FARM MANURES 613 



have had time to leach into the soil or to largely change 

 to a carbonate form. 



516. Composting. A compost is usually made up of 

 alternate layers of manure and some vegetable matter 

 that is to be decayed. Layers of sod or of humous soil 

 are often introduced. The manure is used to supply 

 the decay organisms and to start the action. The foun- 

 dation of such a humus manufactory is usually soil, and 

 the pile is preferably capped with earth. The compost 

 should be kept moist in order to prevent loss of ammonia 

 and to encourage vigorous bacterial action. Acid phos- 

 phate or raw rock phosphate and a potassium fertilizer 

 are often added, to balance up the mixture and make it a 

 more effective fertilizer. Lime is also introduced, to react 

 with such organic acids as may tend to form and to inter- 

 fere with proper decay. Undecayed plant tissue, such as 

 sod, leaves, weeds, grass, sticks, or organic refuse of any 

 kind, may thus be changed slowly to a humus which will be 

 valuable in building up the soil and in nourishing plants. 

 Even garbage may be disposed of in such a manner. 



517. Manure and muck. Muck soil recently re- 

 claimed from a swamp condition is usually treated, if 

 possible, with a dressing of manure. This is not so much 

 for the purpose of adding plant-food as to supply decay 

 and decomposition organisms that will break down the 

 complicated humic compounds into such forms as may 

 be utilized by the crop. Plenty of lime is therefore essen- 

 tial in muck, in order to render the effects of this inocu- 

 lation effective and lasting. 



518. Effects of manure on the soil. The direct fer- 

 tilizing effect of manure is by no means its greatest 

 influence. In the first place, manure as it rots down 

 produces humus. This humus increases the absorptive 



