72 THE AMERICAN APPLE ORCHARD 



These plants, such as vetch, cowpea and the clovers, col- 

 lect more or less nitrogen from the atmosphere. When 

 the crops are plowed under and decomposed this 

 nitrogen becomes available for the trees. As nitrogen 

 is the most expensive element of plant food, this source 

 of supply is always welcome. While the quantity of 

 atmospheric nitrogen available from cover crops has 

 probably been greatly exaggerated in some estimates, 

 it is still sufficient in many cases to supply the entire 

 needs of the orchard. With a good annual growth of 

 cowpeas, soy beans or vetch, apple trees will need no 

 further allowance of nitrogen. 



METHODS OF MANAGEMENT 



The usual method of handling a cover crop is 'to sow 

 the seed broadcast at the last cultivation of the soil. 

 Usually this comes during the first two weeks of July. 

 Later sowing may prove successful in southern states, 

 where a long growing season may be depended on. 

 In northern districts where frost comes early some- 

 what earlier sowing of the cover crop is desirable. 



Indeed, this desirability of earlier sowing has sug- 

 gested a modification of the common procedure as 

 outlined above. This consists in sowing the cover 

 crop considerably earlier, usually the middle of June, 

 but possibly even earlier than that. The cover crop 

 is then put in with a drill, the drills being i8 inches 

 to 2 feet apart. The crop is then cultivated once, 

 twice or three times, by running a light cultivator 

 between the drills. Thus the season of cultivation is 

 made to overlap the growing season of the cover crop. 

 An additional and highly important advantage lies in 

 the fact that this method insures a quicker, evener and 



