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Illinois Natural History Survey Circular 56 



Established trees 



When rainfall is normal, established trees obtain an adequate 

 supply of water from the soil. During a drought or during 

 extended dry periods in the sunimei , all tiees benefit from 

 watering, but trees weakened h\ injury, disease, or insect 

 pests are especially benefited. The relative moistness or 

 dryness of the soil can be determined by inspecting a soil 

 core removed with a spade or soil-profile tube. Soil taken 

 from different depths should be examined as it is crumbled 

 between the fingers. Dry soil will be powdery, but moist soil 

 will retain its structure. 



Water applied to the soil surface fills the capillary spaces 

 from the top down. A daily surface sprinkling that wets the 

 soil to a depth of 1 inch or so is of little value to trees or 

 grass because most plant roots are at greater depths and 

 remain in dry soil. Instead, water should be applied less 

 frequently and in larger quantities. 



Water should not be applied more rapidly than the soil can 

 absorb it. When w ater is applied too rapidly, it is lost through 

 runoff and erodes the soil surface. Heavy clay soils are 





Figure 9. A mound of earth 3-4 inches high around a newly planted tree serves 

 as the dike of a reservoir that holds sufficient water to soak the soil of the backfill 

 and the soil in the ball about the plant roots. 



