NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 153 



over soil is apparently due to better drainage than is obtainable in 

 heavier soil types. Considering the danger of injury from some chem- 

 ical dips and also the fact that the roots are more moist than normal 

 after dipping, chemical dips used prior to heeling-in the seedlings in 

 sand have been found unnecessary. Heel-in sites should be rotated 

 from year to year. In the southern plains, Siberian elm seedlings can 

 best be left in the nursery row over winter and lifted as needed. 



It takes only a short time for the rot to spread rapidly under con- 

 ditions favorable to its development, and special effort should be made 

 to plant the Siberian elm seedlings as soon as possible after they have 

 been removed from the heel-in beds in the spring. While this rot is not 

 so active as to destroy the value of the seedlings, it has been found that 

 it does retard early foliage development. The uninfected or slightly 

 infected plants leaf out earlier than those which have severely rotted 

 roots. This is of considerable importance because the most rapid root 

 growth of the seedlings takes place early in the season, and delayed 

 growth may interfere seriously with the winter hardiness or drought 

 resistance of the trees, due to the lack of adequate food storage. 



For overwinter storage of other broadleaf species, the seedlings can 

 be heeled-in in sandy soil out of doors and the tops protected with 

 straw as recommended for Siberian elm. 



NURSERY COSTS 



The cost of growing nursery stock depends on the size of the nursery, 

 irrigation facilities, the number of species grown, and other variable 

 factors such as seed costs, age class of stock, and grading standards. 



Costs are invariably higher for species which are grown in small 

 numbers, and lower for those nurseries in which the nurseryman can 

 concentrate his efforts on maximum efficiency in large-scale production 

 of a relatively few species, Disease, insects, and unfavorable climatic 

 conditions are other factors which may increase cost in spite of all the 

 nurseryman's efforts to keep losses at a minimum. 



Experience has shown that nurseries in the plains region which are 

 not protected by an irrigation system often suffer severe losses in 

 drought years. Such losses occur either in the form of complete killing 

 of the plants, or in very high nursery costs because of reduced growth 

 rate of the stock to such an extent that 80 or 90 percent does not attain 

 plan table size. 



It has been argued, in some instances, that, regardless of the severity 

 of drought, nursery stock for plains planting should be grown only 

 under dry-land conditions without irrigation or watering, on the 

 ground that trees that cannot survive in the nursery would certainly 

 not survive in the field. This argument loses force when examined 

 critically. In the first place, field-planted stock, because of a much 

 wider spacing, has a maximum of anywhere from 24 to 96 square feet 

 of growing space per plant, while in the nursery each seedling has only 

 from ){ to % square foot of growing space per plant. Secondly, sturdy, 

 well-rooted nurseiy stock planted on typical field sites for shelter- 

 belts can root deeper by midsummer and consequently draw moisture 

 from greater depths than small seedlings. It has been clearly demon- 

 strated that field survival is closely correlated with the size of stock at 

 time of planting. Again, if soil moisture content drops very low in the 

 nursery owing to lack of irrigation, the stock produced will be much 



