DIFFERENT METHODS OF FARMING, ETC. 95 



chanical condition of heavy clays is, however, im- 

 proved by the addition of humus-forming material. 

 The addition of humus to loam or sandy soils is bene- 

 ficial in preventing the soil from drifting, because it 

 binds together the soil particles. There are but few 

 arable soils, under ordinary cultivation, to which it is 

 not safe to add humus-forming materials, either alone 

 or jointly with lime. Ordinary prairie soils, for the 

 first ten years after breaking, are usually well supplied. 

 Swampy, peaty, and muck soils contain large amounts, 

 in fact, they are often overstocked. "Alkali" soils 

 are usually deficient in humus. 



112, Active and Inactive Humus. When soil has 

 been long under cultivation, and no manures have 

 been used, the nitrogen and mineral matters combined 

 with the humus are reduced. The humus from long- 

 cultivated fields contains a higher per cent, of carbon 

 than that from well-manured or new land ; it is also 

 less active because of the higher per cent, of carbon 

 which does not readily undergo oxidation. 18 



Total humus material.. 5.30 3.38 



113. Influence of Different Methods of Farming upon 

 Humus. The system of farming has a direct effect 

 upon the humus content and the composition of the 



