THE VALUE OF MANURE 159 



2. By acting upon the soil, forming humates and 

 rendering the inert mineral plant food of the soil more 

 available. 



3. By raising the temperature of the soil, as the re- 

 sult of chemical action. 



(b) Physically: 



4. By making the soil darker colored. 



5. By enabling soils to retain more water and to 

 give it up gradually to growing crops. 



6. By improving the physical condition of sandy 

 and clay soils. 



7. By preventing the denuding effects of heavy 

 wind storms. 



