Fertilizing 79 



soil acts precisely like a mulch, the capillaries having been 

 destroyed. Hence no water can rise from below into the 

 surface layer, and thus loss of Avater by evaporation is pre- 

 vented. In applying water to the surface, therefore, the 

 compacting of the soil by the water must be avoided, and 

 this is best done by applying the water through ditches or 

 lioles near the tree, by sub-surface watering. 



Where, due to soil and topographic conditions, continued 

 excess of moisture is experienced, and aeration thus im- 

 peded, the drainage must be improved. Usually it is better 

 simply to lower the water table than to attempt thorough 

 draining. An open or coA'ered ditch properh' located at 

 some distance will do the work. Such ditches may be filled 

 up with rubble and then be again covered and sodded. 



It is, however, advisable to be very cautious in attempt- 

 ing the regulation of the water-supply by drainage, for not 

 only do species vary in their water requirements, but the 

 individual trees, having once adapted themseh'es to a wet 

 situation, may resent any sudden change of condition. 

 Time must, therefore, be allowed the tree to axlapt itself, 

 by changing the water level gradually, while at the same 

 time the process of adaptation may be assisted by judicious 

 pruning. 



Fertilizing. Troubles due to deficiency in mineral sails 

 in the soil are of rare occurrence, since most soils contain 

 sufficient quantities of the needful minerals of which trees 

 require only small amounts, their bodies being mainly built 

 up from the carbon of the air. The only mineral likely 

 to be deficient is nitrogen, the lack of which would produce 

 a yellow or even whitish appearance of foliage. In nature 

 this mineral is provided by the decay of fallen leaves, in 

 which the nitrogen-gathering bacteria work. So the practice 

 of raking off the leaves in parks is one way of starving trees. 



