14 



ILLINOIS NATURAL HISTORY SURVEY 



CIRCULAR 52 



STREET 



Fig. 7. — The sites for placing phosphorus and potassium fertilizers in 

 the soil should be uniformly spaced in parallel lines throughout the area to 

 be fertilized. If dry fertilizer is to be placed in holes, the holes are at 2-foot 

 intervals. If liquid fertilizer is to be injected, the sites are 2M> feet apart. 



are mixtures containing nitrogen, phosphorus, and potassium. 

 A satisfactory NPK ratio is approximately 1:1:1 or 2 : 1 : 2. Sug- 

 gested 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 



20-20-20 

 23-19-17 

 25-10-20 



Pounds Per 200 gal. 



30 

 26 

 24 



Fertilizer solutions are injected into the soil at a depth of 

 approximately 18 inches. Injection sites are placed at intervals 

 of 2 1 /o feet in a series of parallel lines 2Vo feet apart throughout 

 the area to be fertilized. There should be approximately 160 in- 



