FERTILIZING AND WATERING TREES 



15 



jections in each 1,000 square feet. Each injection site should 

 receive 1.2 gallons of solution. About 150-200 pounds of pressure 

 is adequate to force the liquid into the soil. Experience is re- 

 quired to distribute the material uniformly. 



Gfe rr 





WATERING TREES 



Water in plants has three vital func- 

 tions. The hydrogen in water is a true 

 nutrient and is indispensable in photo- 

 synthesis. Water also serves as the sus- 

 taining liquid in plant cells, filling them 

 and keeping them turgid. This keeps 

 stems upright and leaves fully extended. 

 In addition, water serves as a carrier. 

 Nutrients can enter plants and be used 

 only in their ionized state, which re- 

 quires an aqueous solution. 



Water in the soil is classified in four 

 groups : water bound chemically to min- 

 eral salts, water bound hygroscopically 

 to solid soil particles as a very thin film, 

 water held in the soil by capillary action, 

 and water moving due to the influence of 

 gravity. 



Water that is chemically or hygro- 

 scopically bound is not available to 

 plants. Gravitational water rapidly 

 seeks a lower level in the soil or runs off 

 on the surface and is of limited impor- 

 tance to plant growth. Capillary water is 

 of paramount importance. The amount 

 of suspended capillary water in soil de- 

 pends on the texture and structure of the soil. The maximum 

 amount of capillary water a soil can hold, after the gravitational 

 water has percolated through, is called field capacity. Water 

 available to plants is at its maximum when field capacity has 

 been reached. 



It is possible to overwater. Plant roots require both moisture 

 and air for normal development. Adding large quantities of 

 water too frequently to heavy clay soils may bring about a water- 



Fig. 8. — A soil needle, 

 fed by a hydraulic pump, 

 may be used to inject 

 water-soluble fertilizers 

 into the soil. It may also 

 be attached to a hose and 

 used to water trees. 



