12 



ILLINOIS NATURAL HISTORY SURVEY 



CIRCULAR 52 



Fertilizers containing pho. phorus and potassium should not 

 be broadcast or spread on the surface. Applying such fertilizers 

 as 10-10-10 at the recommended rate for nitrogen of 6 pounds 

 per 1,000 square feet may cause severe damage to grass. 



Do not use nitrogen fertilizers that have gotten wet and be- 

 come lumpy or caked for surface applications. 



Dry fertilizers in holes 



Another method of fertilizing trees is to place dry fertilizers 

 in holes in the soil. Phosphorus and potassium fertilizers applied 

 to the soil surface are not available to most nutrient-absorbing 

 roots of trees. To become available, these materials must be 

 placed in the soil occupied by plant roots. Contrary to the belief 

 of some, the majority of nutrient-absorbing roots of trees are 

 not at great depths in the ground but are located within 2 feet of 

 the soil surface. Here moisture, aeration, and nutrient conditions 

 are favorable for root growth. 



Holes can be punched in the soil with a punch bar or drilled 



m 



s I 



Fig. 6. — A punch bar 

 (left) or an electric 

 drill with a soil auger 

 (right) can be used to 

 prepare holes for appli- 

 cation of dry phospho- 

 rus and potassium fer- 

 tilizers. 



