FERTILIZING AND WATERING TREES 3 



Nitrogen is a component of chlorophyll pigments and therefore is 

 important in the production of food in plant leaves by photo- 

 synthesis. Nitrogen is also found in some plant vitamins and 

 enzymes and is consequently essential in metabolism. 



An abundance of nitrogen in the soil promotes plant growth, 

 particularly of the above-ground portions as compared with the 

 roots. When nitrogen is deficient, it is common to see stunted top 

 growth, pale green to yellow foliage, and yellowing or drying of 

 the older leaves, especially during droughts. 



Materials commonly used to supplement nitrogen in the soil 

 are ammonium nitrate, ammonium sulfate, and urea. These 

 materials are readily soluble in water. When applied to the soil 

 surface and followed by adequate rainfall or supplemental water- 

 ing, nitrogen will be carried down into the soil where it is avail- 

 able to all roots. Nitrogen is also carried away by water so that 

 it is necessary to add nitrogen to the soil at regular intervals to 

 maintain an ample supply. 



Phosphorus 



Most of the phosphorus in soil came from the rock material 

 from which the soil was derived. This form of phosphorus is 

 abundant but not readily available to plants. The soils with the 

 greatest amount of readily available phosphorus contain abun- 

 dant organic matter and a high percentage of clay. Most soils 

 have sufficient phosphorus for adequate plant growth, but addi- 

 tional quantities supplied as fertilizers may be needed for the 

 best growth. 



Plants use from one-tenth to one-fifth as much phosphorus 

 as nitrogen. Phosphorus is found in all living plant tissues and 

 is essential for good root growth, proper tissue development, and 

 flower bud production. It is abundant in seed and other storage 

 organs. Phosphorus has a direct role as a carrier of energy 

 throughout the plant and is also involved in photosynthesis. 

 When the soil is deficient in phosphorus, plants fail to get a good 

 start at the beginning of the growing season, have poor root 

 growth, and have delayed flower production. 



Commercially, phosphorus fertilizers are available as super- 

 phosphate, double superphosphate, and with nitrogen as ammo- 

 nium phosphate. The available phosphate in these fertilizers 

 reacts rapidly with the soil and remains in the area of application. 

 For this reason phosphorus-containing fertilizers must be placed 



