24- 



20- 



16 



12- 



cu 8 



3 



Roots and rhizomes 



Shoots 



168 336 



N rate ( kg/ha/yr ) 



672 



Figure 61. The effect of nitrogen fertilization on the aboveground 

 and belowground standing crop of S. alterni flora. 



(2) Oak Island . In 1971 at Oak Island an experiment was begun to 

 test the theory of Adams (1963) that iron deficiency may be the cause of 

 the chlorotic condition often observed in stands of S. alterniflova and 

 to evaluate the effect of nitrogen fertilization. The experiment consisted 

 of three randomized complete blocks with plots that were 1.22 by 15.2 

 meters with 1.22-meter borders between plots lying perpendicular to a tidal 

 creek so that each plot contained the tall and short forms of S. alterni- 

 flova. Iron and nitrogen fertilizers were applied in split applications 

 18 May, 30 June and 3 August 1971 (Tab. 39). Ammonium sulphate was the 

 nitrogen source. The iron sources were: (1) a commercial iron chelate 

 applied as a spray to the plants, (2) iron chelate applied in the dry form 

 to the sediment surface and (3) ferrous sulphate applied as a spray. 

 Samples were harvested 4 October 1971 by clipping a 0.25-square meter area 

 from the short S. alterniflova and a 0.25-square meter area from the tall 

 S. alterniflora in each plot. The samples were washed in tap water and 

 distilled water to remove mud from the leaves and stalks, dried at 70° 

 Centigrade, weighed and ground in preparation for nutrient analyses of the 

 plant tissue. 



136 



