18 Illinois Natural History Survey Circular 56 



The readily available, commei( ial, water-soluble fertilizers 

 are mixtures containing nitrogen, phosphorus, and 

 potassium. A satisfactory NPK ratio is approximately 1:1:1 

 or 2: 1 :2. Suggested formulations of water-soluble nitrogen, 

 phosphorus, and potassium fertilizers are listed below with 

 the number of pounds that should be dissolved in 200 gallons 

 of water and injected into 1,000 square feet of soil (select 

 one): 



NPK formulations Pounds per 200 gallons 

 20-20-20 30 



23-19-17 26 



25-10-20 24 



Fertilizer solutions are injected into the soil at a depth of 

 approximately 18 inches. Injection sites are placed at 

 intervals of 2 V2 feet in a series of parallel lines 2 V2 feet apart 

 throughout the area to be fertilized. Approximately 160 

 injections should be made for 1,000 square feet. Each 

 injection site should receive 1.2 gallons of solution. About 

 1 50—200 pounds of pressure is required to force the liquid 

 into the soil. Experience is required to distribute the material 

 uniformly. 



Why should you water trees? 



Water in plants has three vital functions. The hydrogen in 

 water is a true nutrient and is indispensable to photosyn- 

 thesis. Water also serves as the sustaining liquid in plant cells, 

 filling them and keeping them turgid. This turgidity 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 requires an aqueous 

 solution. 



Water in the soil is classified into four groups: water bound 

 chemically to mineral 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. 



