128 MISC. PUBLICATION 4 3 4, U. S. DEPARTMENT OF AGRICULTURE 



Protection from soil movement may also be obtained by cultivating 

 in a manner that will leave the ground rough or ridged. A ridge of 

 soil thrown over the seed rows will appreciably reduce the danger of 

 the seed being uncovered (fig. 52) . Because the destructive hot winds 

 so damaging to young seedlings come generally from the south, nurs- 

 erymen run the rows in an east-west direction whenever the lay of 

 the land permits, to break the sweep of the wind near the ground. 



If at all possible, nursery sites should be located so as to take ad- 

 vantage of natural or artificial tree windbreaks (fig. 53). In planning 





Figure 52. — Ridging of seed rows and use of snow fence aid in giving winter 

 protection to fall-sown seed. 



a permanent windbreak of trees for a nursery site in the plains region, 

 provision should be made to enclose the area at least on the south, 

 west, and north sides from which the damaging winds usually come; 

 the east side may also be enclosed to advantage. The intensive pro- 

 tection afforded by a windbreak has been shown to extend out on the 

 leeward side to a distance of 10 to 15 times the height of the wind- 

 break. Windbreaks should therefore be spaced in such a manner as 

 to provide reasonably good protection when the trees are 10 to 20 

 years old. This means that the parallel belts should not be farther 

 than 660 feet apart, and less on unstable sandy soils. 



Annual plants — such as sorghum, cane, sunflower, and Sudan grass 

 have been tried as windbreaks in many nurseries in the plains region, 

 but results are disappointing. The plants are of little help to the 

 seedlings during the early critical period because of lack of height at 

 that time. Another disadvantage is that they sap the soil moisture 

 and stunt the seedlings in the nearby rows. If used at all they should 

 be planted adjacent to irrigation ditches where their sapping effect will 

 not be so evident. 



