Rotation 93 



Addition of humus. Land is very rapidly improved 

 by the incorporation of fiber. This fiber is secured by 

 plowing under any kind of vegetation, as rye, clover, 

 manure or the refuse of the garden. When this fiber 

 decays it becomes humus. The humus improves the 

 physical condition of the soil by making it loose, open 

 and mellow; by enabling it to hold moisture; by pre- 

 venting the puddling or cementing of clay soils; by 

 decreasing the heat of the surface soil in summer; 

 and by improving the chemical condition. Humus 

 itself contains plant -food. It also affords solvent 

 acids which tend to unlock other plant -foods. If it is 

 derived from leguminous plants, it also adds nitrogen. 

 The chief reason for the almost extravagant use of 

 stable manures by market -gardeners is the addition of 

 humus. Lands which are thus manured year after year 

 become quick and amenable to treatment. Fertilizers 

 work quickly in them. The lands can be tilled at 

 almost any time in the growing season, and when one 

 crop is off another can be put in quickly. 



One great value of the rotation of crops is that it 

 adds fiber and humus to the soil. It is probable that 

 there is a tendency to use stable manure in excess 

 in garden lands; that is, the same results in the incor- 

 poration of humus can be had in many cases more 

 cheaply by the growing of catch -crops. Particularly 

 is this true of those areas which are some distance 

 from the market and in which it is not necessary to 

 practice rapid succession of market crops. 



Land which receives identical treatment year by 

 year tends to depreciate. A rotation is useful because 



