MANAGEMENT 45 



and drained away out of reach of the trees. When 

 the cover crop is growing, these fertilizers are tem- 

 porarily taken up by this cover-crop to be subse- 

 quently made again available when the cover crop 

 decays in the soil. This service is particularly well 

 rendered by such a crop as winter vetch, which 

 grows nearly all winter. 



(3) The cover crop saves erosion of the soil. 

 Many orchard soils wash badly, especially in early 

 spring. This difficulty is made one of the chief 

 arguments against cultivating orchards. The dam- 



FIG. 20 EXTENSION* DISK HARROW 



age can be largely avoided by the use of some cover 

 crop such as winter vetch, which grows at a very 

 low temperature, and which holds its place through- 

 out the winter. 



(4) The cover crop adds humus or vegetable 

 matter to the soil. This addition is extremely im- 

 portant. One of the most serious defects of the 

 tillage system is that it tends to deplete this supply 

 of vegetable matter. This tendency may be wholly 

 corrected by the proper use of cover crops. 



