22 Illinois Natural History Survey Circular 56 



Fertilizing 



1 . Measure ace urately the area to be fertilized and determine 

 its size in square feet. For ease in calculating areas and 

 applying fertilizer, plot a square or rectangular area. 



2. Weigh accurately the amount of fertilizer to be used. 

 A bucket and kitchen scales are useful. 



3. Apply nitrogen fertilizers ainiually to the soil surface at 

 the rate of 6 pounds of nitrogen per 1 ,000 square feet. 

 Uniform applications can easily be made with spreaders 

 commonly used to apply fertilizer to lawns. Nitrogen 

 fertilizers are most effective when applied in April or early 

 May before trees break dormancy. To prevent grass burn, 

 wash fertilizer from grass blades immediately after 

 application. 



4. Applv phosphorus and potassium fertilizers every 3-5 

 years. Phosphorus should be applied at the rate of 3.6 

 pounds of phosphoric acid (P2O5) and potassium at the rate 

 of 6 pounds of potash (K2O) per 1,000 square feet. 



One method is to place dry fertilizer in a series of holes 

 12-15 inches deep at 2-foot intervals in parallel lines 2 feet 

 apart throughout the area to be fertilized. A second method 

 is to use water-soluble inaterials and inject them into the soil 

 using a hydraulic pump and a soil needle. Injections are 18 

 inches deep at 2 '/-'-foot intervals in parallel lines 2 'A> feet 

 apart throughout the area to be fertilized. 



Phosphorus and potassium may be applied in spring or fall 

 but are often applied in spring when hole preparation and 

 needle injection are easier. 



Fertilizing can often be continued indefinitely. Soine woody 

 species, however, may becoirie succulent or develop a 

 weeping appearance after prolonged fertilization. All 

 fertilized plants should be carefully observed each year, and 

 fertilization should be discontinued when it fails to 

 accomplish a purpose. 



