90 MISC. PUBLICATION 43 4, U. S. DEPARTMENT OF AGRICULTURE 



by irrigation. Eight to ten inches is the customary depth for this 

 type of root pruning. The usual tool is a sharp U -blade shrub digger 

 with the lifter removed to prevent unnecessary disturbance of the 

 seedling. 



Blocks which are to be handled as 2-0 stock can sometimes be root 

 pruned to advantage at the end of the first growing season if it appears 

 that it will be necessary to retard the growth during the second season. 

 This also makes it possible at this time, in case of shortage of planting 

 stock of the species concerned, to pull whatever seedlings of usable 

 grade have been produced. Such root pruning if not done in the 

 fall of the year may be done in early spring. The soil should be 

 packed firmly following the operation. If the soil is dry, irrigation 

 will be necessary for best results. Ridging up the soil against fall- 

 pruned seedlings to a height of 2 or 3 inches will also be desirable. 

 Six to ten inches is a satisfactory pruning depth. 



Top pruning to control size and quality of stock has been experi- 

 mentally tried by several of the Forest Service nurseries, and for 

 certain shrub species requiring 2 years of nursery growth it has 

 proved itself worth while as a means of promoting low branching and 

 retarding needless height growth. Top pruning does not appear 

 necessary for most tree species, except in the few instances where 

 prolonged or uneven germination has permitted a part of the stand 

 to overtop and so retard the development of the younger seedlings. 

 It has been suggested but not thoroughly tested as a means of forcing 

 diameter growth in lieu of height growth on some species. 



Cultivation 



Deciduous nursery stock as a crop requires rather intensive culti- 

 vation, for which two major purposes are recognized: To reduce com- 

 petition, i. e., remove weed growth; and to keep the soil in good 

 physical condition, thus permitting aeration, normal bacterial action, 

 and absorption of rainfall. Crusting and baking of the surface soil 

 must be held to a minimum when normal growth is expected. 



Much of the success of cultivation will depend upon the physical 

 condition of the soil at sowing time. Those soils which are naturally 

 mellow or friable or which have been properly prepared, can be cul- 

 tivated much more easily and to better advantage than soils that are 

 hard, cloddy, or in a puddled condition. 



Cultivating tools should not go deeper than 2 to 3 inches; contin- 

 uous deep cultivation, especially close to the rows, will sever the 

 shallow spreading roots of the seedlings. 



Thoroughness of the cultivation job must also be stressed; a careless 

 job may not only result in mechanical injury to the stock, but may 

 destroy only a small percentage of the weeds and make their later 

 removal more difficult. 



Timeliness in cultivation is equally important. Competing growth 

 must be destroyed while it is in the seedling stage, preferably when it 

 is less than 3 inches high. Excessive weed growth invariably makes 

 cultivation more difficult and expensive and less effective, and will 

 cause an unnecessary drain on soil moisture. Timeliness is also of 

 major importance in improving the physical condition of the soil. 

 To keep crusting, baking, or clodding at a minimum, the soil must 

 be cultivated after each heavy rain or following every irrigation, as 



