendered available to plants, but if they are al- 

 lowed to decompose without care, the loss is immense ; the 

 soluble parts are washed away, the gases pass off into the 

 air, and a large proportion of the manure is dissipated. 



The Indirect Action of Manures. Some manures 

 ameliorate the soil by absorbing and retaining moisture 

 from the atmosphere. This property is as beneficial to 

 a clay as to a sandy soil during drought, as at such times 

 clays are often baked so as to be impervious to the dew 

 and suffer nearly or quite as much as more sandy soils. 

 The best aborbents of moisture are stable manure, thor- 

 oughly decomposed tan-bark, and the manure of the cow 

 and pig, in the order named. After these come sheep and 

 fowl manure, salt, soot, and even burnt clay is not with- 

 out its virtue. All these absorbents are much more effec- 

 tual when finely divided, and the soil itself is a good ab- 

 sorbent in proportion to its richness, fineness, and the 

 friability produced by frequent culture. In the power of 

 retaining moisture absorbed, pig manure stands preemi- 

 nent ; next that of the horse, then common salt and soot. 



Some manures are beneficial in absorbing not only mois- 

 ture, but nutritious gases from the atmosphere, which they 

 yield to the roots in a concentrated form. All animal and 

 vegetable manures have the power of attracting oxygen 

 from the air during decomposition. Charcoal and all car- 

 bonaceous matters have the power of absorbing carbonic 

 acid gas in large quantities, supplying constantly to the 

 roots of plants an atmosphere of carbonic acid, which is 

 renewed as quickly as it is abstracted. The same sub- 

 stances are especially valuable for their power of absorb- 

 ing ammonia. Charcoal will absorb ninety times its vol- 

 ume of ammoniacal gas, which can be separated by simply 

 moistening it with water. 



Decayed wood absorbs seventy times its volume, while 



