26 CIRCULAR 112, BUREAU OF PLANT INDUSTRY. 



there is a layer of hardpan and clay. On the other hand, it is far 

 from clear that the diminished output per acre reported for some of 

 the rich, deep alluvial soils is due to their decreased productiveness, 

 especially if such soils are overflowed in winter and thereby receive 

 a deposit of sediment. The fact that the application of commercial 

 fertilizers to some of these soils has as a rule yielded negative results 

 seems to indicate that they are not lacking in available plant food, 

 and a study of the other factors concerned will probably reveal the 

 most important causes of the decline in yield, if such is actually 

 taking place. 



It is the purpose of the present publication to direct attention to 

 the often unappreciated extent of the losses due to imperfect stand 

 and to offer certain suggestions which, if followed, should result in 

 an increased yield without materially increasing the cost of pro- 

 duction. 



CAUSES OF IMPERFECT STANDS. 



In newly planted yards a small percentage of missing hills may 

 normally be expected, owing to the failure of some of the cuttings to 

 strike root. In most cases, after a yard has come into full bearing 

 the stand tends to become poorer and poorer through the dying out 

 of the plants from causes at present imperfectly understood. This 

 dying out occurs in all the hop-growing sections of the United States, 

 but it is far more prevalent in some districts than in others. Many 

 ingenious explanations have been offered to account for this trouble, 

 but a satisfactory one yet remains to be found. From extensive 

 observations made in the hop fields of the United States and of 

 Europe the writers have reached the tentative conclusion that a 

 primary cause lies in too severe or faulty pruning, in the bruising of 

 the roots in plowing, and in the crushing of the crown of the plant by 

 the feet of horses and the wheels of wagons when teams are driven 

 over the fields. 



Hills often die out because of weakness or disease induced either 

 by the rough treatment received when they are uncovered at pruning 

 time or by the injuries inflicted by the plow or other implements used 

 in cultivation. When the roots are bruised or torn they heal slowly 

 and imperfectly and are almost certain to become infected by some 

 of the destructive organisms widely distributed in the soil. 



In most hopyards some attention is given each year to replanting 

 the missing hills, but, since the trouble is rarely taken to make 

 certain that the cuttings are sound and vigorous and that they come 

 from hills selected for their thriftiness and high yield, many replants 

 either die outright the first year or maintain a struggling and un- 

 profitable existence. The vigor of the cuttings is often impaired 

 through the lack of precaution to keep them from drying out before 



[Cir. 112] 



